FAA Aviation Mechanic Airframe (AMA)Hydraulic and Pneumatic SystemsMedium
A hydraulic line supplying a wing flap actuator ruptures in flight. The system is equipped with a device that senses excessive flow caused by the break and automatically shuts off fluid flow to prevent total loss of hydraulic fluid. What is this device called?
- AHydraulic fuse
- BThermal relief valve
- CPressure reducing valve
- DPriority valve
Show answer & explanationAnswer & explanation
Correct answer: A. Hydraulic fuse
A hydraulic fuse detects abnormally high flow rate, indicative of a line break, and closes to shut off flow, preventing complete loss of fluid in that system. Thermal relief valves respond to pressure rise from heat, not flow rate from a broken line.
Why the other options are wrong
- B. Thermal relief valves relieve pressure buildup from temperature, not line breaks.
- C. Pressure reducing valves lower steady-state pressure, not respond to line breaks.
- D. Priority valves ensure essential systems get fluid before non-essential ones.
Hydraulic Fuse
A safety device that senses abnormally high flow (as from a broken line) and shuts off fluid flow to prevent total system fluid loss.
- Responds to excessive flow rate, not pressure
- Protects against total fluid loss from line rupture
- Common in landing gear, flap, and brake lines
Memory trick: A fuse blows when flow floods too fast.