Photo Report – the Force 450 Gale: Serbia’s SILA 450 UL

By me
All photos me too, copyrighted

Back in 2012 while on a short visit to Belgrade, Serbia, a friend and I had decided – in true Achtung, Skyhawk! tradition ๐Ÿ˜€ – that we might as well do some proper sightseeing and head out to the old UTVA aircraft factory in Panฤevo, a couple dozen kilometers up the main road. Once the powerhouse of Yugoslavia’s aircraft industry, this enormous factory was, among other things, responsible for the most ubiquitous light aircraft in the country’s history – the much maligned UTVA-75 – a machine that, despite all its faults, had quickly come to dominate aprons across the land (and the occasional newspaper accident column ๐Ÿ™‚ ). Singularly robust machines – the DC-9s of the light single world – many 75s continue to soldier on even today, with a select few also having seen combat action as impromptu light attack aircraft during the turbulent 90s.

By 2012 however, the factory’s shine had long gone and its successes largely forgotten. A dilapidated ruin that had been heavily damaged during the 1999 NATO air strikes, the factory exists today as a rump facility at best, fiddling with a handful of low-scale projects on a thin shoestring budget. While a sad sight in its own right, the view that had greeted us had also represented a striking metaphor for former Yugoslavia’s aviation industry as a whole – and not least of all for the flat spin it had taken during the country’s violent disintegration. Largely scattered across the land, it would – unsurprisingly – take a crippling hit at the start of the 90s war, losing its supplier and customer bases virtually overnight. The widespread financial disasters that had succeeded the conflict never really gave the industry the breathing space it needed to recover, turning the whole aviation landscape into an archaeologist’s playground of abandoned factories, forgotten companies and rotting gate guards.

May the Force be With You

But, in what is a long-overdue resurrection of the region’s large(r) scale light aircraft industry, one manufacturer had nevertheless managed to part the red tape and defy the economic odds, adding its bit to putting the industry back on the proverbial map ๐Ÿ™‚ . The company in question is Aero East Europe, a small but efficient unit operating out of a historic workshop in the southern town of Kraljevo, and nowadays well on its way to building up a respectable regional reputation for its original STOL ultralight designs. Fighting its way up the sales ladder against various copies and modifications of the legendary Zenair CH-701, the flagship of the fleet is the 450 kg / 992 lbs SILA 450, an example of which had popped into Varaลพdin Airfield (LDVA) on 18 January for a brief promotional visit. No prizes for guessing whether I was there… ๐Ÿ˜€

YU-A102 nice and clean - and ready for its first flight of the day

YU-A102 nice and clean – and ready for its first flight of the day.

Apart from a name that tends to raise eyebrows among Southern Slavic language speakers – literally meaning “force”, but in reality just short for Serbian Industry of Light Aircraft – the 450 appears largely unremarkable at first glance, sharing much of the visual cues of other high wing STOL ultralights. Its specs too (at least on paper) are not enough to set your blood racing; compared to the ICP Savannah XL, the 450’s latest iteration – the 450C – can carry five kg / 11 lbs less, cruises just 6 knots faster, and needs five meters / 16 ft less to take-off and 10 meters / 32 feet more to come to a full stop.

Up front there’s a 100 HP Rotax 912ULS whirling a three-blade ground-adjustable prop – hardly an exciting feature – while equipment-wise you’re looking at electrically actuated flaps, a ballistic parachute recovery system and an optional glass cockpit… essentially the same kit you can get from any other manufacturer out there.

However, once up close and past the preliminaries, a startling number of interesting – and unusual – details begin to emerge ๐Ÿ™‚ . The wing, for example, is a mechanically simple affair that makes do without the slats, slotted controls and vortex generators seen on the CH-701 and its spin-offs. Instead, the 450 uses a plain but very thick airfoil profile that simplifies the wing’s internal structure, while at the same time preserving low speed handling and performance and noticeably reducing drag (which will always be high on a STOL wing). Indeed, the 450 can boast a lift-to-drag* ratio od 1/15, quite a bit up from the 1/11 of the Savannah XL (a number also shared with, of all things, the Cessna Skyhawk ๐Ÿ™‚ ).

