Alatus Initial Test Flight Report

First impressions of the Alatus were very good. The Alatus has been in development for around 7 years, and this is evident in the design and construction of the glider. It certainly did not look out of place at the gliding site where the test flights took place. Only its diminutive size and engine bay doors mark this out as something a bit special.

I would have expected a glider of this weight to be a bit delicate and flimsy, but all of the structural items appeared very hard wearing and durable. Aerola use an impact-resistant gel coat on the machine to reduce crazing and improve surface finish. On the prototype we flew the wingtips housed aluminium tubes which drag on the ground; but Aerola have produced a new simpler wingtip for production versions which have the option of a small wheel for tarmac operation. The example we flew had the new Trilam sailcloth, but Dacron is still available as a lighter, if slightly less durable, option.

Getting into the glider was incredibly easy with the canopy removed. Attaching the canopy is readily achieved even whilst seated, by lifting onto the nose lug, before sliding backwards into the locked position. Alternatively, you can drop into the seat with the canopy attached, as long as legs are kept straight.

The seating position is very comfortable even for extended periods, although pilots with very broad shoulders may wish to have a slightly larger back cushion if they find their shoulder blades resting on the seat frame. At 5’10” I had some good headroom, even with the adjustable seat back on the 2nd position from the front (out of 6 total positions). This position gave me quite a large space behind the seat, perfectly large enough to hold a backpack, or a lightweight sleeping bag and tent. Taller pilots could move the seat further rearwards, or hunker down into a slightly more reclined position by adjusting the foot pedals (an instant process identical to that used in most other sailplanes). This level of adjustability will prove very useful for those planning to share ownership of an Alatus.

After turning on the electrics and ignition systems, a simple push of the start button brought the Corsair engine humming into life. These engines are in common use throughout the world, and did not seem to suffer any problems on the Alatus installation. The level of vibration and noise was light, and caused me no discomfort even at full power with no ear protection, but a headset would probably be preferable on sustained engine runs.

Taxying the aircraft is readily achieved with short application of power combined with rudder deflection. The Aerola test pilot demonstrated taxying crosswind in around a 15kt wind, seemingly without problem.

The takeoff was easily achieved, with roll control proving sufficient to lift the wing off the ground almost immediately. Even in very long grass, and an outside air temperature of 28 degrees Celsius, I estimated the ground roll to be around 150m. Climb rate thereafter was good considering the conditions, giving me a sustained 1.5 m/s (~300ft/min) at 40mph indicated. A level cruise was achievable at 50-60mph with a small reduction in power. The prototype fuel tank was 3.8 litres, giving up to an hour’s climbing. Aerola are investigating fitting a much larger tank separately to the engine unit, or expanding the existing tank to 4.8l. There were no unpleasant reactions in pitch when changing power settings.

Turning the aircraft back into a glider was very simple and will be immediately familiar to pilots of most other SLMGs, although it requires a routine that should be committed to memory before taking flight. First the engine is switched off, before pulling the prop stop lever. This overlaps the decompressor lever, automatically swinging the propeller into a vertical position when flown over 40mph. When the prop is in the correct position (visually checked with a mirror placed on the dash), flicking a switch retracts the mast into the body and automatically closes the doors over the prop (taking around 12 seconds). All of the controls fell immediately to hand, with the sprung-loaded trim next to the stick, and the flap lever in the usual airbrake position on the left side of the cockpit. The engine also recharges the battery in flight, so the number of in-flight restarts is practically unlimited.

The Alatus handles particularly well, with very powerful, yet light, controls in all axis. The roll rate is good, with a 30 degree bank reversal taking only 2.5 seconds. Rolling briskly produces a small amount of adverse yaw, easily countered with a light touch on the rudder. The example we flew had a degree of friction in the stick, particularly noticeable in roll, but the control forces were so light that it was soon forgotten in flight.

Unfortunately, Polish Airlines lost my baggage (including my GPS) on the outbound flight, so I was unable to calibrate the instruments or obtain accurate performance figures. However, I can well believe the claimed 0.6m/s sink rate, and 27:1 glide ratio; the glider gave the impression of being able to stay up in very weak lift. Later that day, Stewart had his first ever flight in a sailplane when he flew the Alatus, turned the engine off at 1500’ and thermalled up to the 6000’ cloudbase. This was all after 6pm local time in the last of the evening thermals. Importantly for transitions, the glider also doesn’t seem to lose much glide at higher speeds, which was surprising given the relatively low wing loading.

All stall characteristics were very benign, with a pronounced pre-stall buffet occurring at around 35mph indicated. Continued raising of the nose produced a gentle mushing stall at around 31mph with a slight nose drop and no tendency to drop a wing. Stalling in a turn created a slight overbank tendency before an identical gentle nose drop. Asking Aerola’s test pilot about the spin characteristics, he said that full rudder deflection at the point of the stall would produce around a ¼ turn before recovery, with ailerons effective in the correct sense throughout.

The flaps proved effective at up to 70 degrees deflection, and with only slight effects on pitch trim, could be used much as conventional airbrakes. Sideslipping the aircraft was possible with no handling problems, but not very effective due to the low profile of the glider. For landing on fields requiring very steep approaches, the mast could be raised to add a considerable amount of drag. The wheel brake was also effective, and the ground roll on short grass seemed to be around 60m.

After the flights, we investigated the rig/derig process. This is where the level of design and thought that has gone into the Alatus is most apparent. Although there is no easy way to remove the wings for storage in a trailer, the full derig process was completed with the wings folded and fuselage breaking down into 3 separate packages (4 including the engine unit) in around 25 minutes. The remainder of the quoted 40 minute derig time could be used packaging the aircraft ready for transport in a car if storage is not available at the airfield. The weight of the combined wings/tail boom package might prove ungainly for those pilots with no-one around to help lift it onto a car roof, but not impossible. All of the component and canopy covers (as well as wing stands) are included in the basic price and were made to the good standards that Aeros hang-glider pilots have come to expect.

Although the deregulated class of microlights requires no airworthiness, we were obviously interested in ensuring that the aircraft is structurally sound. In this regard we were pleasantly surprised, with Aerola eager to show us the testing already completed on the aircraft. Limit loads on the structure have been proved at +4.23/-2.11G (instead of the usual +4/-2 that we are used to on other microlights) at a MTOW of 235kg. With a current pilot weight range of 60-100kg (with plans to test up to 110kg), this gives plenty of room for fuel and your sandwiches.

In short, the Alatus was everything we hoped, and more! The aircraft was very easy to fly, with no vices that I could detect. The performance level is astounding and the Alatus should excel in weak conditions that would have most other sailplanes grounded. The engine unit works well and provides a decent climb rate in summer conditions. Above all, the single-person rig and portability of the aircraft promise to free many of us to do the thing that we want to do most of all- Go Flying!

David Broom.