A&P Hydraulic and Pneumatic Systems 2

Question 1

What type of pump is most commonly used as the primary hydraulic pump in turbine-powered aircraft?

Accepted Answer

Variable-displacement piston pump

Answer

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.

Question 2

How is a hydraulic selector valve different from a check valve?

Accepted Answer

A selector valve directs fluid flow to different actuators, while a check valve only allows one-directional flow

Answer

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.

Question 3

What does a hydraulic fuse (thermal relief valve) protect against?

Accepted Answer

Fluid loss downstream of a ruptured line by automatically closing when flow exceeds a set rate

Answer

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.

Question 4

When bleeding a hydraulic brake system on an aircraft, fluid is introduced at the:

Accepted Answer

Wheel cylinder bleeder fitting and flows toward the master cylinder

Answer

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.

Question 5

What material are most modern aircraft hydraulic lines made from in high-pressure sections?

Accepted Answer

21-4N stainless steel or titanium tubing

Answer

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.

A&P - Aircraft and Powerplant Certification Practice Test

A&P - Aircraft and Powerplant Certification Practice Test

A&P Hydraulic and Pneumatic Systems 2