Definition
The amount of usable fuel currently on board the aircraft, typically measured in gallons or pounds and indicated by fuel quantity gauges in the cockpit.
Plain English
How much fuel is in the tanks right now that the engine can actually use.
Context Anchor
Pilots encounter fuel quantity during preflight checks, fuel planning, and while reading the cockpit fuel gauges in flight.
Derivation
Fuel comes from an old word meaning material used for burning. Quantity comes from Latin words meaning “how much.” Together, fuel quantity means how much burnable fuel is available for the airplane’s engine.
Why Pilots Care
Knowing the exact amount of fuel onboard determines whether the aircraft can complete the planned flight without running out.
Intuition Check
Do not assume fuel quantity means only what the cockpit gauge shows. In flying, it means the actual fuel available to the airplane, which should be checked and confirmed, not guessed.
Example Sentence 1
Before engine start, the pilot checked the fuel quantity gauges and confirmed the readings matched what was seen during the visual inspection of the tanks.
Example Sentence 2
After takeoff the fuel quantity indicator showed 35 gallons remaining, giving the pilot a clear picture of endurance for the return leg.