Exam Questions And Correct Answers

FAA Repairman Certificate – Hydraulic & Pneumatic Equipment Repair Practice Exam Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the main purpose of a hydraulic accumulator in an aircraft

system?

• To remove air from the hydraulic fluid
• To store energy under pressure for system use
• To regulate flow to the actuator
• To increase pump output

Rationale: The accumulator stores pressurized fluid, providing an

emergency source of pressure and dampening pulsations.

• What type of fluid is typically used in modern aircraft hydraulic

systems?

• Water-based fluids
• Petroleum-based fluids 1 / 4

• Synthetic phosphate ester fluids
• Silicone-based fluids

Rationale: Phosphate ester fluids (like Skydrol) are commonly used

because they are fire-resistant and suitable for high-pressure systems.

• What color is used to identify mineral-based hydraulic fluid?
• Purple
• Red
• Green
• Amber

Rationale: Red dye identifies mineral-based hydraulic fluids such as

MIL-H-5606.

• What type of pump is most common in aircraft hydraulic systems?
• Gear pump
• Piston pump
• Vane pump
• Centrifugal pump

Rationale: Vane pumps are often used due to their efficiency and

smooth delivery at moderate pressures.

• What component limits maximum hydraulic system pressure?
• Check valve
• Pressure relief valve
• Restrictor
• Flow control valve 2 / 4

Rationale: Pressure relief valves prevent excessive pressure buildup by

diverting fluid back to the reservoir.

• What is the function of a check valve?
• To regulate flow rate
• To allow flow in one direction only
• To relieve excess pressure
• To maintain constant pressure

Rationale: A check valve ensures one-way flow, preventing reverse

fluid movement.

• In pneumatic systems, compressed air is typically filtered to remove

what contaminant first?

• Moisture
• Carbon dioxide
• Dust
• Oil

Rationale: Moisture can freeze and block lines, so it must be removed

first.

• What is cavitation in a hydraulic pump?
• Air being released from solution
• Fluid expansion under temperature
• Formation and collapse of vapor bubbles
• Loss of pressure due to leaks

Rationale: Cavitation occurs when vapor bubbles form in low-pressure 3 / 4

areas and collapse in high-pressure zones, damaging pump components.

• A pneumatic system differs from a hydraulic system primarily in that it

uses:

• Oil
• Coolant
• Compressed air
• Steam

Rationale: Pneumatic systems rely on compressed air instead of liquid

fluid for power transmission.

• What is the purpose of a restrictor in a hydraulic line?
• To prevent reverse flow
• To relieve pressure
• To control flow rate and actuator speed
• To cool the fluid

Rationale: Restrictors reduce flow rate, thereby controlling the speed

of actuators.

• Which law describes the relationship between pressure and

volume in a pneumatic system?

• Charles’ Law
• Boyle’s Law
• Pascal’s Law
• Bernoulli’s Principle
• / 4