Photo File – Twins of the Adriatic

By me
All photos me too, copyrighted

Even though light aircraft had remained faithful to Croatian airports all throughout the corona crisis – so there was always something to see wherever you went – the recent and quite sudden upsurge in tourist traffic had brought them back in numbers unseen even in record-setting 2019. From Pula (PUY/LDPL) at the top of the coast to Dubrovnik (DBV/LDDU) at its bottom, throughout July 2021 I was spoiled for choice on any GA apron, and more than once did not know where to actually start photographing (a #firstworldproblem if there ever was one). Homebuilts… turboprops… bizjets… touring… STOL… medevac… everywhere you went there was always something for any taste.

I, however, decided to indulge in a particular fascination with piston twins (a summer fling?), of which there were so many that I could easily devote an entire article to them – and, in fact, am doing right now. And while just a handful of them could be considered truly rare and interesting – even by Croatian standards – they should nevertheless make for a fun read for any GA nut!

An interesting airplane, a fine background and an electrically-assisted bike to get around the apron… the GA-loving Dash Driver’s summer vibe! And although it is not actually part of the this work (the covers ruin it for me), I can still tell you that this is a mint 1975 Partenavia P.68B Victor with the serial 00035, one of the many designs penned by brothers Luigi and Giovanni Pascale – the same duo that would later go on to found (and still run) the more famous Tecnam works

1. Piper PA-44-180 Seminole • F-GBPK

The first machine off the line may be the most common of the lot – but for reasons I can’t quite explain, I have a soft spot for Seminoles, particularly mint and sweet examples such as this one (though my colleagues were quick to point out that “sweet Seminole” is like saying “enjoyable tropical disease”).

Before taking selfies on the one on the left, you first need to leave a lot of sweat on the one on the right. While much maligned by students for its wheezy single-engine performance, lack of creature comforts and very many quirks, the Seminole is a real anvil of an airplane underneath, and can take so much abuse that a lesser aircraft would long before split in half. That said, having done my Multi Engine training on a nearly identical 1978 example, I was quite surprised at how potent the design becomes when fitted with a pair of turbos, with the 1982 Turbo Seminole I did my recurrents in feeling like a proper rally version!

Manufactured in 1979 under the serial 44-7994308, F-GBPK is seen here roasting at Split Airport (SPU/LDSP) after completing stage 2 of an epic trans-mediterranean journey that will see it cover everything from France to Croatia to Greece to Morocco to the Azores, before legging it back home across the entire width of the Iberian peninsula*. Having previously flown for the Aeralp flight school of Grenoble, F-GBPK sports a comprehensive avionics setup, including the Garmin G500 glass cockpit system, twin Garmin GNS430 moving-map GPS units, a King KRA10 radio altimeter, and a full suite of backup analogue IFR instruments – all of which makes for far more relaxing long-range flight!

* as originally planned, the whole itinerary reads: Grenoble (LFLS) – Bologna (LIPE) – Split – Ioannina (LGIO) – Heraklion (LGIR) – Megara (LGMG) – Kefalonia (LGKF) – Valletta (LMML) – Pantelleria (LICG) – Palermo (LICJ) – Olbia (LIEO) – Menorca (LEMH) – Malaga (LESB) – Fes (GMFF) – Agadir (GMAD) – Lanzarote (GCRR) – Tenerife Nord (GCXO) – Madeira (LPMA) – Cascais (LPCS) – Biarritz (LFBZ) and then home. At the time of writing, the aircraft had reached Tenerife, roughly 3/5ths of the way in (with a tech stop on Corsica for some maintenance)

A simple, elegant and clean scheme that makes it look far younger and crisper than it actually is. An interesting detail are the three-bladed props (unusual on naturally aspirated Seminoles), which briefly gave rise to the hope that it could be another Turbo model…

2. Piper PA-34-200 Seneca • F-BTMH

No. 2 on the list is another “Frenchie Piper” – but this time one considerably rarer than the Seminole. Even before you look at its serial 34-7250135 – which denotes it as the 135th PA-34 made in 1972 – you’ll note the square windows, the square engine nacelles and the two-bladed props, and immediately recognize it as The Daddy: the first ever Seneca model to go into series production…

The fresh paint job may fool the eye initially… but the angular design quickly gives it away! Made a beeline for it immediately, despite much bizjet eye candy in the background…

As the only Seneca variant to be powered by naturally aspirated engines (Lycoming IO-360s with 200 HP apiece), and sporting a limited payload of just 1,356 lbs | 615 kg (of which 590 lbs | 260 kg is fuel with full tanks), this model was neither overly efficient nor a spirited performer, particularly when on the heavy side and at high ambient temperatures. Quickly surpassed by the more capable turbocharged Seneca II and then the 220 HP Seneca III, the original has nowadays found its niche in the world of flight training, where loads (usually just a student + instructor) are never such that its lack of performance becomes an issue… even on only one engine. Cheap to buy, often with comprehensive avionics setups and big & complex enough to give the student an idea of what it’s actually like to handle an airliner, they can be a realistic alternative to Seminoles and Beech Duchesses, with F-BTMH itself flying in that role with the Sky Explorer flight school of Aix-en-Provence.

To make it even better, it is also only the third of its type I’ve ever seen, alongside the even older YL-ATB and Croatia’s own 9A-LEM. Ironically, given my fascination with it, I now have more photos of the rarest Seneca mark than I do of the common-as-trees Seneca III or the still-in-production Seneca V!

Looking quite cool in the fading light at Dubrovnik. Other interesting bits about F-BTMH are the baggage door window (which became standard only on the Seneca III, but was offered as a retrofit on the original and Seneca II) – and the fact that it has carried its identity since new, not something you see often in GA!


3. Beech 58P Pressurized Baron • N333RF

Third plane’s the charm however – not only for being my first Pressurized Baron, but also for being the only pre-G58 model I’ve ever seen in the metal (Barons of any sort are a pretty rare sight over here in SE Europe)…

It may not be the prettiest twin out there… but that classic teardrop shape is hard to miss on any apron! Developed in 1969 out of the original (and quite pudgy) model 55, the 58 received a 10″ extension of the nose, larger cowls for its more powerful 285 HP IO-520 engines, and a slightly wider wheelbase – all of which contributed to its famous regal stance. Other mods include redesigned cabin windows, split cabin doors on the right side of the fuselage, and a cleaner, re-profiled and relocated panel

The most advanced evolution of Beech’s hard-to-kill twin, the 58P was part of a double act with the unpressurized 58TC, both of which were intended to bolster the type’s sales prospects in the face of new designs from Cessna and Piper. Conceived in early 1973, the 58P ended up being the “marketing department’s airplane”, since it was pushed into development over the objections of the company’s engineering circles, who felt that Beech already had a perfectly adequate high-performance pressurized six-seater – the stunning model 60 Duke. Whats more, at the time the Duke was still holding its own against the only realistic competitor in this segment – Cessna’s 421 Golden Eagle – so it was felt that a pressurized Baron would just undercut the Duke’s sales for no tangible gain. However, strongly positive feedback from sales personnel across the US eventually prevailed, and work soon started on turning the already capable 58 into a Mini Me Duke.

Flying for the first time on 16 August 1973 in the form of a development prototype, the new 58P – as certified in 1974 – was powered by twin Continental TSIO-540-L engines developing 310 HP, whose massive turbochargers could supply enough high pressure air to give a 25,000 ft ceiling, power the pneumatic de-ice boots on the wing and horizontal stabilizer AND pressurize the cabin to a maximum 3.7 psi cabin differential. At the type’s usual cruising altitude of 18,000 ft, the latter translated into a very comfortable 7,700 ft cabin altitude (round about what you get on most airliners) – or a tolerable 11,900 ft at the 25,000 ft ceiling.

At this maximum altitude, the 58P could do 213 kts | 394 km/h in high speed cruise, which doesn’t sound all that impressive compared to the 200 kts | 370 km/h of the stock 58 – and on the original 285 HP engines to boot, well before the 1984 upgrade to 300. However, the stock model achieved this at a pretty low 7,000 ft, well below many safe altitudes in the Western US and Alpine Europe. So, despite objectively being some 75-80% of the way to the bigger and more comfortable Duke, as it went on sale in 1976, the 58P sold 83 examples in the first year alone – not a big number on its own, but quite a success for that market segment.

Despite a number of changes under the skin, from the outside the 58P is, at a glance, almost indistinguishable from the regular model. The only major giveaways are the additional scoops and vents on the cowls – and a single cabin door on the left side, relocated there to avoid creating a structural weak spot and undue pressurization stress in tandem with the crew door

Meanwhile, as test flying and certification were being wrapped up, Beech executives realized that they could use the work done on the 58P to try and break into another niche: unpressurized twins, where Cessna’s 401/402/411 and the Piper Turbo Aztec had cornered the market. To this end, they created the 58TC, which was in essence a standard 58 fuselage and wings mated to the complete engine installation of the 58P, rather than being a 58P with the pressurization system removed (so it retained the right side cabin door). The only other major difference to the standard model were equipment levels; since the 58TC could fly far higher than the stock 58P, it was equipped as standard with the de-icing system, and sported more cabin amenities and an extended IFR cockpit setup. Long range fuel tanks were also a very common option, to cater for the TSIO-520’s higher thirst.

In 1979, both the P and TC received an engine upgrade, swapping the original L model engine for the more potent TSIO-520-WB, now developing 325 HP. The upgrade also saw the P’s maximum pressure differential increase to 3.9 psi, and the top speed to jump slightly up to 216 kts | 400 km/h.

Given the number of unpressurized turbocharged twin types still flying today – Senecas, Cessna T303s, Turbo Aztecs and the like – one would have expected that the 58TC would also be a sales success. Despite being considerably cheaper, less complicated to operate and easier to maintain than the P, the TC was a complete flop, with just 151 sold before production stopped in 1982. While it was easier to live with, it was still more expensive to buy and fuel than its rivals, and despite having roughly the same performance as the P, it did not provide the same level of passenger comfort. As a consequence, the P would outsell it nearly three-to-one, with 495 built by the time production ended in 1986 during the big GA slump.

N333RF itself is an early 1977 example sporting the serial TJ-92, which says it is the 92nd P-Baron made (prototypes included). A quick search online revealed that it had been put on sale in the States back in mid-2020, and the fact that it has found its way to Dubrovnik means it has likely found a new home somewhere in Europe…

It’s not just the shape… it’s also the correct “brown & browner” 70s paint scheme. Despite being an early model, N333RF has been retrofitted with the WB engine by RAM Aircraft, and also sports the optional 196 USG | 742 l long range fuel tanks. Other stuff includes the Garmin GNS530 + 430 moving-map GPS units, the Avidyne Flight Max EX500 MFD, a Bendix King ART161A weather radar and a dated – but still perfectly adequate – Collins AP-107 autopilot

4. Cessna 414 RAM VI • N414SB

Compared to the 58P, the final aircraft for today was a far bigger sales success, with some 1,070 sold… but many people will still struggle trying to identify it. One of the many designs churned out by Cessna during its 60s and 70s market fight with Piper and Beech, the 414 is essentially a quick-and-cheap mishmash of parts from the earlier models 401 and 425, and was primarily intended to take over the Golden Eagle’s job of keeping the Beech Duke in check.

Despite its bright paint job, N414SB is the type of aircraft you could lose on any bigger apron. I myself had initially called it as a 401 or 402, until I had gotten close enough to read the tip tank…

Though it would eventually win and by quite a margin – outselling the Duke’s 596 by almost two-to-one – its lackluster looks and unglamorous origins had quickly made it fall behind the sofa of public consciousness. This, however, does not mean it was a bad aircraft; on the contrary, it would prove to be as tough, capable and long-lived as the 58P, and would in later years become a favorite for third-party upgrades.

N414SB itself – of 1970 vintage & serialled 414-0092 – thus sports the RAM Series VI mod, which sees the original Continental TSIO-520-J engines of 310 HP replaced by TSIO-520-NB units developing a more meaty 335 HP. Apart from a 10-15 knot bump in cruising speeds (depending on the regime), the upgrade also includes a 415 lbs | 188 kg increase in payload – and, despite the added mass, an increase in climb speeds from 1,580 to 1,900 FPM on both engines, and 240 to 310 on just the one.

The Series VI upgrade normally also includes new scimitar-type propellers – but the owner(s) of N414SB had decided to go one up and fit Hartzell’s odd-looking Q-Tip units. Occasionally mistaken for propstrike damage, the Q-Tip shape in essence behaves just like a winglet, increasing efficiency and thrust while reducing noise, vibration and fuel consumption. However – as is the case with Mazda and its pushing of the Wankel engine – the Q-Tip’s actual gains (particularly on a cost/benefit basis) are still fiercely debated online, with discussions on forums often growing quite heated and passionate…

Sources:

Flight Report – Getting a Motor Glider Endorsement

By me
All photos me too, copyrighted

With the financial situation at the airlines still worryingly precarious, I recently came to the conclusion that it’d do me good to become a bit more efficient with my GA flying (a #firstworldproblem right there). Since I usually spend my time in light aircraft joyriding around at low altitude with, at most, one other person on board, it dawned on me (belatedly!) that my usual Cessna 172 is quite a financial overkill – and that if the point is to just soak up the scenery and not actually go anywhere, I could do that for a lot less. Thus, I decided now’s a good time as any to kill two birds with one (cheap) stone, and do what I’d been wanting to do for ages: get a Touring Motor Glider (TMG) endorsement 🙂 .

Unsurprisingly, this had Achtung, Skyhawk! written all over it. And while I had initially planned to do another of my “amateur flight reports”, I soon hit upon a better idea. Since the approach to flying TMGs does differ somewhat from that of conventional aircraft, I decided to have a crack at an interesting mental exercise: try to anticipate what I’d struggle with during training – and then, having gone through the actual course, compare notes. Not only does jumping from the mighty Q400 into an aircraft that is it’s polar opposite promise to be quite an educational and humbling experience, it could also make for an interesting read – particularly on the peculiarities of the brain and the frequently amusing lack of love between the conscious and subconscious…

Another new cockpit for me – and again in windy and turbulent conditions. At least I’d finally managed to catch and ride my first ever thermal (until I unceremoniously fell out of it after just 500 feet)!

Tools of the trade

But, first things first: the airplane itself. The machine that has had to suffer my first attempts at “soaring with cheating” is a neat little Scheibe SF-25C Falke, registered 9A-DHD and based at Zvekovac Airfield (LDZE) to the east of Zagreb. Manufactured in 1976 with the serial 44148, it has lead a surprisingly straightforward life, having been initially known as D-KDEF and D-KLUG (likely temporary identities for delivery), before passing to the Austrian register as OE-9116 in 1977. Operated out of Scharnstein Airfield (LOLC) near Linz, it would be sold to Croatia in May 2018, to later become the founding aircraft of the SZK Dubrava flying club – and the eighth of its type to permanently reside in the country1.

Set and ready for me to take her up… the poor thing!

Future DHD in its original clothes, taken not long after delivery. The key differences (apart from the polish!) are dayglo markings and a dayglo rudder – as well as the installation of modern LED navigation/strobe lights on the wingtips

Like many other motor gliders, the Falke as a type comes with a choice of engines, with the C model’s Type Certificate Data Sheet listing no less than nine! Most of these are converted VW air-cooled four-pops from the 1.7 to 2.1 liter range (either by Limbach or Sauer), but there’s also the option of fitting the garden variety Rotax 912 – and even the turbocharged 914 of 115 HP (in which case the aircraft is sometimes known as the Rotax Falke). DHD itself sports the most basic fit, a 1.7 liter Limbach SL 1700 EA2 unit developing 60 HP for takeoff and 53 HP continuously, spinning a fixed-pitch Hoffmann HO-11*-150-B-65-L2 propeller.

At 580 kg | 1,280 lbs all-up mass, in touring mode this powerplant is good for 120-150 km/h | 65-80 kts in the cruise – while as a glider, a glide ratio of approximately 1/21 can be expected at 70 km/h | 38 kts. The type’s manual states that the usual empty weight is around 375 kg | 827 lbs; DHD however tips the scales at 409 kg | 902 lbs, leaving 171 kg | 377 lbs for the payload and fuel. The latter usually comes in the form of a 44 liter | 11.6 USG tank mounted behind the cockpit; DHD however sports the optional 55 liter | 14.5 USG unit, which will take it… some distance, depending on your use of the throttle and how much of a glide can you get out of it. On the engine alone, the performance figures say you should get up to 750 km | 405 NM at the long-range cruise regime (2,500 RPM and 130 km/h | 70 kts), with the 9.5 l/h | 2.3 GPH fuel flow giving an endurance of 5 hours 45 minutes – though I know no owners who had taken them even remotely that far (delivery flights included).

Inside, it’s all pretty standard; everything’s how it should be and where it should be. Avionics-wise, there’s a brand new TQ KRT2 comm radio, a Garmin GPSmap 196 (an old but pretty reliable piece of kit), the proven Bendix-King KT76A transponder – and a very useful dual USB charging port. There’s also a Blue Mountain Avionics EADI upgrade in the works, both to reduce weight and – more importantly – increase reliability, given the rate at which mechanical instruments tend to fail on grass strips…

Other stuff? Well, the same manual notes that the engine can conceivably take it up to an absolute ceiling of 6,000 m | 19,700 ft, though the service ceiling – the level at which rate of climb drops to 300 FPM – is significantly lower at 4,000 m | 13,100 ft… which begs the question of the length of time needed to climb all the way! Speed-wise, the C Falke is structurally limited to 190 km/h | 103 kts, though in level flight DHD’s SL 1700 will run out of ideas already by 175 km/h | 94 kts. However, the recommended limit in actual operations is 150 km/h | 81 kt, which corresponds to the Falke’s maneuvering speed – that is, the maximum speed at which a full and abrupt control deflection will not overstress the airframe (particularly important in thermals and mountain waves, where things are not always silky smooth).

1 of course, this being Achtung, Skyhawk!, we have to mention the rest, at least in passing. In addition to DHD, as of May 2021 there are six other SF-25Cs on the Croatian register (9A-DBV/DDB/DDT/DLK/DVB/GDK) – and one SF-25B (9A-DGZ) that had sadly been written off due to storm damage. There was also a rare and fully airworthy early model SF-25A Motorfalke (9A-DAG) from 1965 – but that one was sold on to Serbia back in April 2016

Folding wing – no wing – flappy wing – bunkered wing… it’s all here!

Describe your base airfield in one photo: a rare motor glider, a big bale of hay and a WW2 hangar made entirely out of asbestos… yep, that about covers it! Having arrived some months after this article had originally been published, 9A-JOJ marks the long overdue return of the Motorfalke to Croatia. For the time based right here at Lučko, it was known as D-KOKI in its previous life, and its serial 4553 suggests it too is a 1965 model like 9A-DAG (sn 4542)

2 as with many bits of an airplane that do not require sexy marketing names, the designations of both the engine and propeller represent pretty much their entire ID card. The engine is thus a Limbach unit (SL, now just L) of 1,700 cm3 (more precisely 1,680), with a single ignition system (E), and intended for use in a tractor configuration (A) with a fixed pitch propeller (2). The prop itself is a bit more complicated, being a Hoffmann unit with a Type 11 hub connection without any later modifications (*), made of hardwood, 150 cm in span with narrow blades (B) and designed as left turning (L); the 65 is a measure of the geometric shape of the blade and refers to the forward distance in centimetres the propeller would cover in one revolution – that is, its pitch – measured at some reference point along the blade (for this prop at 75% of the blade span)

Great expectations

So, that’s the machine taken care of – now time for the guy flying it. To explain why I think I may struggle a bit with the Falke, we first need to have a look at the scale of the challenge. On the face of it, short haul turboprop operations are often a curious mix of button pushing and stick & rudder flying, and tend to develop a very valuable (but also very specialized) set of skills – which is then hammered into the brain by sheer force of repetition. On one hand, you don’t really need to fly manually except for take-off and landing… but on the other, the latter requires some skill and finesse to get right, and it’s quite easy to make an uncomfortable mess of it if you’re not on the ball. Add to that the fact that four/five/six legs a day are the norm, and, like it or not, you have plenty of opportunity to get your handling & landing technique down pat. Indeed, I myself had already crossed the 2,000 mark just as Pilot Flying (i.e. in actual control of the aircraft, not counting another 1,500 as Pilot Monitoring), which is far in excess of anything I ever did in GA… and there on multiple types to boot. Since all of these landings were, by their very nature, highly structured and regulated, under their sheer numbers my perception and reactions have inevitably become biased towards the speed, power, inertia and control response of the Q400 – but experienced only in a very limited set of circumstances.

