Hydraulic & Pneumatic Systems Flashcards
7 cards from real ACS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Hydraulic & Pneumatic Systems flashcards as text
What is the primary purpose of a hydraulic accumulator in an aircraft system?
Answer: Store hydraulic fluid under pressure to supplement the pump during peak demands
A hydraulic accumulator stores pressurized fluid to assist the pump during peak demand periods, such as when multiple systems operate simultaneously.
Which type of hydraulic seal is most commonly used between two parts that have relative motion (dynamic application)?
Answer: O-ring or lip seal in a dynamic groove
Dynamic seals such as O-rings installed in dynamic grooves or lip seals are designed to prevent leakage between moving components.
When bleeding an aircraft hydraulic system, why is it important to work from the component farthest from the reservoir first?
Answer: To purge all air systematically toward the reservoir and prevent air pockets
Bleeding from the farthest point ensures air bubbles are progressively pushed back toward the reservoir rather than trapped in the system.
What does a hydraulic system pressure relief valve protect against?
Answer: Thermal expansion causing pressure spikes that exceed system design limits
The pressure relief valve opens to bypass fluid back to the reservoir when system pressure exceeds the maximum design limit, protecting components from overpressure damage.
What material are most aircraft hydraulic lines made of when routing through areas subject to vibration?
Answer: Flexible rubber hose reinforced with braided wire
Flexible braided hose is used in areas subject to vibration or relative movement because it can absorb movement without cracking or failing.
What is the function of a hydraulic power transfer unit (PTU)?
Answer: Transfer fluid between two separate hydraulic systems without cross-contaminating the fluids
A PTU allows one hydraulic system to power another using a hydraulic motor/pump combination, transferring power but keeping the fluids isolated.
If an aircraft hydraulic system uses MIL-PRF-5606 fluid and is inadvertently serviced with MIL-PRF-83282 fluid, what action is required?
Answer: Flush the system and replace all seals, as the fluids have different seal compatibility
MIL-PRF-5606 and MIL-PRF-83282 have different base oils and different seal material requirements, requiring a full system flush and seal replacement if mixed.