The hydromechanical Unit (HMU) supplies the injectors with fuel at a pressure which is regulated by such factors as compressor output pressure(P3), compressor temperature(T2), the position of the engine power and condition levers on the flight deck and gas-generator speed(Ng).

What is hydromechanical fuel control?

Fuel controls have two sections, computing and metering, to provide the correct fuel flow for the engine. A pure hydromechanical fuel control has no electronic interface assisting in computing or metering the fuel flow. It also is generally driven by the gas generator gear train of the engine to sense engine speed.

What is turbine engine fuel metering?

The fuel metering device meters the fuel using only outputs from the EEC. Most turbine fuel controls are quickly going to the FADEC type of control. This electronically controlled fuel control is very accurate in scheduling fuel by sensing many of the engine parameters.