Category: Operations

Operations – The Empty Skies of Croatia

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By me

On the whole, I normally do not get much in the way of opportunity to scribble about the operational aspects of flying (and aviation in general) here in Croatia. Most of the time our pedestrian aviation scene simply doesn’t produce any material worth writing home about, while the country’s mostly pleasant terrain and climate – despite my regular rantings 😀 – also leave little in the way of excitement 🙂 .

On 30 July however, my hand was suddenly forced into action by the arrival of cyclone Melisa, another in an increasingly unusual string of low pressure systems to hit the region of late. Having made landfall on a broad front between the Adriatic towns of Pula and Zadar, Melisa had initially seemed to be a strong – but otherwise generally harmless – rainstorm, which would leave behind the occasional flooded street, but little else. However, news reports from Zadar had quickly revealed that this was no usual event, with the nearby island of Silba receiving 218 liters of rain per square meter in just 24 hours – an amount it normally gets in three months!

The red flags here in Zagreb were already beginning to come up by the time the cyclone had crossed the Velebit mountain range, having been replenished along the slopes by a strong, moist southern wind. Increasing in strength, the core of the storm had started turning slowly towards the city, prompting the Zagreb Airport (ZAG/LDZA) met office to issue a series of increasingly pessimistic TAFs – culminating in the dreaded +TSGR, thunderstorms with heavy hail…

The situation during the worst of it, as seen by the State Meteorological Institute weather radar in eastern Croatia (the city of Zagreb is denoted by ZG)…

A

A similar, but more colorful, snapshot from neighboring Slovenia. As you can see, the core of the cyclone had passed several miles south-east of the city center – rolling pretty much directly across the airport.

Though the hail had failed to materialize (at the airport at least), the torrential downpour that followed was about to launch ZAG into a world of issues. One of the day’s METAR reports perhaps best illustrates just what was going on out there:

 LDZA 301300Z 22038G48KT 0400 R05/0400VP2000N R23/0050VP2000N +TSRA FEW013 BKN030CB 17/16 Q1006 BECMG 05010KT 9999 NSW FEW015 SCT030

In normal-person speak, this reads out to:

  • measurement taken at Zagreb Airport on the 30th of the month at 13:00 UTC (15:00 local)
  • wind from 220 degrees, speed 38 knots (70 km/h), gusting to 48 knots (89 km/h)
  • meteorological visibility 400 meters
  • Runway Visual Range (RVR) down RWY 05 varying between 400 and more than 2000 meters, no significant change
  • RVR down RWY 23 varying between 50 and more than 2000 meters, no significant change
  • thunderstorm with heavy rain
  • few clouds at 1300 ft above ground, CBs covering 6/8 to 7/8 of the sky at 3000 ft above the ground
  • temperature 17 Centigrade, dew point 16 Centigrade
  • QNH 1006 hPa
  • weather imminently turning into a wind from 050 degrees, speed 10 knots (18 km/h), visibility greater than 10 km, few clouds at 1500 ft above ground, scattered clouds at 3000 ft above ground (they’d missed badly with this one!)

The first thing to go wrong was the runway midpoint transmissometer (one of three such units that measure RVR). This was not all that unexpected to be honest, since they also have a tendency to fail during heavy snows (and are an endless source of amusement during the winter 😀 ). Pretty soon however, the downpour became so severe that all operations were stopped dead in their tracks, eventually leading to the full closure of the airport (on top of the fact that even before the storm hit, flights were being delayed by 30 minutes due to anti-hale rocket activity in the area).

However, the worst was yet to come. Several minutes later, I was informed by a colleague – who’d been listening in on the tower and ops frequencies – that ZAG had suffered a “complete technical failure”. Tuning to the tower myself, I was to discover that pretty much the entire airspace surveillance system was down; Approach Control, Area Control, the works. Effectively, the whole of the Croatian ATC – with the exception of the individual Towers – had suddenly gone completely blind.

The issue that had caused the problem was later reported to be a leak in the Area Control Center main building, which had allowed rainwater to make it down into the surveillance system’s power supply, shorting it out instantly and plunging the ACC into darkness. While still unconfirmed officially, this had already sparked some local controversy, especially given that the building was purpose-built (at great cost) and commissioned only nine years ago…

EDIT: the cause was later revealed to not be just a mere leak, but a torrent of water that had suddenly flooded the master electronics room (located under the main ACC building). Subsequent reports had put the depth of the water there at between 1 and 1.5 meters…

A far more immediate problem though was the effect this failure was having on the flow of traffic through the country. Unlike its larger neighbors, Croatia has only one FIR – Flight Information Region, the area in which ATC provides its services – which covers its entire territory, and which is further subdivided into six “sectors” for easier management. However, all of these sectors are controlled and managed centrally from the same location, the ACC building at ZAG. With it out of the picture, there was no means to provide any form of control within the country’s airspace, leading Eurocontrol to impose the so called “zero flow rate” *.