At the same time, after thousands of hours of looking at the same gauges and reaching for the same switches in the same positions, the brain inevitably develops a “blind map” of the cockpit, and begins working to a well-rehearsed procedural routine that relies extensively on muscle memory and requires very little conscious effort. In essence, if left unchecked, after awhile the basic business of pulling yokes, pushing levers, turning knobs and poking buttons becomes almost automatic, and starts to depend heavily on the familiarity of the surroundings and the lack of change in them.

Thus, when change does occur – as will happen in a new cockpit – there’s always bound to be some negative transfer, despite all conscious effort to prevent it. For while the brain is well aware that the surroundings have changed and that it needs to adapt accordingly, it will initially struggle to operate without all those blind maps it had previously taken for granted. To compensate for this lack of data, it will start filling in the gaps with an assortment of muscle memory, various preconceptions and all manner of past experiences – all stuff that rarely (if ever) works. The actual magnitude of this effect will vary from person to person; some will be alright almost immediately, while others may suffer for quite some time. In my experience, I’ve noticed that many of my “automated Q400 responses” tend to go away within a few minutes (after the brain builds up a first, crude mental image of the aircraft), and it seems that my dabbling in GA and frequent manual flying of the Q does help in shortening that period. However, whatever the duration and the manners of the new airplane, this is still the sort of thing that would be poor airmanship to ignore – no matter the thickness and contents of one’s logbook.

To apply this newfound “woke-ness” to my TMG training, I racked my head for stories told by experienced Falke drivers, my own observations from watching them fly and impressions from the 30 minutes I’d spent in control of one 15 years ago, and quickly came up with a list of things I feel I should keep an eye on:

  • overestimating the Falke’s mass and underestimating its control response
  • being too apprehensive about throwing it forcefully into a maneuver should the need arise
  • misjudging its drag and coming in too high and fast, without the benefit of big props, flaps and retractable landing gear to control deceleration and rate of descent
  • using the spoilers – not something I’ve had in this form on any airplane in the past – in a ham-fisted “Hulk smash” fashion
  • and getting caught out by the ground effect (low wing + large area) and a) floating for far too long, b) landing too hard for comfort, and/or c) moving the stick with a force and displacement appropriate to the Q and thus setting myself up for an unstable approach

The precedents for this caution and introspection are multiple. In my previous encounters with wholly new airplane types – the UTVA U-75, the SOCATA Rallye and latterly the Diamond Katana – I had noted an initial tendency to flare high and with a sudden movement of the controls, a well-rehearsed Q400 reflex that tackles its quirky combination of inertia, high approach speeds and low tailstrike pitch limits. Unsurprisingly, on light aircraft this usually results in a long float some way off the deck, followed by a firm and inelegant touchdown as the speed finally bleeds off – hardly the proper arrival into the type of soft and uneven strips that I normally operate out of. Given that the Falke is lighter, more agile and aerodynamically far more efficient than any of the above, it is reasonable to be on alert for more of the same – particularly given its eagerness in pitch3 and the fact that a far smaller change in Angle of Attack (AoA) is needed to produce the same results.

3 then there’s the control response with power off. With the engine running, the propwash provides additional airflow over the tail, increasing its effectiveness at all speeds. Remove the wash and that bonus is gone, resulting in a slight (and probably measurable) degradation in both stick feel and aircraft response

A similar point can also be made for use of the rudder. As on conventional gliders, the Falke’s long wings and large ailerons make for significant adverse yaw in the turns, which has to be countered by a lot of footwork – more so than on a “normal” touring aircraft. On the face of it, this should not be a problem, since I’m used to constantly keeping my tail in check; on the Q400, the P-factor of those huge props is such that you need to use rudder/rudder trim for any change in speed or power (down to as low as 3 knots or 2% torque), let alone in a turn. What does require awareness however is the magnitude of the input; the Q has notoriously heavy pedals and a very powerful rudder (part of which deflects up to 36°), and its application requires a firm, but still measured and comparatively short push action – which isn’t always compatible with the rudders and rudder pedals of light aircraft. This too was brought to my attention on the tail-happy Citabria, when the owner inquired as to why I was gingerly pussyfooting with the pedals, unaware that my muscle memory was trying not to yaw the airplane clean out of the sky and make an unholy mess back in the cabin.

Other predictions? Well, the Falke’s track record of docile handling and gentle behavior in the air suggests it has few (if any) naughty gremlins. That first 30 minute experience had hinted that it is very pleasant and relaxing to fly in many regimes (including the stall, which was a complete non-event), with the only oddity being a slow roll response due to the strong damping effect of its wing span. Another thing I imagine will feel weird at first is its low sink rate with power idle/off (me being used to getting 1/10 at best), which will initially make for an uncomfortably low traffic pattern and more than one overshoot in the descent. A further thing to keep in mind in glider mode are the temperature limits of the engine; with a minimum oil temperature of 50 °C required before you can fully open the taps, any extended soaring will have to factor in a potential warm-up period, and consequently an increase in the minimum altitude at which an air start is practical.

One of the “positive transfers” from the Q400 is a high degree of pitch awareness, making the lack of an artificial horizon a non-issue. Being long and low off the ground, the Q will scrape its tail on landing at as little as 6.5° in pitch; coupled with its approach attitude of around 2-3° (with Flaps 15) and a procedural pitch limit of 5°, you really don’t have much room to play with and cannot afford to yank the yoke around at will. What you can do is make one or two precise, well-timed rearward movements of the yoke at low height (usually 10-15 feet) to quickly increase the AoA and arrest your descent – and then gently reduce throttle so that the reduction in propwash over the wing settles you onto the ground (while slowly continuing to pull back on the yoke as needed). All of this promotes – and indeed requires – accurate pitch perception, something I expect (hope!) will serve me in good stead on the Falke

One other feature that had particularly piqued my interest is the landing gear. Though the outriggers mean there’s no chance of pulling a U-2 and tipping over onto one wing, the central main wheel nevertheless looks like it requires extra attention – since it, and not conventional main gear legs, is now the point around which the aircraft pivots during ground maneuvering (which contributes to its somewhat large 13 m turn radius). This I imagine requires a specific technique when operating out of rough or rutted strips, since countering the motion of the main wheel as it goes wherever the terrain wants it to go requires quick and energetic work with both the tail wheel steering and brake. This too is not particularly kosher on the Q400, since its large main wheel span (8.8 m), carbon brakes (which take their time to warm up and lock without regrets if you ride them too hard) and large nose wheel steering arc all require limited, well timed and patient inputs – just like the rudder. However, having put this thought to paper/screen, I then had a chat with a captain of mine who also has a TMG endorsement – and had, more so, done it on DHD itself. After I’d articulated my assumptions, he dispelled many of my ground maneuvering concerns – but did draw my attention to the need to actively keep the wings level during taxi, take-off and landing by using the ailerons, something that had not occurred to me at all in my initial analysis.

And last, but definitely not least, user-friendliness. Here I don’t anticipate any major issues; I know I fit… I’d used the metric system in the air before… and with my fair share of 60s Cessnas behind me, no panel setup – no matter how convoluted – is able to faze me anymore. The only thing that jumps out really are the spoiler levers: two big, handbrake-type affairs located on either side of the pilot seat. The catch is that they also operate the main wheel brake, which is activated by pulling the levers beyond the spoilers’ fully extended position; there are no pedal brakes, which is definitely something to keep in mind in the heat of the moment. However, given the Falke’s sedate touchdown speed – just 72 km/h | 39 kts – and its draggy, tailwheel-first touchdown attitude, there’s little conceivable reason for all-out braking on any GA runway in Croatia… particularly on the 630 m of it available at Zvekovac.

The levers do, however, raise an important question of ergonomics. Personal experience so far has shown that I appear to be ambidextrous as far as flying is concerned (and ONLY then!), and can operate the controls pretty much equally well with both hands. That said, being right handed, I prefer and feel physically more comfortable flying with my right hand, as I do at work (there’s muscle memory for you). When soaring with the engine off, this is a non issue: right hand on the stick and left hand on the spoiler handle, located almost exactly in the place I’d expect to find the up/down controls on the Q400 (the power levers). However, since DHD has only one central throttle lever, when flying under power, I’d have to switch hands and fly with my left (like on the C172), with the right reserved for the throttle, carb heat, the other spoiler handle and ignition/starter. Echoing the dilemma I’d faced on the U-75, the question now is whether to a) fly solely with the left in all regimes, b) switch between left and right as necessary or c) switch to the right only for extended periods of soaring. I guess trial & error will tell!

Off for another round of traffic circuits on a beautiful spring day… between myself and another student, it had logged 33 landings in just one afternoon; quite a busy bird!

Keeping the pointy end forward

So, how did it all work out in the real world? Unsurprisingly, I got some things right – but also missed the mark by quite a lot elsewhere. To make sense of the results, I felt it best to break the experience down into segments, roughly corresponding in theme (if not sequence) with the paragraphs above. Starting then from the top, we kick off with:

GROUND HANDLING

As foretold by my cap’n, this turned out to be quite easy, despite the bumpy runway at Zvekovac and a persistent (and annoying) crosswind. Quick footwork is definitely required, but the Falke’s response turned out to be very predictable, and I managed to get a hold of it already on my second time out. The aforementioned 13 meter turn radius does take a while to get used to, and on narrow runways one definitely needs to keep the outriggers in mind (located just outboard of the spoilers), lest he/she snag a runway marker or park them in a drainage canal. I was also surprised by how little braking was necessary, even during faster taxiing; with comparatively little mass, a low pressure main tire and some assistance of high grass, stopping was usually just a mater of closing the throttle and giving it a few seconds to run out of steam – meaning that I did not really miss classic foot brakes. Indeed, on my very first taxi, I felt distinctly unnerved by the mismatch between engine note (60 HP, so you have to rev it to get going) and the sedate pace of movement (rarely above 10 knots), half expecting it to suddenly accelerate and roar off like all hell broke loose (like the Q400 likes to do).

Another thing that had taken me by surprise was the poor ride comfort. The RWY 22 end at Zvekovac is a bit bumpier than the rest of the strip, and maneuvering there (particularly in a 180 degree turn to line up for take off) quickly showed the limits of the C model’s simple rubber shock absorber. On take off and landing, it was not so bad; but during taxi, when the full weight of the aircraft is on the wheel, it was quite uncomfortable and borderline physically tiring (mind you, I’ve been told this is Rolls-Royce smooth compared to the earlier B model, which had no shock absorber at all!). What’s worse, that this could be an issue had not even crossed my mind previously, being used to light aircraft that had been designed for rough(er) field operation right from the outset.

Adding to the workload was also the need to keep the wings level, as cap’n had also warned me. When rolling for take off or on landing, this wasn’t much of a job, since the ailerons become/remain effective at very low speeds, down to as little as 30 km/h | 16 kts. But, at taxi speeds – and particularly over the rougher bits of the runway – the Falke was quite eager to dip onto its outriggers, making for an even less comfortable ride. However, some experimentation with the opposite rudder – using inertia to tip the entire aircraft back into a wings level position – usually did the trick, though experience will undoubtedly reveal better ways to do this.

The major problem with this tipping tendency that I can see so far is that during touch and goes, the torque and gyroscopic effects of the rapid increase in propeller RPM will swing the nose significantly to the side, making it all but certain that you’ll end up on the outrigger. Its additional rolling drag – as well as becoming a pivot around which the aircraft can turn – could then swing the nose even further out and make for a lively departure. The key, it seems, is not to be aggressive with the power; I found that, even with a long landing, I had more than enough runway to slowly advance the throttle and get into the air with plenty of space to spare. This then allowed me to parry any swing more precisely and with less rudder deflection – though the downside is that the aircraft could become airborne before full throttle is reached (as had happened to me once after touching down with something like 60 km/h | 32 kts – and 70 km/h | 38 kts being at that point enough to get me airborne).

GENERAL HANDLING

On this front, I’m happy (?) to report that my assessment of both the Falke’s handling characteristics and my own response to them was pretty much on the ball! The old Q400 muscle memory had inevitably gotten the better of me in the beginning, and the first few circuits were as elegant as a brick falling down a flight of stairs (and I can’t even scapegoat the day’s thermal turbulence). Thankfully, progress improved dramatically after half a dozen landings, and by the end of the first session, I at least had general handling down pat. Things were, surprisingly, best in pitch; as noted previously, the Falke’s aerodynamic setup means that it is very willing to maneuver around its lateral axis, and that even a small change in pitch/AoA produces a significant change in lift. This I was prepared for; what did surprise me after the initial “shock” was how much its response reminded me to that of the Q400 (except in control feel, which is quite heavy on the airliner). Once I’d gotten used to the sight picture from the cockpit, I was outright shocked at how easy I could read what the nose was doing and how much input was needed to keep things in check. The only thing I really had to concentrate on was the need to correlate extension of the spoilers with a backwards pull on the stick; this took a bit of practice (since I had the impression that the spoilers had a pronounced non-linear effect), but by the sixth or seventh landing, I was pulling tailwheel-first greasers despite the turbulence.

Handling the spoilers had also solved another dilemma: which hand to fly with. As I’d been instructed during the course, for take-off and during normal engine operation, I should keep my left hand on the stick and the right on the throttle – and then, for soaring, approach and landing, switch to right on stick, left on spoiler lever. Though I myself had also considered the option of switching as needed, this particular method seemed flawed, since such a switch can lead to a momentary disruption of the flight path (something I’d experienced already on the U-75), particularly on final approach if you’re short and need to shuffle hands to add a bit of power. However, after the first few approaches, the rationale became clear: the spoilers are incredibly powerful, and you can come in close to the runway – keeping well within safe gliding range – and still make it just by modulating spoiler extension and leaving the throttle alone. To make it even better, the spoiler lever is spring-loaded to the retracted position (full forward), so operating it is simply down to varying hand back pressure; and with moderate and quite informative resistance in the handle, this means you can be incredibly precise in metering out drag.

All of this had three important effects: a) it alleviated my fears of coming in high, fast and without enough drag to slow down, b) it meant that floating would not be an issue and that I could flare late and low without worries, and c) the same time-honored method of controlling speed with the stick and rate of descent with power/drag works beautifully on the Q400 as well (especially since it has a big, four-meter air brake on each wing). Hence, I ended up on an aircraft whose pitch response and performance in the flare are reassuringly similar to that of my daily driver, with the flight path controls all in the same place and operated in exactly the same way – resulting in shocking ease and speed with which the Falke and I had managed to work together!4

4 this similarity/familiarity should not be overlooked. In my case, it enabled my muscle memory to work WITH the aircraft as opposed to AGAINST it. One student, who only ever flew Cessnas and Pipers beforehand (left hand for yoke/speed, right for throttle/vertical rate) ended up doing a nasty hard landing in a Falke when he pulled back on the spoiler lever instead of the stick, and dropped the airplane right onto the runway from an altitude of about 2-3 meters (this had occurred after a long circuit-bashing session, likely a reversion to “previous instincts”)

Could do with a mountain or two to spice up the view… but even so, it’s not a bad one!

However, if at this point I had any illusions about being one with the Falke, they were quickly dispelled by events in the other two axes. As expected, the long wing span makes it quite lazy in the roll; but just how lazy I discovered after entering my first thermal on the climb out, when the aircraft rolled violently to one side – and my full opposite aileron input had no effect for at least a second or two. Though this is perhaps an extreme example (open plains at 3 PM on a cloudless day make for pretty strong thermals), it is nevertheless a welcome one, since such behavior is uncommon on the types of airplanes I normally fly – which definitely warrants keeping it in mind!

But, what let the whole side down at first was my use of the rudder. Here, the Citabria Experience came back in full: countering the adverse yaw of both intended and unintended rolling required quick and occasionally significant inputs, something which my brain was reluctant to do (despite objective evidence that it should) for fear of over-yawing the airplane and sliding it about like something out of Fast & Furious. Compounding the problem was that in a steeper turn, the Falke, like all gliders, wants to continue banking in the same direction. The cause lies once again in its large wing span; in a tight enough turn, the outer wing moves significantly faster than the inner one, thus producing significantly more lift – so much so that it can overpower the glider’s natural rolling stability and effectively tip it over itself. This is easily sorted out with a bit of opposite aileron5 – but this again requires opposite rudder to cancel out the adverse yaw, which results in having to constantly jiggle the rudder from side to side (and even on occasion fly with crossed controls). All of this is perfectly doable – generations upon generations of glider drivers will attest to that – but for a high-performance airplane driver, all of this is subjectively new ground… despite logically being a clear as day.

A new yaw-related problem then appeared on landing – but this time had nothing to do with aerodynamics as such. While I’d quickly managed to nail down my vertical and horizontal profiles, for awhile I persisted in landing with a slight crab, something I was not really aware of until my instructor pointed it out. He said this was common for people transferring from touring airplanes, since the Falke’s smaller engine allows the cowling to taper off significantly in order to eek out a bit of extra streamlining. If you’re used to using a conventional “straight cowl” as one of your visual references on landing (as I am on the C172), you’ll subconsciously try to get the same sight picture on the Falke, and invariably land at an angle (which the grass runway at Zvekovac duly forgave, many thanks!). Rather embarrassingly, this is the same trap I fell into on the Diamond Katana not two months ago; and while in both cases my brain eventually got the message, it was definitely unpleasant to have to add rudder in the flare by conscious force and without a “visible” need to do so. The mind boggles!

5 as always, there’s a catch: if too slow and in too tight a turn, yanking the stick to the other side will cause more problems than it will solve. If conditions are right, the upgoing aileron on the inner wing will raise AoA sufficiently to stall the entire wingtip, converting the turn into a full blown spin

A cellphone shot (I know 😭 ), but I had to capture properly riding my first ever thermal!

SOARING

Being “just” flying without the engine, soaring as such does not present any new problems handling-wise (elegance, however, is another matter entirely!). Indeed, the only things that I had pegged in my analysis were the control response without propwash – and the need to warm the oil to 50°C or above before flooring it. The former turned out to be a non-issue; and while there was a slight drop in responsiveness in yaw and pitch, it was not nearly as significant as I thought it would be – and had I not been specifically looking for it, I might have chalked it up to the effects of thermals or turbulence. Additionally, the Falke’s soild glide performance meant that flying downwind just 600 ft above ground quickly became normal – an impression later reinforced by a simulated engine failure on upwind, during which I managed to make a 270° procedure turn to line up with the opposite RWY 04 and almost overshot the threshold with the spoilers extended (OK, I had 15 knots of tailwind to help, but still).

Unfortunately, the short time I’d spent so far on flying with the engine off – some 10 minutes – meant I could not get a meaningful impression of the latter; with 28°C on the ground and 25° in the pattern, the oil temp went from 92°C to around 75°C in that time, which doesn’t really tell me much. However, I did note that even in the heat, the oil does tend to cool quickly and warm slowly, so the real acid test will be prolonged soaring (later in the course) and/or lower temperatures (later in the year).

One thing that did particularly intrigue me was the whole process of shutting down the engine in flight. Procedurally, it’s a piece of cake: throttle gently to idle, leave it there for a spell so the engine temperatures and pressures stabilize – and then just flick the ignition switch to off. What I did not anticipate was the need to actively stop the propeller from windmilling, accomplished by raising the nose and letting the speed bleed off (and briefly punching the starter if the blades had stopped in a vertical position). The reason for this quickly became obvious, and with hindsight should have been obvious from the outset: like the Rotax line, converted VW units are shut down by cutting the ignition, and not by starving it of fuel as is the case with conventional Lycomings and Continentals. If the prop is allowed to windmill, it will not only create additional drag, but also suck fuel into the cylinders (since it is readily available); and if the cylinder walls and heads are sufficiently hot – which they will be after a prolonged low speed climb – the fuel will spontaneously ignite on contact and combust roughly in the same manner as if the engine was running, adding to the rotation of the prop. Normally this happens only once or twice after an in-flight shutdown (as had happened to me), since the cylinders tend to cool pretty quickly and it doesn’t take long to stop the prop; however, it is nevertheless a potent reminder to be very wary around a VW nose even if the airplane is shut down. Indeed, I’ve been told stories of hot Limbachs and Sauers coughing into life after nothing more than a quick yank of the prop…

Update 19 MAY 2021:

Having gotten a bit of additional soaring time in, I thought I’d report back with a couple of fresh observations; nothing “revolutionary”, but enough to add some extra substance to this section. As I’d noticed previously, the oil does tend to cool quite quickly even at moderate ambient temperatures. Upon reaching 3,000 ft with 17°C outside, the oil was pegged at its usual “power on” 90°C; but after gliding down to 2,000 ft (some four minutes at an average 300 FPM), lighting the engine, climbing back to 3,000 and repeating the process, the oil was down to 60°C, by which time I decided to start the engine again and leave it running to keep it warm despite ample altitude left to go. Having then gently settled into a cruise at 1,500 ft with 20°C outside, at 2,100 RPM it took a good 10 minutes for the oil to go past 70°C. It is worth noting that I had kept the cowl flaps open the entire time (on advice of my instructors, given the hot nature of training ops), and I’ve been told that for prolonged soaring closing them measurably reduces cooling rates for both the oil and cylinders…

The spinny thing isn’t spinning… but the pilot is not sweating. Having been preparing myself for days (especially through writing this piece), flying sans engine turned out to be anticlimactic and natural… a tribute to the confidence the Falke’s handling inspires!

