Putting the Super in STOL

What do you get when you create an aircraft with wings designed to maximise lift, 
a massive energy-absorbing undercarriage, and a max weight of 600kg? The answer is the Just Aircraft SuperSTOL. It’s an aircraft which, in the right hands, 
wins competitions with take-offs of around 77ft and landings that are shorter than the length of a Cessna C172.
The SuperSTOL is a machine which I don’t mind admitting that, before flying it, made me a little nervous, thanks to the edges of its flight envelope being steep angles and slow speeds a fair way beyond the edges of my aviation comfort zone!

Just Aircraft, the South Carolina-based company behind the SuperSTOL, designed it to sit in the USA’s Light Sport Aircraft (LSA) category, so that means a maximum weight of 1,320lb (600kg) a clean stall speed of 45kt or less and a maximum speed of 120kt. The SuperSTOL is Just’s development of the Highlander, which followed the Escapade, an aircraft developed in conjunction with Escapade UK. The Escapade’s DNA can be found in the Sherwood Scout, and that’s now built by The Light Aircraft Company in Norfolk.

In the US, the SuperSTOL can be supplied as a ready-to-fly LSA, or you can buy a kit and build it yourself. In the UK, only the self-build option is available through Bob Pooler, director of Avalanche Aviation, Just’s UK dealer, and it was his aeroplane, G-SSTL, which we flew from its base at Sleap Airfield. (Editor’s note: Since this was first published, Avalanche Aviation has ended its UK agency)

“It’s an aircraft which, in the right hands wins competitions with take-offs of around 77 feet and landings that are shorter than the length of a C172”

Big shoes

Even though it’s a relatively small, two-seat LSA, the SuperSTOL is pretty imposing, mainly thanks to its tall undercarriage and huge tyres. G-SSTL has a pair of 29in Airstreak Bushwheel tyres fitted to its diminutive-looking Matco wheels, and although they definitely add to the look of the aeroplane, they also bring some practical benefits.

In a traditional GA aircraft you have three elements, namely the wheel, the tyre and the inner tube. The tyre’s bead is seated on the wheel’s rim, and is inflated via a valve which protrudes through the wheel.

The Bushwheel is tubeless so there are just two parts, the wheel and the tyre. Rather than the valve pushing through the wheel, it’s moulded into the tyre’s sidewall. With this 
set-up, any movement of the tyre on the wheel’s rim, which is more likely at low tyre pressures, wouldn’t see the valve ripped out, so you won’t get stranded.

Typically, a bush tyre will run pressure of 6-12 psi, so they’re super-soft (think of a kid’s Space Hopper), play an essential role in the suspension and easily roll over rocks, stumps, holes and, rather unhelpfully, chocks. I’m told that they also make waterskiing in an aircraft much easier.

Of course, you don’t get something for nothing, and there are a couple of downsides to having such big shoes. The first is cost, as while a couple of ‘normal’ 21in tyres 
for the SuperSTOL might set you back $300 a pair, the 29in variety are closer to $3,000, and as the slick rubber compound is very soft, they wear out pretty quickly when used on hard runways.

The wheels and tyres sit at the end of some impressive-looking, long-travel 400psi gas struts, which are similar in layout to those on the Pilatus PC-6 Porter. Watch some online videos of the SuperSTOL in action and you’ll see that one landing technique is to drag the aeroplane in and then just cut the power so that it drops to the ground from a few feet, using the gas struts and tyres to absorb all of the energy, without being handed it all back in the form of an embarrassing bounce or three.

Plenty of lift

If the undercarriage and tyres are there to soak up the bumps, it’s obviously the wings which take care of the heavy lifting, and they’re some impressive devices.

Running all the way along the leading-edge are free-moving slats, which float in and out under aerodynamic load – there are two per side and they move forward and outboard when their time comes. If you’re familiar with the slats fitted to the legendary Helio Courier, these will be recognisable. Enormous Fowler flaps cover about two-thirds of the wingspan.
On G-SSTL the ailerons are supplemented by optional spoilers, which are said to reduce adverse yaw and aid roll control in gusty conditions. They can be found on top of the wing, ahead of the ailerons and look a little like glider airbrakes, but obviously operate independently, with the ailerons.

If those wings aren’t complex enough for you, I should mention that they can be folded back for road transport or storage, without having to disconnect any controls. And should you be wondering about what amount of space the SuperSTOL needs when its wings are folded, the answer is something like 8ft 6in wide by just over 20ft in length.

The fuselage looks like it’s a bit short-coupled, and perhaps thanks to that and the ridiculously slow speeds at which you can fly, the tailplane and rudder are proportionally large control surfaces.
This particular aircraft is powered by a 100hp Rotax 912 ULS, driving a two-bladed, fixed-pitch Catto prop. The cockpit is spacious, with adjustable seats and a large, no, make that a huge, baggage area to the rear, which is good for 70lb-worth of whatever. The doors are top-hinged and the instrument panel big enough for anything you’d want to install for a 
bit of VFR bush-flying fun.

