Flight test: Skyranger Nynja
- Credit: PHOTO: KEITH WILSON
Dave Unwin: “I thought the Nynja a great little aircraft that offers outstanding value for money”
Words: Dave Unwin Photos: Keith Wilson
As the Nynja lifts off after a ridiculously short ground roll and soars skyward at a precipitously steep angle, I can’t help but grin. You can have a lot of fun with something like this!
Those who continue to look down on this class of aircraft might want to think again, because the modern microlight offers sparkling performance and is an entertaining, affordable flying machine. Indeed, when I’d mentioned that I was hoping to fly the first factory-built Skyranger Nynja, an associate had sniffed somewhat disparagingly, even though I knew he’d never flown one. But?as Mark Twain observed in The Adventures of Huckleberry Finn, ‘that is just the way with some people. They get down on a thing when they don’t know nothing about it.’
As Paul Dewhurst taxied the Nynja microlight towards me, I thought that actually a more apposite description would be ‘small light aircraft’, for unlike some other microlights I’ve flown, the Nynja is very much an aeroplane. Like me it is in the process of putting on weight, but unlike me this is to its benefit. More on this later.
Designed by Frenchman Phillippe Prevot in the early 90s, the original Skyranger was an object lesson in KISS (Keep It Simple, Stupid). Prevot’s intent was that anyone competent with basic tools could build it, as there was no bending, composites, nor welding involved. It was to be covered in an equally simple material; sailcloth. Easy to build, maintain and fly, more than 1,600 have been produced and there are nearly 300 on the UK register. Although there have been numerous minor improvements, fundamentally the type has changed little over the last three decades: the tail fin has been extended with a neatly profiled cuff and the wingspan has been reduced, but from a distance the Nynja still looks very much like a Skyranger
During the preflight inspection, I was impressed by the design of the aircraft and the construction techniques and materials. Since 2017, Flylight has had the sole design rights and is now rightly considered the manufacturer?albeit it (along with every other aircraft manufacturer) uses myriad sub-contractors for components. The main sub-contractor is Aeros, which is based in Kiev?as is another well-known aircraft manufacturer, Antonov. Aeros makes some of the world’s best hang gliders and is expert in tube and fabric work. Many of the staff are ex-Antonov engineers. The aircraft are assembled in the UK, which I suspect makes Flylight and TLAC (The Light Aircraft Company) the only companies that can currently claim to be a British manufacturer of ready-to-fly light aircraft. Owning the design rights also puts Flylight firmly in the pilot’s seat regarding future developments.
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The airframe is constructed primarily of straight, pin-jointed aircraft grade aluminium tubing covered with a combination of non-structural composite sheets for the fuselage and pre-sewn polyester Xlam fabric for the wings and tailplane. An interesting feature (and one that flags up how speedy the Nynja is) is that the wings feature foam spacers that ensure the aerofoil retains its shape at higher speeds. All the primary controls are actuated by cables, as is the elevator trim. The tailplane is wire-braced and the strut-braced wings feature upswept winglets. An excellent option allows the wings to be folded back for ease of storage.
Earlier Skyrangers were powered by several different engines, including the Jabiru 2200, HKS and BMW R100, but these days the Rotax 912 is the powerplant of choice. Removing the cowling to inspect it requires the removal of a considerable number of screws, and while I agree with Paul that the coolant level and hoses of the liquid-cooled Rotax require checking as well as the oil level, I did feel that either Dzus or Camlock fasteners, or inspection doors would be better. (Paul clearly took this on board, as that evening, he sent me a photo of a very neat new cowling that features generously-sized, hinged doors.)
The engine is fed from a pair of fuselage-mounted, thirty-litre polyethylene fuel tanks behind the pilots’ seats and linked by a balance pipe, replenished via a single filler cap on the starboard side. The tanks feed the engine from one outlet controlled by a single fuel valve. The engine is quite closely cowled and turns a composite two-blade, ground adjustable Kiev propeller. As G-CLOU is the demonstrator, it is loaded with just about every option except a BRS aircraft parachute (which is also an option). If installed, this raises the maximum all-up weight (MAUW) to 472.5kg
The undercarriage features snug fitting spats, the mainwheels being carried by aluminium ‘half springs’ bolted to a steel centre tube and having hydraulic disc brakes. The nosewheel uses an oleo for shock absorption, and steers through the rudder pedals. Beringer wheels and brakes are one further option.
