Aerospool's WT9 Dynamic LSA has struggled to gain traction in Australia, but has been given a boost with a new agent and a 2021 demonstrator. Steve HItchen checked out the new Dynamic and came away enormously impressed with its sportscar-style performance.
In aviation, very few good things happen after someone says "watch this!" So I was a touch apprehensive when instructor Michael Xeni took over the controls of WT9 1783 and proceeded to configure the aircraft for a rate of descent a dive-bomber would be proud of. We went down at ear-busting speed, but the aircraft was stable and pliable through the whole exercise.
I learnt that the latest embodiment of this speedy Slovakian LSA is as docile as it is fast; an impressive combination at a time when people are looking for LSAs to perform better without sacrificing the ease of handling.
My first encounter with an Aerospool WT9 Dynamic was in 2013, when I did a flight test for Australian Flying. Had you told me then that it would take nine years for the second aircraft to be delivered to this county I would have laughed in your face. The WT9 Dynamic contains a lot of what new LSA customers were looking for, so why wouldn't the type be adopted here in numbers?
But reality is sometimes very different from perception, and a lack-lustre marketing campaign kept the Dynamic in the LSA shadows. That was until Aerospool handed the agency to Xeni's company AvXen. For the first time, Australia has an agency of its own and a demonstrator to back it up.
It was that demonstrator that I strapped myself into in February this year, full of excitement to see how Aerospool could possibly have made a better aeroplane in 2021 than the machine I tested in 2013.
For those new to the Dynamic, the WT9 is a composite, low-wing tricycle undercart aeroplane with fixed or retractable gear pulled along by a Rotax 912 ULS, 912 iS or 914 engine. The sleek, flowing fuselage lines are attributed to the glass and carbon-fibre sandwich construction layered on either side of a core of hard foam panels.
What comes from that design is an LSA that can get along at 135 KTAS, has a useful load of up to 290 kg and plenty of room inside the cockpit. It comes from the factory in Prievidza, Slovakia in either Club (fixed gear) or Speed (retractable) models. There is also a Turbo Tow version for launching gliders that employs only the 115-hp 914 engine.
The demonstrator wheeled out of the hangar at Lilydale Airport in front of me was 23-1783, a Club version with a Woodcomp constant-speed propeller and Dynon Skyview avionics.
"It's not like other low wings regardless of what people think," Xeni said as I walked around the aircraft. "Yes, it's a good-looking aeroplane, but it has the performance and handling characteristics that you need. It's fun to fly, but it's also stable and not something that's going to be arduous on a cross-country flight.
"But, it's also something that's going to be fun to take friends and family up. So it suits many purposes."
Not a lot looked different with the new model; slight alterations to wing span and fuselage length are not the sort of things apparent to the eye. The most obvious was the winglets, which were not part of the previous design. Vortex generators had also been added to the leading edge of the wing and the air intakes redesigned.
Naturally for a manufacturer's representative, Xeni enthused over the Dynamic.
"I really love the canopy and the space you've got in the cockpit," said with conviction. "There's more room in there than there is in a Warrior or an Archer; you're not rubbing shoulders with each other. Then you've got the canopy that makes you feel like you're in a convertible. You're looking straight through it; the visibility is awesome."
At Xeni's invitation I lowered myself into the left seat, quickly buckling the three-point harness and stowing my camera in the cavernous baggage compartment behind the seats. Xeni was dead accurate with his assessment of the space. The soaring canopy screen provided plenty of head clearance and the seats were of generous proportions with an armchair feel to them.
The pedals were at first out of my foot reach, but the pedals were adjusted to suit more easily than in any LSA I've ever flown. Pull the knob and a spring pushes the pedals your way. When they're at the perfect distance for you, release the knob. There is no seat adjustment.
Now settled in, I noted the sparseness of 1783's panel. A Dynon D1000 Skyview EFIS dominated the panel along with an iPad holder with built-in cooler; Dynon autopilot and comm systems split the two, whilst a back-up ASI occupied the far left.
A rank of rocker switches ran beneath the D1000, whilst the propeller control panel sat in the middle just above the centre console. The centre console was home to the throttle, fuel selector, parachute handle, choke, brake, trim and flap lever.
Eying the flap lever gave me horrible flash-backs: a T-handle system that has to be slid along a groove around 250 mm from zero to Stage Three. It's awkward to move and if done without warning can quickly trash your passenger's elbow. Xeni was very fast to mention they now have an electronic flap option.
Firing the Rotax
One of the key advantages to running Rotax engines is that, all things being equal, they all start the same. Regardless, I asked Xeni to step me through the procedure.
"Put the master switch on, then turn the key to the on position, you'll feel a click, then hit the Dynon switch," he instructed. "Wait for the screen to come on, then switch the fuel pump on until you have fuel pressure then turn it off. The pressure should stay in the green.
