A turbine fuel control system without electronic interface is known as what type?

• A. Electronic control unit
• B. Electrohydraulic system
• C. Hydromechanical system
• D. Pneumatic servo system

Answer: (C)

Hydromechanical fuel control meters fuel using only mechanical linkages and hydraulic power, with no electronic signals or control units involved. The throttle input and engine speed influence a fuel metering valve through springs, levers, and a hydraulic servo driven by engine‑generated hydraulic pressure, producing the required fuel flow purely through mechanical-hydraulic means. This distinguishes it from systems that rely on electronic interfaces (electronic control units or electrohydraulic control) or air-driven (pneumatic) actuation.