* a common measure of the aircraft’s aerodynamic efficiency, the lift-to-drag ratio – often abbreviated to L/D and sometimes also called the “finesse” – in effect shows how much horizontal distance would the aircraft, unpowered and gliding, be able to cover for each unit of vertical distance lost. The SILA’s 1/15 for example denotes that for every foot of altitude lost, it would be able to glide 15 feet in still air. Scaled up a bit, this means that for a 1,000 ft altitude decrease, it would cover 15,000 ft horizontally (roughly 4.5 km / 2.5 NM). Apart from quantifying the aircraft’s overall aerodynamic prowess, this number also comes in handy during flight planning, allowing you to pick out – in advance – suitable landing fields along your route for the event that your engine decides it has grown tired of working ๐Ÿ™‚ .

Another interesting feature are the wingtip fences, which prevent high pressure air below the wing from spilling over the wingtip into the low pressure air above (similar to the winglets of a larger aircraft). Left uncontrolled, this spillover would eventually detach from the wing in the form of turbulence - the infamous wingtip vortex - drastically increasing aerodynamic drag. A similar setup is - uniquely - found on the horizontal stabilizer.

Another interesting feature are the wingtip fences, which prevent high pressure air below the wing from spilling over the wingtip into the low pressure air above (similar to the winglets of a larger aircraft). Left uncontrolled, this spillover would eventually detach from the wing in the form of turbulence – the infamous wingtip vortex – drastically increasing aerodynamic drag. A similar setup is – uniquely – found also on the horizontal stabilizer.

To compensate for the lack of slats and slotted controls at the lower end of the speed range, the 450 is fitted with drooping ailerons, which lower slightly as the flaps pass their halfway travel mark. Combined with the chunky airfoil, they give the aircraft an almost comically low minimum flying speed in the low 30-ish of knots – which was demonstrated to me graphically against the day’s stiff 30 knot headwind at altitude ๐Ÿ˜€ .

The combination had also acquitted itself well handling-wise, with the 450 displaying unexpectedly impressive flight characteristics in all regimes, high or low, slow or fast. Perhaps its biggest surprise – to a Cessna driver ๐Ÿ™‚ – was not what it could do, but the way it did it, with an almost complete lack of aerodynamic drama, pussycat stall and post-stall response, and virtually no buffeting or waywardness anywhere in the standard part of the envelope*.

* in fairness though, I’ve not had much ultralight experience, so I can’t really make an objective handling comparison with other designs… but I can however draw parallels with the similarly sized (though heavier) Cessna 150, which the 450 – in a number of comparable respects – blows clear out of the water ๐Ÿ™‚ .

Cabin Space – The Final Frontier

But, even before one gets a grip on the stick, he/she can notice a raft of other nice touches scattered all over the airframe. One that I – standing 1.93 m / 6 ft 3 in tall – can particularly appreciate is the wide and roomy cabin, almost an order of magnitude more spacious and comfortable than that of the 150. Entry and egress is unexpectedly easy from both sides, courtesy of an upward hinged door and wing struts positioned behind the doors, at the joints of the main gear legs.

A

Wide doors and a tall door frame make for remarkably easy entry and exiting – so even types of my height won’t be going around bumping into things. The only criticism I have here is that the sticks are too tall, which makes maneuvering to sit down a bit awkward if you have long legs (and can lead to some minor interior scraping if you’re a bit clumsy).

Once

Once in, there’s plenty of room to stretch your legs and sit upright… though at the limit of the latter in my case. Simple and uncluttered, the cockpit of YU-A102 sported only a very basic avionics fit, tailored to the needs of the German market. Interesting features include the side panels canted towards the pilot, as well as the innovative system switches, which light up when activated (as could have been seen in the above video). The two guarded switches on the left panel are the magnets, while the key slot beside them is not the starter – but the battery master switch. The ominous red handle that sticks into the eye next to my knee activates the ballistic parachute system – and is also guarded for your wallet’s safety.

