US electric aircraft pioneer Ampaire has made the first flight of its updated Cessna 337 ‘Electric EEL’ hybrid-electric aircraft conversion, before going to Hawaii for tests on local air routes.
The ‘Hawaii Bird’, as it’s called, will be flown by Ampaire and Mokulele Airlines pilots on air routes in Hawaii later this year.
“Since flying our first Electric EEL last year, we have made substantial improvements to the power train for efficiency, increased performance, reliability, and safety,” said Ampaire CEO Kevin Noertker.
“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 Hawaii.”
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Noertker expects the company to leverage knowledge from the 337 conversion into retrofits of larger regional aircraft that could enter service in just a few years.
The Hawaii Bird is powered by a conventional 310-horsepower 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 aerodynamically-optimised shell. The new configuration frees cabin space for flight test engineers, test equipment and observers.
Ampaire says that an aircraft such as its Electric EEL can cut direct operating costs and emissions by 40-50 percent versus conventional aircraft.
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 120kt for 1 hour and 15 minutes, plus a 30-minute reserve, The Hawaii Bird can fly most Mokulele routes round trip before requiring a recharge.
During its 35-minute first flight, 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 aircraft will fly for a series of checkouts before being shipped to Hawaii in October.
Ampaire is working Elemental Excelerator, a climate tech ‘accelerator’ with more than 99 start-ups within its portfolio, to fund the Mokulele flight trials.
“Ampaire’s hybrid electrically-powered aircraft becoming an integral part of Hawaii’s transportation ecosystem will pave the way towards affordable and sustainable air transit throughout the US,” said Danielle J. Harris, Director of Mobility Innovation of Elemental Excelerator.