USER FRIENDLIESS

Among the many things I did not expect while writing this piece was that this section would end up being the one with the most interesting revelations! The spoiler levers I had tagged as a potential issue turned out to be anything but; instead, what did require additional brainpower was something as basic as reading the Airspeed Indicator. No, not the fact that it’s metric – but that the Pitot tube that feeds it is mounted on the vertical stabilizer (as it is on a “purebred” glider) and thus sits square in the middle of all the propwash. Hence, it over-reads by default whenever the engine is running – and does so by a different amount depending on the throttle position. Thus, despite the Falke’s aerodynamic efficiency and pussycat stall behavior, I found myself adding slightly to my climb speed “for the wife and kids”, ending up at 110 km/h | 59 kts – well above the 85 km/h | 46 kts called for by the manuals and the 90-95 km/h | 49-52 kts briefed by the instructor due to the day’s thermal turbulence.

Then there was a Grade A rookie mistake, one I’m still trying to wrap my head around (when I manage to stop laughing at it): like many light aircraft, DHD has a friction control for the throttle lever, which was set quite high when I first sat inside. I though that a bit too much for my taste (mistake #1) and on subsequent circuits loosened it slightly. However, when I decided to see how far a thermal would take me – keeping the engine at idle since I was just 500 ft above ground at this point – I assumed (mistake #2) that the throttle would stay put, and thus failed to note the exact idle RPM (mistake #3). Having topped out and decided to head back down into the circuit, I was somewhat puzzled to find that I was struggling to descend at nearly 140 km/h | 76 kts and with the spoilers fully extended, barely making 3 m/s | 600 FPM. Normally, this speed with brakes out should be seen with at least 15° of nose down pitch, so my first thought was that I had hit another of the many thermals that had been lingering along the edge of the circuit. However, having covered some distance, my rate of descent actually started decreasing towards 2 m/s | 400 FPM, at which point I started to suspect something else was up. Belatedly, my ears then informed me that the engine note was far too loud for idle; and lo and behold, I noticed that the throttle lever had moved in slightly in all the commotion and increased RPM by 300 revs… quite a lot on the Falke, as I then discovered! Needless to say, I kept the friction pretty much all the way up from then on…

Another prediction that ended up being a bit off is “I know I fit”. While I most certainly do and can get comfortable even with my headphones on (more so than on the similarly tight Katana), problems began to arise when I needed to deflect the stick fully. To enable it to be moved to its extremes in such a small cockpit, the one on DHD is, by necessity, a bit short; and when you place your hand around it, taller people like me find that your legs get in the way left-right – and your “gentleman’s area” to the back. While I successfully managed to hit myself in all three on the first few flights, the frequency of… hmmm… “interfering with myself” soon began to decrease, though I’m still not entirely sure whether due to the reduced deflection of my control inputs (having began anticipating the aircraft better), subconsciously altering my sitting position to compensate, or a combination of both.

One other flight control to get used to is the elevator trim, a small lever located between the seats (and in roughly the same place I’d expect to find the electric trim switch on the Katana). On DHD it is a bit tightly set, which actually suits me just fine, since this too approximates the heavy controls of the Q400. What is an issue however is that to operate it in soaring flight or when at idle, I have to switch hands – again, not something I feel comfy doing at low altitude. However, the good thing is that the control forces are light whatever the trim setting, so you can easily “overpower” the trimmer and just keep additional forward or back pressure until you have time to adjust it.

And though it may not exactly fall under the category of “user friendliness”, all of the Falke’s controls have excellent feedback, so once you get a hang of the airplane, you can almost tell what each bolt is doing just by judging the feel in the pedals and stick. This makes it very relaxing and easy to fly in an old school manner – solely by visual reference to terrain – with just an occasional glance at the oil and cylinder temperature gauges. Indeed, the club is planning to stick on a yaw string, which will then make for a proper “soaring with cheating” experience – and hopefully another Achtung, Skyhawk! article!

Check, check and recheck. DHD getting ready to end the day with a bit of regular maintenance

Sources:

Changelog:

  • 24 SEP 21: corrected some mistakes and added photo of 9A-JOJ
  • 23 MAY 21: added photo as OE-9116
  • 19 MAY 21: added soaring update

Photo File – Piper PA-34-200 Seneca 9A-LEM

By me
All photos me too, copyrighted

In a return to form for a website I claimed would deal with “news from Croatian general aviation” – but which most of the time does nothing of the sort – my second piece for October 2020 could not be more on point: a photo session with the newest addition to the Croatian civil registry, Piper Seneca 9A-LEM. And while Senecas as such hardly qualify for the Endangered Airplane List, this particular example is a nowadays very rare first generation model – and only the second such example I’ve ever come across IRL. Now, if that wasn’t enough to reach for my car keys… 😀

It may not be the most exciting shape out there… but there are enough nerdy bits on it to keep me occupied for hours!

Swiss stability

Like with Soviet aircraft – whose designations and serial numbers amount to pretty much the airframe’s entire ID card – you can tell a lot about pre-80s Pipers just by making sense of all the gibberish on their data plates. 9A-LEM’s, for example, reads PA-34-200 with the serial 347350327, which translates to:

  • 34 – the type designation for the Seneca family
  • 73 – produced in 1973
  • 50 – model code for the original Seneca series* (the Seneca II would be designated 70, while early Seneca IIIs – the last to use the system – were 33s)
  • 327 – the 327th aircraft produced in 1973 (but not the 327th Seneca overall; with 360 produced in 1972, LEM would be no. 687, excluding the prototype)

The 200 suffix is a nugget as well, since it indicates that this model is powered by normally aspirated, fuel injected, four cylinder Lycoming L/IO-3601 engines producing 200 HP – making it the only Seneca mark not to use turbocharging. Its occasionally marginal performance at altitude (particularly in the climb) meant it would soon give way to the PA-34-200T Seneca II, powered by six cylinder Continental L/TSIO-360 engines developing the same 200 HP – but now equipped with turbochargers that could maintain that output all the way to 12,000 ft. Though this did wonders for overall performance, the subsequent PA-34-220T Seneca III would up the take off power to 220 HP in order to cope with the type’s constant mass increases (max continuous remained at 200), a solution that would also be re-used for the Seneca IV – before finally being upgraded to 220 HP both for take off an continuously on today’s Seneca V (achieved by fitting a different engine variant and improved turbocharger w/ intercooler).

* while it does appear in a number of sources on the Internet, the first Seneca series was never formally called the Seneca I; only the four later generations had a Roman numeral to their name

The first of the original Seneca’s several dead giveaways are the boxy engine nacelles – all lumps, bumps and intakes – and the 1.93 meter two-blade, constant speed, fully feathering prop. The type’s familiar three-blade unit of the same span would appear only in 1979 on the Seneca III – and even then initially as just an optional extra

For a light aircraft that’s pushing half a decade in service – and which you would expect has seen its fair share of commercial operators and flight schools – LEM had led an unusually quiet life, having only ever had two previous identities: N56394 for delivery, and HB-LEM from September 1973 to February 2020. Interestingly, its time in Switzerland – among some pretty high terrain – was spent accident-free and in the hands of just one private owner, having never seen a single student or contract pilot in the nearly 5,800 flight hours it had logged over there. In fact, the only blot on its record that I could find is an airprox incident in 2018 that ended without damage.

Proving that you can’t run away from school forever, this would change on 28 February when HB-LEM landed at Pisarovina-Bratina Airfield (LDZR), a private airstrip near Zagreb owned by local flight training provider Pan Avia. Through a combination of maintenance, paperwork and just plain old corona crisis, it would take nearly seven months for it to join the active fleet, by which time it would become known as 9A-LEM. Unsurprisingly, it will be used by future airliner drivers for their Multi Engine Piston (MEP) training, a task for which many operators said it was well suited, despite its asthmatic climb performance on one engine (somewhere around the 400 FPM mark in a typical training configuration, less – but only just – than the purpose-built PA-44 Seminole trainer).

American recycling

Having established that LEM’s history is squeaky clean and disappointingly straightforward, it’s time to get down to best part: the nerdy details! Even though the Seneca had looked thoroughly modern and quite cool when it went on sale in 1972 (particularly in comparison with Piper’s other twins, the 50s PA-23 Aztec and 60s PA-30/39 Twin Comanche), the truth of the matter is that it was still very much a “real Piper”: essentially designed on the back of common off-the-shelf components and structural bits & bobs of the company’s other aircraft. Indeed, the main parts donor – contributing the fuselage, wing, tail, interior and cockpit – was the six seat PA-32 Cherokee Six, traces of which would remain easily identifiable (as will become obvious later!) well until the early 80s Seneca III.

The first of the many telltale signs of the Seneca’s Cherokee Six DNA are the square windows, copied over bolt-for-bolt. With the coming of the Seneca II, they would receive rounded edges – and then be fully recontoured and resized on the Seneca IV (the III would introduce a third set in the cargo bay)

And while you’d be hard pressed to find a manufacturer that did not dip into its own parts bin for every new design, Piper is widely acknowledged for elevating this “Lego approach” to wholly new levels. By keeping things simple and not trying to reinvent the wheel – except in rare moments of madness such as the PA-31P Pressurized Navajo or the PA-35 Pocono regional airliner – they were able to produce good, reliable, middle-of-the-road aircraft quickly and on comparatively small budgets. Low development costs then translated into reasonable showroom prices, which were frequently worth the design’s long-term dynamic, economic and operational inefficiencies.

The Seneca had managed to pull this trick off as well, with the original series being such a hit that 933 would be sold before production shifted to the improved Seneca II in 1975. Piper’s continual pig-headed tinkering with the design and near-constant performance upgrades made the hard-to-kill twin relevant even into the 21st century, with Senecas still rolling off the production lines after nearly 5,050 have been built.

The doors (both in location and size) are another throwback to the Cherokee Six. Some authors even said that if you took the Seneca’s wings off, you pretty much wouldn’t be able to tell the two apart…

Piper archaeology

Having been based on the structure of a single-engine airplane – which was not originally envisaged or scaled to carry the extra mass of a second engine and the additional fuel to feed it – the first generation Seneca naturally had its fair share of limitations. Depending on the fit and equipment options selected, the empty weight for most examples hovered around the 1,200 kg | 2,650 lbs mark – noticeably more than the 820 kg | 1,810 lbs of the PA-32. With full fuel – 371 l | 98 USG (260 kg | 590 lbs) across two wing tanks – you were left with only 355 kg | 760 lbs to play with before hitting the 1,815 kg | 4,000 lbs Maximum Take Off Mass (MTOM). Even considering that people in the 70s were, on the whole, slimmer than they are today, this made for a useful load of only four 75 kg | 165 lbs adult males with 5 kg | 11 lbs of baggage each.

If you wanted to max out the cabin and use all the six seats you paid for, you could be looking at barely 190 l | 50 USG worth of fuel. And while that would be classified as “a lot” on the Cherokee Six, the Seneca’s fuel consumption of 18 USG/h at 65% power meant it would suck its tanks dry in around two hours and 45 minutes. Knock 45 minutes off for Final Reserve Fuel, 30 minutes for a reasonable Alternate w/ a bit of holding, and 15 minutes for Contingency (to compensate for imprecise performance charts, calculation errors and weather avoidance), and you’d end up with an effective endurance of just one hour and 15 minutes – barely 370 km | 200 NM at the 295 km/h | 160 kts cruise speed you’d get at 9,000 ft. Throw in high temperatures, headwinds and “weekend fliers” who may not know all the tricks of economy flight – precise leaning, finding the best fuel/speed/wind ratio, least-fuel climb and descent profiles, etc – and that could very well drop below the 60 minutes mark.

This of course did not fly under Piper’s radar, and pretty soon it came up with an option to boost MTOM to 1,905 kg | 4,200 lbs. Essentially a “paper exercise” in stretching the rules while remaining firmly within them, this mod did not involve any structural changes to the aircraft – but merely the provision that this increase is possible as long as the aircraft’s Maximum Zero Fuel Mass (MZFM) does not exceed the original MTOM (1,185 kg | 4,000 lbs)**.

** in simple terms, the MZFM represents the maximum mass the aircraft may have with no fuel in its wing tanks (i.e. basic structure + payload + fuel in any other tanks other than wing). When loaded with fuel, wing tanks weigh the entire wing down and alleviate some of the upward bending moment caused by lift; and since lift counters mass, the heavier the aircraft, the more lift is needed and the larger the bending moment will be. If the moment is too large, it can cause significant structural damage to the wing – thus the mass of the airplane has to be limited so that in the case of fuel exhaustion, the moment would remain within safe limits. In an extreme example, this meant you could not load you Seneca with stuff up to a mass of 1,860 kg | 4,100 lbs and then just add 45 kg | 100 lbs worth of fuel – since if (or rather when) you ran out, the wings could buckle

In practice, this did go some way to addressing the type’s fuel issues, but there were a few traps along the way – chief among which was the Maximum Landing Mass (MLM). In the “six 75 kg male” scenario above, the mass of the loaded aircraft without fuel on board (Actual Zero Fuel Mass, AZFM) would be 1,680 kg | 3,700 lbs, which meant you could now conceivably take 225 kg | 485 lbs (320 l | 81 USG) of fuel, giving you a much more agreeable endurance of 4.5 hours. Factoring in the same Reserve, Alternate and Contingency Fuel, you got a solid three hours, or approx. 900 km | 485 NM of range (to keep things simple, the math assumes the same cruise speed and fuel consumption as before, despite the higher weight).

The trick***, however, was that the MLM remained unchanged, and was equal to the MZFM and old MTOM. So on landing, the mass of the airplane, everything/body on board and the fuel remaining had to be 1,815 kg | 4,000 lbs or less. So if you packed all six seats, fueled your bird to the brim and then flew for just one hour, you were going to be overweight on landing. The same issue also limited the load; if you planned everything right, you’d have landed at your destination with Reserve and Alternate fuel remaining – roughly 85 l | 22 USG (60 kg | 135 lbs) using the numbers above. With an empty weight of 1,200 kg, your load then could not exceed 555 kg | 1,225 lbs – which is right on the limit for today’s average passenger weights (six 80 kg | 175 lbs males with 10 kg | 22 lbs of baggage each).

*** another issue to be mindful of was a significant drop in performance at the new MTOM, particularly on one engine. The manuals show that the absolute single-engine ceiling went down from 6,600 to 5,000 ft – while the max sea level rate of climb on one engine dropped from a meager 230 FPM to just 190

While this explanation is, admittedly, a bit long-winded and heavy on the numbers (being a byproduct of my own airline flight planning traumas), it does serve a couple of vital functions: one, LEM has the 4,200 option on it – and two, it goes to show just how “offbeat cool” and charmingly flawed the original Seneca really is. And more is to follow!

Since it was intended right from the outset to be a comfortable and serious touring aircraft with an eye on commercial ops, its systems, avionics and general equipment fit are considerably more extensive than on any previous Piper light twin. On the outside, the most notable is the optional de-icing system, available in several different configurations – but in the event taken up in full by the vast majority of aircraft, LEM included. Certified for flight into known icing conditions, it uses traditional pneumatic boots for the wing and tail surfaces (inflated by the same vacuum pump that drives the primary instruments, albeit a more powerful model to cope with the higher demand), while the props, fuel tank vents and windshield – where equipped – are heated electrically (in addition to the usual Pitot tube heat).

The limitations of electrical systems on light aircraft mean that “windshield heating” can be a bit misleading. While it is indeed physically possible to install full-pane heaters as seen on airliners, their current draw would simply be too much for the types of generators fitted to piston engines – especially in case of an engine failure at night and in icing conditions, when demand for electricity from the remaining unit is at its highest. To get around this issue, many twins and high performance singles use so-called “plate heaters” or “hot plates”, bolt-on heated glass frames whose size is small enough to avoid overtaxing the airplane’s electrical network – but still big enough to provide at least some form of forward visibility. Information on the net suggests this model has a 15 A current draw – for comparison some five amps less than the propeller heaters

Inside, the “front office” could be equipped with enough kit to rival some high-end twins, with a full IFR suite being standard – and buyers offered enough avionics options to fill several pages (quite literally). Since LEM was intended to operate in the occasionally complex weather conditions common to the Swiss Alps, it sports pretty much everything it was possible to fit, and had over the years been retouched with more modern avionics in place of the old 70s Kings, Narcos and Bendixes. The setup as of October 2020 includes:

  • Sandel SN3308 Electronic Horizontal Situation Indicator (EHSI)
  • Garmin GNS530 NAV1/COM1 w/ FLARM input from an external module
  • Bendix King KX 165 TSO NAV2/COM2
  • Bendix KN 62A TSO DME
  • Garmin GTX 330 transponder
  • S-Tec Fifty Five X two-axis autopilot w/ ST-645 remote announciator
  • S-Tec ST-360 altitude alerter
  • King KWX 50 TSO weather radar
  • King KRA 10 radio altimeter
  • and a PS Engineering PMA 6000M audio panel

The type’s “quirky coolness” continues on the inside as well with more bits of the Cherokee Six. A familiar sight to Warrior drivers, Piper’s traditional panel layout does have its drawbacks on the Seneca – clutter and a lack of space being the biggest ones. Despite that, it would be carried forward all the way to the Seneca III, at which point it would be made taller, more efficient and fully metal, allowing for a far more ergonomic layout. A neat detail is the hand pump next to the sill, which inflates the seal around the door in order to reduce wind noise and prevent entry of cold air in flight

The lack of space on the main panel is so acute that pretty much all electrical and light switches had to be relocated to a custom panel on the pilot’s left. In the Seneca III and above, these would be moved to where they (sort of) belong, on the main panel under the yoke and near the plot’s left knee; while far from ideal, this did free up some elbow room and reduced the likelihood of inadvertent switch activation (the narrower, tighter Seminole also sports a roughly similar panel)

Few things beat the night-time on the flight deck – no matter how small. This sight brings me back to my own MEP training on the Seminole and Turbo Seminole 10 years ago (which had a broadly similar panel, though with less stuff). Unfortunately, while setting up this shot – and doing it quickly as not to drain the battery – I apparently nudged the tripod to the side, so the photo is at a bit of a (frustrating) angle…

Back in the cabin, there are few surprises – the biggest being the seating arrangement, with two rows of two seats all facing forward. Yet another hand down from the Cherokee Six, it would be retained even on early examples of the Seneca II, at which time the familiar “club layout” – two rows facing each other – would be introduced as an optional extra (and finally made standard on the Seneca III).

Even on cursory inspection, it is obvious that LEM was very well cared for – and the simple, clean & classy cabin further proves it. The seats had been reupholstered in leather not too long ago and are quite comfortable despite being a bit on the small side. In the later club configuration, the rear row would be pushed slightly back into the cargo bay to give both sets of passengers usable legroom

One of the reasons late model Senecas were (and still are) popular with air taxi operators is that passengers did not have to climb up onto the wing to get in – unlike on the original. To get at the second row of seats with any dignity, you have to squeeze through the copilot’s door, past the front seat, and then plonk yourself down without hitting your head on the roof-mounted air gaspers. A detail that also catches the eye is the space between the second row seats; it was wide enough to actually allow installation of an optional “jump seat”, bringing the total capacity to seven (this would also be offered on Seneca IIs that did not have club seating; in the latter arrangement, this space would be occupied by a hollow armrest used for storing drinks and small items)

While the sitting position in the second row is OK as such – even for me at 1.9 m in the vertical – legroom can be an issue if the crew is taller and needs to move their seats further back

Given LEM’s overall state – nearly mint, with just a few flakes of (original) paint missing – I was not the least bit surprised to learn that its previous owner did quite a bit more over the years than just reupholster the seats. To get a bit more go out of its limited power, LEM sports several aftermarket aerodynamic tweaks, the most obvious being LoPresti Zip Tips. One of the many upgrades2 from the workshop of famed “speed merchant” Roy LoPresti, Zip Tips are carefully profiled wingtip extensions that alter the dynamics of wingtip vortices, rotating air currents that form when high pressure air below the wing tries to flow over its tip to the low pressure area above. Since the aircraft is continually moving forwards as this is happening, this swirling flow ends up being left behind the tip – in clear air – quickly developing into a full-blown vortex that slowly sinks and eventually dissipates when it uses its energy up (usually within a minute on Seneca-sized aircraft). As well as being the root cause of wake turbulence, these vortices also disturb the flow of air coming off the upper surface of the wing (the “downwash”), altering its direction so that the wing now operates at a lower Angle of Attack (AoA), reducing its lift. To compensate, the aircraft now has to either fly faster or at a higher pitch in order to maintain level flight, which increases both drag and fuel burn.

