Company Profile |  Mobility

Boonsri Dickinson: August 20, 2010

An All-Electric Helicopter: How Far Will It Fly?

Is Project Firefly at Silkorsky Innovations the start of silent flight?

When Chris Van Buiten was at a White Zombie drag race a couple of years ago, he had a flash of inspiration when he saw the electric drag cars zip around the track in a flash. He thought: If this tiny electric car can beat this dragster down the line, what would happen if you could put an electric propulsion system in a helicopter?

That question propelled Van Buiten's curiosity when he returned to Sikorsky Innovations headquarters in Stratford, Connecticut. During a routine conference meeting, Van Buiten proposed making an electric helicopter. That fateful discussion laid the groundwork for the next two years.

Jonathan Hartman was named project manager and was put in change of developing the first electric helicopter for SI. Hartman remembers the conference room meeting well because it was where Project Firefly was born.

Soon, Project Firefly will undergo ground testing. The electric system consists of two lithium polymer batteries. The electric system sits nicely in a 1950s S-300 CTM helicopter minus the 190-horsepower four-cylinder gas engine.

Hartman said that there are no commercial uses for the aircraft and that it is the company's first attempt at learning about the electric technology in this evolving field. Still, if anyone is ever going to electrify flight, even partially, Silkorsky isn't a bad candidate. Helicopter pioneer Igor Silkorsky, who invented the first helicopter, founded the company, which is now part of mega-conglomerate United Technologies.

The most challenging part of the project was pulling all the parts together. The technologies in the engine haven't been used for aerospace before and have been tweaked so the motor runs on air-cooling instead of water. U.S. Hybrid, a company in California, tweaked the electric motors it uses in trucks and street sweepers.

Additionally, Eagle Aviation Technologies was called upon for their expertise in custom fabrication and aircraft assembly to make structural adjustments to the S-3000 CTM helicopter. The two 45Ah lithium-ion batteries come from Gaia Power Technologies.

As an unfortunate side effect of using batteries to power the helicopter, the familiar noisy engine isn't humming to let the pilot know that everything is OK. That's why SI is outfitting the helicopter with sensors and an LCD screen in the cockpit to provide real-time data to the pilot.

"By avoiding a noisy combustion engine, you lose the cues that the engine is running properly. We have a real-time health monitor, a temperature gauge, and something similar to a gas display to tell the pilot how much time is left on the battery packs," Hartman said.

To be of any commercial use, the helicopter would have to run for at least an hour. But with only two lithium batteries, it's only expected to last 15 minutes in the air. You can't just strap on more batteries, either -- for every pound you put on the aircraft, it's another pound you have to lift.

The batteries are heavy. Each battery pack weighs 585 pounds, so that's why there are only two in this rotor craft.

"Energy storage is the main roadblock for developing an electric-powered helicopter," Hartman said.

But who has time for the batteries to get up to speed? SI wants to develop an electric propulsion system that could work in new technologies along the way. As helicopter fuel costs soar (up 90 percent in 2008), the role of helicopters in the police force might literally be grounded due to financial constraints.

Energy storage and electric propulsion have to meet the flight requirements before a 100%-electric-powered helicopter becomes a realistic possibility.

"We are looking forward for battery technology to catch up to our aspirations, " Hartman said.

The only way to know if Project Firefly will carry its weight is to fly it.

The piloted test flight is expected later this year -- that is, if the ground tests and safety reviews run smoothly. At an airport in Connecticut, Hartman is pretty confident that Project Firefly will fly, but he knows the helicopter is limited by the existing technology.

Despite SI's impressive track record, Project Firefly might be way ahead of its time. Flying a manned electric helicopter later this year might be a one-off, but even still, it will mark the beginning of a new era in manned electric aviation.

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