Risks associated with lithium-ion aerospace batteries became evident following Boeing 787 battery issues last decade.
But those incidents helped engineers better understand and prevent such risks, leading to development of technologies that will ensure the safety of Eviation’s in-development all-electric aircraft Alice, says Eviation’s chief executive.
CEO Omer Bar-Yohay outlined those technologies, which include an advanced battery management system, on 9 February. He also said Alice is “literally a few days away” from making first flight.
Speaking at the Pacific Northwest Aerospace Alliance’s annual suppliers’ event in Lynnwood, Washington, Bar-Yohay acknowledges previous troubles with lithium-ion batteries, citing the 787’s troubles, which forced that jet’s grounding.
He also notes Eviation itself lost one Alice prototype from a January 2020 ground fire – an incident involving lithium-ion batteries, according to a Federal Aviation Administration report.
Alice is a nine-passenger aircraft powered by twin 640kW (858hp) Magnix Magni650 electric propulsion systems. It will cruise at 250kt (463km/h) and have 440nm (815km) of range, according to Eviation. The company has aimed at 2023 certification.
Bar-Yohay says the 787 incidents spurred development of improved battery standards and new designs that can prevent battery fires and, in the case they do break out, keep fires from spreading.
A company called AVL, which makes battery systems for automakers Volkswagen Group and Porsche, is manufacturing and testing Alice’s batteries, Bar-Yohay says.
Alice’s battery system includes 75 “battery cassettes – or sub-batteries”, he adds. “Each one of those could be lost with no damage… to another cassette, so [fire] doesn’t propagate.”
The aircraft will be capable of flying for 30-45min after losing a cassette, though Bar-Yohay concedes serious problems could arise if multiple battery cassettes fail.
But he says Eviation developed an advanced “battery management system” to prevent fires from ever starting.
He describes the system as providing “envelop protection to the battery”. It accounts for factors including power demand, energy supply, weather and details related to the aircraft’s specific flight mission.
“That’s the heart” of the aircraft, Bar-Yohay says. “If you manage it correctly, something bad never happens.”
Alice will have sufficient battery power to fly for about 2.8h at maximum take-off weight – sufficient duration to operate countless regional routes, Bar-Yohay says. A 30min charge will allow for about 1h of flight time.
Alice’s batteries will be good for about 3,000h of flight – or about 1,000 flights. At that point, the batteries will have lost about 10% of their energy capacity, and will need to be replaced, Bar-Yohay says. But electric motors cost about half as much to maintain as do turboprops, he adds.
Eviation has in recent weeks been performing ground tests of Alice at Arlington Municipal airport in Arlington, Washington, where the company is based. The aircraft has reached ground speeds of 82kt. It takes off at 100kt, Bar-Yohay says.
Eviation intends to perform Alice’s final assembly, and to deliver aircraft, at Arlington. The company already has sufficient infrastructure there to produce 50 aircraft annually, and expansion could allow for annual production at Arlington of 150 aircraft, Bar-Yohay says.