A&P A&P Aircraft Hydraulic & Pneumatic Systems

Question 1

What type of fluid is most commonly used in aircraft hydraulic systems certified under modern FAA standards?

Accepted Answer

Phosphate ester-based fluid (Skydrol)

Answer

Mineral-based oil (MIL-H-5606)

Answer

Water-glycol mixture

Answer

Castor oil

Question 2

In a hydraulic system, what is the primary function of the hydraulic accumulator?

Accepted Answer

Store pressurized fluid to supplement the pump during peak demand and absorb pressure surges

Answer

Filter contaminants from the fluid

Answer

Control the direction of fluid flow

Answer

Convert hydraulic pressure to electrical power

Question 3

What component in a hydraulic system is responsible for maintaining a constant system pressure by allowing fluid to bypass back to the reservoir when pressure reaches a set limit?

Accepted Answer

Pressure relief valve

Answer

Check valve

Answer

Selector valve

Answer

Filter bypass valve

Question 4

How is hydraulic fluid contamination most commonly introduced into an aircraft hydraulic system?

Accepted Answer

During maintenance when seals, lines, or components are replaced improperly

Answer

During normal operation

Answer

Through the hydraulic pump

Answer

Through the accumulator charge valve

Question 5

What does a hydraulic system's power transfer unit (PTU) do?

Accepted Answer

Transfers hydraulic pressure from one system to another without fluid transfer

Answer

Converts hydraulic power to electrical power

Answer

Stores hydraulic fluid

Answer

Actuates the landing gear doors

Question 6

When bleeding a hydraulic system, what is the primary goal?

Accepted Answer

Remove all trapped air from the system to ensure positive pressure and proper actuator operation

Answer

Replace old fluid with new fluid

Answer

Increase system pressure

Answer

Clean the hydraulic filter