FAA Aviation Mechanic Airframe (AMA)Hydraulic and Pneumatic SystemsMedium
During a hydraulic system functional check, a technician notes that system pressure repeatedly spikes above the normal operating range before dropping back down, even though the pump and regulator appear to be functioning correctly. Which component is most likely malfunctioning?
- AThe system relief valve
- BThe priority valve
- CThe thermal relief valve
- DThe hydraulic fuse
Show answer & explanationAnswer & explanation
Correct answer: A. The system relief valve
The system relief valve is designed to open and dump excess fluid back to the reservoir whenever pressure exceeds a preset maximum, protecting the system from over-pressurization. If it fails to open promptly or reseats incorrectly, pressure spikes above normal range will occur repeatedly.
Why the other options are wrong
- B. A priority valve controls which subsystems receive flow when pressure is low, not high-pressure spikes.
- C. A thermal relief valve only protects isolated line segments from heat-induced expansion, not overall system pressure spikes.
- D. A hydraulic fuse shuts off flow after a line rupture; it doesn't regulate normal operating pressure.
System Relief Valve
A pressure-limiting valve set to open at a pressure slightly above normal system operating pressure, protecting components from damage due to overpressure.
- Opens at a preset maximum pressure
- Routes excess fluid back to reservoir
- Distinct from thermal relief valves, which protect isolated segments
Memory trick: Relief valve = the 'pressure cop' that stops things from blowing up.