* a common misconception is that a zero flow rate is equal to airspace closure. This is not so. When the airspace is closed outright, no flight is allowed to operate in it, be it an airliner, bizjet, private, IFR, VFR, training or any combination thereof. With a zero flow rate on the other hand, Eurocontrol’s Central Flow Management Unit (CFMU) simply does not approve any IFR flight plans that cross the target airspace. So, while the big birds were not allowed in, I could have taken my Skyhawk and gone flying without problems (apart from the rain obviously 🙂 ).

The first of Eurocontrol’s “non-availability” messages for Zagreb FIR (LDZO).

Eurocontrol’s Network Situation snapshot showing the average delay per FIR. Taken during the peak of the storm, it shows that even before the ACC failure the weather was beginning to have a severely adverse effect on the traffic picture.

By the time all flights had left Croatian airspace – or diverted to nearby airports – we’d gotten a scene we haven’t seen since the eruption of Ejyafjallajökull back in 2010… and right in the middle of one of South-Eastern Europe’s busiest corridors.

Activated at 13:40 UTC (15:40 local), the restriction was initially specified to last until 15:40 UTC, but was in the event extended to 16:40 and then finally 17:00. With the ACC restored to a minimal operational status, the restriction was lifted at 17:03, allowing traffic to resume using Croatian airspace. However, with the impetus being the get up and running as quickly as possible, the ACC had resumed operations with just three of its six sectors operational, each running at just 25% capacity – with expected effects on delay times…

50 minutes into the resumed operation, the delays were still in excess of 45 minutes. However, the priority was to get the flights on the ground back into the skies, as well as smooth out the flight paths of aircraft swerving to avoid both the storms and Croatian airspace.

Within the hour, all six sectors would be up and running, though still at just 25% of their nominal capacity. However, as the technicians worked their spanners off in the ACC, delays had started steadily dropping up until 21:00 UTC (23:00 local) when they dropped below the 15 minute mark and Croatia became grey again 😀 .

Other effects and consequences:

Unsurprisingly, Hungary had borne the brunt of the traffic diverted around Croatia. The high volume of aircraft suddenly crowing their airways – combined with the cyclone’s continued northward path – would cause a cascade effect, causing delays on par with those experienced in Croatia at the start of the storm (glowing bright red on the Network Situation snapshot). However, with only the west of the country affected, things had soon stabilized and delays dropped back to more manageable levels 🙂 .

Back at ZAG, other buildings had also suffered during the downpour. Drainage canals swamped by the sheer volume of water were responsible for the partial flooding of TWY F, ZAG’s only parallel taxiway and the only way to get to the RWY 23 without backtracking along the runway. The passenger terminal had suffered the same fate, though I’m told the flooding was on a very small scale and quickly taken care of…

Photo Report – Exercise Jackal Stone 2012 Preparations @ Lučko

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While our placid little airfield generally deserves the epithet of “the airfield at the edge of town” – despite what has been written here over the years 😀 – it does occasionally have its bright moments. Due to the relatively poor condition of its grass runway – among other issues – precluding the landing of any “serious” fixed wing aircraft, these tend to occur only when something rotary is in town, like the previously photographed US Navy Knighthawk or Bundespolizei Super Puma.

However, while these very welcome one-of visitors do make for a pleasant change of tempo – often becoming major attractions in their own right – they hadn’t really prepared us for the miniature assault fleet that had pitched up camp on the military apron between 8 and 12 September… 🙂

Jackal Stoned

In town to participate in the annual Jackal Stone multinational military exercise – this year starting on 13 September – this fleet had included no less than four transport helicopters (nothing to sneeze at when Lučko is concerned!), and even a supporting Cessna Caravan that had occasionally popped into the field on general transport business. And while their numbers alone were enough the cause widespread interest, their composition – once confirmed by a quick search on the Net – had elevated them to “must photograph at all costs” status :D.

The “less interesting” pair – using the term lightly – were two already familiar US Navy Sikorsky MH-60S Knighthawks, pretty much identical to the example that had visited us a couple of months back, save for being equipped with turret IR cameras on their noses.

