Definition
In a turbine engine fuel control unit, the fuel pressure measured at the outlet of the engine-driven fuel pump, before the fuel passes through the metering valve that sets the actual flow to the fuel nozzles.
Plain English
It is the fuel pressure on the pump side of the system, taken before any valve has reduced or controlled how much fuel will actually be sent to the engine.
Context Anchor
Seen in aircraft engine fuel-system maintenance, troubleshooting, and pressure checks.
Derivation
‘Unmetered’ comes from ‘meter,’ meaning to measure or portion out. So unmetered fuel is fuel that has not yet been measured or portioned by the metering valve. ‘High’ refers to its position upstream in the system, where pressure is still at full pump output.
Why Pilots Care
Unmetered pressure tells technicians whether the fuel pump is producing enough output. If it is too low, the engine cannot get the fuel flow it needs at high power; if it is abnormally high, something downstream may be restricted.
Grounding Statement
This term is about pressure on the supply side of the fuel system, before the fuel amount is controlled for engine use.
Intuition Check
Unmetered does not mean “not measured by a gauge.” Here it means the fuel has not yet passed through the part of the system that controls the amount delivered to the engine.
Example Sentence 1
The technician connected a test gauge to the fuel control to check high unmetered fuel pressure during the engine run.
Example Sentence 2
High unmetered fuel pressure readings led the technician to inspect the fuel pump and lines before the next flight.