Entry to the cockpit is excellent as the sills are low, although care must be taken not to bump the large throttles. The split doors are large but seemed overly-complicated to me-I prefer one-piece top-hinged doors (which I believe are an option). Up to ten kilos can be carried in a small baggage bay behind the P1 seat. Settling myself into the cockpit, the first thing that struck me was the width of the cabin. At 1.1m, it is commendably wide (in fact wider than the Cessna 152 I’d been flying the month before) and the extensive glazing actually made it feel even more spacious. Although there is no provision for adjusting the pedals the seats can be moved, but it’s currently a bit of a faff (but see p.55). The control layout is slightly unusual: pitch and roll control are via a shared stick, mounted between the seats?and each pilot has his own throttle, located on the fuselage wall.
Those throttles are worthy of comment. Some 912 installations use a ridiculously powerful spring, and if the friction lock isn’t set correctly and you let go of it, the engine will go to full power in a second. This obviously has the potential to be extremely dangerous (and particularly so on a hard surface). The Nynja has a counter-spring in the system, which ensures the throttle stays where you left it.
The trim lever and three-position flap lever are both located between the seats. Initially I found the flap lever slightly awkward, although I soon got used to it. The instrument panel is set into a centrally-mounted binnacle with large stowage bins either side?an excellent feature. This binnacle is wide and provides more than enough space for comprehensive instrumentation. The flight instruments, tachometer and slip ball are positioned in front of P1 (seated on the left) and the oil pressure and temperature, coolant temperature and voltmeter in front of P2. There’s a mount for an iPad in the centre, and below that a row of tumbler switches for the electrics. The avionics (a Trig TY91 transceiver and TT21 transponder) are mounted next to the oil gauges. All OK, but I’d be minded to relocate the slip ball to the top of the panel, bringing it closer to the line of sight, and move the tachometer upwards for the same reason.
The Nynja’s instruments are particularly interesting. Made in Slovenia by a company called Kanardia, they are sophisticated electronic devices which present flight and engine information in both analogue and digital formats. An excellent feature is that each click clockwise on the rotary knob fitted to the altimeter increases the barometric pressure by one hectopascal. (On conventional instruments the hPa setting knob is turned anti-clockwise to increase the pressure setting as indicated in the Kollsman window. This is counter-intuitive). Furthermore, the tactile rotary action makes it obvious to the pilot that the pressure setting has changed by one hectopascal with each click. The VSI incorporates a flight timer and the tachometer an engine hours’ totalizer.
There are two nearly identical plungers in the panel, one for cabin heat and one for carburettor heat. Apparently, the carb heat control is rarely used, as the carb is located where it stays warm enough from residual engine heat to preclude the possibility of carb icing. Nevertheless, I’d still prefer the plunger knobs to be distinguishable by either colour or shape, and preferably both.
The Rotax started readily and we followed the EuroFox cameraship carrying photographer Keith and pilot Al towards Saltby’s runway 25. A quick test of the brakes with a squeeze on the control column-mounted bicycle-type brake lever revealed they not only work, but work well. Although I prefer toe-mounted differential brakes, I found the single lever system perfectly adequate. A neat little catch on the control column locks the lever ‘on’ for use as a parking brake. The nosewheel steering has a nice, positive feel to it and offers a reasonably tight turning circle.
Out at the run-up point I waited patiently for the oil temperature gauge to rise above 50°C before starting the power checks. Even though Paul had flown in from Flylight’s Sywell base, by the time we’d finished the air-to-air brief the oil had already cooled down considerably. Like many 912 installations the Nynja’s sump is quite small, at only 2.5 litres (for comparison, a 100hp O-235 has six quarts/5.67 litres) and they do tend to cool down quite quickly. It took a surprisingly long time for the oil to warm up and I suggested that Paul might consider fitting an oil cooler flap, as this would speed the process and give some control.
With such simple systems, the rest of the pre-takeoff checks were completed quickly, and once the oil had begrudgingly reached fifty, we rolled out onto the runway and opened the Rotax up to full power. With fifty litres of fuel on board we were right on the 450kg MAUW, while the OAT of 14°C meant that Saltby’s elevation of 480ft and the density altitude were the same. There was a slight crosswind from starboard.
