Flight test: WT9 Dynamic LSA
PUBLISHED: 16:11 23 October 2018 | UPDATED: 16:11 23 October 2018
Now certified as an EASA LSA, this former microlight can lift a sensible load while maintaining its great performance and handling. It's also beautifully made... Words: Dave Unwin - Photos: Keith Wilson
When I wrote a flight test report about ten years ago on the first factory-built Aerospool WT9 Dynamic to come into the UK I almost ran out of superlatives. It looked great, and had performance to match. It was − without doubt − the most impressive microlight I had ever flown... and that was the problem.
Being registered as a microlight meant that the allowable MAUW was only 450kg, or 472.5kg if fitted with a BRS (ballistic recovery system), and with an empty weight of 260kg the useful load was a not-very-useful-at-all 190kg.
Even the most cursory calculation soon confirmed that with two average adult males aboard and VFR reserves, you could barely carry enough fuel to get into trouble−let alone get out of it! However, the aircraft flown for this test is registered as an EASA-certified LSA (maximum weight 600kg) and the extra 150kg has completely transformed the type’s viability.
LX Aviation’s Jonathan May, accompanied by my old mate Nick Kelly, recently brought the latest version over to Saltby for me to evaluate. And I was not disappointed!
A good place to start a Pilot appraisal is often from a distance; from there sometimes features such as the undercarriage’s base and track, prop clearance, and fin area are more apparent. And as the WT9 taxied towards me it certainly did look good.
From the sharply-pointed spinner through the wide cockpit to the elegantly elongated empennage, I thought it looked great, and my initial impressions of a top-quality, well-made machine were reinforced on closer inspection.
As you’d expect of a high-performance 21st century VLA, reducing total drag was high on the designer’s priorities. Indeed, the quality of the overall finish is on a par with that of a modern high-performance sailplane (Aerospool supplies airframe components to German glider manufactures).
The WT9 is extremely well made. The wings, fuselage and tailplane are constructed entirely of composites and beautifully finished. The main spar and all other load-bearing structures are made with carbon fibre-reinforced polyester, while the wings, tailplane and fuselage use an aramid foam core covered with GRP skins. An interesting anomaly is that the leading edges on the aerodynamic ‘stall strips’ mid-wing are almost sharp enough to cut yourself on.
Access to the ubiquitous Rotax 912S engine is good. The top cowling is secured by Dzus fasteners and can be removed quite quickly, although there is also an excellent inspection hatch on the cowling’s starboard side. Why excellent? Well, unlike many Rotax installations (and I’ve flown well over fifty Rotax-powered aircraft) on the WT9 you can check the coolant levels as well as the oil via this hatch.
The three-blade Evra propeller is ground-adjustable, and features scimitar-shaped blades, while either side of the radiator air inlet in the lower cowl are powerful taxi and landing lights. The nosewheel strut looks rugged, as do the main undercarriage legs. All three wheels have snug-fitting spats; in fact, possibly too snug, as it isn’t easy to inspect the tyres, brake pads and discs with the spats in place.
The straight wing uses an MS (1)-0313 aerofoil and features a gentle taper to the large winglets, and only a small amount of dihedral. The trailing edge is dominated by large, manually-operated slotted flaps which have four positions: ‘Up’, 15°, 24° and 35°.
Strangely, the POH refers to ‘Flap 3’ as ‘Emergency’ which struck me as rather odd, although this may be an EASA thing. The ailerons are driven by pushrods, the starboard one having an electrically-actuated trim tab.
The tailplane, fin and rudder are entirely conventional. The tailplane is fixed with separate horn-balanced elevators driven by pushrods, and the fin is stylishly swept back and carries a horn-balanced, cable-operated rudder. Pitch trim is provided by a spring bias system, which is electrically-actuated.
There’s a large tail bumper, which will carry an optional glider tow hook as soon as approval is granted. I couldn’t help but wonder if Aerospool are looking at the Edge 120 engine, or even Rotax’s own 915. With a 915 turning a constant-speed prop, I suspect the WT9 would make an amazing tug!
