aircraft pneudraulics repairer Interview Questions and Answers

1. What is the difference between pneumatics and hydraulics?

   • Answer: Pneumatics uses compressed air to generate power, while hydraulics uses pressurized liquids (typically oil). Hydraulic systems generally provide higher power density and more precise control than pneumatic systems, but are more complex and prone to leaks.

2. Describe the components of a typical aircraft hydraulic system.

   • Answer: A typical system includes a reservoir, pump, filter, pressure regulator, valves (selector, check, relief, etc.), actuators (cylinders, motors), lines, and fittings. It might also include a heat exchanger and accumulator.

3. Explain Pascal's Law and its relevance to hydraulic systems.

   • Answer: Pascal's Law states that pressure applied to a confined fluid is transmitted equally and undiminished in all directions throughout the fluid. This is fundamental to hydraulic systems because it allows a small force applied to a small area to generate a large force on a larger area, enabling powerful actuation.

4. What are the different types of hydraulic pumps used in aircraft?

   • Answer: Common types include gear pumps, vane pumps, and piston pumps (radial and axial). Each has different characteristics regarding flow rate, pressure capability, and efficiency.

5. How do you troubleshoot a hydraulic leak?

   • Answer: Start by identifying the location of the leak, then check the pressure and flow rate. Inspect the lines, fittings, seals, and components for damage. Use appropriate leak detection techniques such as dye penetrant or pressure testing to pinpoint the source. Consider the type of fluid leaking (hydraulic fluid, fuel etc) for safety.

6. Explain the function of a hydraulic accumulator.

   • Answer: An accumulator stores hydraulic energy, smoothing out pressure fluctuations, providing a backup source of power in case of pump failure, and absorbing shock loads.

7. What are the safety precautions you should take when working on a hydraulic system?

   • Answer: Always relieve pressure before servicing, use appropriate personal protective equipment (PPE), including eye protection and gloves, be aware of high-pressure hazards, follow lock-out/tag-out procedures, handle hydraulic fluid carefully to avoid skin contact and environmental contamination, and consult relevant maintenance manuals.

8. What are the common types of hydraulic actuators?

   • Answer: Linear actuators (hydraulic cylinders) and rotary actuators (hydraulic motors).

9. How do you test a hydraulic cylinder?

   • Answer: Visual inspection for leaks and damage, checking for free movement, measuring the extension and retraction force, and potentially using a hydraulic test bench to verify performance.

10. What is the purpose of a hydraulic filter?

    • Answer: To remove contaminants from the hydraulic fluid, preventing damage to system components.

11. Describe different types of hydraulic system failures.

    • Answer: Leaks, pump failure, valve malfunction, actuator failure, contamination, and loss of pressure.

12. What tools and equipment are commonly used in hydraulic system repair?

    • Answer: Wrenches, specialized fittings, hydraulic presses, leak detectors, pressure gauges, fluid collection containers, and cleaning supplies.

13. Explain the importance of proper fluid levels in a hydraulic system.

    • Answer: Insufficient fluid leads to cavitation (formation of vapor bubbles), reducing efficiency and causing damage. Excessive fluid can lead to over-pressurization and system failure.

14. What is the significance of hydraulic fluid viscosity?

    • Answer: Viscosity affects the system's performance, especially at different temperatures. Incorrect viscosity can lead to poor lubrication, increased wear, and reduced efficiency.

15. How do you identify different types of hydraulic fluid?

    • Answer: By checking the fluid's color, viscosity, and using testing strips or a spectrometer to determine its type and properties (e.g., phosphate ester, mineral oil).

16. What are the common causes of hydraulic system contamination?

    • Answer: Dust, dirt, moisture, and metal particles from wear and tear.

17. How do you prevent hydraulic system contamination?

    • Answer: Use proper maintenance procedures, clean the system thoroughly before servicing, use clean tools and fluids, install and maintain filters effectively, and wear appropriate PPE.

18. What are the different types of pneumatic valves?

    • Answer: Solenoid valves, pressure relief valves, directional control valves, and check valves.

19. Describe the components of a typical aircraft pneumatic system.

    • Answer: Air compressor, receiver tank, pressure regulator, pressure switches, valves, and actuators (air cylinders, air motors).

20. Explain the function of a pneumatic pressure regulator.

    • Answer: To maintain a constant downstream pressure regardless of fluctuations in upstream pressure or demand.

21. How do you troubleshoot a pneumatic leak?

    • Answer: Similar to hydraulic systems: identify the location, check pressure, inspect components, use soapy water to detect leaks.

22. What are the safety precautions when working with compressed air?

    • Answer: Be aware of high-pressure hazards, wear appropriate eye and hearing protection, ensure proper venting, never point an air nozzle at yourself or others, use caution with moving parts, and follow lock-out/tag-out procedures.

23. What are the common causes of pneumatic system failures?

    • Answer: Leaks, compressor failure, valve malfunction, actuator failure, and contamination.

24. How do you test a pneumatic cylinder?

    • Answer: Visual inspection, checking for free movement, measuring the extension and retraction force, and checking for leaks.

25. What is the purpose of a pneumatic receiver tank?

    • Answer: To store compressed air, smoothing out pressure fluctuations and providing a reserve of air.