"Magnetos go on and the choke if it's cold, then the key goes to start. Set the throttle to about 2800 RPM, which is about a quarter of a turn on the vernier throttle. The let the choke off and the RPM will settle to about 2200 or so. Avionics go on and the iPad cooler if you have an iPad in the mount."
It all happened just that way, and after waiting the prerequisite time for the oil temp to move into the green, we taxied for Lilydale's grass runway 18R. The Dynamic's nosewheel steering made ground navigation easy and I found the aircraft didn't bobble around like some LSAs can on grass.
I ran through the pre-take-off checklist with Xeni pointing out the relevant bits to save me wasting time having to locate them in the unfamiliar cockpit. Some extra attention was needed when it came time to cycling the Woodcomp prop.
The FlyBox prop controller has constant speed and manual modes, with an inc/dec switch to change the pitch angle. With Xeni's guidance I selected the CSU switch to manual, ran the RPM up to 5000 and reduced the pitch with the selector knob. Like any other CSU, the RPM dropped back and the manifold pressure (MAP) increased.
"In the top right-hand corner of the CSU screen there is a figure that the prop is actually doing," Xeni said. "So if you're on base and you set the prop to 5700 then back off the MAP, the prop is not actually going to be doing 5700, so that figure tells you what the prop RPM really is. This figure is also displayed on screen on the D1000."
Happy that the prop was functioning correctly, I completed the checklist and asked Xeni to give me a take-off brief. Even though I was confident in my ability to get off the ground safely, every LSA performs a little differently and only experience can find that sweet spot.
"On take-off, wind in the vernier throttle to apply power–it doesn't take too much to get it to full–or you can press the button on top of the knob and push the knob in like a standard push throttle," he explained. "You'll get airborne with the ASI in the 40s or 50s, then get the nose down and get the speed into the 60s and climb away at 70 for best rate."
Vernier throttles: you either love them or you hate them, and I have to say this one endeared itself to me very much. Unlike the stiff verniers fitted to most Bonanzas–where you seem to be winding forever–it took only three or four flips of the hand before the Dynamic throttle had reached the firewall.
The WT9 revealed her spirit early in the take-off roll, leaping forward with enthusiasm and leaving the ground before the ASI had reached 50 knots. I didn't time the take-off roll, but it can't have been too long because I was still checking the temps and pressures when the wheels broke free.
As coached, I lowered the nose to 60 knots, which seemed an irrelevant exercise as the ASI passed 70 almost immediately and it was time to assume the climb attitude. That should have given me some warning about the acceleration potential of this airframe and the need to make sure I bulls-eyed that 70 knot climb-out speed.
At 250 feet I wound the prop back to 5500 RPM and soon learned that you can get very busy during a WT9 climb-out.
"You wouldn't take off with two or three stages set: it's either one stage or none," Xeni said. "This aeroplane is easy to fly too fast with flap down on take-off."
When I released the single stage of flap we had set, the nose of 1783 pitched up snappily. That put us into a very nose-high climb at 70 knots, caused by the streamlined nature of the fuselage. Hitting the numbers is also important to make sure the MAP doesn't redline on you.
"You'll also notice that if you don't get the nose up on climb out and you're climbing at around 85 knots the MAP will go into the yellow," Xeni pointed out, "so get the nose up so the speed drops back to 70 and the MAP will go back into the green."
I turned eastwards and set-up decent rate of climb, achieved with the throttle wide open and the prop at 5500. That returned an ROC of 1100 fpm. It can get better, but only by keeping the prop RPM at 5700, which is the maximum limit for the Rotax and can be sustained for only five minutes. Still, 1100 fpm was nothing to sneeze at and we saw flashes of 1300 fpm on the VSI.
We chose 4500 feet to run the TAS check and set power at 24.5/5250. The D1000 revealed a TAS of 129 at density altitude of 6523 feet. It was one of those impossibly sultry days that Victoria endured in February: QNH 1011, OAT at 4500 was 23°C. The fuel flow with those conditions was 19 lph.
"If you keep a constant MAP and change the RPM between 5000-5300 it doesn't make too much difference to the speed of the aircraft," Xeni said, "but it will make a difference if you change the MAP.
"The cruise settings for 18-20 lph will give you 125 KTAS at 4000 feet, or 135 KTAS at 7500 feet. They are slippery, but they can be very draggy once you get the flaps down. You've got to think ahead like any high-performance aeroplane."
I gave myself just a few moments to soak in the WT9 cockpit for awhile before getting back to work. Xeni was right about the convertible-style feel. The view was almost completely unobstructed and there was nothing rubbing against me anywhere. The trim system is the stick-setter type rather than aerodynamic and the grips on the joystick-style controls that protrude from the front of the seats are turned slightly inward to match the more natural position of your wrist.
