The potential of electric and hybrid-electric propulsion has not yet impressed industry heavyweight Textron Aviation, according to the company’s top engineer.
The Wichita-based manufacturer has conducted several projects to investigate electric power as a full or partial substitute for jet fuel, Textron Aviation’s senior vice-president of engineering, Brad Thress, said during a press conference on 28 May.
So far, the arithmetic of electric storage devices, such as lithium ion batteries, still does not provide a persuasive case to replace standard, hydrocarbon-based fuels in aviation, he says.
“We’ve had several projects where we looked into it and did some I think respectable math and try to understand the physics of what’s good and what’s maybe limiting,” he says.
“I think that really fundamentally it comes back to power density. The ability to have about 2% the amount of power stored in a lithium ion batteries as Jet-A, that fundamental math is just hard to overcome.”
Some new entrants to the industry, such as Seattle-based and Boeing-financed Zunum Aero, are working on a hybrid-electric propulsion system for a six- to 12-seat aircraft with a range of about 700nm, with a goal of lowering operating costs by 30% compared with hydrocarbon-powered alternatives.
But Thress says that Textron Aviation’s studies have not provided persuasive evidence to support such a programme.
“You can hybridise it so you can at least use some stored electric power, but it’s very difficult to make an intercontinental airplane just because the power density isn’t what it needs to be,” he says.