Ampaire will begin taking letters of intent for its Electric EEL hybrid airplane next week at EAA AirVenture in Oshkosh, Wisconsin, the Hawthorne, California-based manufacturer announced yesterday. EEL is a retrofit of a Cessna 337 Skymaster.

“The Ampaire Electric EEL is the first step in bringing lower emissions, lower operating costs, and quieter operations to general aviation through electrification,” Ampaire CEO Kevin Noertker said. He added the push-pull airplane’s hybrid-electric conversion will reduce its fuel cost and maintenance by about 50 percent. 

Two variants will be offered: one with a 310-hp Continental IO-550 piston engine and a 215-hp (160-kW) electric propulsion system and the other with a 300-hp Continental CD-300 diesel engine and the same 215-hp electric system. Customers have a choice of selecting a pressurized or unpressurized cabin, as well as four or six seats. Winglets and a STOL kit are standard. “This is something new and exciting in general aviation—twin-engine redundancy and performance on as little as 10 gallons per hour in cruise flight,” Noertker added.

Last month, the EEL completed its first test flight and is undergoing systems evaluation and envelope expansion in a 30-month-long flight-test program. Certification is expected in 2021. Ampaire said the EEL will be priced competitively with comparable in-production piston twins.