Laden with soldiers, “Jackhammer 81” is seen lifting off from the military apron for another afternoon mission. Operating mostly during sunset and at night, all four helicopters had spent their time here flying training missions and deployments in advance of the Jackal Stone 2012 exercise

“Jackhammer 81” (left) and “Jackhammer 82” (code 166347) are seen blasting out of the field for an afternoon mission in the hilly Zagorje region north of Zagreb. Operating entirely over Northern Croatia, these flights had caused significant disruption to the normal flow of GA traffic, with exercises held in temporary prohibited zones established right on – or very near to – the most commonly flown cross-country routes

Far more interesting by any measure – objective or otherwise – were the “big guns”, two US Army Boeing MH-47G Chinooks. Significantly more potent than the stock transport CH-47s, the MH-47G is a dedicated special operations model, conceived and designed on the back of lessons learned during special forces deployments and insertions in Afghanistan and Iraq. The rarest – and among the newest – of all Chinooks, these models carry virtually no external markings (apart from faint titles and an incredibly-difficult-to-find serial) and sport a distinctive matte black finish that makes them impossible to photograph effectively in all but early morning light 🙂 (which had presented a slight problem for yours truly, since none of them had actually operated during the early morning).

A very famous silouette air taxiing back to the military apron after a special forces rappelling exercise. In addition to significantly improved avionics – including full night vision gear – the MH-47G also comes equipped with a slightly conspicuous refueling probe. Long by necessity – to prevent the front rotor from slicing through the refueling hose – the probe can most often be seen plugged into the KC-130 dedicated tanker, or on occasion even the MC-130 Combat Shadow, the Herc’s special operations support version

Caught in some fantastic light, “Crazy 21” is seen repositioning itself towards the helicopter start gates for a late afternoon mission with sister ship “Crazy 22”. Brutish looking machines, they’re amazingly quiet and (subjectively) make less of a racket than the CroAF’s own Mi-171s

Forming up at the start gates, “Crazy 21” and “Crazy 22” made for a sight that even my friends in the States wholeheartedly assure me is an incredibly rare sight – two special ops Chinooks at the same place and the same time, rearing to go

Of course, being the hopeless GA enthusiast that I am, both of these incredible – and incredibly rare – machines were overshadowed somewhat by a brief, five-minute visit of one of my favorite prop singles, the Cessna Caravan :D. The first one I’ve ever seen in person – which says much about the traffic at Lučko – this specific example belongs to the military U-27 family, operated in this instance by the US Army. Based on the stock 208B Grand Caravan, the U-27 differs mostly in its more spartan interior fittings – suited to its military transport role – and the absence of the imposing cargo pod seen on many civil versions…

What is probably the first Caravan to ever visit the field, “Army 1276” is seen rolling in along (the very uneven) taxiway A to pick up some foreign journalists covering the pre-exercise maneuvers. In a (fully justified) slap to Lučko’s infamously rough runway, even this off-road, rough-and-ready machine had exercised due care and caution during takeoff and landing

Finally up close – and I must admit the 208 is quite a bit larger than I had imagined! Interestingly though, the aircraft is surprisingly quiet, no louder than a stock 172 or 182 (which had operated out of the field for the whole time). Of note here is the slightly offset propeller (and engine) axis, intended to partially compensate for the prop’s relatively high P factor

Photo Report – Can’t Snow Me Down: A Winter Shakedown at Lučko

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While this year’s game of Lučko Roulette – trying to fly your aircraft out before the field closes due to bad weather 😀 – has been generally successful, the constraints of the limited apron capacity at Zagreb Intl. meant that a few aircraft (notably those with a hangar above their heads) have nevertheless remained at the field. Faced with the prospect of them sitting idle in sub-zero temperatures until the runway melts and dries out – which can take awhile – the “flight ops department” of Aeroklub Zagreb had once again decided to clear out its hangar and give everything in there a thorough shakedown :).

While at first it may seem a bit pointless to fire up the engine, proverbially rev the bolts off it, and turn it off again without going anywhere, the procedure does have a host of beneficial effects. Primarily and most importantly, it allows the engine to periodically clear itself of all the deposits and substances that can (and will) accumulate in its piping and systems during a long stay on the ground. If left to settle firmly over the winter, these substances – the most common being carbon deposits on the spark plugs – can seize and/or severely damage the engine when it is finally started; but, if anticipated during these shakedown runs, they can be easily removed by simply revving the engine to raise the temperatures in the cylinders until the deposits burn away and the engine starts to run smoothly.

