FAA Aviation Mechanic Airframe (AMA)Hydraulic and Pneumatic SystemsMedium
An aircraft's main hydraulic system normally operates at 3,000 psi, but the wheel brake system is limited to a maximum of 1,500 psi. Which component allows the brake system to safely share the same hydraulic power source?
- APriority valve
- BPressure reducer (reducing) valve
- CSequence valve
- DThermal relief valve
Show answer & explanationAnswer & explanation
Correct answer: B. Pressure reducer (reducing) valve
A pressure reducer valve lowers system pressure to a fixed, lower value for a subsystem such as wheel brakes, protecting components rated for lower pressure. A priority valve instead restricts flow to nonessential systems during low-pressure conditions, and a sequence valve controls order of operation, neither of which reduces pressure level.
Why the other options are wrong
- A. A priority valve manages flow priority during low pressure, not pressure level reduction.
- C. A sequence valve controls the order of actuator movement, not pressure magnitude.
- D. A thermal relief valve relieves pressure buildup from thermal expansion in isolated lines.
Pressure Reducer (Reducing) Valve
A hydraulic valve that reduces main system pressure to a lower, regulated value for a subsystem such as wheel brakes.
- Protects lower-pressure-rated components
- Different function from priority valve (flow priority)
- Maintains constant reduced outlet pressure despite main system fluctuations
Memory trick: Reducer valve = a pressure 'step-down transformer' for brakes.