Based on the 1940s research by German aerodynamicist Sighard Hoerner (who did most of the legwork on the superlative Fi-156 Storch) and the 1920s ideas of aviation pioneer Ludwig Prandtl, Zip Tips work by extending the upper end of the wingtip beyond the actual end of the wing, forcing the vortex to form further out – and then use its kinetic energy and inertia to push it away from the tip so it remains clear of the downwash. Since Zip Tips are actually wingtip extensions, they also increase wing area slightly and up the aspect ratio (AR), the ratio between wing span and the chord that has a major influence on vortex strength (the higher the AR, the weaker the vortex). Another trick is relocating the navigation and strobe lights into a common cluster with the landing light; this reduces drag, further smooths the airflow around the tip, and makes the Hoerner Effect more effective – but at the price of reduced visibility of the lights. LoPresti don’t publicly say what the net results are – but I’ve read reports that people have been getting approximately 5 knots more in the cruise on the same power. Improvements in the rate of climb – particularly on one engine – remain a mystery; informed speculation suggests that up to 50 FPM would be a realistic figure. As fitted to LEM, the tips also include the Boom Beam, a High Intensity Discharge (HID) landing light that boasts a 20-fold increase in luminosity over factory lights, 20,000 lux vs 1,000

Other LoPresti mods fitted to LEM include:

  • Speed Seals – fair over the gap between the wing and flaps to prevent the high pressure air underneath the wing from escaping upwards, which gives 2 knots more in the cruise + a bit of extra maneuverability in the roll
  • gear fairings – improve the airflow around the main gear wheel well (which is not covered by the gear doors when the landing gear is retracted), reducing drag and noise and reportedly adding a further 3 knots

All in all, the LoPresti kit on LEM should be good for a solid 10 knots extra in the cruise at the same power setting – though the actual gains will depend on atmospheric conditions and flight regime, and may not be that impressive in the type of low-weight, low-altitude, low-speed situations that are typical of MEP training.

Money had been spent under the hood as well, with the engines sporting a full set of GAMInjectors, aftermarket fuel injectors developed by General Aviation Modifications that are built and calibrated to much much tighter tolerances than Lycoming’s own factory units – and provide a more uniform fuel/air mixture across all four cylinders, giving better power delivery and a quicker throttle response with reduced engine wear and lower fuel consumption.

The lopsided airplane. Surprise surprise, the wing is another Cherokee Six item, sporting the same planform, the same NACA 65-415 airfoil and the same 7° dihedral (the upward angle of the wing) – but now with two meters of span more, 12 vs 10. Unlike the Cherokee Six though, early Senecas were prone to Dutch Roll in turbulent conditions, an uncomfortable combination of rolling and yawing motion that did not always sit well with passengers. A byproduct of a design’s optimization for efficient cruising flight, the Dutch Roll occurs when the aircraft’s roll stability (along the longitudinal axis) is more powerful and acts more quickly than its directional stability (in yaw along the vertical axis, provided by the vertical stabilizer). When the aircraft is disturbed from straight & level flight, the coupling of these two stabilities sets the airplane up for an oscillating slipping motion that – left alone – can persist for quite some time. Dihedral wings increase roll stability and thus tend to exacerbate this effect – as do the Seneca’s draggy engine nacelles, increased wingspan and longer nose with a larger side area, all of which create additional & unhelpful yawing and rolling moments that combine together to cause problems the Cherokee Six did not have. This tendency would be corrected to a degree on the Seneca II with a modification of the rudder (in order to increase the vertical stabilizer’s responsiveness), which would eventually be offered as a retrofit for the originals as well

Intended to be user friendly even for less experience pilots, the first gen Seneca had interconnected ailerons and rudder (by means of light springs), so that when the control wheel was turned to initiate a roll, the rudder would automatically deflect to counter the adverse yaw (also useful with an engine out). However, this made the controls feel quite heavy, so the springs were removed on the Seneca II. As is common on most pre-80s Pipers, the flaps are actuated mechanically by a lever on the floor between the front seats, and can extend to 10°, 25° and 45° (electrical flaps would debut only in 1985 on the Seneca III, being a necessity since that version’s larger flaps required too much muscle power to actuate)

Third time’s the charm

Naturally, this being Achtung, Skyhawk!, it was only a matter of time before I’d try and fit LEM into some sort of wider historical context. As I was combing through its history while preparing this piece, I began to recall seeing mention of other early Senecas that had carried the 9A prefix. And sure enough, having checked my historic registry, I discovered that there were indeed two examples preceding LEM, both – sadly – well before I had my first camera:

  • 9A-BIL | 1973 | s/n 34-7350314: just 12 airframes ahead of LEM, not much is nowadays known about BIL, except that it had previously been operated by Lošinjska plovidba out of Lošinj Airport (LSZ/LDLO). The only recent mention I have of it is from 2017 under the identity N351MC, when its registration was cancelled by the FAA (even though Flight Radar 24 showed this reg active in July 2020)
  • 9A-BPW | 1972 | s/n 34-7250191: originally registered N4978T for delivery, BPW would spend the first 20 years of its life in Germany as D-GEAR, before being be delivered to the AK Zadar flying club of Zadar Airport (ZAD/LDZA) sometime in mid-1992; it would later pass to North Adria Aviation of Vrsar Airfield (LDPV) – and then join Airmed of Spain as EC-HCA, where it is still happily flying as of October 2020

Being lucky #3, LEM is poised to outlive them all, with tentative plans already being made for further avionics upgrades and a fresh new paint job. And all the students that have flown so far it have been reported to like it very much – so it may even get off easy in life… 😀 (speaking as a former MEP student!)

What photo shoot would be complete without having a bit of fun? It is also interesting how the shadows and contrast seem to make the Seneca look far meaner in the dark…

1 in common with many other Piper light twins, all Seneca models have counterrotating engines, where the left propeller spins in the normal clockwise direction (when viewed from the back) – but the right propeller spins counterclockwise (hence L for “left turning”). The idea behind this approach is to improve handling in an engine-out situation by removing what’s called the critical engine. In a nutshell, each propeller blade generates more lift going downwards than going up; hence, one part of the prop disc will always produce a higher lift than the other. In engines with the normal clockwise spin, the lift will thus be greatest on the right side of the disc.

On conventional twins – both engines spinning clockwise – this becomes an issue during an engine failure. Should one engine go belly-up, the other one has to keep the airplane in the air – and that means it has to run at maximum continuous power for the prop to produce the highest possible lift. In this situation, failure of the #2 engine is the “lesser evil”, since the right side of the #1 prop disc is fairly close to the fuselage/Center of Gravity (CG) – so the highest lift will be acting on a short arm and thus produce a comparatively small yawing moment. However, should the #1 engine fail, the right side of the #2 prop disc is considerably further out – so both the arm and the yawing moment will be correspondingly higher.

The only way to counter this moment in any of the above cases is with the rudder; but, since its effectiveness depends on speed, there is a point below which it will not be able to generate enough lift to oppose the yaw. This point is called the minimum control speed in the air (VMCA), and effectively represents the aircraft’s minimum permissible speed on one engine. Unsurprisingly, it is higher if the #1 fails since the yawing moment is higher – and is taken in practice as the value to be printed in manuals and indicated on instruments in order to avoid confusion in the heat of the moment (and provide an additional safety margin). For this reason, the #1 engine is called critical.

In a counterrotating setup however, the #2 engine rotates counterclockwise, so the part of the disc that produces the greatest lift is now inboard of the engine, next to the fuselage – and on an equal arm to that of engine #1. Now there is NO critical engine, since failure of either will result in a yawing moment of the same magnitude. Despite this – and for the reasons stated above – the Seneca POH will nevertheless reference VMCA to engine #1, a nice round 70 knots on the first gen models, a full 10 knots above the stalling speed. But, while handy, this solution is practical solely on light piston twins, since the #2 engine has to be built slightly differently (“ass forward”) to both spin in the opposite direction AND fit in a cowling of the same size – which is far from cheap even on the types of “little bangers” used on Seneca-sized aircraft.


2 at this point, you may be wondering why it took a funny old man in a small factory to fix something Piper itself – with all its vast resources – failed to do. The answer, as ever, lies in cost/benefit analyses: in bygone times of cheap airplanes and even cheaper fuel, “small issues” such as wasteful wingtip vortices were not considered problematic enough at Seneca speeds and utilization rates to warrant fixing – especially since the fix itself was bound to increase cost, complexity and/or adversely affect payload (the latter always a premium on the early Seneca).

However, times, priorities and fuel prices do change, leading many third-party providers – LoPresti, Knots 4U, Laminar Flow Systems, etc – to tackle with problems like these on a wide variety of light aircraft, using materials and manufacturing techniques that simply did not exist (or were prohibitively expensive) when those aircraft were first designed. But, that’s not to say they are immune from the cost/benefit demon – far from it in fact. The Zip Tips for the 1st gen Seneca, for example, cost USD 4.000 without installation – which may not make much financial sense for an owner who doesn’t fly nearly enough to recoup the cost within a reasonable time frame, despite them offering a clear benefit in both fuel consumption and overall efficiency.


As ever, I’d like to extend my sincerest thanks to Mr. Domagoj Čingel – owner of Pan Avia (and, by extension, 9A-LEM) – as well as my Q400 colleague F/O Nikola Renčelj for his detailed knowledge of aerodynamics and help in making a coherent picture of all the mechanisms and gains of LEM’s LoPresti mods!

Sources:

Photo File – Flying In The Time Of Corona: Foreign GA Snapshots

By me
All photos me too, copyrighted

While going through my photo database in search of material for my previous Flying In The Time Of Corona photo file, I discovered that there’s plenty of stuff in there for a follow-up post as well – but this time focusing solely on foreign visitors to Croatia’s many coastal airports (+ Lučko of course). Like our own birds, these too could not be scared off that easily, arriving into the country in quantity and quality rarely seen even in years past. And since it would be rude of me to keep them all for myself, another summer time Photo File is obviously in order! (to build on the two bonus Cessna 172RGs already featured in their own post)

Before they can learn how to fly, young gliders must first learn how to taxi. To make that big step easier, their owners often fit them with training wheels and take them for short strolls around the apron. With time, they will progress to longer walks all the way to the runway – and eventually, when they feel more comfortable at the airport, they will finally be able to spread their wings and start flying all on their own…

A 210 on a hill… in the middle of an airport… next to a fire trainer… by a fuel farm… in the shade of an olive grove… well, that’s this week taken care of! What may eventually become the new static exhibit at Split Airport (SPU/LDSP), OK-TKN had arrived into town unexpectedly following an in-flight engine failure, and is now caught up in the financial and logistical nightmare of getting it going again…

Another skydive PC-6 – and another drive to see it right after the night shift. What makes this 2006 example a little bit more special is that it sports the 680 HP PT6A-34 engine instead of the stock 550 HP 27 series – and is seen carrying the type’s somewhat uncommon external fuel tanks. Carrying another 200 liters each, they give the PC-6 an impressive seven hour endurance – itself quite a neat trick on workdays when F-HBSF is used as an aerial imaging platform (for skydive ops they’re empty, but to simplify handling they’re usually left on the wing, since their performance penalty is quite small all things considered)

One of only 30 or so ever made (and the second one to end up in front of my camera), this beautiful Ruschmeyer R90 is one of those fantastic “what could have been” machines that make GA so special. Designed by Horst Ruschmeyer of Hannover in Germany, the R90 was an attempt to bring together all the cutting edge tech of the late 80s and combine it into a high-performance four-seat touring aircraft made squarely to European – rather than American – measure. Built entirely out of fiberglass (which was tested to destruction) and sporting a speedy laminar flow wing, it could touch 300 km/h in the cruise on just 230 HP – making it faster than pretty much every other aircraft of its power class. Its real party piece, however, was its noise signature: at full chat, it could do just 66 dB – roughly equivalent to the noise level of a typical office, and some 8 dB below the strictest level required by law. To do this, it was fitted with specially-designed exhaust stacks and a bespoke short-span four-blade composite prop – while the engine itself, a Lycoming IO-540, was actually derated down to 230 HP from its default 260 to cut down on all the yelling. Beautifully finished and with handling characteristics that were described as “a real treat”, the 230RG was supposed to launch an entire family of aircraft, including everything from a 190 HP fixed-gear “budget” model to a 470 HP Rolls-Royce 250 powered speed machine. Unfortunately, the design took until 1990 to sufficiently mature, by which time the market had slumped so hard that even Cessna had to throw in the towel. The results were depressingly predictable: after just five years of production and a single variant, the Ruschmeyer works filed for bankruptcy – and, despite attempts by other companies to revive the design, that was that for the sleek little R90…

So similar, yet so different: two “budget speedsters” that show just what can be done with some clever engineering and a bit of compromise. An aircraft that had set new standards for efficiency in its class, the Mooney M-20J (on top) was rebranded as the “201” when it became the first four-seat touring aircraft to reach 201 miles per hour (175 kts; 320 km/h) on just 200 HP. Though it had paid the price in payload and interior space – and required an extensive aerodynamic cleanup by the legendary Roy LoPresti – the J had set the stage for today’s M-20V, which needs only 280 HP and a turbocharger to cruise at 242 kts (450 km/h)… two thirds of the Q400’s maximum speed // But the more interesting machine is the Duruble RD.03 Edelweiss, an aircraft that needs only 180 HP and a fixed-pitch prop to do 147 kts (270 km/h) while sipping just 8.7 gallons an hour – roughly what a Cessna 172 would drink, using exactly the same engine and prop, to do 110 kts (204 km/h). What’s even more fascinating is that the RD.03 is actually a homebuilt, and was designed in the 70s by Roland Duruble, a marine engineer by trade. Other interesting bits include hydraulically operated landing gear and flaps, the latter extending automatically to the desired setting in response to airspeed – stuff unheard of even on turboprop twins. Another neat trick is that the horizontal stabilizer has a slight dihedral – it is mounted at an upward angle – so that it remains clear of the turbulence coming off the flaps (an effect that is quite pronounced on the Q400 at Flaps 35, and results in noticeable airframe vibration). This particular machine had been completed in 2003, and aside from the uprated 180 HP engine (the type standard is 160), it also sports a Lancair-style air intake that gives an additional performance and efficiency boost. In fact, the build is so sweet that it had featured in several GA magazines – often with the tagline “France’s homebuilt Mooney”

I may be small – but at least I’m weird. An aircraft whose elegance immediately belies its Italian origins, the Partenavia P.68 boasts quite an unusual cocktail of characteristics for a “serious six-seat touring aircraft”: a high cantilever wing, a pair of “small” IO-360 engines and – most interesting of all – fixed landing gear. But, while this may raise eyebrows, there’s quite a lot of method to its madness: from the outset, the P.68 was designed to be an efficient, affordable and user-friendly alternative to conventional twins of the 1970s, using sleek lines and clever aerodynamics to cruise at 300 km/h on just 2x 200 HP – and calculating that the drag penalty of the gear is a lesser evil than the weight, cost and complexity of retractable units (an approach later also taken by Cirrus). And it worked: in continuous production since 1971, more than 430 have been sold so far – including 20 of its glass-nosed patrol & observation models, the P.68 Observer & Observer 2 –  making it one of Italy’s most successful GA designs. And if it reminds you somewhat of Tecnam’s new P.2012 Traveler, rest assured that the resemblance is NOT coincidental: the P.68 was in fact penned by the brothers Luigi and Giovanni Pascale, who would in 1986 go on to found the same “Costruzioni Aeronautiche Tecnam”…

Another speedy Italian Job – but with an unusual address (in Latvia no less). One of the many LSA designs to come out of Italy during the late 80s homebuilt boom, the Century 04 is a fixed-gear derivative of the earlier Century RG, featuring a 100 HP Rotax 912 w/ a constant speed prop – both of which are good for a solid 200 km/h in the cruise while sipping just 10-15 liters per hour. With space for a proper 2+2 config – but sporting only two seats to give more baggage space – YL-ARV will likely become a Lučko native soon…

Photo File – Flying In The Time Of Corona: Croatian GA Snapshots

By me
All photos me too, copyrighted

Due to reasons beyond my control (to put it mildly), I had quite a bit of free time on my hands this summer, which I decided to spend – like in the good ol’ days – by enjoying the scenery at various airports and airfields throughout the land. While one would have assumed that the lockdown (pretty mild in Croatia, but still keenly felt) would have had a negative impact on GA ops, the truth of the matter was that the number of aircraft buzzing about had actually increased – which meant that there were always plentiful photo opportunities wherever you went. A perfect setting then to get the camera out and see what I’d been missing over the winter… 😀

If you’re sad for the demise of Cold War underground air bases and bomb-proof aircraft hangars, don’t despair – Dubrovnik Airport (DBV/LDDU) has something for you! Not so much a Hardened Aircraft Shelter as a “Hardened Vehicle Garage”, the brand new semi-subterranean storage depot along the airport’s northwestern perimeter may seem like an unlikely place for aircraft photography… but as you can see, it pulls it off nicely!

Concentration at 120% as a young colleague readies his ship for a late afternoon training flight. Somewhat fortunately, this student-weary veteran of the Croatian Aviation Training Center – to whose weariness I myself had actively contributed a decade ago – will soon give way to…

… this. It’s startup may not have been as smoky as I would have liked (thankfully for the engine!), but it was nevertheless worth frying like sushi on the superheated apron to catch my first ever Duchess. Conceived on the same train of thought as the Seminole, the 76 was always a typical Beech design: built up to a standard rather than down to a price. Unfortunately, that made it quite expensive to buy and maintain, meaning that only 437 would ever be produced… barely half the Seminole’s ~930 (and counting). Ironically, being a replacement for 9A-DZG means that Walter Beech may still have a tiny last chuckle!

Number 2 for departure after three incoming arrivals, holding short on a parallel runway being used as a taxiway since it is too close for proper simultaneous operations… this is not Lučko – it’s Gatwick on grass!

Of course he’s happy – he’s going flying… and on an aircraft he built himself from the wheels up, and from parts of half a dozen factory Super Cubs!

The 70s are back – as an airplane. While this “50 Shades Of Brown” interior may not be all that hot by today’s style standards, it is nevertheless so throwback cool that it warrants a “10/10 would sit” rating! (it also helps that the entire cockpit is crisp, clean, neat – and fully original, with the same trim it had back in 1986 when it rolled off the production line) (and yes, despite the D- reg, this machine is a fully-fledged local)

Even on its own territory, the Reims Rocket is a shy and reclusive species, easily frightened by noise and sudden movement. Because its colorful plumage makes it easy prey for photographers, it has evolved the ability to escape and hide quickly and without warning; always approach it silently and patiently, using local terrain and foliage for cover whenever possible…

And finally, one little Cherokee I’m VERY happy to see again! Covered previously in two some of my earliest posts here (part #1 and #2), DJZ is the sole “pre-Warrior” PA-28 in the country, and had years & years ago been based at Dubrovnik (DBV/LDDU). Unfortunately, a while back it had fallen on some hard times and was left to rot in the corner of the apron. Thankfully, about a year ago it had been brought to Medulin Airfield (LDPM) in Istria, where it is now undergoing a complete restoration – and will be happily flying already in early 2021!

Photo File – The Swing-Leg Skyhawk: Cessna 172RG Cutlass RG

By me
All photos me too, copyrighted

To properly kick off my return here after an unintentional pause of nine months (!), I’ve decided to revisit an aircraft type I had mentioned in passing some time ago – seeing that, by a stroke of sheer dumb luck, I managed to snap TWO in the space of just one week (which is twice as many as I’d managed over the past 18 years). The machine in question – as the post title infers – is the Retractable Gear (RG) version of the common Cessna 172, an aircraft whose rarity and cool factor is matched only by its apparent uselessness and absurdity…

A mint 172RG, in a modern paint scheme, under clear skies on a beautiful summer morning… I could do worse for a pre-dawn spotting session I must admit!

Swinging 80s

To immediately get an idea of why the 172RG stands out like a sore thumb within the traditionally conservative Skyhawk family, it seems best to start off with its main party pieces, as compared to the stock 172P of the same period (1980):

  • fully retractable gear
  • a longer snout to house the nose gear when retracted
  • cowl flaps
  • 180 HP Lycoming O-360-F1A6 w/ constant speed prop (vs the standard 160 HP O-320 and fixed pitch unit)
  • 66 USG fuel capacity (up from the standard 42)
  • and a 1,202 kg MTOM (vs the 1,088 of the P)

Performance-wise, the extra grunt (particularly the increased efficiency of the constant speed prop) and cleaner lines meant the RG could pull up to a 20 knot lead over the stock P, with High Speed Cruise pegged at 140 knots. The new prop also made for slightly better after take-off climb performance (800 fpm vs 700), while the increased fuel tankage gave a pretty chunky range boost, from 440 up to as much as 770 NM.

