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 type of hydraulic pump is most commonly used in high-performance aircraft as an engine-driven pump due to its variable output capability?
Answer: Variable displacement piston pump
Variable displacement piston pumps can adjust their output flow based on system demand, maintaining constant pressure while reducing heat generation and power consumption when demand is low.
When inspecting flexible hydraulic hose for serviceability, which condition requires immediate replacement?
Answer: Wire braid visible through the outer cover at any point
Exposed wire braid indicates the outer protective cover is compromised, meaning the hose is susceptible to further damage and must be replaced immediately.
What is the correct procedure if a hydraulic system fluid sample indicates particle contamination above allowable limits?
Answer: Replace the hydraulic fluid and clean or replace contaminated components per maintenance manual
Contamination above allowable limits requires fluid replacement and inspection/cleaning of components because dispersants are not approved and portable filtering may not address the contamination source.
What is the purpose of a hydraulic system case drain line on a variable displacement piston pump?
Answer: Return low-pressure fluid that bypasses the internal piston seals back to the reservoir
Case drain lines return internal leakage fluid that bypasses piston seals back to the reservoir, preventing case pressure buildup that could damage pump shaft seals.
In a pneumatic de-icing system, what is the function of a distributor valve?
Answer: Sequence the inflation and deflation of individual de-ice boot sections
The distributor valve sequences inflation of leading-edge boot sections in the correct order to most effectively shed ice while minimizing bleed air consumption.
What condition causes a hydraulic pump to cavitate?
Answer: Inlet pressure is too low, causing vapor bubbles to form in the fluid
Cavitation occurs when fluid pressure at the pump inlet drops below the fluid's vapor pressure, causing vapor bubbles to form and then violently collapse, damaging pump internals.
What is the purpose of a flow control valve in a hydraulic system?
Answer: Control the rate of actuator movement by limiting fluid flow regardless of pressure differential
A flow control valve meters fluid flow rate to an actuator, controlling movement speed independently of the pressure differential across the valve.