The same also applies to the oil system – which, on the face of it, is the very system that allows the engine to run in the first place. And while winter temperatures in Zagreb rarely go below -15 Centigrade – well above the temperature at which winter-grade oil thickens dangerously and freezes – the system itself has a number of moving parts (the most important being the oil pump) that are also susceptible to the above stated. Running the engine at a higher throttle setting allows the pump(s) to run up to speed and warm up, breaking off any deposits on their blades and bearings. In addition, the flow of oil through the system picks up any impurities that might have settled on the bottom of the pipes and deposits them on the (removable) oil filter, thus cleaning out the entire system.

The fuel system too needs some attention, mostly to purge it of water deposits that – inevitably 😀 – form in its low points. Being heavier and thicker than Avgas, water tends to sink and collect at the bottom of fuel tanks and pipes – and if ingested into the cylinders in a large enough quantity can cause a lot of (very expensive!) damage. By its very nature, water is incompressible; and when it winds up in the part of the engine DESIGNED to compress, something has to give… which is usually the piston 😀 (however, there are systems that inject water into the cylinders on purpose – but this is on a controlled and measured basis. These systems – usually known as Anti Detonation Injection, or ADI – squirt a small amount of water into the inlet pipes, which then absorbs excess heat in the cylinder and prevents uncontrolled spontaneous ignition, as well as providing a significant increase in power… as seen on the P-47 Thunderbolt 🙂 ). Thankfully, the unwanted water can be easily removed from the system by draining the bottom of the fuel tank using a special valve, as well as dumping the contents of the pipes at the low point of the system – usually just after the fuel selector normally mounted on the cabin floor – using a small lever in the engine bay.

Draining fuel from a wing tank drain valve on a Piper or Beech. A small amount of fuel is drained into a cup or bottle and checked for water, which would show up as a transparent sediment on the bottom – one of the reasons why Avgas is colored 🙂 (the other being that fuels of a different octane ratings are colored differently for easy visual recognition) (photo from: cdn.wn.com)

Less visible benefits of these high-power runs also include recharging of the battery, which will – again inevitably 🙂 – discharge or even go flat after awhile (as had happened to our Piper Warrior). The ready supply of electricity from the alternator allows too for a check of the aircraft’s other electrically-powered systems, such as the radios, flaps (where available), lights and so on…

However, before all of that, you first have to take care of one small detail – pushing everything out into the open :D. Normally this is not a problem – but our efforts that day were a tad complicated by the inch or two of fresh snowfall from the night before… 🙂

A welcome splash of color on an otherwise completely white Lučko. While it did us no favors with the main task of the day, last night’s snow – still ongoing at the time this photo was taken – did at least provide for some nice photo opportunities!

The art of icing? 😀 Even more ironic given that this specific aircraft is usually based on the warm and sunny island of Brač on the Adriatic coast 🙂

Preparing to fire up 9A-DDA, AK Zagreb’s very-rarely-seen Piper Warrior. Not having flown for ages, a flat battery is pretty much a permanent state on this aircraft, requiring the use of a Ground Power Unit for starting

9A-DBS doing its best to clean up the airfield :D. Despite the odd childish impulse to gun the engine and see how big a cloud you’d create, these high-power shakedown runs have to be done with caution – especially on an aircraft like the Super Cub. With its high power-to-weight ratio, an unsecured Super Cub could – despite the brakes being locked full on – easily start sliding forward on the snow. To protect against that as much as possible, the wheels need to be secured with chocks, preferably dug into the snow (and if possible, it’d be a prudent move to tie the aircraft down)

Complete and total whiteout as 9A-HBC lifts off from the main apron. Sporting a cabin full of Christmas presents – and even a helicopter-pilot-turned-Santa 🙂 – HBC was the centerpiece of a small celebration organized for the children of the Police helicopter squadron pilots. Now, what would an aviation-oriented kid have thought of that? a) look, Santa has flown in from the North Pole!, or b) look, Santa has been arrested by the Police for flying a multi-deer sled without a valid JAA license! 😀

A modern replica of the first aircraft designed and built in Croatia – the Penkala P-3 of 1910 – looking gorgeous out on the snow during an ad-hoc photo shoot :). Not an exact one-for-one copy, the Cvjetković CA-10 Penkala has been modified with today’s aerodynamics knowledge (since the original hadn’t so much flown as hopped along) and an 80 HP Rotax, replacing the original 5-cyl radial :). Normally protected from the elements in the field’s various hangars, this was one of the few times 9A-XCA – as it had been registered a few months back – was seen out and about since September’s Lučko Airshow

Oil, smoke and fire as the I-3’s big M-14P radial labors into life. Not having ran for almost three months, the engine had normally put up quite a fight, spewing liberal amounts of oil from the exhaust during a number of previous startup attempts… also, like virtually all Russian/Soviet light aircraft, the I-3 uses a pneumatic system to start the engine – a system that normally depletes itself when not in use. To fill it up before the engine’s own compressor takes over, an external air source – such as the compressed air cylinder seen here – is necessary