Cutlass #2 undergoing a wheels-up restoration after a (heh) wheels-up landing in Germany. You can definitely tell it apart in a normal Skyhawk crowd!

However, the ~80 kg added by the gear retraction mechanism also upped the empty weight, now standing at 740 kg vs the P’s 660. Normally, this was not much of a payload issue if you took on only your required fuel – but if you went all out and brimmed the tanks, you’d be left with barely 260 kg of headroom… roughly two 2020 adult males, some luggage and all the stuff normally carried around when away from home (additional oil, tow bar, cockpit/wing covers, emergency equipment, survival kits, …).

The higher MTOM also made for longer take-off and landing runs, both up by roughly 70 meters even on concrete; and while some owners have been known to fly them out of rough fields (and even back country strips), it generally goes without saying that the new legs did not take too kindly to prolonged use on the types of runways normal 172s take for granted.

While the main gear legs are no thinner than those on the standard 172 (where they’re set inside streamlined fairings), Cessna’s electro-hydraulic RG systems are quite complicated things and can go bananas even when mollycoddled. As on the 177RG, 182RG and 210, the main legs of first swing downwards and the fold back into recesses in the fuselage (barely visible here). Early 210s – which were the first to use the system – also had main wheel well doors, but they proved problematic and were deleted well before the 172RG appeared

The Cessna Retractable Dance. Go to 0:30 for retraction and 1:30 for extension. You’ll note that the pilot leaves the gear down for quite some time after take-off; the standard wisdom on RG Cessnas is to leave it hanging until clearing obstacles, since the retraction sequence causes so much drag it can noticeably impair climb performance at a critical stage (this is also SOP on airliners during windshear escape maneuvers). Indeed, the main legs drop by a whopping 60 centimetres during retraction!

Maintenance-wise, private owners, commercial operators and various incident reports all tend to agree that the upsides of its commonality with the stock 172 are frequently balanced out by the many gremlins of the RG system – though user experiences vary considerably, particularly when comparing leisure and training ops.

Persistent weak spots and items that require frequent inspection are the main electric-driven hydraulic pump, down-stop pads that (if damaged) may prevent the main gear legs from locking down, and the main gear pivots that are worn out by the legs’ aerobatics during retraction and extension. There’s also the need to periodically cycle the gear on the ground during checks – which requires jacks and additional man-hours – as well as the costs of servicing the propeller governor (though that’s a pretty standard job).

And while none of these are deal-breakers in themselves – the 182RG and 210 say Hiii! – the cost-benefit math of doing all that on a lowly 172 did not make the RG everyone’s cup of tea…

Mission-ready

So, when all was said and done, the 172RG was a cheap & simple aircraft made expensive & complicated for just a few marginal gains – so much that even the fixed gear 210 HP Reims FR172 Rocket could keep up with it in a pinch (and for noticeably less money). What’s more, if you really wanted the “Full RG Experience”, five numbers up was the (slightly) more powerful, (much) more efficient, (oodles) more comfortable and (far) more elegant 177RG Cardinal – an aircraft conceived outright for the touring role, offering 182 series frills without many of its financial chills.

The 172RG thus appears to be – in technical terms – a complete crock. However, outright performance and mass market appeal are not what this airplane is about; its forte was to corner a very specific niche of the training market by offering a suitable and affordable “quick fix” for a problem few manufacturers seemed interested in tackling.

The niche in question was for what’s termed a complex aircraft, a surprising demanding specification that calls for a simple, easy-to-fly, robust and cost-effective airplane that can also boast toys such as flaps, retractable gear and constant speed props – all the complicated and fiddly stuff that future airline drivers are supposed to deal with (did mine on an old, student-weary PA-44, so the full set of traumas is there!)*.

And with the Skyhawk’s 25 years of active service to its name, the type’s well-known middle-of-the-road handling, off-the-shelf components (even the landing gear, nicked off the Cardinal), a reliable and frugal powerplant and a developed global support network, the 172RG had hit all the nails it needed to hit. Even though it would be born on the eve of Cessna’s decade-long single engine production pause, 1,191 would be made between 1980 and 1984… not bad for a niche design!**

* the original specification for complex aircraft had not set a specific minimum power limit; in 1997 however, the FAA set the bar at 200 HP, thus disqualifying the 172RG. However, the type still remains in widespread use as an introductory platform for more complex touring machinery – as well as a charismatic “left field” personal airplane

** though there are frequent parallels with the Beech 24 Sierra and the Piper Arrow, the 172RG is actually not a direct competitor to either. Both designs boast thirstier 200 HP fuel-injected engines (the Arrow with the option of turbocharging), better performance, more amenities – and are generally set up more for the posh end of the touring market; their closest Cessna analogue would be the aforementioned 177 Cardinal. The only aircraft on equal footing with the 172RG was the very first version of the Arrow – the 180 HP PA-28R-180 – which debuted in 1967 and remained in production for only a couple of years before being superseded by the first of the 200 HP models

What’s in a name?

While all of the above ticks quite a few Achtung, Skyhawk! boxes, one more thing remains that is very worthy of mention: it’s name.

While it does say “Cessna 172” on the tin, the 172RG is techno-legally not a purebred Skyhawk – but rather an offshoot of the nearly forgotten 175 Skylark. Billed as the next step towards the larger 182 (a role that would later be filled by the 177), the 175 was in essence an up-market high-trim version of the 1956 172A, fitted with a geared 175 HP Continental GO-300 instead of the standard direct-drive 145 HP O-300. Unfortunately, reduction gearboxes were at the time an unheard of feature on such a small civilian engine, meaning that very few pilots had ever encountered one before. The specific way in which such an engine had to be handled – flown at around the 3000 RPM mark – was so alien and absurd to private pilots that many drove them at the more usual 2000-2200 RPM, leading to a ton of breakdowns, failures and bad PR. By 1962, things had gotten so bad that Cessna was forced to pull the plug on the entire design, and retire both the 175 designation and the Skylark name…

A stunning late model 1962 Skylark with the original GO-300. Note the hump on top of the cowling; the propeller axis had to be raised up in order to accommodate the reduction gearbox without relocating the engine mounts

To salvage at least some of the effort invested in the design, the company decided to keep the 175’s Type Certificate (and some mechanical bits) and use them as the legal basis for all future high-performance variants of the 172:

  • the 195 HP R172 Hawk XP
  • the 210 HP Reims FR172 Rocket
  • the military T-41 Mescalero
  • and the 172RG

Traces of the Skylark’s original DNA can still be seen in the R172, FR172 and T-41, since they all sport the tall narrow-track landing gear of the 172A, which would be replaced by the squatter wider-track variant we all know and love on the subsequent 172B.

However, this would not be the end of Cessna’s marketing shenanigans; in 1983, the company would launch the 172Q Cutlass (sans RG), an attempt to “schlepp” on the RG image by fitting the 172P with a 180 HP Lycoming O-360-A4N driving a fixed pitch prop. Quite a rare model today – which did not offer much meaningful superiority over the P – only a handful would ever be built before the Skyhawk family as a whole went into its prolonged 80s coma…

Fixer Upper

While at this point in any normal Achtung, Skyhawk! post I’d go off with a ton of (more or less) descriptive external photos, in this instance I decided to “stay inside”, since the opportunity to snoop around a full-blown rebuild (currently at ~60%) was an opportunity too good to miss! The photos are not my best work – it’s hard to maneuver my 1.91 m frame w/ camera and tripod inside a 172 – but hopefully they’ll be interesting enough for the common avgeek!

I don’t know… it feels something is missing… free from all its kit, the Skyhawk panel looks far more commodious than it actually is! Note the (now very visible) sections for the flight and navigation instruments and the radio stack. Before its wheels-up landing and rebuild, D-EGGF also sported an autopilot (fitted above the glove compartment), and will – when completed – also carry a full set of digital engine instruments. Note also the rudder trim wheel next to the elevator trim; a very useful convenience/borderline necessity with a constant speed prop

A peek “behind the scenes” shows just how many wires, cables, ducts – and even chain drives – there are in a light aircraft. The complexity, weight and maintenance headaches of the average analogue panel have been one of the key drivers behind modern glass cockpit systems built around digital buses and remote sensing systems

Lots of wires… and lots of levers too. With carburetor heat, throttle, prop, mixture and cowl flaps controls, the 172RG could be handful for inexperienced pilots used to the trouble-free operation of the classic Skyhawk (but ideal for the well-meaning masochism of flight training!). Indeed, this was Cessna’s most complicated throttle quadrant short of the 182 (even the 177RG had one level less, being fuel injected)

The most out-of-place level in a Skyhawk: the landing gear handle. One of the more unconventional operational features of Cessna’s RG system is that the “gear up and locked” lamp is – red… which on everything up to and including airliners means either “NOT locked” or “in transit”. Somewhat annoyingly, the light remains continually illuminated as long as the gear is retracted… which is mildly disconcerting from a Q400 driver’s perspective!

Like all RG airplanes, the 172 has a backup gear extension system, whose lever is located under a cover between the front seats. The trick here is that it is just a hand pump, to be used in case the electric one fails (~35 strokes are necessary, according to the POH); it still requires the hydraulic system to be fully operational, and there is no gravity drop or a standalone reserve hydro system. This “unusual feature” is the 172RG’s main Achilles’ heel: the gear is actually held up by hydraulic pressure, and to keep it from dropping, the hydraulic pump occasionally operates in flight to keep the pressure within limits (between 1000 and 1500 PSI). However, if there’s a leak in the system – which seems to happen with some frequency – the pump’s operation will simply dump the hydraulic fluid overboard, eventually emptying the entire system and rendering the gear completely inoperable

The more normal end of the Cessna RG system. The nose wheel doors are mechanically connected to the nose leg so they open and close with gear motion; their biggest operational problem is that they’re quite large and hang low, so it’s easy to damage them if you’re a bit too enthusiastic with the tow bar

Who would have thought that all of this cabling lies hidden behind the teeny panel of the Skyhawk? Another detail unique to the 172RG is the raised floor (best visible below the CDI), necessary to accommodate the main gear legs when retracted. The main wheels however stow behind the normal luggage compartment, so the loss of space there is minimal

Boxes boxes everywhere, not a place to sit… thankfully, the lack of space for maneuvering about with a tripod is taken up by some pretty cool kit: Garmin G5 x2, GMA350, GNC225… should be quite a looker when finished, very much looking forward to trying it out!

As ever, I would like to extend my sincere thanks to Dorian Delić of Medulin Airfield (LDPM) in Istria, for allowing me to snoop through his family’s hangar and drool a bit over D-EGGF!

POST UPDATE – 8 SEP 2021: it may have taken awhile, but I’m happy to report that D-EGGF has been cheerfully flying for awhile now, shuttling around the northern bits of the Adriatic all summer long. To make it even better, I’d managed to catch it recently at Split, making for a proper photo update!

Waiting for its turn to taxi out for the hour-long hop back home to Medulin

Aircraft pictured:

  • D-EGGF: c/n 172RG-0301 • mfd 1980 • ex. N107JB
  • D-EPAW: c/n 172RG-0757 • mfd 1980 • ex. N6532V, I-ALEU

Sources:

Changelog:

  • 08 SEP 2021: added photo update

Photo File – Contrafun: Flying On The Kamov Ka-26

By me
All photos me too, copyrighted

Even though I’ve been a fixed wing driver from Day One (private and training helicopters being so rare in Croatia), I’ve nevertheless always maintained a fancy for all things rotary. Indeed, my first ever flight – back when I was just a toddler – had been on a Yugoslav Air Force Mi-8, followed up later in adulthood with hops on the Bell 429 demonstrator, and with Red Bull’s own Rainer Wilke on the fully aerobatic Bo-105 (an experience I’m not likely to forget!). From then on however, my contact with the helicopter world had been reduced to being on the working end of the camera viewfinder – a situation that would dramatically change for the better in the summer of 2019 🙂 .

Having been aware of my long-standing desire to photograph a piston engine Kamov up close, a friend from neighboring Hungary – himself an avid helicopter spotter – had managed to do me one better, arranging not only a “free hand” photo session… but also a short semi-aerobatic flight. The only string attached was that I get my arse to Budapest on my own accord – a condition I was more than happy to accept! 😀

It may be the textbook definition of the world “fugly” – but on that day it was the most beautiful helo in the world!

The HA Ka

The rather colorful bird that would be my ride for the day goes under the name HA-MPB, and sports the serial 77 061 09 – a typical Soviet sausage that tells you (almost) everything you need to know:

  • 77 … manufactured in 1977
  • 061 … as part the 61st batch made (out of 65 in total)
  • 09 … and the ninth example in the batch

This puts it among the youngest examples of the 848 made in total between 1969 and 1978 – and one of at least 149 that would eventually serve in Hungary (either straight from the factory, or through resales). Unlike the vast majority of its brethren however, MPB is still very much active, and spends most of its uptime dusting crops up and down the country. Indeed, on this day it had popped into Budaörs Airfield (LHBS, not a stranger to me) solely to participate in the upcoming Budaörs Airshow, following which it would quickly depart back into the southern fields and resume normal operations 🙂 .

While my roster at work had prevented me from staying the show’s full three days, I had nevertheless had ample time to pour over MPB in much detail. Though many of the design’s finer nuances will inevitably be lost on me – Fixed Wing Guy, remember* – there is nevertheless still enough eye candy here to arouse the interest of even the most basic aviation enthusiast!

* any corrections from whirlybird drivers would be most welcome!

Getting ready for the day’s practice run with a lick of paint and a thorough wash. Despite the performance penalties of the extra weight, MPB would fly its routine in full crop spraying kit…

In addition to their distinctive main spray bars, many Ka-26s feature a secondary unit slung from the horizontal stabilizer. Specs I found online indicate that with all three in operation, the average 26 could dispense up to 12 liters of fluid per minute (though dispersion system upgrades in 1978 and 1979 would improve on that by a couple of liters/minute)

In the crop dusting configuration, the hopper can accommodate up to 900 kg of fluid. A neat trick is that it’s actually part of a removable payload module that can be easily taken out in the field, and replaced with the minimum of specialized tools by a selection of other factory-made modules (passenger, ambulance, freight platform, sling hook, …)

Not your usual view! Despite its unwieldy look and apparent bulk, from the top it is obvious that the Ka-26 is actually quite compact, sporting the minimum amount of structure necessary to bring together the engines, cabin, rotor system and payload module. There blades themselves are actually composite and very light, and feature substantial leading edge protection at their tips – all of which gives them a solid 5000 hour service life, even in the rough-and-tough going at low altitude

The party piece of (almost) every Kamov design: the counter-rotating coaxial main rotor. Though mechanically more complex than the conventional arrangement, this setup allows for greatly increased efficiency, since the blade area – which produces the lift – is now doubled, and there are no mechanical and friction losses inherent to the tail rotor and its transmission system (which also does wonders during autorotation). Another benefit – epitomized by the Ka-50/52 gunships – is a very high degree of maneuverability in all axes, as well as a much more neutral mass distribution that does wonders for hover characteristics, general handling and overall agility

Arretir! Drawing heavily upon Kamov’s naval experience, the Ka-26 could be equipped with a full IFR panel and some pretty sophisticated kit for its class – stuff that didn’t always sit well with operators, since it tended to add complexity and increased maintenance costs. Many examples (especially those used at very low altitude) would be stripped down in actual operations; MPB however had retained most of its factory setup, minus the blind flying gear

Having spent the majority of its life in Hungary, MPB sports a typically curious mix of Russian and Hungarian dials, which do add a lot of charm to the cockpit…

Being one of the very few (maybe even only) production light helicopter with TWO piston engines, the Ka-26 does sport a lot of powerplant-related switches and knobs – so much so that it seems you need three arms to successfully start it first time out…

More traces of the Ka-26’s Soviet design heritage: the single primer pump in the middle (which is turned into the direction of the desired engine before being actuated), and the air system valve w/ pressure gauge, which provides the juice for the main wheel brakes (a common solution on Soviet aircraft to avoid the weight penalties and poor cold weather performance of conventional hydraulics)

Another icon of Soviet general aviation: the venerable and dependable M-14 nine cylinder radial, here in its V-26 version developing 325 HP. To tackle the unique aspects of helicopter flight – high RPM, high throttle and low (or no) forward airspeed, the fit on the Ka-26 features powerful cooling fans (visible behind the fully opened cowl flaps), which force air over the cylinders to keep them sufficiently cool regardless of flight regime. They also make a LOT of noise!

Two big Soviet radials, two huge coaxial rotors, a traditional cockpit fan – and a semi-aerobatic duet with a 1950s Hiller UH-12… yep, didn’t mind the four hour drive one way!

One a pristine vintage “oldtimer”, the other a no-nonsense everyday working machine… one conventional on Lycoming power, the other coaxial with twin radials… one user-friendly Western, the other utilitarian Eastern… fun is guaranteed! Another interesting feature of the Ka-26 – negated here by the open door – is that the cabin is actually pressurized to slightly above ambient, to prevent spray and chemicals getting in during crop dusting ops

And finally, a bit of video from the inside… admittedly, not the best quality (the lighting was marginal all throughout the day), but hopefully the action will make up for it! Also not the piercing turbine-like noise in both clips; those are the aforementioned cooling fans spinning their heads off 😀 .

Bonus content: Hiller UH-12D • HA-MIG

Drooling all over the Ka-26 is fine and well – but when you get to fly in a duet with a vintage Hiller, you should at least try to make an effort to snap it as well! 😀 Returning back to the apron after our run, I was lucky enough to stumble upon said helicopter and its owner, who kindly allowed me to snoop around and bit and soak up the beauty of one of the world’s earliest mass produced light helicopters…

Halfway through a thorough wash following its practice display. Manufactured in 1959 with the serial 1145, MIG would serve first with the US Army as 58-5496, before going civilian as N67664 and N16MQ. Sold to Hungary in 1997 (as one of a number of UH-12s coming into the country during the 90s), it would eventually end up in the hands of Fly-Coop, one of the largest aircraft operators of the Budapest area. Note the exposed tail rotor transmission atop the tail boom

Though the type normally sports the six cylinder Lycoming VO-435 developing 265 HP, this particular machine had at one point been retrofitted with the more powerful Lycoming VO-540, developing a chunky 305 HP (it showed during the display!). Of note is the engine V prefix, which stands for “vertical” – denoting the modifications for the only possible way of installing it into a light helicopter

A panel that can easily provoke traumas in anyone who had flown a 1960s Cessna – no rhyme or reason in the layout, and made by someone who studied economics, not ergonomics. That notwithstanding, surely a cool place to sit!

Traditionally, I would like to extend my sincerest thanks to all the people – ground and air crews alike – that had made this photo shoot possible, particularly Gergely C.!

Sources:

Photo File – Pratt My Ride: The PT6 Cessna 206, S5-DOT

By me
All photos me too, copyrighted

Some choices in life are actually pretty easy to make. Take, for example, my options the other day following a 4 AM wake-up to work a dawn flight: A) get some sleep; B) get some exercise; or C) drive an hour and half (one way) to a neighboring country to try and catch a pretty rare turbine Cessna 206… I mean, the choice is self-selecting! 😀

The machine that had managed to score higher than my own bed (!) is a Turbine Conversions Turbine 206, a fresh crack at mating a mid-life Cessna 206 airframe to a (moderately) powerful low-altitude turboprop engine. But, whereas the most successful attempt so far – the Soloy 206 – is based around the same Rolls-Royce/Allison 250 series engine used on the Bell JetRanger, Turbine Conversions’ mod relies instead on the far more famous Pratt & Whintey PT6A – and is the first time this engine had ever been fitted and certified on a member of the Stationair family. With only three examples flying in Europe so far, delaying sleep was definitely a better call, so I plonked myself into the car and went off to see what’s what 🙂 .

A real Quasimodo: ugly as hell on the outside, but with a heart of pure gold underneath

Born to Haul

The recipe for this sort of thing has always been pretty straightforward: take an older generation utility 206, give it a large improvement in hauling performance as cheaply and simply as possible – and then make it work on paper so that it can legally carry paying passengers. And while sticking in an engine that may be worth three times the rest of the aircraft may not sound like the best way to do it, the idea does have a fair amount of economic sense behind it. Stationairs have always been tough birds with long lives, so even a model several decades old can be reasonably expected to have quite a few years of service left; being several decades old means that they were likely paid off in full ages ago, and have none of the fiscal baggage that newer models are often burdened with; and they can be cheap to buy, spares are plentiful, support is available worldwide – and there’s enough accumulated user experience out there that even a fresh operator can learn the ropes quickly and without undue trouble.

Get all of these right (admittedly, not an easy task!) and the turbine conversion can end up being a pretty cheap, sufficiently efficient and very reliable ticket into the utility turboprop world, especially for smaller operators who cannot afford a bespoke type such as the Pilatus PC-6, PAC 750 or Quest Kodiak – or are in regions where Avgas is fast becoming a thing of the past. Get it right and even the conversion’s many downsides – such as fuselage-limited capacity and higher long-term operating costs – may not be critical enough to offset the advantages of having a turboprop – ANY turboprop – at your disposal.