In the cockpit
Access to the cockpit is via the trailing edge of the wing, which features sensibly-sized non-slip wingroot walkways. It’s easier if the flaps are left down. The enormous canopy hinges forward, opens wide, and is well supported by gas struts, providing excellent access to the surprisingly spacious cockpit (it has a maximum width of 1.15m) and the big, ninety-litre baggage bay behind the seats.
Care needs to be taken when getting in and out. Not only are the Dynon units quite vulnerable to an errant boot but the tumbler switches below the P1’s Dynon look rather flimsy. Personally, I’d recommend rocker switches, which are more robust.
The slightly-reclined seats are very comfy but do not adjust. Having the seats fixed makes them strong and crashworthy, and also helps keep weight down.
The rudder pedals do adjust, but the system incorporates two potential ‘gotchas’. Firstly, the pedals can be set asymmetrically, which isn’t ideal. Secondly, and more pertinently, if the pedals are adjusted while the rudder is deflected, it is possible for the pedals to be set neutral when the rudder is not.
Once strapped down with the neat four-point harness I familiarise myself with the layout of the instruments and controls. The panel is deep and wide, and Aerospool have used every square centimetre. It is loaded, in fact, overloaded. I know it’s the demonstrator, but with a pair of Dynon Skyviews you simply don’t need a pneumatic VSI, mechanical tacho, electric hour meter or analogue fuel pressure gauge.
Apart from this, I thought the panel was nicely and intelligently laid out, with many of the controls being colour-coded as well as having different shaped knobs.
There’s a standby ASI, altimeter, and a slip ball to the left of the P1’s Dynon, with the transceiver, transponder and intercom centrally located. The fuses and circuit breakers are on the right side of the panel, with the master, starter and mag switches below the transponder.
The avionics are amazing. The Garrecht TRX1500 is fully integrated into the system and provides Flarm In and Out, ADS-B In and transponder warnings In. As well as the audible “Traffic! Traffic!” these targets are also shown on the Dynon displays.
A sub-panel carries the Vernier throttle, a T-handle for the BRS, rotary fuel valve and plungers for the choke, carb heat and cabin ventilation. Again, there’s a bit of overkill here as the BRS T-handle has a safety pin and a safety catch! One or the other is fine; you don’t need both.
A large centre console drops down from the base of the sub-panel and continues aft between the seats. It carries rocker switches for aileron and elevator trim, a black T-handle for the flaps, and a blue handle for the combined wheel/park brake. To set the elegantly simple park brake you simply click the lever into a cut-out (curiously there are two: ‘park’ and ‘max’, the latter presumably for use when starting) at the back of the console.
The flap lever is to the right of the brake, and is a spring-loaded T-handle that snaps into the detents for each flap setting. It has a long travel and − as I was to discover − there’s a bit of a knack to operating it. On the ground, without the airflow to assist, the retraction force is quite high, and it needs a full-blooded push.
The pitch-trim changes with flap selection turned out to be quite strong and I feel the elevator trim control really should therefore be on the stick, not the centre console.
There’s a neat row of annunciator lights above the P1’s Dynon, and I also approved of the fact that, as well as the airspeed limitations being placarded on the panel, both the Dynon’s speed tape and the analogue ASI are colour-coded.
Overall, I was impressed by the Dynamic’s ergonomics. All the controls fell naturally to hand, and as you can clearly see from the photos on these pages, many have different shapes and colours. The brake is blue, throttle black and carb heat yellow.
I would have liked the flap lever to be white and the choke red (same as the fuel valve) but, overall, this is how a well-designed cockpit looks.
Regular readers will know that I have a major issue with the lack of ventilation in modern aircraft, particularly those fitted with bubble canopies as the cockpit soon gets too toasty in the summer. If you can’t open a door or window in flight then you should at least have a DV panel.
The Dynamic has two DV panels and fresh air vents, but it could also use a concertina-type sunscreen built into the canopy. The canopy is locked with a simple, single centre-mounted latch that is very positive.
In the air
With Jonathan in the other seat we set off towards the runway with the geared Rotax emitting its characteristic muted whine. Taxying was delightfully simple, with a fine view forward except for directly in front, as the nose is pitched slightly up.
The nosewheel steers through the rudder pedals very accurately but, despite the myriad variations of brake operation currently available, I will always prefer toe brakes. I know why ULA and VLA manufacturers like hand-operated brakes: they’re lightweight, easy to make and simple to install.
