AMT AMT Hydraulics, Pneumatics & Landing Gear 1 — Questions and Answers
Question 1: What principle states that pressure applied to an enclosed fluid is transmitted equally in all directions?
- Bernoulli's principle
- Pascal's law (Correct answer)
- Boyle's law
- Newton's third law
Correct answer: Pascal's law
Pascal's law states that pressure applied to a confined fluid is transmitted undiminished in all directions throughout the fluid.
Question 2: Which type of hydraulic fluid is most commonly used in modern commercial transport aircraft in the US?
- Mineral-based (MIL-H-5606)
- Vegetable-based fluid
- Skydrol (phosphate ester-based) (Correct answer)
- Water-glycol mixture
Correct answer: Skydrol (phosphate ester-based)
Skydrol, a phosphate ester-based fluid, is the most widely used hydraulic fluid in modern commercial transport aircraft because of its fire-resistant properties.
Question 3: What is the primary function of an aircraft hydraulic accumulator?
- To filter hydraulic fluid
- To store pressurized fluid and dampen pressure surges (Correct answer)
- To convert hydraulic pressure to electrical power
- To cool hydraulic fluid
Correct answer: To store pressurized fluid and dampen pressure surges
A hydraulic accumulator stores pressurized fluid under a pre-charged gas pressure to dampen system pressure surges and provide an emergency fluid reserve.
Question 4: What safety precaution must be taken before opening any hydraulic line on an aircraft?
- Increase system pressure to purge contaminants
- Depressurize the hydraulic system completely (Correct answer)
- Run the hydraulic pump at full speed
- Drain only the reservoir
Correct answer: Depressurize the hydraulic system completely
The hydraulic system must be fully depressurized before opening any line to prevent high-pressure fluid injection injuries and uncontrolled actuator movement.
Question 5: What does a hydraulic system relief valve do?
- Increases system pressure when demand is high
- Limits maximum system pressure by bypassing fluid back to the reservoir (Correct answer)
- Filters contaminants from the fluid
- Controls flow direction to actuators
Correct answer: Limits maximum system pressure by bypassing fluid back to the reservoir
A relief valve protects the hydraulic system by opening to route fluid back to the reservoir when system pressure exceeds the maximum allowable limit.
Question 6: What color is MIL-H-5606 mineral-based hydraulic fluid used in some general aviation aircraft?
- Blue
- Red (Correct answer)
- Clear
- Green
Correct answer: Red
MIL-H-5606 is a red, petroleum-based hydraulic fluid used in many general aviation aircraft and some military applications.
AMT AMT Hydraulics, Pneumatics & Landing Gear 1
What principle states that pressure applied to an enclosed fluid is transmitted equally in all directions?