To try and achieve the above, Turbine Conversions – a longtime PW&C user – decided to bank once again on the company’s most famous engine, which – while heavier and more expensive all round than the RR 250 – has an enviable reputation and true global reach on its side. Initially, the mod started out with the 550 HP PT6A-20, but this was changed before production began to the equally powerful PT6A-21 – the difference being that the -21 is in essence a de-rated version of the 680 HP PT6A-27, which retains the latter’s more potent core for a bit added torque and improved hot-and-high performance.

Being a cheap-and-cheerful “firewall forward” solution intended for the rough-and-tough utility market, the Turbine 206 is not really loaded with features; apart from the new engine and its associated accessories, propeller, mountings and structural changes, the only things that stand out are custom exhaust stacks that eek out a bit more thrust – as well as the company’s own air inlet design with is said to improve the flow of air into the engine. The upgrade is rounded out by an Electronics International MVP-50 digital display panel – which replaces all traditional steam gauges – as well as modified engine control levers to cater for its different operation.

Unlike turbine conversions of touring aircraft – where the interior often has to match the performance – both Soloy and Turbine Conversion mods retain the utilitarian equipment levels of the aircraft they were based on. Really the only dead giveaway that there are 550 horses living up front is the MVP-50 display, located above the right-hand panel guard

Another change – albeit not as easily noticed – are the engine control levers, which now behave differently to those on the piston 206. The throttle lever now has to incorporate a reverse function, the prop has to have feather – while the condition lever is actually simpler, with just two discrete positions (HIGH IDLE & CUT OFF)

On the DOT

While all of this is pretty interesting in itself, the machine I had actually gone out to see is just that bit more special 🙂 . Nowadays called S5-DOT, in its past life as N7351Q it had actually served as the prototype and validation vehicle for the entire Turbine 206 mod, and was the one put to the test in order to receive the Supplemental Type Certificate (STC) needed for sale and commercial use.

Originally a stock U206F manufactured in January 1973 with the serial U206-02179, DOT is a fresh addition to the fleet of Letalski klub Šentvid, based at the picturesque airfield of Šentvid pri Stični – the same place I had gone last year to have a one-on-one with another Cessna turbine mod. Replacing the smorgasbord of outside aircraft that previously had to be leased at significant cost, DOT has arrived right on the dot for the beginning of the commercial skydive season – so with any luck, it should be a frequent dot on the Slovenian sky!

Rolling full laden toward RWY 14 for another afternoon run. Though turbine power could not change the type’s hauling capacity all that much, it did wonders for both take-off and climb performance at high weights – not an insignificant feature given the close-in hills in all directions and high daytime temperatures…

Like all piston-to-PT6 conversions, the Turbine 206 looks quite brutish from the front. Note also the offset propeller (and engine) installation, designed to reduce the adverse gyroscopic and aerodynamic effects of the new powerplant

Waiting for the next load. Like any self-respecting skydive machine, DOT has a full set of handles, steps and door covers, and can comfortably accommodate up to six skydivers at once

The Dependable Engine (unless you’re talking about the GTF!). An interesting operational feature is that engine starts are performed with the assistance of an outside battery kart, since the huge current draw from repeated spool ups would drastically shorten the service life of the on board battery

As always, I would like to thank the people who made this photo shoot possible – in particular Mr. Tone Dolenšek, who spent quite some time keeping me company and answering my Achtung, Skyhawk!-y questions!

Sources:

Photo File – Moraning Around: Flying The Rallye 150

By me
All photos me too, copyrighted

It had always been said that the gut feeling is a powerful tool and that it would be wise to (at least occasionally) listen to what it has to say. Returning home from town one day, I decided to do just that, and on a whim stopped off at my base airfield of Lučko (LDZL) to see what’s up – since, hey, it was on my way anyway. Rolling onto the parking lot, I noticed a Morane-Saulnier Rallye standing in front of the hangar, the same machine I had seen at Zagreb (ZAG/LDZA) a few days earlier. Sporting a Polish reg, it had immediately caught my attention – so, naturally, I headed over to see what’s what.

It would transpire that its owner had moved to Zagreb for work, and would be basing his airplane here at Lučko. Immediately intrigued (even more than before), I struck up a conversation, which would culminate some two hours later with an invitation to eventually go flying 😀 . Having always had a thing for the Rallye family, I needed little persuasion – so a day later we met up again for a one-hour introductory flight around the vicinity 🙂 .

In keeping with character, I had my camera ready and my brain open to impressions, keen on getting some proper Achtung, Skyhawk! material – possibly even enough to repeat my previous UTVA U-75 piece. However, in the end I decided to take the opportunity to simply cruise around at leisure and enjoy the view, so apart from a couple of basic maneuvers to get a feel for the aircraft – and several touch-and-goes to judge its landing characteristics and low-speed behavior – we spent most of our time zipping around straight & level, with just an occasional spot of moderate maneuvering. Nevertheless, I felt it fitting to try and hazard a few parallels with both the U-75 and the C172 I normally fly, if anything to attempt to illustrate some of the charm and charisma of one of France’s most successful and timeless designs…

Author’s note: despite these parallels, this is NOT a proper, professional review – as was also the case with the U-75 – since I have neither the skills, experience nor qualifications to make any sort of objective conclusion or comparison. Rather, this is just a condensed (if structured) personal experience of a life-long GA fan, a bit of light reading that I hope enthusiasts could find interesting!

The proper way to enjoy your first flight on a new type: sunny skies above, excellent light all around and fine terrain below!

Rallye around

The little bird in question is a 1973 SOCATA* MS.892E Rallye 150, sporting the reg SP-IKY and serial 12238. As its name implies, it has 150 HP on tap, provided by a garden variety Lycoming O-320-E2A – the same basic unit found in the most common Cessna 172 variants (the M and N) and the Piper Warrior – which spins an equally common 1.93 m McCauley 1C series two-blade fixed pitch propeller (though a 1.88 m Sensenich M.74 can also be fitted). With 980 kg of Maximum Take Off Mass to move, this combination gives roughly the same performance ballpark as the other two, while a fuel capacity of between 180 (standard tanks, fitted to SP-IKY) and 220 liters (optional long-range fit) gives broadly similar endurance and range.

* though the basic design – the MS.880 – was designed by Morane-Saulnier, by the time the MS.890 rolled by, the company had been incorporated into the Societe de Construction d’Avions de Tourisme et d’Affaires, the Company for the Manufacture of Touring and Business Aircraft – or SOCATA for short

As was the case with the U-75, the type’s specifics (and indeed its charm) become apparent only after you stop looking at the numbers and start fiddling with the aircraft itself. The interior, for example, looks deceptively small from the outside; my fears of fitting in – being 1.9 meters tall and all – turned out to be completely unfounded, since the front seats provide space enough fore, aft and to the sides to rival the Cessna 182 (a near-identical experience to that of the U-75). The only letdown at this point was the height of the convex canopy, which was a bit restrictive with headphones on (the Utva says hi again); however, in my case sliding the seat fully backwards did the trick – and even though I could have done with a few more centimeters of extra headroom even then, I was never really uncomfortable at any one point.

Top of the world, ma! Flying, both on and off work, a high wing aircraft, this is somewhat of an unusual perspective for me. As on most low-wing aircraft, climbing aboard is as easy as step-grab-pull; being lower off the ground than the U-75 (though slightly higher than the PA-28), the process is also not awkward nor physically strenuous. One slight complaint is that the size of the canopy precludes the fitting of handles, meaning you have to grab hold of the canopy frame if you need help to haul yourself aboard

The large sliding canopy means that getting in is a complete non-issue. However, since the wing spar passes underneath the front seats – and an additional cross-brace is needed to keep the fuselage stiff since it lacks a load-bearing roof – leg space in the back is a bit of an issue… you definitely cannot stretch out like you can do in the 172. Interestingly, the same issue plagued the U-75’s four-seat variant – U-75A – but was not a worry since only three were ever made…

Once inside and with the seat fully back, I found the sitting position to be one of the best I’ve ever experienced in a light aircraft, with good elbow room, all controls within easy reach – and a near-ideal position and distance of both the control wheel and rudder pedals. Unlike some Cessna 172s I’ve flown, I could turn the wheel fully** to either side without interference from my legs, and never needed any gymnastics to fully actuate both at once (not even when crossing them as if to initiate a side slip).

** conversely, a colleague of roughly the same height and build flew the more powerful Rallye 180 that comes equipped with a stick as standard; he reported that in some conditions, he could not always move it to the sideways stops without first moving his knees to the side

Being a low wing aircraft designed for (among other things) flight instruction and utility roles, the view outside is, unsurprisingly, very good. Since the canopy frame is not load bearing (unlike on the U-75), it can be pretty thin and light, making it unobtrusive (conversely, the large frame of the UTVA gives the impression of peering through a postbox, though it is very easy to get used to). A notable criticism from my end is the aforementioned convex canopy shape; its low front lip means you either have to fly with it slid back to half-open, or fully closed, otherwise there’s no space left for your head

Though SP-IKY’s owner – who also had an original MS.880 – says that pretty much no two Rallye cockpit setups are alike, this one is pretty conventional, with the usual Basic T and all levers and switches where you’d expect to find them in any Cessna. Unlike 80s 172s however, the Rallye has two sets of warning lights below the glareshield, as well as more engine instruments as standard (such as CHT, EGT, carburetor temperature and the like). A sign that the MS.890 series was from the outset intended for utility roles is the red pull handle at the top of the panel, which operates the tail hook (also a standard fit, as on the U-75). Another feature of the MS.890 series are the electric flaps; the original 880 had a Piper-like mechanical system operated by a lever between the seats. Naturally, being designed in Europe, at least one instrument has to be Metric – in this case the Airspeed Indicator (ASI)

With a slat and a bump

Once ready to start, things move in pretty much the same manner as on any O-320-equipped aircraft. The major difference here is that the Rallye does not have a standalone primer pump; priming is achieved by operating the electrical backup pump and then advancing the throttle lever several times to its forward stop (five worked wonders for us that day). The electrical pump is also used when switching between tanks to ensure a positive fuel feed until the engine-driven pump builds up enough pressure in the pipes (like the PA-28 – and unlike the C172 and U-75 – the little Morane does not have the option of drawing fuel from both tanks at the same time).

Taxiing out is pretty straightforward despite the lack of nose wheel steering and a reliance entirely on differential braking. Mercifully, the Rallye has conventional Cessna-style pedals, heel for rudder, toe for brakes – and not separate controls for each as seen on the U-75. Since the aircraft had – as mentioned – been designed for utility roles from the outset, the brakes are quite powerful, which makes ground maneuvering pretty easy after a bit of stumbling about (SP-IKY’s excellent pedal feedback certainly helped… changing direction, not the stumbling 😀 ). With some practice, very tight turns are possible – but my lack of experience on the type and Lučko’s wide apron and taxiways made that redundant (at least at this stage). However, as soon as I rolled off the smooth apron and onto the grass taxiway, I ran straight into another issue: keeping a constant speed across the uneven ground requires some practice, since even a slight jab at the brakes to maintain direction results in a noticeable drop in speed. After some time (the taxi to the RWY 10R end takes awhile!), I got the hang of adding a brief burst of power with each brake application – standard stuff, but it definitely feels odd after stepping out of an aircraft with nose wheel steering.

Having successfully – albeit far from elegantly – reached the holding point, it was time to experience the Rallye’s party piece: its wonderfully quirky full-length retractable slats. A feature seen on many short take off designs, slats do their magic by channeling additional air through the gap between themselves and the wing. The benefits are most prominent in the most difficult regime of them all – flight at high Angle of Attack (AoA) and low speed – where they help the airflow to stick to the wing down more of its chord, delaying its separation and the resulting stall. Apart from obvious benefits to general handling and a reduction in the stall speed, this also serves another vital function: it keeps the air flowing over the ailerons, ensuring adequate roll control even at very low speeds – and reducing the risk of the downgoing aileron increasing the AoA to the point of stalling the entire wingtip (the reason why some STOL planes have slats only on the outer sections of the wing).

A sure sign that an airplane means business! Of interest, sporting full length retractable slats is quite unusual for an aircraft of this size; in most cases, they’re either fixed (then called “slots”) or fitted, as mentioned, only to the outer portions of the wing

As on many light aircraft that feature them (up to the 5.5 ton An-2), the Rallye’s slats are fully automatic, and are “operated” by changes in air pressure along the leading edge of the wing; at high AoA, the reduction in pressure simply pulls them out of their retracted position – while the increase in pressure as AoA begins to reduce pushes them back in. All good, solid aerodynamics – the quirk being that on take-off and landing they deploy so suddenly and loudly that you’d be excused for thinking something fell off the airplane (a point SP-IKY’s owner was keen to stress before departure… and one on which he was not exaggerating by any means).

The Big Bang occurred – as foretold – at around 60 km/h (32 kn), roughly halfway to our briefed 100 km/h (54 kn) rotation speed. With the two of us on board, very nearly full tanks, flaps at their first notch (15°) and a 5 knot headwind component, we left the ground in just under 300 meters – not a bad show for a draggy and bumpy runway, and considering that we opted for the standard vs short take off technique (which would have called for maximum flaps and a rotation speed of just 85 km/h (46 kn) ). The performance specs for a full aircraft call for 365 m over a 50 ft obstacle in standard conditions, so that puts us almost right on the money.

The slats came into their own again immediately after departure, staying fully deployed throughout the initial climb and allowing for sprightly “vertical performance”. Whereas the 172 becomes asthmatic immediately after leaving the ground effect with the flaps still down, the Rallye never missed a beat, and we were quickly at our 130 km/h (70 kn) climb speed while still in configuration, doing a not-at-all-bad 700 FPM. With flaps retracted, our vertical speed increased to 800-900 FPM, slightly better than what a similarly loaded N model Skyhawk could do in these conditions (bearing in mind our 10 horsepower deficit).

Interestingly, throughout the entire climb to pattern altitude – and particularly during turns around the circuit – the slats kept extending and partially retracting in response to airflow changes (it was a slightly turbulent day too), being designed to fully stow only above 150 km/h (81 kn) in straight & level flight conditions. An observation that particularly intrigued me is that despite their constant motion, I had very little sense of it in the control wheel, and needed to make almost no corrective input to compensate for their effect – which inspired a good deal of confidence in the Rallye’s handling as a whole.

As noted previously, my plan for the day was to spend most of the time just cruising around, soaking up the low wing views – and giving the owner a tour of the Lučko CTR and some of its more pertinent features and points. Because of this, I had not gone through the same set of PPL skill test maneuvers as I did with the U-75; but nevertheless, I did get to spend enough time at low speed and high AoA to at least get a basic & very rough idea of what the little Rallye is capable of.

Straight off the bat, I was impressed with how docile it behaved in all of the flight regimes I went through – equally as impressed as I was when I first flew the U-75, which shares that very same trait. The smaller and “hotter” wing (9.6 m span / 79.8 kg/m² loading vs 9.73 m / 65.3 kg/m² for the U-75 and 10.97 m / 64.4 kg/m² for the Skyhawk) made for sprightly maneuvering, while the slats kept things from getting out of hand even at low speeds. Indeed, even at 100 km/h, the Rallye exhibited none of the hesitation in pitch and roll common to slow-going C172s – and no sense in the control wheel of impeding drama should you reduce speed and/or increase AoA further. Put simply, even in the limited experience I had that day – and considering my acknowledged lack of flight test credentials, knowledge or skills – through the controls it felt like it could cheerfully handle reasonably everything you threw at it without much fuss or undue effort.

Other characteristics that I very much liked were the effective vertical stabilizer and powerful rudder, which made for very little footwork in any turn and at any speed – yet another parallel with the U-75. Interestingly though, SP-IKY needed very little right foot even during the take off roll and climb, a stark contrast to S5-DCI, the Utva I had the privilege to fly; though this may be simply down to the specific rigging of their rudder tabs.

Keeping up with the Skyhawks

The manuals, however, suggest that the aerodynamics that make this possible do come at a price in the cruise. The Pilot Operating Handbook (POH) for the MS.892 quotes a True Air Speed (TAS) of 160 km/h (86 kn) at 55% power (2,300 RPM) in standard conditions at 500 m (1,650 ft); the C172N POH states 53% power (2,200 RPM) will give you 185 km/h (100 kn) TAS in standard conditions at 2,000 ft.

In a particularly fortunate turn of events, 2,200 RPM just happens to be the setting I use most often on the 172 – while 2,300 RPM was the number SP-IKY’s owner suggested I stick to since we weren’t really in a hurry to get anywhere. Likewise, I do most of my local flying at 2,000 ft – like I did in the Rallye – usually traveling with just one other person on board – like I did in the Rallye – so I conveniently ended up with a somewhat solid baseline from which to try and work out how they actually behave in real life (bearing in mind that one example a poor statistic makes!). In these sort of mid-spring conditions with temperatures between 10 and 20° Centigrade, 2,200 RPM on the N model Skyhawk usually gives me about 175 km/h (95 kn) indicated; on that specific day, with an OAT of 18° C on the ground, 2,300 on the Rallye showed me 180 km/h (97 kn) on the ASI.

The difference may be down to the engine or prop or even the number of dead bugs on the wing; whatever the cause, it does seem to indicate that in the sort of everyday flying practiced around here – mostly low altitude across short to moderate distances – performance-wise both the mid-model 172 and the Rallye have very little between them (the discovery of the century considering the vast 10 HP difference 😀 )***.

*** one other route performance metric – fuel consumption – is a bit difficult to compare precisely, since SP-IKY does not have a fuel flow meter. However, the owner had told me he uses 9 GPH as a low altitude benchmark – which is within tolerances of the measured ~8.5 GPH I see in the same conditions on our 172N’s engine monitoring system

Same altitude, same speed, same region – but a different view… flashing back to my first cross-country flights and related cross-country flight traumas (many caused by our famous hilltop church-to-hilltop church navigation method)!

AS_SPIKY_190510_002

First time on an aircraft with a sliding canopy – and loving the photo possibilities!

Other stuff? Well, apart from improved visibility (and the option of opening the canopy in flight for a bit of natural aircon), the experience of cruising in the Rallye vs cruising in the 172 boils down mostly to subjective criteria and the differences in trim and furnishings of individual aircraft – something the U-75 in particular does not suffer from, since its production run was just 4% of the Rallye’s (and 0.3% of the Skyhawk’s), with only one “military spec” trim level provided. Personally, the only niggle I had that’s worth writing home about is the overly sensitive pitch trim wheel, with very little rotation producing a very noticeable result; a situation I had also encountered on the U-75, with the added trouble of S5-DCI’s wheel having been far coarser and generally significantly less user-friendly than SP-IKY’s.

The Rallye, however, comes back into its own once on approach. The wing’s low-speed finesse becomes obvious already on base leg, since the airplane’s 1/13 glide ratio in clean configuration (achieved at 140 km/h (76 kn) ) means it does take a bit more persuasion to go down than the 172N (which sports a 1/9.2 glide ratio; mind you, the U-75 “outclasses” them both at just… 1/8.4). Selecting flaps to the second and final notch (30°) makes things easier, resulting in a standard approach speed of 120 km/h (65 kn) – a figure that can be brought down to 105 km/h (57 kn) in an emergency.

Flying the final approach is generally pretty humdrum, with the only real difference being the better visibility over the nose, which does wonders for depth perception and glide path control. Life starts to become interesting again once in the flare, not only due to the cushioning effect of the low wing – but also to the quirkiness of the slats, which will suddenly**** slam fully open at around 90 km/h (49 kn), setting you up for an embarrassing ballooning float if you’re not fully ready for it (as I was not). Having “seen the elephant”, my subsequent approaches were… hmm… less worse, and with more experience I am certain I would be able to plant it gently right onto the aiming point, using all the benefits of the slats to their fullest. One of these was actually obvious right from the outset, since the Rallye has an uncharacteristically flat (but still two-point) touchdown attitude, which affords an excellent view ahead – a consequence of the improved airflow along the entire wing that allows the same lift to be generated at a lower AoA… and thus at a lower pitch.

**** the reason why the slats are so “quirky” – i.e. why they extended so suddenly and so late in the landing – has everything to do with the oft-misinterpreted aerodynamic principle behind them. Despite constantly using SPEED to describe their operation – indeed, the 150 km/h retraction and 90 km/h extension are straight from the POH – the slats in fact respond solely to ANGLE OF ATTACK. In the climb, the AoA is high, and the air pressure on the upper wing surface low enough to keep the slats fully or partially extended; on the approach however, the combination of the shallow downward path of the aircraft and the extended flaps means that the AoA is still moderate (despite the low speed), and the air pressure is still such that the slats can be kept pressed in. The flare itself – when the AoA suddenly increases to near stalling values – is the first time during a normal approach and landing that adequate pressure conditions for slat extension actually exist.

