Definition
Cockpit instruments that display the rate at which fuel is being delivered to the engine, typically shown in pounds per hour (PPH) or gallons per hour (GPH). On reciprocating engines they usually measure fuel pressure at the carburetor or fuel injection unit and translate that into an equivalent flow rate. On turbine engines they measure actual mass flow of fuel passing to the combustion section.
Plain English
Gauges that show how fast the engine is using fuel right now, usually in gallons or pounds per hour.
Context Anchor
Seen in instrument flying, engine monitoring, power setting, and fuel planning discussions.
Derivation
Gauge comes from an old word meaning to measure or judge the amount of something. That helps here because a fuel flow gauge is not a fuel tank indicator; it measures the rate of fuel use.
Why Pilots Care
Readings allow pilots to monitor engine health, calculate remaining range, and adjust power settings to prevent fuel exhaustion or detect system malfunctions.
Grounding Statement
If a fuel flow gauge reads 10 gallons per hour, the engine is using fuel at about that rate at the current power setting.
Intuition Check
Do not read a fuel flow gauge as a fuel quantity gauge. It shows fuel use rate, not fuel remaining.
Example Sentence 1
After leveling off in cruise, the pilot leaned the mixture and watched the fuel flow gauge settle at 8.5 gallons per hour.
Example Sentence 2
A sudden increase in the fuel flow gauge reading prompted the pilot to check for a possible leak or rich mixture condition.