Hydraulics and Pneumatics Flashcards
7 cards from real AMT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Hydraulics and Pneumatics flashcards as text
What is the typical precharge pressure of a dry-type (nitrogen-precharged) hydraulic accumulator in relation to system operating pressure?
Answer: Approximately one-third of system operating pressure when system is depressurized
Nitrogen precharge is typically set to one-third of normal system operating pressure to maximize usable fluid storage volume.
When inspecting a hydraulic system filter, a red 'pop-out' indicator is visible. What does this indicate?
Answer: The filter bypass valve has opened due to excessive differential pressure across the element
A pop-out (differential pressure) indicator signals that the filter element is clogged enough to open the bypass valve, allowing unfiltered fluid to flow downstream.
In a power brake system using hydraulic pressure, what is the function of a brake debooster?
Answer: Reduces high system pressure to a lower pressure suitable for brake application to prevent tire damage
A debooster valve steps down main hydraulic system pressure (often 3,000 psi) to a lower pressure appropriate for the brake assembly, protecting tires from over-braking.
What is the purpose of a thermal relief valve in a hydraulic actuator or line?
Answer: To release excess pressure caused by thermal expansion of trapped fluid when the system is static
When a hydraulic system is shut down with fluid trapped in a line, thermal expansion can generate dangerously high pressure; a thermal relief valve opens to protect the system.
What is the minimum bend radius rule's purpose when installing aircraft hydraulic tubing?
Answer: To prevent kinking or work-hardening that weakens the tube and restricts flow
Bending tubing tighter than the minimum radius kinks it, restricts flow, and creates stress concentrations that lead to fatigue cracks and eventual failure.
What is the function of an aircraft pneumatic system pressure regulator?
Answer: To reduce high-pressure bleed air or bottle pressure to a constant lower working pressure for system components
A pressure regulator downstream-senses pressure and modulates a valve to maintain a steady output pressure regardless of variations in supply pressure or downstream demand.
Why must hydraulic fluid samples be taken for spectrometric analysis during scheduled maintenance?
Answer: To detect metallic wear particles that indicate internal component deterioration before catastrophic failure
Spectrometric oil analysis (SOAP) identifies trace metals dissolved in the fluid that reveal which internal components are wearing excessively, enabling predictive maintenance.