Sound of Silence: Testing the e-Spyder
By Willi Tacke
German aviation reporter Willi Tacke shares his experience test-flying the prototype e-Spyder at the factory in China. Willi’s firm, Flying Pages GmbH, represents EAA publications in Europe and Asia.
I’m in Jinxi, west of Shanghai, just two days after the opening ceremony of the new Yuneec International factory. I have the chance to be the first journalist to fly the prototype of what will be the world’s first commercial production electric ultralight aircraft. It’s the e-Spyder, an American-Chinese collaboration with a Flightstar-designed airframe. At the final takeoff check, Clive Coote, U.K. managing director of Yuneec International, explains the engine controls of this unique aircraft. The plastic case on my left hand looks more like part of a video game than the throttle control of an engine. I basically know the aircraft itself, though; a Flightstar was one of the first tube and fabric ultralights I flew back in the ‘80s. Lastly, the rudder, elevator, and engine check is completed.
I’m now ready for takeoff, the wind perfect down the runway, but there’s another interruption. They send a worker to clear a Caterpillar machine 200 meters down my runway. It’s because the runway we’re using isn’t really a runway. It’s one of the many brand-new streets in the Jinxi-local eco-industrial park in which the new Yuneec factory is located. The yellow machine moves out of the way. Now it’s free and my turn. I shift the little button on the top left from off to on and press the Yuneec logo that appears on the liquid crystal display of the control unit. After five seconds, “ready” appears. Now I press the green button, and after a few seconds the screen with the battery voltage appears in the top left position. The engine is ready to go.
The e-Spyder engine controls
With the little panel, I have the information on voltage, current time, rpm of the prop/engine, temperature of controller and engine, as well as a low-battery warning. The engine normally operates at 66.6 volts, and the controller sits between the batteries. “The voltage of the battery at takeoff is 75 volts, and during the flight it constantly drops,” explains Yuneec CEO Tian Yu, who is standing next to the cockpit. “When it’s under 67 volts, you should come in to land as they are only five minutes engine time left in the battery. At less than 59 volts, the controller cuts off the engine to protect the batteries, which will be damaged if they would be discharged more.” Tian adds. The only other instrument I have on board is a Bräuniger/Flytec hang-gliding variometer/altimeter on my leg, not including the Hall wind meter on the left wing strut.
“Clear prop.” I shift the lever on the right side forward, a warning sounds, and then the prop begins to turn. I push the power lever slowly forward till the end. Instead of an engine roaring, there’s just the sound of the accelerating prop and a background sizzling of the electric engine as if an electric golf cart is accelerating. The aircraft accelerates normally, and after about 100 meters I reach the rotating speed of 25 mph. Seconds later I’m airborne and climbing with a speed of about 30 mph as indicated by the Hall wind meter. The variometer indicates around 3 meters per second climb. I level off at 150 meters and reduce the throttle from the 2000 rpm at takeoff to a gentle 1550 rpm. This now is the real “sound of silence.” There’s just the whispering of the airflow behind the windscreen at 45 mph, very little prop noise, and that’s it. The silence, the warm evening, wind in the open cockpit—this is really something special. It’s almost like flying an open glider such as a SWIFT (swept wing with inboard flap trim) or a hang glider.
Handling of the aircraft is very fine with light forces and immediate reaction at three axes. The aircraft is autostable. At one point when I push the stick forward, it levels itself out rapidly. With the machine trimmed at 40 mph, I push the slider forward and it starts climbing; when I reduce thrust, it descends. I measure the roll rate at about 2.5 seconds. When I slide the “gas” forward till the end and push the stick forward, the Hall wind meter reaches its top at 65 mph. The nose nicks down gently when I pull the stick back with no thrust in level flight at about 25 mph indicated airspeed.
After about 20 minutes, I try my first approach. I use a short steep final, so if the engine quits, I still would make the “runway” because the ground around this new street is not very flat. I fly one low pass for the pictures. After another round, the voltage drops below 67 volts and I come in to land. A soft flare-out is no problem, thanks to the very responsive elevator. Although the e-Spyder has no brakes due to the microlight weight regulations, it’s no problem as it stops after only 50 meters. I taxi back to the beginning of the runway and ask Clive, “Can we quick change the batteries? I want to get airborne again; this e-flight is addictive.” After only three minutes, I’m airborne again and I fly until sunset.
