In a hydromechanical fuel control, how is fuel metered to the engine?

In a hydromechanical fuel control, how is fuel metered to the engine?

• A. By electronic servo
• B. Through cams and servo valves
• C. By manual lever
• D. By gravity feed

Answer: (B)

Fuel metering in a hydromechanical fuel control is achieved by translating throttle and engine speed inputs into a precise valve position using cams that drive a hydraulic servo valve. The metering system is fed by high-pressure fuel, and the cam surfaces set the allowable range and timing of fuel flow. As the throttle moves and the engine responds, the cam arrangement governs how much the servo valve opens or closes. The servo valve then modulates hydraulic pressure to the metering valve, which directly controls the amount of fuel that can reach the engine’s fuel metering passages and ultimately the combustors. This combination of cam-driven timing and hydraulic servo control provides accurate, responsive metering without relying on electronic control or manual levers.

Fuel metering in a hydromechanical fuel control is achieved by translating throttle and engine speed inputs into a precise valve position using cams that drive a hydraulic servo valve. The metering system is fed by high-pressure fuel, and the cam surfaces set the allowable range and timing of fuel flow. As the throttle moves and the engine responds, the cam arrangement governs how much the servo valve opens or closes. The servo valve then modulates hydraulic pressure to the metering valve, which directly controls the amount of fuel that can reach the engine’s fuel metering passages and ultimately the combustors. This combination of cam-driven timing and hydraulic servo control provides accurate, responsive metering without relying on electronic control or manual levers.