Creating its own weather out back as the big prop revs to its maximum RPM. By the time the 10-minute run was finished, DOG had managed to clear half the apron 🙂

Short Photo Report – Multi-Engine Fun

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Having been warming the chair with my ATPL studies for a good part of the month – not the most fulfilling of activities I must say, especially since it’s 35 Centigrade outside… and probably more inside – I was naturally through the roof when my name finally came up on the multi-engine training roster :). Eager to fly (and photograph :D) any day of the week, I was doubly excited this time, since I’d finally get to try my hand at the university’s sole Piper Seminole – in a nutshell my first Piper, first low-wing and first twin 🙂 (greetings from fixed-gear Cessna land!).

The aircraft in question is 9A-DZG, a trusty 1978 normally-aspirated Seminole that has pretty much passed through the hands of almost every multi-engine qualified pilot in Croatia in the last few years. Powered by two 180 HP Lycoming O-360s, it may not be the most exciting or high performing aircraft in the world – but after half a dozen Skyhawks, it is pretty much the top of the line :D.

Training-wise, first up was the Multi Engine Class rating, done under VFR (thankfully we’ve been having some excellent VMC lately). This pretty much revolves around the most important skills multi-engine aircraft require – the ability to fly on only one of those engines. As well as zone work – to familiarize ourselves with the aircraft and its handling characteristics – the course includes a broad range of “one engine inoperative” (OEI) situations, such as in cruise, during landing, during takeoff, after takeoff and on go-around. Lacking any navigation elements (such as IFR flying), we could have done the course at Lučko or Pleso – but given that they do have a lot of traffic nowadays, and OEI ops tending to disrupt the normal traffic flow, we decided to head somewhere else, most often the coast :).

To compensate for the increased transit time, time we could spend on honing our OEI skills, we usually flew in pairs of two students, where one would fly outbound and do his/her training, after which we’d land and swap places. The other student would then do a similar set of exercises and fly the return leg, while the backseater would observe and learn… and in my case, snap a photo or two :D.

Heading for Rijeka (LDRI) on the coast, climbing to 5500 ft. Given the recent heatwave, forming cumulus clouds were a common occurrence. Many never developed far enough to carry any rain, but the few that did ended up wreaking havoc all round... (at Lučko two Skyhawks - including one I flew on my IFR course - were damaged when the sudden wind tipped them onto their wingtips)

A busy view up front as we near the first substantial clouds near the Velebit mountain range. Blowing perpendicular to it, the week's north-easterly wind was the perfect trigger for the formation of vertical clouds

On approach to Rijeka's RWY 32. Situated on Krk, one of the largest islands on the Adriatic Sea, the airport's comparatively low traffic volume, a long runway and an abundance of radionavigation aids (not to mention it being just 30 minutes flight away) makes it a popular training destination 🙂

On any of the Cessnas I normally fly, this sight would be cause for immediate - and considerable! - alarm :D. However here, with the other engine still pulling, you can breathe a bit easier :). Normally, engine-out training is simulated - with the throttle on one engine retarded - but in some cases the instructor will actually shut the engine down completely. The propeller is then feathered (turned parallel with the airflow) to keep the drag - and all of its unwanted side-effects - down to a minimum. Also, the small mirror on the cowl is provided for the pilot to visually confirm that the nose gear is down (generally, if the nose gear is down, probably the mains are as well).

Encountering a spot of rain on the way back with me at the controls. Photo courtesy of the aircraft's autopilot :D. While I generally prefer hand-flying - sharpens the skills - a (finally) functioning autopilot was just too good an offer to pass up 😀

Still more working atmosphere on day 2 :). Flying back home from Zadar along the islands, the long - but far more pleasant - way around. Capitalizing on the fine weather, the military had activated several of its training zones - which basically cover the entire Velebit range - so to avoid close encounters with supersonic MiG-21s, we were routed around them

Aaah, the sea! Always a beautiful sight for us landlubbers :).

DZG ticking itself cool - as much as it could have, given it was +40 on the apron - at Banja luka airport in neighboring Bosnia :). For our final multi-engine class flight, we'd decided to go international - which, to add to a list of firsts, this was my first ever international flight as pilot :). Succumbing to the traditional culinary delights of Bosnia - "čevapi" for any locals who might read this 😀 - we decided to stay in town for lunch. In the end, this turned out to be by far the tastiest training flight I've ever had!