Getting in is simple, or at least it is if you aren’t me, but like most things I imagine that it gets easier with practice, which I’m basing on the fact that Bob Pooler hopped in with the elegance of a ballet dancer. Inside, you’ll find comfortable and adjustable seats, a couple of sticks, a central vernier throttle, the obligatory Rotax choke control, and rudder pedals with toe brakes. Between the seats, there’s a very long flap handle and a basic but functional trim lever, and forward of that there’s a tailwheel lock and an Andair fuel valve.

The panel in ’SSTL is very simple – there are two iPads, the one on the right running SkyDemon and the one on the left acting as a PFD, plus a backup altimeter and ASI, an engine monitor and a radio and transponder.

Bob very diplomatically pointed out that the STOL characteristics would be perhaps a little subdued, given that we’d be operating on a hot day at mauw. Before we flew together, he offered to demonstrate the aircraft solo, so that I could see what it was capable of at lighter weights. That suited me just fine, so Ed and I watched as Bob applied full-power, lifted the tail then raised the nose to what looked like a climb angle you might only match with a rocket, and seemed guaranteed to be followed by a stall and spin.

Happily, it wasn’t and the demonstration was repeated a few times so that Ed could take photos, with each departure followed by a less dramatic but perhaps even more impressive landing.

Fly the SuperSTOL with power on the back of the drag curve and it advances very slowly indeed, and with so little energy once the wheels are down that it’s stopped almost instantly, and this was on a day with very little wind!

Demos done, it was my turn to fly, and although I’m not particularly short I found the view ahead to be a bit limited, thanks to the deck angle when taxying. There are some slightly larger seat cushions in the pipeline and the cabin has plenty of headroom going spare to accommodate them. Until then, it’s a case of weaving along and, as the castering tailwheel isn’t steerable (it’s that big rudder and a bit of differential brake instead), being careful not to scrub off 
too much valuable bush tyre rubber on hard surfaces which, luckily, I wasn’t.

Take-off technique

There are various take-off techniques, with extreme versions which call for simultaneous application of flap and backward stick – how Bob had been flying – or even a levitation with full flap applied from the outset. However, none of them make sense for a first take-off on type, so we opted for the fairly standard technique of one stage of flap, stick-forward to raise the tail and then back to break ground at the appropriate time.

I didn’t raise the tail enough, and I allowed us to accelerate a bit more than was strictly necessary, but even with my very cautious flying we were still off the ground much sooner than I’d imagined. I’d like to say we climbed away at a constant 500fpm but we didn’t, partly because there wasn’t quite enough rearward trim available, but mainly due to the fact that I was struggling to calibrate 
the pitch angle and airspeed required with the mental picture which had been burnt into my brain from many hours flying ‘normal’ aircraft.

We eventually had enough height to look at the full-flap stall. Vfe, the max flap extension speed, is 75mph, and we were at about 70mph when I reached for it. The aerodynamic resistance on those huge flaps felt quite high, and although I could’ve hauled on the long flap lever, I was worried that I might bend it. The easy answer was to slow down, and the best way to do that is to raise the nose, again to an angle which takes some getting used to.

With flaps deployed and speed decreasing, there was suddenly a whoosh and tremor through the airframe, which was the leading-edge slats deploying – a pretty obvious sign that things are getting slow.

Eventually, the stick was full-back, the ASI reading 30-35mph and we were stalled. The wings were level 
the nose was bobbing up and down, so gently and serenely that you could almost forget you’ve got the mother of 
all descent rates going on. No matter how tough the undercarriage is, you don’t want to be hitting the 
ground at that rate so then it’s stick-forward and apply power to turn the descent into a climb.

In the circuit, speed control was straightforward, with a bit of care needed not to get too slow – the back of the drag curve may be the way to win competitions, but it’s bad form to be doing it on a mile-and-a-half final at 500ft or so.

I came over the ‘real’ hedge at about 65mph, slowed further, thought I was getting a little too much so and added a bit of power, which of course only served to move the touchdown point further into the strip, and there was plenty of it left.

Mental adjustment required

The SuperSTOL is an aeroplane which forces you to mentally adjust your flying paradigms and without doing so you’ll be forever tugging a heavy flap lever, floating along the runway, bleeding excess energy, or failing to climb because Vx and Vy seem to want to put the nose 
way too far above the horizon.

In competent hands, it starts flying before you’d expect, keeps doing so when most types would fall out of the sky and stops in distances which are measured in tens rather than hundreds of metres. In skilled and current hands, the SuperSTOL is capable of doing all of that, but even slower and even shorter.

The flipside of the STOL coin is the cruise performance. If you don’t have too far to go, the 70kt relaxed cruise is just fine, but if you live on the south coast and dream of flying to the Orkneys at weekends, you probably won’t want to be making that trip on a regular basis!

The bottom line is that this aeroplane is about fun, adventure and exploration. It’ll open up hundreds of sites which just aren’t practical with most types. Those who are good at making friends will likely find all sorts of off-piste possibilities, from fields to farm tracks, and if they can find themselves a garden big enough, there’s a bit of aviation paradise just waiting for them…