Their dependence on AoA also means that you can essentially activate them at any speed – provided you increase the AoA sufficiently enough. If you take the Rallye to its maneuvering speed of 210 km/h (113 kn) – the maximum speed at which a full control deflection will not cause structural damage to the airframe – and yank it over into a combat break, the slats will pop open instantly, despite being 64 kn above their “landing extension speed”.

Unfortunately, the day’s conditions meant I had no opportunity to see how it behaves in a crosswind, something I was particularly interested in due to the possibility of significant sideways drift in the float – and scraping the wingtip along the ground with too enthusiastic a correction. The manual itself quotes a crosswind component limit of 20 kn – noticeably higher than that of both the 172 (15 kn) and U-75 (8 kn).

The wide cabin, extensive glazing and narrow cowl all make for surprisingly good views downward, which makes life far easier in the circuit

Lučko’s rough runway also made for a good test of the type’s trailing link suspension, which sports a similar setup to that of the U-75. Though the Utva is far superior in its handling of uneven terrain – having been designed from Day 1 for eventual wartime operation out of auxiliary dispersal fields – the Rallye handled things with ease, ironing out the bumps without any undue sloshing from side to side. On the last, full stop landing, we needed roughly 300 meters to decelerate from touchdown to taxi speed, using only as much braking as was necessary to maintain direction; the manual quotes a 265 meter landing distance over a 50 ft obstacle for a fully loaded airplane (980 kg Maximum Landing Mass), which seems easily attainable by avoiding greasers and applying maximum braking immediately after touchdown (as well as flaring late and letting the slat extension slow your rate of descent).

Spiky ticking itself cool after our sortie… definitely one of the better flying experiences of the year so far!

Vive la France!

Though I must once again stress that one hour aloft with no professional flight test background does not make for reliable (or even usable) conclusions, on a purely subjective note I was as smitten with the Rallye as I was with the U-75. Despite being multipurpose machines that can, like the C172, do many things well, both could boast a fun factor that was completely alien to the Skyhawk, comparable even to (dare I say it?) the Super Cub and Citabria. While that may simply be down to my perception of their specifics – such as the Rallye’s slatted low-speed wing or the Utva’s military heritage – both are a hoot beyond even subjective doubt, and can boast a mix of genuine joie de vivre and everyday usability that’s tough to beat.

Or could that be a just low wing thing? 😀

ADDENDUM – 7 JUN: it may have taken me awhile – for the Q400 bids often during the summer! – but eventually I managed to plonk myself back into the left seat of SP-IKY and finally head into one of Lučko’s training zones for a bit of air work. Due to my pretty obvious fascination with its slats, I’d decided to put it through a couple of textbook stalls and see what’s what on that edge of the envelope…

In short, the Rallye’s behavior was just as one would expect – but with a slight twist. Throughout the entire maneuver, SP-IKY held rock-steady despite the day’s turbulence, and showed no inclination to drop either wing even as the indicated airspeed reduced to below 90 km/h (49 kn); indeed, even my attempts to provoke it with a bit of aileron came to naught, and it kept at it well into the 70 km/h (38 kn) range. When the stall finally did come, it was as dramatic as watching paint dry: just a slight forward tug on the wheel and all was well… not even U-75 “went” so cleanly. If anything, the slats meant that the wing regained a healthy airflow as soon as the AoA reduced even slightly, returning to “normality” at a pitch that would be quite unnatural on a non-slatted wing. The downside of this ease of recovery is that it can be quite deceptive, and a conscious effort is needed to continue to push the nose down and build up a healthy AoA margin, despite all feeling well in the wheel.

And the twist? As on landing, the sudden deployment of the slats and the resulting rapid increase in lift along the entire wing can come as quite a surprise, leading to a pronounced and very visible ballooning motion that looks and feels VERY odd… as the following vid shows! Even more so, in a more aggressive stall, the change in airflow distribution will actually rock the ailerons slightly; aerodynamically this is not much of an issue – since at that point the wing still has quite a bit of life in it left – but an instinctive/panicked counter movement of the wheel could in some conditions cause more problems than it solves…

As always, I would like to extend my sincere thanks to Lukasz for the opportunity to fly his baby and cross another aircraft from my To Fly List!

Changelog:

  • 7 June 2019: stall characteristics + video added
  • 10 May 2019: added slat operation videos + additional photos

Sources:

Photo File – My Kingdom For Some Horsepower: The Caravan Blackhawk XP42

By me
All photos me too, copyrighted

It is perhaps a sign of the state of general aviation on the Balkans that the arrival of a single Cessna Caravan can stir up so much interest that even people from neighboring countries head over to see it. While a perfectly common “garden variety” airplane everywhere else, the 208 is still a pretty exotic beast in these parts, with myself having come across only four examples in the 16 years I’ve spent hanging around light aircraft. Therefore I could be excused for packing up my photo gear and driving 120 km one way to Šentvid Airfield in Slovenia in order to catch it 😀 .

The machine in my sights, however, had a bit more going for it than just being a big Cessna with a turbine. On the one hand, it is a comparatively rare short-body Caravan I – and on the other it sports the impressive Blackhawk XP42 engine conversion that is not that common even in the more affluent bits of Europe. So as it spent its three days there hauling skydivers to altitude, I could take my sweet time and get to know it Achtung, Skyhawk! style 🙂 .

A handful of horses in the back – and 850 charging straight at me. Looking imposing in the soft afternoon light, D-FOXY returns from yet another series of skydive runs. Manufactured in 1999 with the serial 208-00303, Foxy spent its early years in the US, flying as a seaplane under the name N984J. In 2006 it would move to Italy as I-SEAA, before heading north into Germany in 2013, where it would eventually lose its floats, get buff and become a no-nonsense jump platform

Blackhawk Up

Though much can be said about the qualities and exploits of the rugged Caravan, what interested me most in this case was in fact Foxy’s nose job. One of the many products to come out of the Blackhawk Engineering works – the people who put third-party turboprop upgrades on the map – the XP42 mod involves replacing the 208’s standard engine (in this instance a “small series” 675 HP PT6A-114A*) with a much more potent “medium series” 850 HP PT6A-42A. In addition to the improved power, the 42’s larger core also noticeably adds to the torque, with take-off figures now up from 2,535 to 3,045 Nm. To soak all this up, the original three-blade 2.69 m McCauley prop gives way to a variety of four- and five-blade aluminum and composite units, with Foxy in particular sporting a conventional 2.54 m Hartzell for a bit of extra ground clearance.

* up until serial number 208-00276, most short-body Caravans were powered by the 600 HP PT6A-114 unit. From aircraft 277 onward, they switched to the same 114A as used by the bigger Grand Caravan. Also of note is PW&C’s engine class system: “small series” engines develop between 500 and 900 HP, “medium series” cover the 850-1,050 range – while “large series” go from 750 all the way to 1,900.

But, the XP42 upgrade is as much about added grunt as it is about the nature of its delivery. Unlike a simple engine swap, this conversion is what’s called a “firewall forward solution”, which includes – where necessary – extensive modification to the engine compartment itself in order to get the most out of the new powerplant. Since the majority of XP42s will be used for rough-and-tough hauling in arduous conditions, the folks at Blackhawk had gone to some length to make the upgrade more than just a course of steroids. To this end, the most obvious alteration is to the cowl, now widened at the front to accommodate a 40% larger oil cooler in order to keep things in the green even during operations in hot-and-high conditions or repeated back-to-back flight cycles. The new twin exhaust stacks (a consequence of the 42’s slightly different architecture) can be profiled to either eek more thrust out of the exhaust gasses (5 knots worth in fact) – or increase mass flow at the expense of cruising efficiency to lower turbine temperatures during the type of prolonged high-power climb common to skydive ops.

For comparison, a stock Caravan I, here in its military U-27 guise. Note the single large exhaust duct and narrow cowl

Other stuff? Well, the engine is now mounted at four points instead of three, there’s an improved air intake system with a modified inertial separator to further reduce the likelihood of foreign object ingestion at rough strips, the battery is now a Li-ion affair instead of lead/acid to save roughly 13 kg in weight – and there’s an optional 325 A starter generator instead of the stock 200 A unit to reduce wear and tear on the engine by shortening spool up and light up times. The package is also rounded up by custom Hawkeye engine gauges, generally similar to the Caravan’s originals – but now with an additional digital readout for most parameters.

Dear passengers, your flight is now ready for boarding. Though all of you will leave half way, we would like to thank you for flying with us! Though the prop is now noticeably shorter in span, it still spins at very similar speeds as the original, meaning the XP42 is still a pretty quiet machine, even at full chat

A peek under Foxy’s skirt. Though the 42A sports a larger core than the 114A, it is only 27 kg heavier dry, 190 vs 163 kg. Interestingly, it is also 34,7 cm longer than the 114A (1.68 vs 1.34 m) – but at the same time 13.2 cm narrower, sporting a 46.4 cm diameter vs the “smaller engine’s” 59.6. Also note the fuel/oil heat exchanger at the extreme right, which helps cool the oil by transferring some of its heat to the fuel on its way to the combustion chamber

And the conversion’s other party piece, the new oil cooler. A pretty good illustration why the XP42’s nose now looks like it had been rammed into a wall!

In addition to Blackhawk’s efforts to keep oil temperatures manageable even during repeated short cycles (as well as the day’s very agreeable 17 degrees Centigrade on the ground), Foxy came equipped with a custom cooling adapter, essentially three fans running off a 12 volt external battery that circulate air through the oil cooler to prevent the formation of local hot spots when the engine is not operating

With a load of between 10 and 15 skydivers every 15-20 minutes, Foxy’s modification sure had their work cut out for them (even more so since start-ups are more critical to turbine engine wear than running hours)!

What a truly wonderful way of spending an afternoon: sitting on the ground behind a revving 850 HP short-body Caravan to the background of rolling hills and lush forest…

As always, I would like to thank the very friendly staff at Šentvid Airfield – as well as Foxy’s pilot for allowing me to snoop around the aircraft inside & out!

Sources:

Photo File – Summer Snappin’

By me
All photos me too, copyrighted

While the summer season of 2018 was not really my most productive one (and is far below the bar set by 2017, which gave us classics such as this and this and particularly this), it nevertheless was not a total bust photography-wise. While I’m still smarting from having missed a couple of proper Achtung, Skyhawk! classics by mere minutes (including a Dash 7), I’ve still managed to hoard enough quality material for one jolly Photo File, to at least keep the ball rolling until something else comes up… 🙂

Silver Eagle is silvery! Easily the most popular aftermarket conversion for any Cessna piston single, the Silver Eagle mod entails a major rework of the classic 210 powerplant, substituting its original 310 HP Continental TSIO-520 six cylinder boxer for a 450 HP Allison/Rolls-Royce 250-B17 turboprop – the same type of engine fitted to the most popular helicopter in the West, Bell’s JetRanger. While just the power increase sounds worth the trouble (and cost), the conversion’s real party piece is the engine’s high mass flow, a trait inherent to all turboprop engines. The classic P210 had made its name for its 23,000 ft ceiling, full cabin pressurization and a pneumatic de-ice system for the wing and tail surfaces – all services that require a tremendous amount of compressed air. To cater for all of them, the turbocharger had to massive, which increased weight, maintenance complexity – and occasionally made the engine tricky to operate (especially with regards to shock cooling). Since half of a turboprop is essentially just a large compressor, it handles so much air that it can keep everything sufficiently supplied while still providing a care-free high performance experience – and all for a 158 kg wright reduction (the 250 tips the scales at 96 kg dry vs. the 254 of the TSIO). N700RS also features a frequent optional extra, a weather radar housed in a streamlined dome below the right wing.

Just when I thought it would be G400/G500/G600s or nothing for me here in Europe, into the mix comes this immaculate classic G-III. While you do have to stare at it for awhile to recognize it as an older model, its dead giveaway are the engines, old Rolls-Royce Spey units that are sufficiently loud to warrant the addition of “hush kits” – aftermarket (but certified) silencers that improve mixing between the exhaust gasses and ambient air and reduce the shearing forces between than that are the main “source” of jet engine noise.

Another meeting with the very colorful LY-DSK, which I already had the chance to snap – and elaborate on! – in a previous post. Thankfully, Split Airport (SPU/LDSP) had recently decided to park most of its surplus aircraft steps right on the edge of the GA apron, affording plenty of opportunity to go elevated!

Got contrast? The only proper way to end a working day – with a beautiful GA classic! One of the last mass-produced touring types developed by Italy’s traditional large manufacturers, the original S.205 was conceived in the mid 60s along similar lines as the contemporary Piper PA-28: a simple but versatile aircraft that could be developed into a diverse product family with comparatively little effort. To this end, the basic four-seat fixed-gear S.205F was quickly followed by the retractable S.205R and the more powerful five-seat S.208 – with the top of the range dominated by the planned six-seat S.206 and the S.210 twin. Unfortunately, despite the type’s undoubted qualities and robust build, it would nevertheless never fulfill its potential, SIAI-Marchetti having always lacked the production capacity, support and market reach of its Big Three rivals across the Pond…

The primary towplane of the Celje Flying Club intimidating ants as it awaits the start of the afternoon soaring session at Slovenia’s Celje Airfield (LJCL). An aircraft with a history dating all the way back to 70s Yugoslavia, TNC had during the early 2000s been a resident of my base airfield of Lučko (LDZL), where it had intrigued me – a green student pilot – with its unwieldy and lumpy looks. Despite not being easy on the eye, the Pawnee had far outlived its original role of cropduster, becoming the staple of glider clubs all over the world.

“Molki” throwing out the anchor as it decelerates after a training flight round the Celje Airfield (LJCL) circuit. Developed in the late 80s based on operational experience from the original L-13 Blanik, the L-23 came equipped with a completely new swept T-tail, a slightly larger cabin with new high-vis canopy (one piece on later models, such as this one) – and a revised wing that did away with the 13’s large flaps. Though it had bettered its dad in almost all respects, the Super Blanik would nevertheless fail to replicate its market success, with only limited numbers having been sold in Europe. Interestingly, the type had made somewhat of a name for itself overseas, with 12 examples used by the US Civil Air Patrol as trainers under the designation TG-10B Merlin.

Mirror mirror on the apron, which Learjet should I escape on? The 55 Longhorn you say? No problem! The first of the so-called “large cabin” Learjets, the model 55 was intended to be the starting point for a whole series of “premium” models (such as the shortened 54 and lengthened 56), but a tough market and lots of competition in the early 80s meant that the 55/55A/55B and 55C was as far as it ever made it. Even though the family would later serve as the basis for the very successful 60 series, the 55 was nevertheless a total sales flop, with just 147 having been sold during an eight year production run. Of particular interest is its Longhorn nickname – after a breed of Texas bull – which actually has a long association with the LJ line. The first model to carry it was the mid 70s 28, which had swapped the original 23’s characteristic tip tanks for a pair of imposing, NASA-designed winglets – becoming the first production bizjet to be so equipped. As they became a standard feature on all future Learjets, the Longhorn name was left to slowly fade, eventually dying out with the 55…

For most, a bunch of useless old relics… for Learjet fans, pure pornography! Winglets vs tip tanks as the very attractive fleet of Munich (MUC/EDDM)-based Jet Executive catches some rays on a beautiful summer afternoon. A round of beer for the folks responsible for keeping these machines in the air!

No horizons in the future for Future Horizon as it continues to deteriorate for another year in a remote corner of Dubrovnik Airport (DBV/LDDU). Not a stranger to my camera, DGS was the odd man out in the fleet of MD-80s operated by Air Adriatic, one of Croatia’s first post-independence private airlines (though it was actually owned by a local investment company). Formed in 2001 and well known locally for giving its aircraft names that bordered on the cheesy, Air Adriatic would eventually fold in 2007 when its finances were exhausted, leaving the fleet stranded at various airports in the Balkans. While some of its MDs did survive in some form or another (as fire trainers of museum exhibits), DSG today remains pretty much the last visible example of the carrier’s existence…

I go and visit Lučko for the first time in a month and straight out of the gate have this to see: 280 HP, 350 km/h, 20,000 ft – and a bucketload of charisma characteristic of all Mooney designs. Ever since the original single-seat M18 Mite, all of the company’s aircraft could boast impressive speeds for their power, outstanding performance and flight characteristics all round – and dragging tails with “flipped” vertical stabilizers (which Al Mooney claimed improved yaw control in a stall). Even though it had been under Chinese ownership for some time now, today’s Mooney remains true to its origins, with the top-of-the-line Acclaim Type S pushing a jaw-dropping 470 km/h with a turbocharged version of the Ovation’s engine… (and for those interested, the small mosquito at the top of the screen is actually Mi-8MTV-1 “215” of the Croatian Air Force)

EDIT: and a bit of video as well… when you need a break from boring a hole in the sky, you can rent a Skyhawk and go get in the way at a neighboring airbase. The guy up in the tower must have died laughing: PC-9s regularly fly high speed breaks down the runway, occasionally even F-16s “request permission for flyby”… and into the mix comes me with a 40 year old 172 doing a blistering 125 knots…

Flight Report – That 70s Plane: Flying The UTVA 75 Trainer

By me
All photos me too, copyrighted

Ever since the early days of Achtung, Skyhawk!, I’ve always been on the lookout for rare, interesting and historically significant aircraft puttering around the region – you know, the sort of machines that had it all really: rarity, backstory and a rich history to boot. As the winter’s soaked runways, persistent fog and oppressive low cloud finally gave way to dry grass, pleasant temperatures and clear sunny skies, I decided I might as well go one up this time and actually – fly one 🙂 .

Having spent my formative flying years listening to “oldtimers” and their stories of adventure on the many aircraft types indigenous to former Yugoslavia, the choice made itself really, especially since many of them are nowadays well up on the endangered list. The simplest solution was thus to go for the most modern and popular one, which eventually led me to Slovenia’s Maribor Airport (MBX/LJMB) and its resident UTVA U-75 two-seat trainer.

Responding to S5-DCI and owned by the Letalski center Maribor (LCM) flying club, this particular aircraft is itself already good for a classic AS review – but, being one of only a dozen or so still airworthy, I decided to bin tradition and focus this time on what this interesting machine is actually like to fly. So, instead of digging deep into its history (s/n 53171, mfd. 1980, ex. YU-DGF of AK Maribor, then SL-DCI and S5-DCI of the Slovenian Air Force until 2010, then to LCM 😀 ), I though I could put together a short flight report and attempt to describe what the U-75 feels like in its element…

The shape that launched a thousand student traumas… while it certainly won’t be winning any beauty contests, the U-75’s stocky build and generous size nevertheless make it stand out among its peers!

Author’s note: given that I have no experience flight testing aircraft (nor do I have the required skills or qualifications), this work is not a proper professional review – but rather the personal experience of a long-time light aircraft pilot and lifelong GA fan. As such, my observations will definitely not be something they will print in textbooks – but given the rarity of the U-75, they should nevertheless be an interesting read for the enthusiast!

Part 1: the basics

Even though the U-75 had already featured here in depth as part of a review of the type’s sole surviving four-seat example, for the sake of clarity and ease of reading I though it best to nevertheless run quickly through some of its more pertinent characteristics. Flying for the first time in 1976, the U-75 is a simple and robust all-metal semi aerobatic two seat trainer, designed to be suitable for everything from basic flying instruction (civilian and military) to initial aerobatics and even air-to-ground gunnery. Despite its not inconsiderable bulk, the U-75 weighs only 685 kg empty and 1,200 kg at maximum take-off (though it is usually flown at its maximum landing weight of 960 kg), which makes its 180 HP Lycoming IO-360 and its associated two-blade constant speed prop good for about 115 kts in the cruise. More importantly, its +5.5/-3 G stress limits with one person on board (and +4.4/-2.2 with two) give it a wide berth during maneuvers, while the tall wide-track landing gear, long-travel shock absorbers and large low pressure tires make (student) landings a doddle even on rough and unprepared strips.

With 138 examples made in total between 1978 and 1985, the U-75 would go on to become former Yugoslavia’s second most produced indigenous design – right behind the G-2 jet trainer – and was throughout the 80s and 90s used by civilian clubs and air forces across the land (in the latter often known as the V-53). And while it is today viewed with fond nostalgia, its life in service was much tarnished by a popular reputation for violent spinning (sometimes fatally), which bred considerable distrust in the design. In fact, the problems stemmed from the rearward position of its center-of-gravity, which made it a peppy and nimble performer – but at the expense of reduced longitudinal stability*. When pushed hard and then poked with a stick, it would indeed want to spin and keep on spinning; but when flown in moderation and per SOP, it had shown itself to be pretty docile in all flight regimes, a fact attested to by numerous operators who went aerobatic on a regular basis and without incident.