Some more dramatic weather at 6,000 ft on our flight back to Zagreb

Photo Report – Novespace Zero-G A300

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While idly browsing the BBC News website a few days ago, I came across an interesting article featuring Mr. Tim Peake, the first UK resident accepted into the European Space Agency (ESA) as an astronaut-trainee. A former Royal Army helicopter pilot, he has made a rather unusual jump into spaceflight, becoming part of new multinational European crew – currently undergoing microgravity and zero G training – slated to man the expected 2013-2014 mission to the International Space Station.

Alongside Mr. Peake’s fantastic personal achievement, the centerpiece of the article – posted here – was the unusual Airbus A300 used for the group’s training, getting a new lease on life as a zero G simulation platform. And having had the great privilege of visiting the said aircraft at last year’s Paris Air Show, I thought I could just as well do a short feature on it, to break my single-engine piston trend of late :).

Operated by the French company Novespace on behalf the government space agency Centre National d’Études Spatiales (CNES) and ESA, F-BUAD is a very interesting Airbus. A very rare first-generation A300B2-103 from 1973, it is the third A300 – and the third Airbus of any sort – ever produced. The first production-standard A300, it is also the oldest Airbus aircraft still flying, which is, given its current age and mission, a more than impressive testament to the design’s durability and reliability.

Since the BBC article explains its mission and flight profile in greater detail than I could achieve here – including a handy graph that says a thousand words 🙂 – I’ll skip that and head straight for the juicy bits: the photos :D.

Banking left for a "dirty" low pass during one of the show's trade days. Despite being built 37 years ago, F-BUAD still looks sharp, courtesy of a thorough maintenance program carried out by Sabena Technics in Belgium. Lacking the later models' central fuselage fuel tank, the B2-100 series were the lightest of all A300s, which made them suitable for various test work - indeed, at one point in its life, F-BUAD had served with General Electric as an engine testbed

Size does matter? 🙂 Dwarfing the small CH650, F-BUAD easily dominated this part of the ramp. Even by airshow visit standards, this aircraft was absolutely spotless!

According to an aircraft register I've found, F-BUAD has never flown with an air carrier in regular commercial service. Owned for most of its life by Airbus, then GE and now Novespace, it appears to have been used exclusively for promotional and test flights, which probably means that - despite its "advanced" age - it is one of the lower-time A300s remaining...

While it still looks like the run-of-the-mill A300 outside, inside it's a different story. From the second passenger door back, the cabin has been cleared and lined with soft padding. Configured depending on the needs of the mission (which can also include experiments requiring microgravity), here it is set up for astronaut training - which, for very understandable reasons, includes covering up the windows 😀

Front of the doors, the cabin looks more familiar, and is intended to accommodate both the "passengers" and tech staff - as well as additional crew if required - during non-mission flight phases such as takeoff, landing, climb and descent. A similar arrangement is also set up in the back of the aircraft

Quite understandably, almost every panel and station on board is equipped with a G meter 🙂 (small multicolor gauge in the center). Though missions are flown between 0-1.8G, the safe limits for the aircraft are -1 to 2.5G, leaving plenty of room to spare. The station pictured is (I think) the main mission control station, used - among other things - to monitor the aircraft's flight path. Note also the floppy disk drive above the left screen 😀

A view backwards showing how commodious an airliner actually is when you remove the stuff inside. At Paris, short tours were offered to a limited number of people per day, one of which - combined with press accreditation and my mediocre knowledge of French 😀 - had allowed me to snoop a bit more around this fantastic aircraft

Now this is a cockpit! 🙂 The piece de resistance of my extended tour, this was my first visit to a widebody flight deck (excluding the DC-10 I was too young to remember). Flown like all early A300s with a crew of three - including a flight engineer - F-BUAD has however been modernized with two Garmin IFR-approved GPS units, a TCAS system and a Mode S transponder - all needed to make the aircraft compatible with today's congested air traffic system. It's current mission too required some upgrades of it own, including additional reinforced controls 🙂

Further additions include omnipresent G meters, seen here to the right of the artificial horizon, provided for both the pilot and copilot. As I've been told at Paris, the aircraft is normally flown by three experienced test pilots of the French state arms procurement company. Because of the high stick forces during parabolic flight, both the pilot and copilot have their hands full with the yokes (hence the reinforcements), leaving the third pilot - who acts as the flight engineer - to operate the throttles. Due to the sheer physical effort required for this maneuver, the crew rotates between stations (pilot, copilot, engineer) every 2-3 parabolas. A standard astronaut training zero G mission could see anything up to 20 parabolas in one flight, giving a total zero G time of about 7 minutes

