A&P A&P - Aircraft and Powerplant Hydraulic and Pneumatic Systems

Question 1

What type of fluid is used in most modern commercial aircraft hydraulic systems?

Accepted Answer

Skydrol (phosphate ester-based)

Answer

Skydrol, a phosphate ester-based fluid, is used in most modern commercial aircraft because it is fire-resistant.

Question 2

What is the primary function of a hydraulic accumulator in an aircraft system?

Accepted Answer

Store pressurized fluid to dampen pressure surges and provide emergency power

Answer

A hydraulic accumulator stores pressurized fluid to dampen pressure surges and provide a reserve for emergency operations.

Question 3

Which component in a hydraulic system prevents pressure from exceeding a safe maximum?

Accepted Answer

Relief valve

Answer

A relief valve opens automatically when system pressure exceeds the preset maximum, bypassing fluid back to the reservoir.

Question 4

A hydraulic system pressure gauge reads zero with the engine running. What is the MOST likely cause?

Accepted Answer

Failed engine-driven pump or broken drive shaft

Answer

Zero pressure with the engine running most likely indicates a failed engine-driven hydraulic pump or its drive coupling.

Question 5

What is the purpose of a hydraulic system's case drain line on a variable-displacement pump?

Accepted Answer

Return leakage fluid from the pump housing back to the reservoir

Answer

The case drain line returns internal leakage fluid from inside the pump housing to the reservoir to prevent pressure buildup.

A&P - Aircraft and Powerplant Certification Practice Test