Behind the seat bulkhead there are two cavernous cargo compartments, which I soon found can actually be problematic. I stored my camera there on take-off, and in the cruise realised the cargo compartment was so deep I couldn't reach the bottom of it from the seated position. Some forward planning here would not go astray if you want to access anything in flight.
Steep turns in 1783 were just delightful. The stick doesn't demand a lot of effort before the ailerons respond and if you apply any discernible back pressure you'll be climbing before you understand what's happening. The responsiveness was more like that of a helicopter cyclic: just thinking about where you want to go has the aircraft starting to go there. I shy away from talking about fighter-style response, but if the shoe fits ...
In the clean stall the WT9 is interesting and almost comic in its reluctance, clinging onto the airflow for as long as it possibly could. With the power off and the nose pointing at the clouds, 1783 did a lot of wallowing and shuddering, with the innovative stick-shaker and audible alarm doing their best to warn us of something that never seemed to come. The wings began somewhat of a see-saw action, but a touch of dancing on the pedals kept them level.
Eventually the wings let go and the nose rotated slowly towards earth, breaking the stall.
"They can be difficult to get the stall going," Xeni admitted as the ASI began to recover, "they don't want to stall, which is good. They're a pretty benign aeroplane."
I elected to cruise back to Lilydale for circuits, and I should have twigged that something was up when Xeni had me holding 3000 feet at an inbound point at which I'd normally be at 2000. At that point he asked for the controls.
"In a 500 fpm descent, you can go for anything between 4000 and 5000 RPM," he briefed. "You'll have to bring the MAP back to 16 or even less and it will sit comfortably in the descent.
"If you want a high rate of descent, get the speed back into the white and drop three stages of flap. The speed will get back into the high 60s and the attitude will be very nose-down. You do have to hold the nose down and get the trim right. There's a lot of drag on the flaps, so you'll slow down very quickly.
Thus configured, 1783 wiped out that excess 1000 feet of altitude in moments without the ASI threatening the yellow arc. The Dynon registered an ROD of 1300 fpm as we headed earthward in a smooth, stable fashion, thanks largely to the impressive plank-like wing flaps. It's a very handy back-stop capability if you have underestimated the cloud base and need to get under it quickly, or have simply made a hash of your top-of-descent calculations.
We recovered back to straight-and-level at a more appropriate altitude and entered the circuit for Lilydale's runway 18R. I set downwind power at 23/5000 and 1783 settled into 100 KIAS. After rattling off the customary pre-landing checks, Xeni delivered the landing brief.
"You can set the prop to 5700 on downwind or as part of a PUFF check on base. Once you bring the power back to turn base the prop won't be doing 5700 RPM; you can see the RPM in the CSU panel screen or on the D1000.
"Get the speed back to 70, which is pretty easy because the power will be back to about 13-14 MAP."
After throwing out two stages of flap, I quickly understood I needed to get the nose down or 1783 would wash off speed to a dangerous level. That made me reluctant to use the last stage.
"On final you can set a third stage of flap if you want to do a short-field landing, but otherwise two stages is fine," Xeni said. "With two stages you'll get 65 KIAS over the fence compared with, say, three stages and 59 KIAS. There's not too much difference."
The Dynamic was a gentle as a falling leaf on final, but a lot more stable. I do have a tendency to completely destroy my first landing in any new LSA and carried too much speed, which gave the aircraft a formula it just couldn't live with. We got down in a very ugly fashion.
Redemption occurred on the second circuit. My number discipline was better and the WT9 proven it could roll on to the runway with the best of them. After the debacle of the first landing, I found I could tune myself to the airframe quite quickly and more easily that, say, an A32 Vixxen. We exited the taxiway with me feeling pretty good about the Dynamic.
Addressing the baggage
Back in the hangar with our feet up, I confronted Xeni with the WT9s biggest head-scratcher: the baggage capacity. The WT9 has a large bags compartment in the back, but also can carry stuff in cargo bags under the legs of the pilot and passenger.
Mathematics showed that we had departed on the test flight with two 85-kg people and 60 litres of fuel in the 100-litre tanks. The demonstrator has a basic empty weight of 333 kg, meaning there was still 54 kg until 1783 hit the 600-kg MTOW. But ...
"This aircraft is designed to the German ultralight standard, which says that someone should be able to follow the maximum weights for bags in front and back and fuel, and shouldn't have to do a weight-and-balance," Xeni said.
"Under those conditions, the WT9 can be flown at up to 10 kg in the back and 20 kg in the front; 10 under each seat. If you get the WT9 certified to the EASA standard then you will have to do a W&B because the limit in the back is 40 kg and in the front is a total of 20 kg."
The moral of the story is that if you want the full bags capacity you should tick the EASA certification box when you order your WT9.
And electric flaps … get those too.