Ampaire flies second version of its Electric EEL for the first time


USA-based hybrid-electric aircraft developer Ampaire flew its second technology demonstrator last week, a refined version of its Cessna 337 conversion called the Electric EEL.

During the 35 minute flight, which took place on September 10, test pilot Justin Gillen climbed to 3,000ft and made a series of handling and power checks, assessing engine and motor performance, temperatures and other readings, with both powerplants performing as expected.

The flight test aircraft, the Hawai‘i Bird will fly for a series of checkouts before being shipped to Hawai‘i in October. The aircraft will then be used in a series of demonstration flights to be conducted by Ampaire and Mokulele Airlines pilots on air routes in Hawai‘i.

The Hawaii Bird will be able to fly most Mokulele routes round trip before a required recharge.

The flights will be the first time an electrically-powered aircraft has flown under an FAA market survey experimental aircraft certificate in order to gain real-world flight experience.

Ampaire CEO Kevin Noertker said, “Since flying our first Electric EEL last year, we have made substantial improvements to the power train for efficiency, increased performance, reliability, and safety.

“This technology is scalable with wide applications for scheduled passenger and cargo services, as well as charter services. Our flights with Mokulele will be an opportunity to test both the aircraft and the infrastructure required to advance electric aviation and transport access in Hawai‘i.”

Noertker said he expected the company to leverage knowledge from the 337 conversion program into retrofits of larger regional aircraft that could enter service in just a few years.

The Hawai‘i Bird is powered by a conventional combustion engine, a 310-horsepower/231 kW Continental IO-550 in the tail, and a 200kW-capable electric motor in the nose, limited in this application to 120 kW.

In this second conversion, the aircraft’s battery pack has been relocated from inside the cabin to the underside of the fuselage and enclosed in a composite aero-optimized shell. The new configuration frees cabin space for flight test engineers, test equipment, and observers.

In this latest conversion, the Electric Power Unit (EPU) used by the aircraft is designed for improved energy efficiency with less weight. The EPU has better thermal margins thanks to a liquid cooling system versus the previous air-cooling system.

The aircraft also has improved cockpit instrumentation and power controls for monitoring outputs from the combustion engine and electric motor. Designed to cruise at 120 knots for 1 hour and 15 minutes, plus a 30- minute reserve,

Amparie believes its Electric EEL and similar hybrid-electric aircraft can cut direct aircraft operating costs and emissions by up to 50% versus conventional aircraft.

Stan Little, Chairman and CEO of Southern Airways, which owns Mokulele, said, “Electric aviation is the future for the commuter airline industry, and through our partnership with Ampaire, we intend to be at the forefront of that innovation.

“These test flights hold the promise of expanding inter-island service by lowering costs while reducing our environmental footprint—both great benefits to the people of Hawai‘i . What we are doing today is what everyone will be doing someday.”

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Ben has worked as a journalist and editor, covering technology, engineering and industry for the last 20 years. Initially writing about subjects from nuclear submarines to autonomous cars to future design and manufacturing technologies, he was editor of a leading UK-based engineering magazine before becoming editor of Aerospace Testing in 2017.

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