By Bernard Eckey
the Australian agent for Alexander Schleicher
After two years of Covid travel restrictions, it was great to say ‘goodbye’ to winter in Australia and head off to see family and friends in Europe again. Of course, a visit to the Schleicher factory was another good reason for the long trip. The highlight was an opportunity to fly the new, all electric AS 34 Me. After its EASA type approval, the prototype and factory demonstrator was recently upgraded to production standard and is now released for test flying by interested pilots.
The timing of my factory visit couldn’t have been better. A few cumulus clouds had already popped up as early as 9am and by the time I arrived at the factory, the sky was full of them. Uli Kremer, the Schleicher MD, kindly conducted the briefing on the AS 34 Me himself. It didn’t take long but when I tried it for comfort we swapped the slim pack for a backpack parachute and even added a small cushion for additional lumbar support. Even then I had to put the adjustable rudder pedals in the middle of the available range and with my height of 178 cm there was still plenty of clearance between the canopy and my almost totally bald head.
By early afternoon the moment of truth had arrived. The AS 34 Me prototype was rolled from the hangar onto the little 1,380ft high airstrip right behind the factory. Now I could see for myself what the hype has been all about and whether the engine operations were as simple as advertised.
I had self-launched from the little factory airstrip quite a few times before but only in gliders with combustion engines. Due to obstacles in the narrow valley, takeoffs and landings are always in opposite directions. This time I even had a slight tailwind to deal with. “That’s not a problem, Bernard,” Uli Kremer assured me while at the same time reminding me of the almost invisible fenceposts on landing, just short of the threshold.
Uli levelled the wings and gave me the thumbs up. As the engine master switch was still turned on, I just moved the power leaver – or ‘throttle’ – to the first indent. An unmistakable high-pitched noise sounded for about 12 seconds and confirmed that the extension mechanism was working. When it went silent again the propeller was fully extended. But if you think that pressing the START button activates the drive system, think again. For safety reasons, the little leaver first needs to be moved into the 'Power' range. But when this happens the beast comes alive.
Applying the entire 35 kW (48 Hp) of electric power created a low frequency roar in the cockpit while the aircraft accelerated on the runway. At around 50kts, the AS 34 Me left me in no doubt that it wanted to fly and I let it do so. While climbing at a speed of around 55kts the variometer hovered just above 3.5m/s or 7kts – equivalent to a tow behind a generously powered tow plane. Very impressive indeed!
I was briefed to keep an eye on the engine instrument and reduce power to 25kW (34hp) when the display changed colour from green to amber. That happened after about two minutes and at around 1,300ft AGL. Now the climb rate was between 2.5 and 3m/s (5kts) but on approaching the first wisp of a cloud, I was already at 2,700ft AGL and figured that it was about time to turn the aircraft into a glider again. Putting the little ‘throttle’ into its bottom position promptly stopped the motor and the propeller rotated into a vertical position before it retracted automatically. A rather loud clonk confirmed that it was back in its box and that the engine bay doors were fully closed. Just magic!
Flying an unfamiliar glider with metric instruments made me stop in broken 2kts of lift for a while and thermal a bit faster than necessary. It took a while to work out that the ideal thermalling speed is just under 50kts. Not bad for a self-launching Standard Class glider, I thought, but soon a nearby pretty neat looking cu tempted me to look for something a bit stronger. Sure enough, my climb rate promptly doubled and I decided to stick with it until cloud-base, which turned out to be around 6,500ft.
From then on, plenty of fluffy thermal markers made for relaxed flying. I had to remind myself that I wasn’t here to enjoy myself but to find out what this aircraft is capable of. So, forward with the stick until the ASI read between 80 and 85kts, but this changed the sound from the front air vent to an almost irritating hiss. The solution was to open the fully adjustable airliner style vent on the right cockpit wall and close the one in the nose, which not only restored the cockpit serenity but also made for a more pleasant and more effective airflow in my little office.
The wing loading was in the 43kg/m2 range courtesy of 33kg of batteries in each wing plus the weight of the motor, propeller and whatever else is necessary to turn a glider into a self-launching aircraft. On a day like this you can’t be heavy enough, I thought, and that must have occupied the minds of other pilots as well.
There was no shortage of other traffic around, partly due to the nearby historic Wasserkuppe mountain with its famous airfield right on top. So I pointed the nose towards another glider climbing further north but on my arrival its pilot decided to level out and head north. That’s great, I thought, let’s fly side-by-side for a while and keep an eye at each other. Sadly, the opportunity was short lived, because my newly found flying buddy was in a 15m glider and couldn’t keep up with my modern 18m ship. At the end of our next climb he or she was too far below and we went on separate tracks again.