Maybe it’s because I have a lot of tailwheel time (and taildraggers are easier if you have good differential braking), but I do like toe brakes. In fairness, it is a nosedragger, and has such low landing speeds that the brakes are only really needed for taxying and parking − and toe brakes are an option on the kit version.
With all the pre-takeoff checks complete, I line up on Saltby’s Runway 25 and open the throttle smoothly.
Ambient conditions are well above ISA, as an OAT of 22˚C, combined with Saltby’s 480ft elevation, is producing a density altitude of over 1,200ft−and there’s barely a breath of wind. On the plus side, we’ve no baggage, and with the fuel tanks less than half-full we’re around 60kg below the 600kg maximum all-up weight, which gives us a fine power-to-weight ratio of 5.4kg/hp.
And anyway, with around 1,000 metres of tarmac in front of us I didn’t even think about the takeoff performance. Our next stop is the strip at Shacklewell Farm near Rutland Water, which I knew would provide us with much more valid test conditions.
Even though I add power quite slowly, the acceleration is still excellent. Forty knots come up almost by the time the throttle hits the stop, so I ease the stick back and the Dynamic is off the runway and climbing away very rapidly. I’d taken off with the first stage (15°) of flap deployed, and as we climb rapidly though 500ft I push the flap lever forward into the ‘Up’ position.
The flaps retract instantly, and there’s a strong pitch up. Best climb speed is 69kt, but this gives a steep deck angle and commensurately poor forward visibility, so I trim for eighty. Passing rapidly through 1,000ft, I sweep the Dynamic through a curving turn and onto a southerly heading toward Shacklewell Farm.
The Red Arrows are due to pass perpendicular to our track within fifteen minutes, and I’m keen to be on the ground before they do, so as soon as we’re clear of the circuit I level out at 2,000ft and set it up for high-speed cruise.
This simply entails setting the throttle to 5,500rpm, then trimming forward. The Dynamic promptly settles into a 120kt IAS cruise, which is pretty quick for a 100hp fixed-gear, fixed-pitch aeroplane. Of course, it’s quite thirsty at this speed, although even at 21-22 lph the air miles per litre are very impressive at around 6nm/litre or−in old money−25mpg. And if you pull the power back a fair way you’ll still get an easy 100kt IAS and greatly improved fuel consumption of around 12-14 lph.
We zip down to Shacklewell Farm well before the Red Arrows flypast, and after a brief perusal of the windsock I elect to land on R06. Jonathan recommends sixty over the hedge, which seems a bit fast to me, but we’ve never flown together before and he’s probably adding a couple of knots until he knows I can fly.
I turn in slightly too early and am a bit high on final, but a side-slip soon puts me back on the glide slope.
Over the hedge with the speed nailed to the briefed figure of sixty and − unsurprisingly − we float a fair way up the strip, although I admit I’d forgotten to give the Vernier throttle an extra half-twist to ensure the engine is at idle.
Manoeuvring on the ground suddenly presents me with a conundrum. The strip is narrow with crop either side, and at times (such as when doing a 180) one of the wings is over the crop. During the walkround I’d noted that the large pitot was out towards the wingtip, but I couldn’t remember which one. Reluctant to drag it through the barley, I ask Jonathan, who does remember.
After the traditional formation briefing we follow Keith and Steve Waddy in the Rutland Flying School’s PA-18 into a beautiful evening sky. The OAT is a bit cooler and Shacklewell lower, but the improved density altitude is probably offset by the grass runway, although we still use very little of it.
The TRX1500 doesn’t care to be so close to the Super Cub, and the constant calls of “traffic” soon become an irritation, especially when they are interspersed with occasional “low fuel” warnings, caused by the amount of slipping and skidding I do for Keith’s camera.
With the shoot over I begin to assess the general handling characteristics. Except for the rudder, the controls are all actuated by pushrods, and these confer a taut feel and powerful, precise control in both pitch and roll. Several 360° turns and steep reversals confirm my initial impressions: the handling is impeccable, and both control response and harmony eminently acceptable, with the ailerons being the lightest control and the rudder the heaviest.
Breakout forces are low and the roll-rate pleasingly brisk, with a 45°-45° reversal taking less than two seconds. There is negligible adverse yaw.
