The annual fly in at Arlington, Washington was an electric landing zone for Mark Beierle’s Gull 2000, powered by his own design 20-kilowatt motor. The 36-coil, 42 magnet disk, weighing 16 pounds, is mounted on a truss arrangement behind the airplane’s high wing, and drives a ground-adjustable pusher propeller.
Flying five half-hour demonstration flights during the half-week event accounted for almost half the six hours total time on the airplane so far.
The airplane has a 74-Volt Rhino Lithium-polymer battery pack made up to 11 packs in a parallel/series arrangement. Beierle says this array, and taking voltage from the ends of each 3.7-Volt series pack, allows balancing of all 210 cells. Power is run through a 500-Amp Kelly controller, which weighs about 12 pounds: Beierle hopes to try a new Kelly unit which will be half that weight and less expensive. Battery protection is provided by circuits in the charger, which will be the same Kelly unit Beierle uses in recharging his electric cars. Incidentally, he uses the same battery packs in his ground vehicles.
A Cycle Analyst device monitors motor performance and battery status. Normally used on bicycles, the Analyst is a low-budget instrument which fits the economical approach favored by Beierle.
Originally powered by a PMG 132 motor, the Electric Gull 2000 was a bit short on performance. The new motor, designed with the help of a German physicist, is a considerable improvement, according to Beierle. He built the motor from computer drawings by his designer, who then joined Mark for early testing and tweaking of the machine.
The new combination provides an attractive performance profile. The airplane can maintain flight for 1.5 hours at a cruise of 65 miles per hour.
Beierle reports pulling 217 Amps on takeoff, 211 in climb, and only 40 Amps at 55 mph. He has not used full power yet, but will after adjusting the pitch of the propeller to require more amperage for takeoff.
He is also looking at Joby Motors’ JM2 series, noting the even greater power and reasonable price. This would make a nicely-priced power package, with the motor at $1,299, the controller at $1,000, and the battery pack costing about $2,000. A $4,299 system (not including instruments and cabling) attached to a $10,000 airplane could give hours of inexpensive flying.
Beierle claims ultralight status for the airplane, which like Dale Kramer’s electric Lazair, could make electric flight a realizable objective for many pilots. Both craft will be at AirVenture 2011 in Oshkosh, Wisconsin late in July. Live examples of what simple electric airplanes can be will probably excite a lot of interest on the ultralight field.