With a power-to-weight ratio of less than ten pounds per horsepower, acceleration was excellent and after what seemed a ridiculously short ground roll, the Nynja leapt off the runway and clawed itself skyward at an impressively steep angle. With the VSI indicating in excess of 1,200 fpm and a relatively low forward speed of only 62kt, I would say that we crossed the airfield boundary at well over 1,000ft agl. Of course, the nose is really pitched up, greatly reducing the field of view, but even lowering it to more of a cruise-climb attitude still gave about 700fpm at 80kt and 5,000rpm.
Catching up with Al and Keith in the EuroFox cameraship was easy. I’d initially assumed that to expedite the join-up I’d need plenty of geometric cut-off, as during the brief Al (the lead) had assumed he would have more performance, but as we closed rapidly it soon became apparent that this was not so, and a classic ‘curve of pursuit’ would more than suffice. With plenty of power and crisp controls the Nynja was easy to place where Keith wanted it and the pictures didn’t take long.
Nicely harmonised controls
With the cameraship heading home, I start working through all the items on the flight test card. Close formation often shows up any handling deficiencies from a qualitative perspective, but when I switch over to a more quantitative evaluation, I soon discover the Nynja is nicely harmonised around all three axes. Expanding the envelope with some more energetic manoeuvres confirms the controls are authoritative with agreeably light stick forces. The roll rate in particular is distinctly sprightly, while both pitch and yaw control are equally effective. Only small amounts of rudder are required to keep the slip-ball centred, and control weighting is as it should be, the ailerons being the lightest and the rudder the heaviest. Breakout forces are low, with little ‘stiction’?even though cables are used throughout and this is a relatively new airframe. The trimmer is effective.
For a high-wing aircraft, the field of view is quite good, although as is a feature of practically all high-wingers, the Nynja is a tiny bit blind in the turn. Another nice touch is the transparent panel in the roof, so if the aircraft is rolled to a steep angle of bank it is possible to look into the turn
Moving on to an exploration of the stick-free stability around all three axes, I get the impression the Nynja is strongly positive longitudinally, weakly positive directionally and neutral laterally. I suspect the reason for the soft directional stability is?as is often the case?that the airflow around the nosewheel spat is holding on some rudder at high yaw angles, through the steering link. Slowing down to explore the low-speed side of the flight envelope reveals no disagreeable mannerisms. Indeed, with flaps down and carrying a reasonable amount of power, the Nynja shows no desire to stall at all, but a more vigorous approach to the stall with the engine off produces a more positive g-break at about 33 knots, combined with a slight wing drop, which is easily controlled by the rudder. I increase power for a look at a departure stall and?as expected?this manoeuvre does provoke a slightly more vigorous response, although the ensuing stall is easily recovered from with minimal height loss. Flaps up, the stall is still less than forty knots. Full flap is currently only 25° (a legacy from the earlier, lighter engines) but Paul explains they’re examining the possibility of increasing flap travel to help steepen the approach angle, as long as it doesn’t negatively affect other aspects of the handling, such as pitch stability during a go-around or the ability to sideslip with full flap.
Full flap causes a slight change in pitch trim, which is easily trimmed out. A minor gripe here is that I find the flap lever slightly awkward to use, and would recommend making it slightly longer, although I did get used to it. (Upon reflection, my reduced mobility?I’m still recovering from injuries sustained in the Sea Fury accident?may have been a factor here.) The claimed glide angle is a reasonable 9:1 at 55kt, while ‘min sink’ is around 500fpm at 45kt. A couple of minutes with the throttle pulled back appeared to confirm both these figures.
The next item on the flight card was to examine the various cruise speeds achieved at different power settings, and then by a process of extrapolation back on the ground calculate range and endurance. It should be noted here that the propeller is only ground adjustable, but under the new 600kg allowance, Nynjas will probably be offered with a constant-speed prop as an option.
A fairly rapid cruise of 95kt was achieved at 5,100rpm, which gave a TAS of 101kt at 3,000ft for a fuel flow of about 18lit/hr, but here the engine did sound somewhat frenetic. A much more comfortable cruise rpm is 4,000, which still gives an IAS of 70 (76kt TAS) for a fuel flow of less than 10lit/hr and a still-air range of over 400nm, including Day-VFR reserves.
Currently there are trade-offs that must be made regarding the useful load (you can’t carry two bloaters, baggage and full fuel) but at 600kg it would probably be physically impossible to overload the aircraft (unless the load was lead!) And anyway, forget refuelling, after a couple of hours in the cockpit I’m usually ready to defuel!