To my delight, the next thermal turned out to be the strongest of the day. It catapulted me back to cloud-base where the opportunity presented itself for some handling tests. First, I checked the stall characteristics by slowly moving the stick back until it hit the stop. It made the nose go up and it went eerily quiet in the cockpit but other than that, nothing else happened. Only after applying some rudder the glider protested by wanting to drop a wing, but just easing the stick forward a little gave me full control again. That was very reassuring and exactly what can be expected from a modern glider.
Now to the next test – ‘rolling on a point’. As an Open Class pilot I’m used to a rather sluggish rate of roll but there is none of that in the AS 34. Its agility is truly impressive and so is the perfect coordination of the controls.
Some air starts were next on the agenda. With the throttle in the first notch, I pressed the Start button and when it was put in the Power range, the glider immediately climbed under its own steam again. No ifs or buts, as a long-time pilot of aircraft with combustion engines, my already high expectations were definitely exceeded.
What a pleasant change! No need to wait for temperatures to come up, no observing engine revs, limiting flying speed or keeping an eye on maximum temperatures. Unlike conventional ‘turbo’ sustainers, the motor revs can even be freely selected just by adjusting the power. Of course, there’s no drop-off in engine output with altitude like there would be with a combustion engine. Another advantage of electric!
Because I was still near cloud base, there was no point in keeping the motor running. Therefore, the throttle was promptly put into the bottom position again and the propeller disappeared almost instantly from view in the rear vision mirror before that unmistakable clonk confirmed that it was fully retracted again. The automation is truly impressive – just one pilot action and the rest happens by itself. No cooling down the engine and no ensuring that the propeller is in a vertical position for retraction. This was really good fun! No wonder that I did another air start a little later but with a longer motor run – just to experience this innovative technology in action again.
On the way back to the factory airstrip, I could not resist the temptation to make a little detour and fly right over the Wasserkuppe mountain. After all, this is where gliding started all those decades ago and where I used to slope soar radio controlled sailplanes in my younger days. Plenty of pleasant memories came back and I could hardly believe my luck to see this part of Germany again in such luxury and from such a lofty position.
But all good things must eventually come to an end. After almost two hours it was time to land, though not without trimming for around 85kts and a lap around the provincial city of Fulda. However, on my return over the little airstrip, I still had height to burn. It allowed me to do a few orbits around the factory and check the effectiveness of the airbrakes before landing and taxiing back to the hangar.
Uli was waiting for me and asked, “What do you think?” I replied, “You are definitely on the right track with this aircraft, Uli. It’s just so easy to fly and the motor management is almost unbelievably simple. Even early solo pilots can self launch in it and the performance definitely exceeded my expectations. I must admit that on takeoff, the cockpit noise level was not as low as expected but that seems to be due to the proximity of the propeller tips to the ears.”
“That’s right, but it is much quieter than FES or petrol powered gliders and the external noise emissions of only 55 dB(A) are scarcely noticeable on the ground,” Uli said. “Our tests have shown that an AS 34 Me overflying at full power and at 1,000ft will hardly be detected by people in the streets, especially in the presence of ambient noises or traffic sounds.”
While putting the aircraft back in the hangar Uli stressed that the AS 34 Me’s simple operation is complimented by simple power plant maintenance. “It is limited to visual inspections and systems checks, and all three main components – namely battery, power regulator and electric motor – are basically maintenance free,” he said.
“Only the main bearing on the EMRAX motor must be replaced after 500 hours. However, given that a normal self-launch takes less than 5 minutes of motor running time, this will only become an issue after approximately 6,000 launches. Just keep in mind that the power plant operates on 400 volts, and in the unlikely event that a service becomes necessary it is recommended to return a damaged or faulty component to the manufacturer for repair or exchange.”
“Can you check how much juice is left in the battery, please?” I asked. “That’s very easy,” Uli replied, and while he rotated the push-button on the engine instrument he said, “68%.”
“That’s amazing, given that I launched to 2,700ft and did a couple of air starts as well,” I replied. “It means that I could have easily climbed another 6 or 7,000ft.”
“Yes, that’s right,” Uli said. “The avionics battery doesn’t need charging either, because it is automatically topped up in flight by the engine battery.”
After a while, he continued, “Safety was paramount during the development of the AS 34. The two battery packs for the electric motor are shaped like slender sticks, which slide into safety enclosures in the inner wing panels. We decided on Lithium-ion batteries in 18650-Format with a metal shell and with a capacity of 8.6 kW.
