Flying The Elf
by Pete Crowhurst. Glider & Microlight Pilot.
When Brian Harrison invited me, as an experienced glider pilot, to fly the Elf, I really didn’t know what to expect.
I already knew that the microlight test pilot had been impressed by the overall handling, vice-free characteristics and engine-on performance but what was still to be investigated was its performance as a glider and whether or not the figures would be attractive enough to interest the soaring pilot.
Designer Jerzy Krawczyk has many aircraft designs to his credit including the Puchatek sailplane and for the Elf he has drawn on the success of the Polish PW-5 and utilised its NN18-17 aerofoil. The construction is all-composite employing carbon and Parabeam, a double skin glass fabric, which gives the structure substantial rigidity, particularly in the cockpit area.
Assembly, after removal from the trailer, is simplicity itself. The wing spars slide into the fuselage box section and, as the controls are self-aligning, only three pins, two main spar and one rear spar, are required to secure each wing in place. The tailplane is attached by two bolts, and a bolt and pin are used to connect the elevator. Job done! Two people, 20 min at most.
Sitting in the cockpit, one is immediately struck by the available space and the seating position, although more upright than that usually found in a conventional glider, is very comfortable and all controls fall readily to hand.
I had five flights in the Elf.
The first took place on a ‘good’ gliding day with cloud base at 4,500 ft and moderate thermal activity.
Very early in the take off roll I was aware that I had good aerodynamic control and with only slight back pressure I was off and climbing out. I had already been told that the instrumentation was “out” and within the first 500 ft this was certainly confirmed. No meaningful figures on this flight then!
Having reached 2,000 ft I throttled back to level cruise and settled down to get the ‘feel’ of the aircraft. My first impression was that of excellent stick and rudder harmonisation. Co-ordinated turns were achieved without adverse yaw or tendency to slip. The stall was completely un-eventful with mild pre-stall buffeting, followed by the nose dropping straight through and without any tendency to drop a wing. Even when held in a 60 deg. bank, on stalling, the Elf simply rolled out level without any input required. In a remarkably short time I was completely at home with this little aircraft. Even with hands and feet off the controls it was so stable that I did not find the lack of accurate instrumentation a handicap. This was starting to be fun!
Next I tested the engine restart. Having experience of pylon retraction systems I am aware of the need to make early decisions regarding re-start. Pylon extraction can take 20secs or more and it can, on occasion, be 30 sec from decision to ignition. This can represent a significant height loss particularly if you are in sink and it has caught out several pilots when a late decision was made on extraction of the engine.
On the Elf the starting procedure is; primer bulb, throttle open slightly, switches ‘on’, and press the button. Total time from decision to ignition, 7 sec! I tried this 4 times over a ten minute period and the engine started, first time, every time! Very reassuring.
Before any more testing we had to sort out the instruments. A new ASI, electronic vario and Digi Fly Pilot 2 were installed.
One week on, the weather was looking good for the next test flight. This time on climb out I could maintain accurate speed and max climb rate. Being confident in both the handling and engine’s ability to re-start, it was time to investigate the performance in thermals. The Elf appeared to be very lift sensitive and I was quickly into a small thermal in which ,with 45 deg bank, I climbed from 2,000 to 4,500 ft at about 450 ft/min. Impressive!.
With lift about, I decided to go on a small x-c and flew successive thermals down a cloud street for 25 miles at which point I turned for home, only to find that conditions were starting to deteriorate and I had descended to 900 ft. With various fields available, I pressed the fuel bulb, flicked the switches and the engine fired up immediately. After a ten minute climb to 3,600 ft I switched off and headed home arriving back at the airfield 1.hr 25 min after take off. Distance travelled 50 miles with an engine off time of 1 hour.
On approach, the airbrakes, although not very powerful, did help to control the descent on to my chosen spot on the runway.
Overall this flight was a big surprise. Apart from the excellent handling, it was the engine off performance which surprised me most. This is a superb little glider which is particularly eager to climb in the slightest lift. Although not wonderful into wind, at no time did I feel I was limited by the low weight and the Elf’s 11m span.
In my experience the Elf flies just like a K6 CR which has a reputation for its ability to stay up when everyone else is on the ground.
As it is, at prototype weight, the Elf can be sold now in France and certainly, after its appearance at Blois, there is a lot of interest. Other countries with an Experimental class will also be interested in the Elf at its current specification.
My remaining flights took place some days later in still-air conditions and utilised calibrated instruments, both standard and digital. The following figures were recorded and are, I believe, accurate. Elf flown at a gross weight of 260 kg, including, pilot, ballistic parachute and 12ltr fuel.
© 2007 X-C Aviation All