Fuel pressure from the fuel metering unit is used by FADEC to operate which components?

• A. The variable geometry guide vanes of the N2 compressor and the Operability Valve
• B. The N1 fan blades and the bleed air valve
• C. The turbine nozzle and the exhaust valve
• D. The oil pump and fuel pump

Answer: (A)

Fuel pressure from the fuel metering unit provides the hydraulic power FADEC needs to drive two key actuators: the variable geometry guide vanes of the N2 compressor and the operability valve. By supplying controlled fuel pressure, FADEC can adjust the N2 compressor inlet geometry to optimize performance and surge margin across different operating conditions. It also uses the operability valve to manage fuel delivery during startup and transient events, helping maintain safe and stable operation. Other components operate from different systems or drives (for example, N1 fan blades are mechanically driven by the engine core, bleed-air valve and turbine nozzle use separate hydraulic/pneumatic controls, and pumps are powered through separate paths), so they aren’t actuated directly by the FMU fuel pressure.