As always a bewildering sea of dials and switches, the flight engineer station is not for the weak of heart :D. Replaced on the more modern A300-600 by a comprehensive electronics suite linked to an EFIS system, this station provides thorough insight into the minute workings of each part of the aircraft. Despite not being manned by a "proper" flight engineer during parabolic flights, all three pilots - being some of the best test pilots in Europe - had naturally received thorough training in the A300's systems

And finally, to illustrate how all of this comes together, I’ve found three suitable YouTube videos  – the first of which was played in the aircraft itself at Paris – that show what no amount of words can :):


Photo Report – Banner Towing Above Zagreb, Feb 2008

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Looking back through all the articles I’ve posted here, I saw I’d made quite a few boastful promises about topics that in the end never materialized :). So, still waiting for something to happen here in the present, I’ve decided to clear my topic backlog, starting of with my first true air-to-air photo experience – banner towing :).

1. Fly-by-wire

While banner towing in flight seems – and is – a pretty straightforward affair, down on the ground, getting the thing airborne, is a different story altogether. Despite popular myth, taking off with the banner attached causes more problems than it solves, particularly on uneven grass runways such as at Lučko – where it would promptly be torn off and shredded, not to mention all the adverse effects it would cause for the unlucky towplane.

To get around this problem, somebody somewhere at some point had borrowed a WW2 method – why not snag the banner inflight? To quote Jeremy Clarkson of Top Gear, “How hard can it be?” :D. The idea is that the banner’s tow cable is suspended between two poles at some height above ground, usually about 2-3 meters. The towplane would then, trailing a hook on another cable, come down low and snag the banner, lifting it off the ground as it climbs away. Those of you who have seen images of Dakotas picking up troop transport gliders during WW2 will immediately see the similarities.

A visual illustration as 9A-DMJ goes down for a snag. Note also the hook cable attachment assembly at the base of the tail. Sorry for poor quality, but for the life of me I can’t find the original, so I had to take this one of my Facebook photo gallery 🙂

9A-DDD going down for the pickup. The approach is usually flown at about 70 knots and 10 degrees of flaps in the Skyhawk. The speed has to kept at around that figure – any faster and the sudden drag and inertia of the banner will stress the airframe unnecessarily, while any slower means that when the banner yank does come, it can pull the aircraft very near the stall (with the added complication of the engine run-up delay at low throttle settings)

During taxi and takeoff, the hook end of the cable is carried in the cabin by the second crew member. Once airborne, the hook is lowered into the airstream until all the slack in the cable is picked up

A frontal view on a recent mission

Side view. Note the reinforced cable mid-section that acts as a sort of bungee to absorb some of the forces and inertia during pickup

A nice and clean hook up. Sometimes the hook and banner cables can tangle up, with the banner towed not by the hook, but by the tangled cables. This can be quite problematic if the knot untangles in flight – the banner then freely falling away – the reason for which there is always a “ground spotter” with a radio station observing the pickup. If the cables tangle up, the SOP is to jettison the entire thing and start over

Banner snagging being pretty much a visual art, it is not uncommon to miss the banner cable altogether (by anything from inches to meters). In this case a go-around is executed for another attempt

After a successful snag and climb away, the rest of the flight becomes routine – with careful monitoring of the engine temperature gauges that is. Despite most banners weighing not more than 20-ish kilograms altogether, their large surface area creates a lot of drag. This necessitates a higher throttle setting and if not flying fast enough for sufficient engine cooling, it’s not really that difficult to overtemp the engine.

With the mission completed, the banner is then dropped from the aircraft during a slow, low pass. The release itself depends on the hook and tow mechanism, but in our case the whole cable – all the way from the attachment hook below the tail – is jettisoned, to be untangled and separated on the ground. This leaves the aircraft free to perform a normal, unencumbured landing.

Note that the entire cable is released, with only the fixed tail hook remaining in place. For many pilots, hitting an exact bull’s eye with the cable is almost a sport 🙂

2. A skiing competition, a casino and some fog

While all of the above is fine and dandy, back in the winter of 2008 my aeroclub had gotten a bit ambitious :). The mission was to tow the largest banner ever towed in Croatia, measuring 5 x 30-something meters. Doesn’t sound like much the first time you hear it, but in effect that’s a 150 square meter airbrake – more than three times the surface area of my apartment!

The venue was the Snow Queen skiing competition held on the northern slopes of the Medvednica mountain between 15. and 17. February 2008. And the customer – a large casino near Šentilj, on the border between Slovenia and Austria. Connection – I see none, but it didn’t matter since it got us up in the air with no questions asked :).