"However, the core of our safety concept is the Battery Management System BMS. It monitors and displays voltages, temperatures, current flow and remaining battery power. Incorrect operations are impossible as the BMS also avoids deep discharging, overcharging or overheating. In case of mechanical battery damage, the individual cell connectors act as fuses and limit a possible short-circuit to a confined area."
While Uli connected the automatic battery charger, he added, “A totally flat battery requires charging for only 4 ½ hours, provided a 15 Amp power outlet is available. Of course, it takes longer with a lesser power supply but that doesn’t matter as recharging usually takes place over night. Owners can also select a lower charging rate on the engine instrument.
“However, we are reluctant to quote a service life for the battery pack. Our supplier has quoted 300 full charging cycles before the battery capacity might begin to decline. This assumes that the batteries are always fully discharged, but usually only a small battery top-up is required. Therefore, it is likely that the batteries will last much longer. Of course, even an ageing battery doesn’t require a swift replacement, but before we can comment further we need more practical field experience.” Please note that 300 charging cycles correspond to approximately 100 hours of engine running time.
“What made you go down this path, Uli, and what was the thinking behind your AS 34 Me development?” I asked.
He replied, “After the successful introduction of our ASG 32 El the logical next step was to apply this technology to a single seater and make it capable of self-launching. Our ASG 32 is a much heavier two-seater with 20m wingspan and in this glider our new electric power plant only serves as a sustainer. Our AS 34 Me is aimed at clubs and individual pilots interested in relaxed flying, even from airfields without any gliding infrastructure. In other words, this aircraft is for aviators who are looking for total independence and the freedom to fly whenever they want, wherever they want.
“Therefore we have integrated wingtip wheels for unassisted takeoffs and made sure that this glider is very simple to operate on the ground and in the air. As long as pilots can find a power outlet at the end of the day, they can expect a fully operational aircraft when they want to fly again.
“As most early customers have ordered the aircraft with 18m span we have decided to make the 18m version our standard but offer exchangeable 15 m wingtips as an optional extra. With the longer wingtips the best L/D is 48:1 and, with a 75kg pilot on board, the wing loading is in the 41kg/m2 range. As you would have just noticed, the polar curve remains rather flat well into the mid to upper speed range. For competition purposes, or for pilots preferring to fly with wing loadings of around 50 kg/m2, we can install an optional water ballast system.”
Then I asked him why he had not gone for an FES system. “This is what I get asked a lot,” Uli replied and added, “The FES system is also an easy-to-operate drive system and when used as a sustainer, the poorer efficiency of the small diameter propeller does not play such a big role. But the majority of our customers want a powerful self-launcher, which even allows trouble-free takeoffs from soft, unsealed airstrips.
“But that alone doesn’t explain why we selected a fully retractable drive system. We also considered aerodynamic and performance aspects as well as pilot comfort. A foldable but external propeller creates a turbulent airflow along the entire length of the fuselage. It affects a glider’s performance and that holds true even when fellow manufacturers claim an ‘almost negligible performance degradation’.
“Also, the space requirement for the motor dictates that the rudder pedals have to be mounted further aft, which often becomes problematic, especially for taller pilots. Another problem is the cooling of the internal motor. The heat and noise generated impacts on pilot comfort, which is totally contrary to our philosophy. Poor motor accessibility and high voltage cables in the cockpit are other reasons for our decision to put the motor in a fully enclosed box behind the pilot.”
“That makes perfectly good sense,” I said. “But do you think that batteries will be the dominant power source in future?”
Uli replied, “Our research indicates that the rapidly increasing acceptance of electric cars is slowly swapping over to glider pilots. That’s not surprising. After all, to get airborne we only need power for a few minutes and a battery is ideal for that. Still, for today’s customers, total independence is usually right on top of the list of priorities, although reliability, a low cost of ownership and environmental friendliness are also important factors.
“Our AS 34 Me ticks all these boxes and, on top of that, it offers a very simple motor management, low noise emissions, no relevant power reduction at altitude, vibration-free running and – last but not least – it eliminates fuel smells and exhaust fumes. Finally, not carrying the batteries in the fuselage gives the AS 34 Me a wide cockpit load range of 70 to 115 kg plus an additional payload for baggage. I’m sure this technology will revive the attraction of our sport in all corners of the globe.”
I thanked Uli for taking half a day off and for letting me test his latest creation – but not without first adding my 2 cents worth on the future of gliding. “In the long run, only gliders will prevail that require no more power plant maintenance than a mobile phone,” I said. With these words of wisdom it was time to say “Auf Wiedersehen” and get back to my brother’s granny flat to crack a cold one and put another sausage on the barby. Yes, I know, it’s a tough life, but...