HEFOEHydraulic Electrical Fuel Oxygen Engine
References in periodicals archive ?
I was unclear why he couldn't put his boards in, so I gave him a HEFOE signal and then the international signal for "What?
The solo again appeared to be showing HEFOE signals, this time with two fingers.
We tried to use HEFOE signals during the RTB to have our solo check and report on his systems.
When asked about his first HEFOE signal, the one he gave just before breaking away from the flight, he thought he'd passed four fingers.