Fortunately for our towplane, the temperatures had plummeted during the weekend, down to around -15 Centigrade at the altitude at which we had expected to do our run. (round 2,000 ft) With such a draggy mass behind it, and the requirement to fly at 70-75 knots so people on the ground could actually read what was being towed, engine cooling was a serious issue, so the lower the outside temp, the better.

Now, the original plan was to do a run on the 15th, with DMJ acting as the towplane and DMM – with me on board – acting as the photo ship to immortalize the whole event :). However, even before leaving the ground we had run into a small problem…

Going up! As you can see, the weather was, for our intents and purposes, crap. It was still okay here in the open, but north of Medvednica – where the wind kept blowing moisture up the slope – it was downright awful

Rounding Medvednica from the west near Zaprešić. As you can see, the weather was steadily deteriorating, but undaunted we went ahead to see what’s what 🙂

In an ironic twist, our 100 HP Cessna 150 turned out to be faster than the 210 HP Reims Rocket, so we had to orbit around a bit to let DMJ gain some distance before our photo run 🙂

Lining up for another run, showing just how large that banner actually was :). While weighing just under 20 kilograms, its sheer area caused so much drag that DMJ – lightened, with half-full tanks and one person on board – needed to be run at near maximum continuous power

Closeup of DMJ while skirting the northern slopes of Medvednica. The visibility was still good compared to what we hit a few minutes later…

Pretty soon however we ran into problem #2. The ski track which we were supposed to fly over – a track very popular with local skiers – is quite narrow and tucked away between two mountain crests. To follow it, we’d have to fly up the through, climbing continuously, in formation and poor visibility, with one aircraft that was underpowered and another that was barely hauling itself as it was. Realizing conclusively that it would all end in a pretty big accident, we turned round and scurried back toward Zagreb, to try and at least save some of the mission there.

Following one of the city’s fast peripheral roads, with visibility mercifully increasing

Keeping low above town. Though the minimum altitude for flyovers is 2,000 ft – about 1,600 AGL – during banner-towing missions this can be lowered by approval. We may have taken that a bit too seriously… 🙂

A wide view of the historic city center, with the Cathedral and old Kaptol fortifications easily identifiable

So far so good as far as the towing was concerned, but my photo session was turning into a bit of a mess. The poor visibility and light, coupled with the turbulent downdraft from the mountain, meant I couldn’t really do much with my unstabilized telephoto lens, so to conserve fuel, we turned for home, leaving DMJ to fly two more short runs above town.

3. Cold, cold, cold!

While the results of the first run were mildly disappointing to say the least, the designated god of aviation – Murphy 😀 – allowed us to make it all up on the 17th, when the weather finally cleared. Beautifully clear skies, still air, visibility one can only hope for and an even lower temperature were just too good to pass up, so we  saddled up and full of optimism decided to give it another shot…

A spirited low-level departure above the field to kick off an excellent mission!

Now this is more like it! 🙂 Shot with the window open – and -17 C outside – with a wide angle to give an impression of size and distance

What a beautiful setting for a photo shoot! Looking north above the northern foothills of Medvednica, with the track right behind us

Because the shoot was going so well, Mr. Murphy decided to intervene again and as we neared the ski track, our coordination sort of broke down :). The problem was that to get good shots, we had to fly to the left, above and somewhat in front of DMJ. This meant that my photopilot couldn’t see DMJ because I was in the way, DMJ couldn’t see us because it’s wing was in the way, and the need to maneuver around hills and keep station above the track meant that our graceful aerial ballet quickly degenerated into a left-footed cha-cha-cha as we tried to keep our little formation together.

My favorite shot of the day, just as DMJ is about to pass below us – without actually seeing us until we were right on top of it 😀

A beautiful day, the throaty roar of the engine, and playing catch above the mountaintops. Can it get any better than this? 🙂

With my hands trembling and my skin cracked from the cold – -17 C at 70 knots in propwash without gloves, absolute genius on my part – and our mission completed (relatively, given there were few spectators out :D), we set course for home. As before, DMJ went to do a circuit of the town, while we proceeded directly to Lučko, so I could catch a shot from the ground as well 🙂 (I was having a photo field day).

Turning final for RWY 10 after one of my best photo experiences to date 🙂

DMJ inbound for release. The angle exaggerates the size of the banner, but it looks cool 🙂

Unfortunately, getting some “inside” photos from the towplane is a bit difficult and impractical – mostly because both crew are busy with other things… and there’s honestly not much to see; most of the time the banner itself is outside the the crew’s field of view, so it pretty much looks far better from the outside :). I’m also hoping to get a good, systematic sequence of the pickup, but that will have to wait for some warmer weather… 🙂