Plain English Meaning

Built-in size and shape differences between fuel ports and fuel nozzles that physically stop someone from putting jet fuel into a piston aircraft, or vice versa.

Full Definition

Physical features fitted to an aircraft's fuel filler port and to fuel nozzles that prevent the wrong type of fuel from being introduced into the aircraft. On piston aircraft, the filler opening is sized so that the larger jet fuel nozzle will not fit, blocking accidental fuelling with jet fuel.

Context Anchor

Seen in preventive maintenance discussions, aircraft fueling procedures, and inspections of the fuel filler openings.

Derivation

‘Misfueling’ combines ‘mis-’ (wrong) with ‘fueling.’ The devices are ‘anti-’ (against) misfueling — physical safeguards against putting in the wrong fuel.

Why Pilots Care

Putting the wrong fuel in an engine can cause immediate failure or long-term damage; these devices block that error at the .