Hydraulic and Pneumatic Systems Flashcards
6 cards from real A&P practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Hydraulic and Pneumatic Systems flashcards as text
What type of pump is most commonly used as the primary hydraulic pump in turbine-powered aircraft?
Answer: Variable-displacement piston pump
Variable-displacement axial piston pumps are standard on turbine aircraft because they automatically adjust output to maintain constant system pressure without a separate pressure regulator.
How is a hydraulic selector valve different from a check valve?
Answer: A selector valve directs fluid flow to different actuators, while a check valve only allows one-directional flow
A selector valve (directional control valve) routes pressurized fluid to one side of an actuator while returning fluid from the other side, whereas a check valve simply prevents reverse flow.
What does a hydraulic fuse (thermal relief valve) protect against?
Answer: Fluid loss downstream of a ruptured line by automatically closing when flow exceeds a set rate
A hydraulic fuse detects abnormally high flow rates (indicating a downstream rupture) and closes to isolate that section, preserving fluid for the rest of the system.
When bleeding a hydraulic brake system on an aircraft, fluid is introduced at the:
Answer: Wheel cylinder bleeder fitting and flows toward the master cylinder
When pressure-bleeding aircraft brakes, fluid is forced upward from the wheel cylinder bleeder fitting toward the master cylinder to push air bubbles up and out.
What material are most modern aircraft hydraulic lines made from in high-pressure sections?
Answer: 21-4N stainless steel or titanium tubing
High-pressure hydraulic lines in areas subject to vibration and high stress are made from corrosion-resistant steel (CRES) or titanium alloy tubing rated for the system pressure.
What is the purpose of the desiccant in an aircraft pneumatic system?
Answer: To remove moisture from compressed air before it reaches system components
Desiccant (moisture-absorbing material) in the pneumatic system removes water vapor from compressed air to prevent corrosion, ice formation, and seal damage in system components.