26. Explain the importance of air dryers in a pneumatic system.

    • Answer: To remove moisture from the compressed air, preventing corrosion and freezing in cold climates.

27. What are the common types of pneumatic actuators?

    • Answer: Linear actuators (air cylinders) and rotary actuators (air motors).

28. What is the difference between a single-acting and a double-acting pneumatic cylinder?

    • Answer: A single-acting cylinder extends with air pressure and retracts by spring force or gravity. A double-acting cylinder uses air pressure for both extension and retraction.

29. What are some common aircraft pneumatic system applications?

    • Answer: Brakes, landing gear, doors, and flight controls.

30. What are some common aircraft hydraulic system applications?

    • Answer: Flight controls, landing gear, brakes, flaps, spoilers, and other flight surfaces.

31. Describe your experience with troubleshooting hydraulic or pneumatic systems.

    • Answer: [Candidate should describe specific examples of troubleshooting experiences, including the problem encountered, steps taken to diagnose the problem, and the solution implemented.]

32. What is your experience with different types of hydraulic and pneumatic seals?

    • Answer: [Candidate should discuss their knowledge of O-rings, backup rings, lip seals, etc., and their applications.]

33. How familiar are you with aircraft maintenance manuals (AMMs)?

    • Answer: [Candidate should describe their experience using AMMs to troubleshoot and repair systems.]

34. How do you stay current with the latest advancements in aircraft pneumatics and hydraulics?

    • Answer: [Candidate should discuss their methods for continuing education, such as attending workshops, reading industry publications, or online courses.]

35. Describe your experience with hydraulic and pneumatic system testing equipment.

    • Answer: [Candidate should list and describe their experience with various test equipment.]

36. What is your experience with hydraulic and pneumatic system schematics and diagrams?

    • Answer: [Candidate should describe their ability to interpret and utilize schematics and diagrams for troubleshooting and repair.]

37. Explain your understanding of hydraulic and pneumatic system maintenance schedules.

    • Answer: [Candidate should demonstrate understanding of preventative maintenance, inspection intervals, and fluid changes.]

38. Describe a time you had to work under pressure to solve a hydraulic or pneumatic problem.

    • Answer: [Candidate should provide a specific example, highlighting their problem-solving skills and ability to work effectively under pressure.]

39. How do you handle a situation where you encounter a problem you've never seen before?

    • Answer: [Candidate should explain their approach, emphasizing resourcefulness, problem-solving skills, and seeking assistance when needed.]

40. How do you ensure the safety of yourself and others while performing maintenance on aircraft hydraulic and pneumatic systems?

    • Answer: [Candidate should detail their safety procedures, including lockout/tagout, PPE use, and adherence to regulations.]

41. Are you familiar with different aircraft types and their specific hydraulic and pneumatic systems?

    • Answer: [Candidate should specify their experience with different aircraft models and their systems.]

42. What is your experience with the documentation and record-keeping required for aircraft maintenance?

    • Answer: [Candidate should demonstrate understanding of the importance of accurate record-keeping and compliance with regulations.]

43. What are your salary expectations?

    • Answer: [Candidate should provide a realistic salary range based on their experience and research.]

44. Why are you interested in this position?

    • Answer: [Candidate should express genuine interest in the role and company, highlighting relevant skills and career goals.]

45. What are your strengths and weaknesses?

    • Answer: [Candidate should provide honest and thoughtful responses, focusing on relevant skills and areas for improvement.]

46. Do you have any questions for me?

    • Answer: [Candidate should ask insightful questions demonstrating their interest and engagement.]

47. What are the different types of hydraulic reservoir designs?

    • Answer: There are various designs, including integral, remote, and combination reservoirs. Each has advantages and disadvantages related to location, capacity, and maintenance access.

48. Explain the operation of a pressure relief valve.

    • Answer: A pressure relief valve is a safety device that opens automatically to release fluid when the system pressure exceeds a preset limit, preventing damage to components.

49. What is the purpose of a check valve in a hydraulic system?

    • Answer: A check valve allows fluid to flow in one direction only, preventing backflow and maintaining system pressure.

50. Describe different methods for bleeding air from a hydraulic system.

    • Answer: Methods include using bleed screws, a vacuum pump, or pressurizing the system to purge air bubbles.

51. Explain the concept of hydraulic power assist.

    • Answer: Hydraulic power assist uses hydraulic pressure to augment the pilot's control inputs, reducing the effort required to operate flight controls.

52. What are some common problems associated with hydraulic lines and fittings?

    • Answer: Leaks, corrosion, cracking, and improper installation.

53. How do you properly dispose of used hydraulic fluid?

    • Answer: According to local environmental regulations and using approved disposal facilities.

54. What is your experience working with different types of hydraulic seals?

    • Answer: [Candidate should list various seal types and discuss their applications and limitations.]

55. Explain the importance of proper torque values when installing hydraulic fittings.

    • Answer: Incorrect torque can lead to leaks or damage to the fittings.

56. Describe different types of pneumatic system failures and their causes.

    • Answer: Compressor failure, leaks, valve malfunctions, and contamination. Causes range from wear and tear to improper maintenance.

57. What are the different types of air compressors used in aircraft?

    • Answer: Various types exist, including centrifugal and reciprocating compressors; each has different performance characteristics.

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