* in simple terms, the two extremes of aircraft behavior are stability and maneuverability. An aircraft that is stable is not maneuverable; likewise, an aircraft that is maneuverable is not stable. Given that this principle acts along all axes of the airplane separately, nailing down the exact amount of each is an art. In prototype form, the U-75 was found to be too stable longitudinally, which reduced its maneuverability in pitch and made it less suitable for the training role. The root cause was determined to be a CG position that was too far forward; to solve the problem, the heavy battery – originally fitted behind the cockpit – was relocated to the tail cone. This shifted the CG backwards sufficiently to solve the problem, but at the same time made the U-75 “nervous” in pitch when it reached its limits. In a hurried or badly executed maneuver, it was not hard to stall and send the aircraft over one wing, initiating a spin that – if not countered immediately – just kept getting worse. Approved procedures therefore called for entry into spin practice at a minimum of 5,000 ft AGL, and recovery to be initiated after just one turn; done properly, flight tests showed an 850 ft altitude loss could be expected. Done lower, slower and sloppier, you can well imagine the results…

Aside from its significance to the locals, the U-75 is then a classic ab-initio trainer, the sort of aircraft produced by aeronautical establishments all around the world. This itself invites a comparison to some of its peers, such as the Slingsby T.67 Firefly, Scottish Aviation Bulldog, the PAC CT-4 or the SAAB S.91 Safir; however, what I am actually going to do is compare it to the restrained and very unmilitary Cessna 172. The reasoning behind this approach is simple: many GA flyers have at one point or another flown a Skyhawk, with most (myself included) having logged treble figures in at least one of its variants. Despite their different roles, the two aircraft are alike in a number of respects, which makes establishing a baseline for the U-75’s comparison all the easier. And anyway, there’s no point in drawing parallels with an equivalent aircraft if there’s nobody reading (or writing) who flew them, is there? 🙂

Part 2: getting in

But, first things first. Entry into the cockpit is pretty straightforward and is standard stuff for low-wing aircraft: hand in recessed handle, foot on step and up onto the wing from behind. However, since the U-75 was designed from the outset to operate out of unprepared strips, the wing root is a good 80 cm above the ground, so the whole maneuver requires a bit of gymnastics – though not much more than trying not to trip over the 172’s main gear leg.

Once on top, the two-part sideways hinged canopy (jettisonable in flight) opens upwards, and is then fixed in place by a manually folding arm tucked to the inside of the canopy frame. This setup is not really ideal for tall people (like me), since it is quite easy to bang one’s head against the canopy while maneuvering to enter the seat. Thankfully, the frame is pretty large overall so – heads notwithstanding – getting in and out is not difficult or haphazard by any measure.

Thankfully for its crews, the U-75’s exterior size is matched by its interior, with more space on offer than in Cessna’s premium piston singles, let alone the Skyhawk. The elbow room for either seat is impressive, and even larger pilots would still have plenty of space to work without body contact. Note the chunky seat belts and the canvas cover behind the seats that doubles as a parcel tray

While it is immediately obvious that all structural components and cockpit controls are built to last – everything feels decidedly more robust and durable than on the 172 – the overriding impression is of rudimentary finishing work, with rough and unprotected edges in abundance all over the cockpit. Admittedly, given the U-75’s military nature, comparing these and other creature comforts with those of the Skyhawk is apples to oranges – but despite the lack of padding and soundproofing and any form of interior trim at all, the cockpit is physically very comfortable and quite airy. Headroom however is slightly less generous than on the 172 (even when you lower the seat fully), and anybody over 1.8 m and wearing a headset will fill slightly hemmed in from above – though it is still manageable and not much of an inconvenience on shorter flights (under two hours).

While there are no basic Ts and sixes here, the U-75’s cockpit is in some respects pretty well though out, with a couple of good ergonomic touches. One in particular is the central pedestal, which contains pretty much all system controls, including the throttle (yellow lever), propeller control (blue lever), mixture control (plunger), alternate air source (red-topped plunger), demist controls on the side, parking brake (orange switch) and, out of shot, the fuel selector (which, like on the 172, has a very welcome BOTH setting). One particular level that is missing – and would have been fitted in the hole below the alternate air – is the underwing stores emergency release handle. Like many trainers, the U-75 also includes another set of throttle and prop controls on the left of the pilot’s seat. Absent from the shot is the flap level, a large Piper-like affair between the seats; its settings are simple, UP, notch 1 (take-off and landing) and notch 2 (landing only). For my taste, the sticks are of perfect height – not to low, not to high – and though they’re designed to accept either hand, they fall slightly more easily into the right. The only really annoying feature is that on both throttle quadrants the prop control is on the left and the throttle on the right; whereas the manifold pressure gauge (controlled by the throttle) in on the left and the RPM gauge is on the right. As is the norm for all Yugoslav designs, the flight instruments are all metric, while the engine instruments – usually cherry-picked from various Western designs – are mostly imperial.

Once seated, both the sitting position and the view ahead are pretty good, though the frame of the canopy initially gave me the impression of peering through a postbox; once on the move though, I quickly got used to it. The rudder pedals can be adjusted fore and aft, but this is generally avoided since the mechanism is known to stick. The brakes themselves are actuated by separate toe-operated paddles inboard of the pedals – a solution similar to that used on the Super Cub, where they’re heel-operated. With larger shoes (or military boots) on larger feet, this does not seem to be a particularly used-friendly solution, and it took me some fumbling and toe jabbing before I’d gotten used to it. The rudder pedal edges are also contoured to accept the outline of a thick boot – a feature not really compatible with the sneakers I was wearing that day.

Helping matters however is that the brakes are quite powerful, so even a slight jab at them (regardless of its elegance) produces some results. Then there’s also the fully steerable nose wheel, which makes ground maneuvering pretty painless – indeed, I’d managed to get the hang of it after just a few dozen yards. In fact, on steering alone (without differential braking), the turn radius is just 7 meters – noticeably less than the 8.3 the Skyhawk can achieve using BOTH steering and brakes at the same time. The shock absorbers and tires make the ride quite smooth even over rough terrain, but at the same time do not let the aircraft roll to much in the turns if you keep the speed moderate (though the aircraft’s low CG position has a lot to do with this).

Part 3: airborne

System-wise, all pre-departure checks are no more complicated than on the 172, and follow pretty much the same pattern. Having been designed from the outset to meet the FAA’s FAR Part 23 criteria, the U-75 holds no surprises, and there’s none of the “Eastern Bloc system exotica” that its looks and origin would lead one to believe. With the engine being essentially the same as on today’s Cessna 172S (albeit with a constant speed prop), the run-up is also straightforward and over in a jiffy.

As I was briefed by the instructor occupying the right seat, the standard flap setting for departure from both paved and soft fields is notch 1, which gives 20° of flap. The aircraft manual quotes a 225 meter max performance run on grass and with zero wind; however, we had the advantage of concrete and a quartering eight knot wind, so despite the 880 ft field elevation and 25° Centigrade outside, we opted for a more leisurely departure. Adding power, there’s a very noticeable swing to the left – far more pronounced than on the Skyhawk – which can be neutralized only with a large amount of right foot. What’s more, significant pressure on the pedal is constantly needed at high power, and with no rudder trim available, this tends to become wearisome after awhile (though I suspect the rigging of the tab of the vertical stabilizer was to blame for this). Being both lighter and more powerful than the 172, the acceleration was noticeably better, and with slight backward pressure on the stick we were already airborne at 110 km/h (59 kts), having used up around 300 meters of runway.

Passing 50 ft, LCM club procedures call for acceleration to the U-75’s best climb speed (Vy) of 130 km/h (70 kts), retracting the flaps at 300 ft AGL and then setting maximum cruise power, an easily remembered 25″ MP and 2,500 RPM (equivalent to roughly 80% power). In this regime, the rate of climb with full fuel and two of us on board varied between 4 and 5 m/s (800-1,000 fpm), but the day’s thermal turbulence made getting a constant figure impossible.

Once in the cruise – in our case at 3,000 ft towards one of Maribor’s training areas – the power came back to the 65% setting of 22.5″ and 2,350 RPM, which gave a solid 160 km/h (86 kts) indicated and 169 km/h (91 kts) true. While this is not particularly impressive for the available power, the thick wing profile and large landing gear do create a quite lot of drag; increasing the power by two inches MP gave around 170 km/h (92 kts) indicated, but since we were in no hurry, I soon throttled back to best cruise and set about seeing what’s what.

Given my previously noted lack of flight test qualifications, I decided to try and get an impression of the U-75 by flying a program based on the average PPL skill test (bits of which I dimly remember from ages past 😀 ). This I thought would give me the best impression possible in the allotted time frame (one hour 30 minutes), since I would get to see both how it behaves in regimes I’m familiar with from the 172 – as well as how a student might experience it during basic training. To this end, my “program” consisted of:

  • standard, 60° and 90° banked turns + snap roll
  • slow flight
  • stalling, both power on and power off
  • sideslip descent + gliding
  • flaps notch 1 and notch 2 approaches w/ crosswind
  • and route flying and navigation

Sadly, the pattern at Maribor was quite crowded that day, so there was no opportunity to perform a simulated engine-out approach without inconveniencing half the sky. To compensate, the ambidextrous nature of the U-75’s flight controls had allowed me to fly most of my program with each hand in turn and judge the ease and practicality of both. In the end – though I favor using my right hand as I do at work – flying with the left is often far simpler, since all relevant controls – flaps, lights, radio – are on the right side, allowing me to push and pull everything without having to constantly switch hands.

To cut to the chase without going through each maneuver separately, the handling came as quite a positive surprise – especially after everything I’ve heard said about it. The numbers themselves offer some clue to the above, as the U-75’s 65.3 kg/m² wing loading – only slightly up from the 172’s 64.4 kg/m² – promised similarly forgiving all-round behavior, while its 9.73 m wingspan – noticeably shorter than the Skyhawk’s 10.97 – bode well for rolling rates and a general willingness to maneuver.

Immediately after leaving straight & level fight, I found the stick to be very precise and informative, its travel pleasingly light in both axes – enough to get a good feel for the aircraft, but not twitchy enough to become tiring. Interestingly, the stick moves noticeably lighter in roll than in pitch, a setup exactly opposite to that of a glider. Thanks to the type’s large ailerons and powerful elevator (both blessed with considerable travel), the feel was matched by the aircraft’s physical response, with rolling and pitching done quickly and eagerly – but without the aggression of a thoroughbred aerobatic machine. Unsurprisingly, rates across all three axes were significantly higher than on the Skyhawk.

This harmony between stick and machine meant that I could achieve a remarkable degree of precision in most maneuvers already on the first time out, and all without any unnecessary flailing at the controls. Following my observations on take-off and in the climb, I was also quite surprised how little rudder was needed in turns – and that even left-hand maneuvers occasionally needed a poke of right rudder (though I again suspect tab rigging to be the cause). An additional characteristic that caught my eye/hand was that even in high bank turns, comparatively little backpressure was needed on the stick – and when I did find myself losing altitude, little additional force was necessary to return everything back to textbook state. As the numbers in the previous paragraph suggested, the U-75 was indeed very willing to sustain most maneuvers without much fuss and manhandling from my side, which immediately inspired a dose of confidence in its handling as a whole.

But what impressed me most of all was its stall response. Given the legends, tales and accident reports relating to U-75s going vertically, I was ever so slightly apprehensive about this part – not due to fears of ending up in a spin**, but a perception that an aircraft with such a reputation will likely not be well behaved once the going gets tough. I am pleased to say that I was quite off the mark, for the U-75 had exhibited flight simulator-like behavior, even with power on: just a very slight shudder and forward tug on the stick saying that it would like its nose to point down if I don’t mind. Honestly, it made the 172 look dramatic! Another thing of note is that despite the day’s turbulent thermal weather, it resisted wiggling its wings near the stall – and as soon as it even slightly went to the side, quick pedal action would sort everything out in an instant.

** although owners who had spun the U-75 say it is not as big a deal as folklore suggests (again, if done properly), I had shied away from attempting one, due to both my lack of experience on the type – and the fact that S5-DCI itself was barred from spinning by LCM club rules.

Some mention should also be made of the engine. Despite its nominal take-off rating of 180 HP, throughout the program we kept it at its 25″/2,500 RPM maximum cruise setting, which – according to the manuals – left us 150 HP to play with. Despite the abuse and the 20 °C at altitude, the engine oil temperature remained hovering around 95 °C (right in the middle of its 80-110 °C normal operating range), while the designated cylinder registered around 190 °C (deep enough for comfort within its 80-220 °C green arc) – which says a lot about the airflow through the engine compartment. Helping matters were the U-75’s distinctive cowl flaps, located on top of the cowl just ahead of the windshield, which lead to the odd situation of the front cylinders running hotter than the rear pair. Another thing of note is that despite its semi-aerobatic credentials, the U-75 sports the standard version of the IO-360, which is not equipped with fuel and oil systems for inverted flight (these would have been identified by the additional prefix AE).

Criticisms? Well, the only major thorn in my eye at this time was the trim wheel, which was far too coarse and lacking in feel; it resisted operation too much and even a slight turn resulted in an out-of-proportion change in stick force. However, as with the rudder, this may very well have been down to the rigging of this specific aircraft.

With the program completed, we settled back into the cruise, where the plan was for me to do some navigation of the greater Maribor area and see how the U-75 behaves en-route. In a number of critical areas, it didn’t fare all that well: its military genes mean that comfort was never allowed to compromise the training experience, the result of which is a cockpit with no soundproofing at all (as noted previously). The upshot is that ambient noise is off the scale, and even with headphones on it all becomes pretty annoying pretty quickly (especially since S5-DCI has no squelch control, which leaves the headphone mikes free to pick up the drone and amplify it back to you). The position and height of the stick also mean that you have very little space in your lap – so with a kneeboard on and the right seat occupied, you’re going to struggle to read an unfolded map, despite the nominally generous size of the cockpit.

However, as uncomfortable as it may be, the U-75 nevertheless does have something going for it as a navigation platform. In common with most other low-wing aircraft, the view outside is excellent, and the relatively small span of the wing means you can often have a good look down. Once trimmed (after much frustration), it will fly hands off for a surprising amount of time – without rudder input even – though having someone in the right seat to balance things out certainly helps. More importantly, the extensive glazing means you can easily keep tabs on surrounding traffic, and it never took us long to spot neighboring aircraft without having to bank or pitch or stand on our heads. So while the average GA tourer is in a completely different league in terms of comfort – so much so you’d be excused for sending hate mail to the UTVA works following a long cross-country – the U-75 is nevertheless a practical and safe platform for finding your way around.

In that other important route performance metric – fuel – the U-75 is pretty much on par with the 172, with our 65% power setting (mixture full rich) registering 30 liters/hour (7.5 GPH) on the flow meter. With the manufacturer’s 15% reserve fuel policy giving us 128 liters (34 USG) usable out of the 150 liters (40 USG) carried in total, this works out to an endurance of around 4.5 hours. At the same altitude, power/mix setting and ambient conditions, the POH for a late 70s 172N puts out a fuel flow of 25 liters/hour (6.7 GPH) which, with 136 liters (36 USG) available before hitting the 45 minute reserve, gives an endurance of 5.3 hours. However, I normally fly a 1979 Skyhawk with a very accurate digital flow meter, and the real-world figures in nearly identical conditions are all in the lower 7s, which gives an actual endurance of between 4.75 and 5 hours.

A charismatic 70s Yugoslav trainer, more noise than is believable, a green ergonomic mess of a panel and a guns/rockets/bombs toggle switch on the stick – fine ingredients for a fulfilling afternoon! Despite the large canopy frame, the view out is excellent in all directions (even back), though on clear days the sun coming in through the top of the canopy does lead to sauna-like conditions.

Part 4: stopping being airborne

With both zone and en-route work completed, I opted for a handful of touch-and-goes, to see how the U-75 manages that most difficult of maneuvers – landing. On the first three approaches, I went with a flaps notch 1 configuration – and quickly discovered that the little Utva could out-accelerate a brick going down. All that drag means that its glide is quite steep, with the manual quoting a L/D ratio (flaps up) of just 1/6.72 at 150 km/h, 1/7.1 at the 140 km/h (76 kts) recommended engine-out speed, and just 1/8.42 at its 116 km/h (63 kts) best glide – a condition where even the unaerodynamic 172 manages 1/9.2. In our case, these figures were decidedly lower, partly due to my ham-fisted flying – but mostly due to keeping our speed high to avoid disrupting the traffic flow and potentially shock cooling the engine. The ideal speed was therefore pegged at the same 130 km/h as in the climb, which gave more than adequate circuit performance while still keeping us below the maximum flap extension speed of 140 km/h.

Flying, both on and off work, a high-wing aircraft blessed with ample wingtip clearance, I was naturally apprehensive about touching down wing low in the day’s 6 knot crosswind. While this is just a light breeze everywhere else, the U-75 is deemed to be particularly sensitive to it, and is in fact limited to a 90° crosswind component of just 8 knots – HALF of the 15 knots limiting the Skyhawk. To avoid making a complete mess of it so early on, I elected instead for a jet-style crabbed approach with an appropriate bootfull just before the wheels hit the ground. The type’s powerful rudder made this a non-issue, though with experience I’m sure a proper sideslip approach could be flown easily and without danger to both the airplane and ego (especially since the dihedral places the wingtip approximately 1.1 meters above the ground).

Glossing over my first landing – an inglorious thump from too high a flare – I’d soon gotten my hand in and discovered that the U-75 is quite easy to land softly, mostly due to the very tolerant trailing link main gear. As can be expected, the cushioning of the low wing and a more pronounced ground effect mean you can float a long way if you’re not careful, but it doesn’t take too long to get used to it. Indeed, pilots who flew the U-75 in precision landing competitions told me that it is far easier to place on a specific spot than the 172, and it was always the preferred mount with many podium finishes. Interestingly, despite the high degree of flap, the touchdown attitude is noticeably nose up, far more than on the Skyhawk; however, the slope of the nose does not impair forward visibility at any point. The touchdown speed in our case was around 100 km/h (54 kts), though this can be brought down a bit if a greaser is not your intention.

To step up the fun – and illustrate just how draggy the U-75 can be – for the next approach I was instructed to come in high, fast and close, rolling onto the runway heading just 1,200 meters away at 1,100 ft above ground, doing 150 km/h (81 kts). To reach the threshold, I’d have to fly a virtual glide slope of 16° – 10 more than the steepest ILS recognized by law. Pulling the throttle back to idle, setting the prop full fine and dropping flaps fully to notch 2 (30°), I found myself in a visually disconcerting steep descent at 110 km/h (59 kts) and slowing – eventually even having to add power just to make it to the runway. The maximum rate of descent I remember seeing was on the order of 8 m/s (1,500 fpm) with no forward acceleration.

As an encore, I had planned for the final landing to be a “minimum stopping distance” affair – but the traffic crowding in behind us and the necessity of taxiing a full kilometer to our turn off point meant I had to scrub the idea and get my behind off the runway ASAP. But, since I’m already throwing numbers around, the manual suggests a landing distance over a 50 ft obstacle of around 450 meters, with the run itself just 240 meters.

Post script / conclusion time

While the comparatively short time aloft (and my aforementioned lack of test pilot credentials) prevent me from making any worthwhile objective conclusion, from a purely subjective standpoint I was nevertheless pretty smitten with the U-75 – perhaps most of all because it was nothing like popular lore said it would be. While a pure aerobatic aircraft might have been more exciting (at least during maneuvering), the Utva is definitely not boring or dull; indeed, on fun factor alone it might even top the Super Cub and Citabria (both of which I’d had the privilege to fly). While it is not perfect – and living with its faults day to day would likely start to wear quite thin very soon – its charisma, origins and historical relevance had definitely been worth the trip!*** Simply put, to actually go somewhere, I’d undoubtedly choose the better equipped, more comfortable and far quieter Skyhawk; but to have a bit of good old fashion stick-and-rudder fun without much fuss and effort, it would definitely be U-75 all the way 🙂 .

*** despite their widespread use across the width and breadth of ex-Yugoslavia, airworthy examples are nowadays increasingly difficult to find, with – by my count – less than 10 still operational and in civilian hands. Their somewhat expensive maintenance, pretty specific role and an increasing lack of spares make them a financial handful for smaller flying clubs, while their specific character is unlikely to tempt the wallets of many private pilots and owners. Despite this, the few examples that are flying will likely continue to do so for some time to come, with one – 9A-DIH at Čakovec Airfield (LDVC) in Croatia – soon set to return to flight after nearly a decade on the ground!

DCI back in the hangar, dwarfing pretty much everything in there…

Sources:

  • ab-ix.co.uk – UTVA 75 production list
  • UTVA 75 and Cessna 172N POH and checklists
  • and various human sources and U-75 crews