Back at Saltby I wrapped up the test with a few circuits. Truth be told, the appeal of flying circuits has never palled for me. I love flying touch ’n’ goes, circuits and bumps and ‘splashes and dashes’. I find flight endlessly fascinating, and the moment when the wheels touch the ground is where it all comes together (and sometimes doesn’t!) That one second where speed, sink rate, zero drift and the aircraft’s attitude must all be exactly ‘right’ has always exercised a fascination that is both hard to explain and difficult to resist?but I love the challenge, and also the sense of achievement when it all comes together perfectly.
And the Nynja is a fab machine for flying circuits, primarily because you can re-acquire circuit height so promptly. Anyway, I flew several: full flap, half flap, no flap, glide approaches, powered approaches, steep sideslips…. The whole gamut, and each one was great fun. For the last I sat up a little straighter in my seat, held the brakes on against full power?and was airborne in less time than it takes to read this sentence. On the approach I nailed the ASI’s needle to fifty with just a smidgen of throttle and then chopped the power as we floated over the peritrack. The mainwheels touched ‘firmly and fairly’, then I lowered the nose and applied maximum braking?so much so that I actually locked up the wheels and we skidded momentarily on the damp grass. We’d used about 100m, maybe less?and even Paul (who has won microlight championships) seemed impressed, and allowed he couldn’t have got us down and stopped much quicker (although he did also point out the takeoff was slightly protracted, and I should’ve been more aggressive when rotating). It was also good to note that the Vref of 50 is 25kt below the Vfe (flap limiting speed) of 75. I like this, as on some microlights the spread between a reasonable approach speed and Vfe can be barely five knots.
An interesting aspect of the envelope is the relationship between the distance required to clear the standard fifty-foot obstacle when landing or taking off. Most propeller-driven aircraft require less distance to land than take off, while the inverse is true for jet aircraft. With the Nynja, the good power-to-weight ratio, efficient flaps and low wing loading provide sparkling take off performance and fine landing characteristics, and intriguingly the distance required to clear that fifty-foot obstacle, whether taking off or landing is essentially the same; only 280m.
What’s in a name?
Overall, I thought the Nynja a great little aircraft that offers outstanding value for money. I got the impression Paul doesn’t really care for the name but I thought it was quite apposite, as it is agile and tough. It is also a lot of aircraft for the money, and when the MAUW is approved to 600kg it will actually be nicer to fly on strong days, as Va (the design manoeuvring speed) increases with weight. This is the paradox of the modern microlight. Most aircraft fly more ‘nicely’ when they’re light, but machines like the Nynja are better heavier, as the higher wing loading provides a smoother ride on bumpy days. But what a cracking little aircraft! Fast, frugal and fun, the latest iteration of the seminal Skyranger might just be the best one yet.
Where heavier for once means better
All indications are that the UK will transition during 2021 to a 600kg microlight category. Details are still being worked out, but Flylight has been preparing for the change. The Skyranger LS was initially approved at 500kg, and work towards a higher MAUW continues. The wing has already been tested satisfactorily at 600kg, and currently the last piece in the jigsaw for approval at the greater MAUW is a new main undercarriage.
With the increase in the microlight MAUW to 600kg, Flylight are looking at several significant improvements to the Nynja. As it’s still relatively early days for factory-built ‘Ready to Fly’ Skyrangers, the company’s ‘start point’ has been the kit spec. The current method for repositioning the seats uses pins and ‘R’ clips but the recently-approved sliding seats for the homebuilt versions should soon be on the type approval options list for the RTF version.
Wing tanks are currently an option outside of the UK and these could become a possibility for G-registered aircraft after the weight limit change. This would then free up the current fuel tank location for additional baggage, which is currently limited to 10kg. There are also plans to make secure stowage bags that fix to the front of the seats. Future plans include a taildragger version, different engine options, and electric propulsion.
Base price £43,000 exc VAT, as tested £50,500 exc VAT
Wing span 8.90m
Wing area 12.8sq m
Weights and loadings
Empty weight 260kg
Max AUW 450kg
Useful load 190kg
Wing loading 35kg/sq m (7.24lb/sq ft)
Power loading 4.5kg/kw (9.92lb/hp)
Fuel capacity 60 lit
Climb rate 1,200fpm
Service ceiling 14,700ft
Take off to 50ft 280m
Land over 50ft 282m
100hp Rotax 912ULS driving a Kiev composite two-blade ground adjustable propeller
Flylight Airsports Ltd
Tel: 01604 494459