An evaluation of the stick-free characteristics reveals the longitudinal stability to be positive as, from an IAS of 100kt, it took barely one long wavelength, low amplitude phugoid to recover from a ten-knot speed displacement. Lateral stability was just barely neutral, while directional stability was strong.
This was particularly noteworthy, as when I tested the original microlight version its yaw stability was quite ‘soft’.
The field of view is excellent, as the large bubble canopy provides a 270° view above the wing, and there is plenty of fresh air provided by the vents and DV panels. Talking of cooling, I get the distinct impression that the engine is slightly over-cooled, as it never really gets up to temperature. For winter flying it warms up quite quickly as it has an integral thermostat, but the oil certainly seemed on the cool side.
Slowing down to investigate the low-speed side of the flight envelope isn’t easy as the Dynamic is so slippery. With the flaps up and a suggestion of power, stalls are a total non-event. If the speed is reduced very slowly, the aircraft never truly stalls.
Instead, the sink rate starts to increase, albeit not alarmingly. Recovery is simple−just lower the nose and the wing begins flying again almost instantly, with minimal height loss. Stall strips near the wing root ensure that the airflow separates from the laminar-flow wing at the root first, and the separating airflow buffets the tailplane warningly.
With the flaps down it did drop a wing very gently, but to be frank the deck angle is so ridiculously steep you’d have to be asleep to stall inadvertently. At such high angles of attack the ASI is almost useless, due to position error, so the indicated stall speed is almost irrelevant.
Adjusting the power sees negligible changes in pitch trim, although the pitch trim changes are significant with adjustments to the flap setting. However, although these pitch trim changes are easily held on the stick, they are quite strong, and reinforce the case for putting the elevator trim switch on the stick.
Back at Shacklewell a couple of circuits confirm the landing characteristics to be as undemanding as the rest of the flight envelope. We can see Keith lurking in the crop, and as he’s looking for touchdown shots I need to be accurate.
The stalling tests had revealed that the flaps-down stall had occurred at around 35kt, and so application of the time-honoured 1.3Vs rule indicated that a speed of around 46kt on short final would be about right. However, low weight equals low inertia, so I decide that I’ll try 55 and 20˚ flap.
Over the hedge, this time I pull the throttle all the way back and then give the Vernier the extra half-twist. This works well, as do the subsequent circuits, although even with ‘flap 3’ I still can’t quite shake the feeling that the Dynamic is slightly under-flapped.
Perhaps ‘flap 2’ should be 30˚ and flap 3 40˚? On the way back to Saltby I shot an approach into the farm strip where Buzz lives, and the float could’ve been embarrassing if I’d intended to land. On the plus side, the Dynamic is very speed-stable.
Remember how I said at the start that the microlight version’s useful load wasn’t very useful? Well, having greatly enjoyed evaluating the aircraft from a qualitative perspective, that evening I dug into the POH for a more quantitative examination.
With a 600kg MAUW, we have 250kg to divide between bodies, baggage and fuel, and with both tanks filled to the brim the total of 126 litres (119 useable) weighs 91kg, leaving 159. However, with full fuel the still air range is over 760nm, while the endurance is a bladder-busting, buttock-bruising eight hours! A more representative half-fuel load still gives you 300nm, VFR reserves and 204.5kg for bodies and bags.
Conclusions? Well, it’s fast, economical, roomy and comfortable, with a fine field of view, excellent handling, exceptional performance and amazing avionics. Negatives? Although the Vernier throttle is probably OK for the private owner, it wouldn’t be so good in the club environment − and as a glider tug (which is an option) forget it. It’d drive me mad!
There are also way too many warnings. For example, we were cautioned when the fuel got down to fifteen litres a side, but at the economy cruise power setting of 4,300rpm you could still fly about 140nm, and then land with thirty minutes of fuel left.
The aspect of the Dynamic I find least attractive, though, is the price. The test aircraft is valued at €155,000 plus VAT, and it’s irrefutable that this is a lot of money for a Rotax-powered two-seat aircraft with a ground-adjustable propeller and fixed undercarriage.
However, LX are currently in negotiation with the LAA regarding the introduction of a kit-built WT9, and although I can’t say too much at this stage, this machine could be a real game-changer!