Firefly Front Angle Pad

Stratford, Connecticut, USA

The Sikorsky Firefly is a modified Schweizer S-300C announced on July 26, 2010 at AirVenture 2010 in Oshkosh, Wisconsin, USA, as a technology demonstration and was said to be a stepping stone to successful electric helicopters. Sikorsky had been working on the project for more than two (2) years and has never revealed the cost of the project.

There are 300 battery cells, installed in two battery packs (150 cells in each pack) located on each side of the helicopter, weighing 1,170 pounds (530 kg) and were manufactured by Gaia Power Technologies based in Germany. U.S. Hybrid, with several offices in the USA, modified a land vehicle’s electric motor and built a 190 hp (142 kW) electric motor custom-made for the helicopter. The modifications of the electric engine included adding an additional 40 horsepower, provided consistent 3,200 RPM and used forced air cooling instead of water cooling. Engineers at Eagle Aviation Technologies, based in Virginia, USA, modified the airframe and motor mount, then installed the motor and digital controller for the helicopter.

The Sikorsky testbed figures showed huge improvements in efficiency. The main rotor output is 76.3% efficient in the electric version versus 25.5% for a Sikorsky 76-D luxury helicopter running two (2) Pratt & Whitney PW210S turboshaft engines on JetA fuel. The other notable comparison is heat loss, where the electrical system loses just 15% compared to 73.4% on the 76-D helicopter. They used software to slow the electric engine, to mimic a gas-powered engine to help the pilot and the rotor’s bearings, apparently on start-up, during flight and shut-down.

Sikorsky also noted that this electrically powered helicopter simplifies the complexity of the propulsion system by reducing the quantity of moving parts, reduces heat loss, increases reliability, reduces noise inside and outside the helicopter, reduces vibration, has no emissions and reduces direct operating costs.

Sikorsky estimated that with one pilot only, it could fly for 12 to 15 minutes at a top speed of 80 knots (92 mph/148 kmh). The helicopter could still autorotate, if the batteries lost their power, and a helicopter pilot could safely land the helicopter in any open space. The aircraft was never flown.

While the Sikorsky Firefly has been called the world’s “first all-electric helicopter”, a French based company flew the world’s first all electric helicopter named Solution F with a manned-tethered flight on August 4, 2011 and the first free manned-hover flight on August 12, 2011.

Sikorsky Firefly side view
Sikorsky Firefly side view
Sikorsky Firefly internals
Sikorsky Firefly cross-section
Sikorsky S-300C internals
Sikorsky S-300C cross-section

Specifications (predicted):

Passengers 2
Maximum Take Off Weight 2,050 lb 929.9 kg
Max Flight Time
15 min
Maximum Cruise Speed 86 kt 159.3 kg
Max Motor Horsepower
190 hp 141.6 kW
Battery Weight
1150 lb 521.6 kg
Battery Voltage 370 volts



Sikorsky, Electric HelicoptersScaled PrototypeDefunct2 PassengersElectric/Batteries, PilotedVFS Member