Month: April 2019

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!

Rallye around

The little bird in question is a 1973 SOCATA¹ 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.

¹ though the basic design – the MS.880 – was designed by Morane-Saulnier, by the time the had 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.

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 fully² 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).

² 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

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).

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 😀 )³.

³ 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

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 suddenly⁴ 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.

⁴ 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).

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).

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:

• EASA – MS.890 series Type Certificate Data Sheet (PDF)
• MS.892 & C172N Pilot Operating Handbooks