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

Skydrol (phosphate ester-based fluid) is the most common hydraulic fluid in large commercial aircraft due to its fire-resistant properties, while MIL-H-5606 (mineral oil) is used in many general aviation and military aircraft.

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

The accumulator stores a quantity of pressurized hydraulic fluid (using a gas charge) to supplement the pump during high-demand situations and to dampen pressure surges.

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

The pressure relief valve protects the hydraulic system from overpressure by opening and directing fluid back to the reservoir once system pressure exceeds the preset limit.

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

Contamination most often enters hydraulic systems during maintenance activities such as opening lines, replacing seals, or handling components with dirty tools or hands.

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

A PTU allows hydraulic pressure from one system to drive a pump that pressurizes a second system, transferring power but not fluid between the two circuits.

A&P - Certified Aircraft Mechanic Practice Test

A&P - Certified Aircraft Mechanic Practice Test

A&P A&P Aircraft Hydraulic & Pneumatic Systems