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Two sections of a hydromechanical fuel control

Aviation Mechanic Powerplant (AMP) practice question 1 of 20 on Engine Fuel and Fuel Metering Systems. ACS element AM.III.I.K6 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Powerplant (AMP) practice mode.

Question bank updated 2026-09-22

QUESTIONA hydromechanical turbine engine fuel control is made up of which two sections?

  1. AComputing and metering
  2. BPressurizing and dumping
  3. CSensing and pressurizing
Show the answer and explanation

Correct answer: A. Computing and metering

  • A — correct The handbook states that fuel controls have two sections, computing and metering, which together provide the correct fuel flow for the engine.
  • B — incorrect Pressurizing and dump valves are separate downstream components that divide and trap fuel for the nozzle manifolds; they are not the two sections of the control itself.
  • C — incorrect Sensing is part of the computing function, and pressurizing is done by a valve located downstream of the metering valve rather than by a section of the control.

BACKGROUND

Hydromechanical fuel controls were used and are still used on many engines, although their use is giving way to electronic controls. Fuel controls have two sections, computing and metering, that work together to provide the correct fuel flow. A pure hydromechanical control has no electronic interface assisting in computing or metering, and it is generally driven by the gas generator gear train so that it can sense engine speed. Other parameters it senses mechanically include compressor discharge pressure, burner pressure, exhaust temperature, and inlet air temperature and pressure. Once the computing section determines the correct fuel flow, the metering section delivers fuel to the engine through cams and servo valves.

STUDY TIP

Remember that every fuel control, regardless of type, first computes how much fuel is needed and then meters that amount. In a FADEC the computing moves into the electronic engine control while the metering stays in the valve.

KEY POINTS

  • Fuel controls consist of a computing section and a metering section.
  • A pure hydromechanical control has no electronic interface in either section.
  • It is driven by the gas generator gear train so it can sense engine speed.

SOURCES

  • amp-powerplant/ch02.txt "Hydromechanical Fuel Control"
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MORE ON ENGINE FUEL AND FUEL METERING SYSTEMS

SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-32B Aviation Maintenance Technician Handbook – Powerplant, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.