The view forwards in flight is pretty much on par with that of the 150; however, the large side windows, rear-mounted wing struts and smaller pillars mean the Sila excels when you want to look left, right or down. Like the Savannah, the design also features a small triangular window on the ceiling which helps with ambient lighting and provides some semblance of upward visibility.

The view forwards in flight is pretty much on par with that of the 150; however, the large side windows, rear-mounted wing struts and smaller pillars mean the SILA excels when you want to look left, right or down. Like the Savannah, the design also features a small triangular window on the ceiling which helps with ambient lighting and provides some semblance of upward visibility.

There’s other evidence of the design having been thoroughly thought out. The ailerons and elevators, for example, are actuated by pushrods rather than conventional cables (which are retained for the rudder only), giving a quicker control response and eliminating a number of maintenance issues (delaminating cables being one of them). The space behind the panel is remarkably clean as well, with plenty of legroom and none of the wiring, piping and mechanical whatnot frequently found on Cessnas and Pipers. And – what had caught my attention right from the start ๐Ÿ™‚ – there’s a small double L mount hanging from the ceiling just aft of the windshield, allowing you to securely deposit your headphones when not in use*.

* while this is not much of an issue in the grand scheme of things – and certainly not the reason to choose the SILA over any other design – loose headphones can become quite a nuisance. In light Cessnas for example, you either have to hang them from the yoke (not the most practical solution in a small cockpit), leave them on the seat, or, worst of all, put them on top of the panel where they’re exposed to sunlight – and where their speaker magnets can play havoc with the magnetism of the compass.

These practical details continue on the outside as well. The fuel tank caps open, close and latch only with the master switch key, avoiding unintentional flight with the tanks unsecured (and, since we’re on the Balkans after all, also avoiding intentional fuel theft ๐Ÿ˜€ ). Up front, large access panels are provided on the cowl, allowing for quick inspections and repair without the need to dismantle the whole nose. And – unusually for an aircraft that has a small, light prop and barely treble digits of power – YU-A102 also came equipped with a rudder trim system, operated electrically (like its elevator equivalent) by push buttons located on the tops of both sticks.

Another interesting feature not seen on the CH-701/Savannah/similar is the cut-down rear fuselage, allowing for some semblance of rearward visibility. Two rear windows also give the cabin and airy and less claustrophobic feel. Note also the small black bag visible through the window, housing the ballistic parachute.

Another interesting feature not seen on the CH-701/Savannah/similar is the cut-down rear fuselage, making for decent rearward visibility. The two rear windows also give the cabin a brighter, airy and less claustrophobic feel. Note also the small black bag visible through the window, housing the ballistic parachute.

Certifiably good?

But, while everything said so far sounds very enticing, one other important item still remains – the naughty business of price ๐Ÿ™‚ . What you’d eventually pay for one of these naturally depends on what equipment options you’d go for, but the base model – broadly identical to YU-A102 – would set you back about EUR 62,000. Around 30,000 more would get you the top-of-the-line version, equipped with digital avionics (a Dynon Skyview/Garmin G3x mix) and full interior night lighting.

From what I’ve seen while scouting through the European classifieds and various vendor sites, this is a fair bit (EUR 10,000+ to be exact) more expensive than the performance and engine-wise very similar Savannah XL. While at face value this does seem to be a mystery, the SILA’s higher purchase costs can be attributed to its certification ambitions,ย  having been designed to be fully compliant with the JAR VLA Part 21ย standard – while already holding Germany’s own equivalent, the LTF-UL certificate.

But, will this paper be enough to overcome the higher price – and will the aircraft’s features manage to overcome the lingering stigma of its country of origin – still remains to be seen…

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A soon-to-be familiar sight in ex-Yu skies?

Specifications:

Sila 450C manufacturer specs & detailed info

Manufacturer links:

Other links & sources:

One thought on “Photo Report – the Force 450 Gale: Serbia’s SILA 450 UL

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