Landing at the factory in China
The next day, I have the chance to fly the aircraft several more times from the little grass strip at the Yuneec factory by the lake. Each flight is about half an hour, and some are even in thermal conditions where I see another advantage of electric power. While thermalling, just pull the slider back to make the engine stop. As soon as power is needed again, it’s there. For motorgliders, there’s a nice option to combine the engine regulation with the variometer; you just set it for level, and the engine adds exactly the power needed to maintain altitude. As soon as you start climbing, the engine stops totally.
On one flight I discover why the engine regulating/throttle system must be modified. After taking some air-to-air shots of paramotor world champion Michel Carnet flying with the Yuneec e-pack, I come back to the airfield and want to reduce engine power to get down. I accidentally bump the on-off switch with my thumb, causing the engine to stop, when I put my hand on the control unit to pull back the throttle slider. I know it takes some time to go through the start procedure until it will run again, so I begin a pattern for a landing without the engine. Luckily I’m close to the airfield and high enough that I can go through the start-up procedure. Switching to on, the display ready (green button—numbers showing on the display), then pushing the throttle slider forward, I hear the engine warning sound, and a second later the engine runs again. I turn on final approach over an old-style fishing boat and make a smooth landing on the grass strip. When I speak with Clive and Flightstar’s Tom Peghiny about the incident, they both confirm that the solution is already under development. The on-off switch and the engine instruments will be on a small instrument panel in the carbon nose fairing, and for the throttle, there will be a real lever for the pilot’s left hand.
Clive Coote of Yuneec International and e-Spyder designer Tom Peghiny (on right in helmet)
The idea for the e-Spyder was born in April 2009 at Aero Friedrichshafen when Tian met Tom at the Flying Pages/EAA booth. Tian was already planning to be in EAA AirVenture Oshkosh with his E430 two-place electric airplane. To round out the Yuneec program with an ultralight single seater, the idea of the e-Spyder was born. The engine was delivered in the summer, and the aircraft flew for the first time shortly before Oshkosh. “Basic work was to reduce the weight of the engine with its two 12.5-kg battery packs to fit into the part 103 ultralight limit of 115 kg,” Tom says. “A carbon nose fairing with a smaller windscreen , some lighter tubing, lighter main and nose gear, smaller wheels, and no brakes were the major changes. As the engine arrived quite late, I did not have time to adjust much for flying in Oshkosh. For example, the prop we used was not ideal, and we have made big progress with the bigger Helix prop we now are using here in Shanghai.”
Now that the decision to bring the e-Spyder to the market as the first serial e-plane has been made, Tom will work on additional details. For example, a light aerodynamic covering for the engine is planned, and the batteries will be moved out of the drag zone at the main boom to a place where they produce less drag. “For the second prototype, I also want to enlarge the wingspan from about 1 meter to about 10 meters and perhaps add some formed wingtips,” continues Tom enthusiastically. “We probably will work with another sailcloth to reduce the weight again. All these changes are made to reduce drag of the aircraft and to increase glide ratio and sink rate because this is the simplest way to stay in the air longer.”
If the schedule can be kept, the aircraft will be ready for sale by next spring as Tian is right now ramping up the engine production. In the long term, the whole airframe will be produced in China. The good thing for many markets is that the aircraft can be flown in the deregulated ultralight class, which wouldn’t require engine certification as with the light-sport aircraft (LSA)/ultralight class in some countries. For the moment in the United States, the LSA electric engines aren’t allowed and cannot yet be implemented through the American Society for Testing and Materials standard which requires that an LSA must have a single combustion engine. In Germany, heavier versions could be flown as microlight since the Flightstar already has full microlight certification. The future of flying with the “sound of silence” is here. To learn more, go to Yuneec International or contact Flightstar Sportplanes.
Contact Willi Tacke through www.Flying-Pages.com. Flying Pages publications include the World Internet Directory of Leisure Aviation. Listen to Willi on UltraFlight Radio talking about electric flight and other types of power sources for the future of flight.