A&P A&P - Aircraft and Powerplant Hydraulic and Pneumatic Systems 2 — Questions and Answers
Question 1: What is the primary purpose of a hydraulic system's thermal relief valve?
- Relieve pressure caused by thermal expansion of trapped fluid (Correct answer)
- Reduce system pressure during normal operation
- Open when a selector valve is activated
- Allow fluid to bypass the filter element
Correct answer: Relieve pressure caused by thermal expansion of trapped fluid
A thermal relief valve opens to relieve excess pressure caused by thermal expansion of hydraulic fluid trapped in a closed loop.
Question 2: Which seal material is compatible with Skydrol hydraulic fluid?
- Butyl rubber or ethylene propylene (EPDM) (Correct answer)
- Buna-N (nitrile) rubber
- Natural rubber
- Neoprene
Correct answer: Butyl rubber or ethylene propylene (EPDM)
Butyl rubber and EPDM seals are compatible with Skydrol; nitrile and neoprene seals are degraded by phosphate ester fluids.
Question 3: How is a hydraulic actuator classified when it can produce force in both directions using hydraulic pressure?
- Double-acting actuator (Correct answer)
- Single-acting actuator
- Tandem actuator
- Rotary actuator
Correct answer: Double-acting actuator
A double-acting actuator uses hydraulic pressure on both sides of the piston to produce powered movement in two directions.
Question 4: What is indicated when hydraulic fluid appears milky or foamy?
- Water contamination or air entrapment in the fluid (Correct answer)
- Normal fluid aging and oxidation
- Overheating of the reservoir
- Incompatible fluid mix causing gelation
Correct answer: Water contamination or air entrapment in the fluid
Milky or foamy hydraulic fluid indicates water contamination or air entrapment, both of which degrade system performance.
Question 5: What is the function of a hydraulic fuse in an aircraft system?
- Automatically shut off fluid flow if flow rate exceeds a preset limit due to a line break (Correct answer)
- Filter large particles from the fluid
- Maintain constant system pressure
- Prevent fluid from flowing backward
Correct answer: Automatically shut off fluid flow if flow rate exceeds a preset limit due to a line break
A hydraulic fuse shuts off flow automatically when it detects excessive flow, protecting against system loss from a ruptured line.
Question 6: In aircraft pneumatic systems, what component limits output pressure to a preset value regardless of source pressure?
- Pressure regulator (Correct answer)
- Relief valve
- Restrictor
- Unloading valve
Correct answer: Pressure regulator
A pressure regulator reduces and maintains downstream pressure at a constant preset level regardless of upstream pressure variations.
A&P A&P - Aircraft and Powerplant Hydraulic and Pneumatic Systems 2
What is the primary purpose of a hydraulic system's thermal relief valve?