Airframe Mechanic Aircraft Landing Gear Systems Questions and Answers — Questions and Answers
Question 1: An aircraft's retractable landing gear system is equipped with a squat switch, also known as a weight-on-wheels switch. What is the primary function of this switch?
- To illuminate the 'gear down and locked' indicator lights in the cockpit.
- To automatically apply the brakes upon landing.
- To prevent inadvertent retraction of the landing gear while the aircraft is on the ground. (Correct answer)
- To control the nose wheel steering system during taxi operations.
Correct answer: To prevent inadvertent retraction of the landing gear while the aircraft is on the ground.
The squat switch is a safety device that opens an electrical circuit when the weight of the aircraft is on the landing gear, preventing power from reaching the gear retraction motor. This ensures the gear cannot be raised while the aircraft is on the ground.
Question 2: When servicing an air/oil oleo shock strut, a mechanic notices that the strut bottoms out on landing but functions normally during taxi. What is the most likely cause of this issue?
- Excessive air pressure.
- Low hydraulic fluid level. (Correct answer)
- Worn-out seals.
- Incorrect type of hydraulic fluid.
Correct answer: Low hydraulic fluid level.
If an oleo strut bottoms on landing, it indicates a lack of hydraulic fluid to cushion the initial impact. During taxi, the loads are less severe, so the remaining fluid and air pressure may appear to function correctly. Excessive air pressure would make the strut too stiff, and worn seals would likely cause fluid leaks.
Question 3: What is the primary purpose of the torque links (also known as scissors) on a landing gear strut?
- To assist in retracting and extending the landing gear.
- To absorb the initial shock of landing.
- To provide a mounting point for the brake assembly.
- To prevent the piston from rotating within the cylinder and maintain wheel alignment. (Correct answer)
Correct answer: To prevent the piston from rotating within the cylinder and maintain wheel alignment.
Torque links connect the upper, fixed part of the strut to the lower, sliding piston, preventing relative rotation between them. This keeps the wheel aligned with the aircraft's direction of travel and prevents shimmy.
Question 4: A mechanic is performing a landing gear retraction test on a large aircraft. Which of the following is an essential safety precaution that must be taken before beginning the test?
- Ensure the hydraulic reservoir is overfilled to account for fluid displacement.
- Disconnect the battery to prevent electrical surges.
- Install all landing gear ground locks and safety pins.
- Ensure the aircraft is properly supported on jacks and all personnel and equipment are clear of the gear. (Correct answer)
Correct answer: Ensure the aircraft is properly supported on jacks and all personnel and equipment are clear of the gear.
A landing gear retraction test involves the full movement of the gear. It is critical to have the aircraft securely on jacks to simulate an in-flight condition and to ensure the area is completely clear to prevent injury or damage. Ground locks must be removed to allow the gear to retract.
Question 5: Which of the following is the correct fluid and gas combination for servicing a standard oleo-pneumatic shock strut?
- Skydrol and compressed oxygen.
- Mineral-based hydraulic fluid and nitrogen. (Correct answer)
- Engine oil and compressed air.
- Automatic transmission fluid and carbon dioxide.
Correct answer: Mineral-based hydraulic fluid and nitrogen.
Standard oleo struts are serviced with mineral-based hydraulic fluid (like MIL-H-5606) and an inert gas, typically nitrogen. Nitrogen is used because it is dry and less susceptible to pressure changes with temperature compared to compressed air, and it does not support combustion.
Question 6: During a walk-around inspection, a pilot reports that the nose gear of a tricycle-gear aircraft is not centered after engine shutdown. What component is designed to straighten the nose wheel before it enters the wheel well during retraction?
- The shimmy damper.
- The torque links.
- Internal centering cams or an external roller. (Correct answer)
- The squat switch.
Correct answer: Internal centering cams or an external roller.
Retractable nose gear systems incorporate a centering device, often internal cams or an external centering roller, to ensure the wheel is aligned fore and aft before retraction. This prevents the tire from striking the sides of the wheel well and causing damage.
