ACS Troubleshooting Techniques & Inspection Standards 3 — Questions and Answers
Question 1: When using a dial indicator to check crankshaft runout, the total indicated reading (TIR) is 0.006 inches. If the maximum allowable runout is 0.004 inches, what action is required?
- The crankshaft is within limits and may be returned to service
- The crankshaft must be replaced or sent to an overhaul facility for evaluation (Correct answer)
- The crankshaft can be re-indexed to reduce runout
- Polish the crankshaft journals to correct the runout
Correct answer: The crankshaft must be replaced or sent to an overhaul facility for evaluation
When TIR exceeds the manufacturer's maximum allowable limit, the crankshaft must be replaced or sent for overhaul evaluation—it cannot be returned to service as-is.
Question 2: An aircraft landing gear extends normally but the green 'gear down and locked' light does not illuminate. The FIRST troubleshooting step should be:
- Perform an emergency landing immediately
- Check the position switch and wiring circuit associated with the indicator light
- Assume the gear is down and locked since it extended normally
- Manually verify gear position via the viewing port and check the indicator light bulb (Correct answer)
Correct answer: Manually verify gear position via the viewing port and check the indicator light bulb
The safest first step is to visually verify gear position via mirror or viewing port, then check if the indicator bulb is burned out before assuming a more serious fault.
Question 3: What is the purpose of a magnetic particle inspection on steel aircraft components?
- To detect surface and near-surface cracks in ferromagnetic materials (Correct answer)
- To check material hardness and tensile strength
- To identify corrosion beneath paint coatings
- To verify material composition and alloy type
Correct answer: To detect surface and near-surface cracks in ferromagnetic materials
Magnetic particle inspection reveals surface and near-surface discontinuities in ferromagnetic materials by attracting iron particles to areas where magnetic flux leaks at defects.
Question 4: During an aircraft fuel system inspection, you discover water contamination in the fuel sumps. After draining until clear fuel appears, what additional check is recommended?
- Drain the entire fuel system and refuel completely
- Check the fuel caps and vent systems for leaks that allowed moisture ingress (Correct answer)
- Add a water-dispersant fuel additive
- Ground the aircraft for 48 hours to allow remaining water to settle
Correct answer: Check the fuel caps and vent systems for leaks that allowed moisture ingress
After removing water contamination, investigate the source by checking fuel caps, vent systems, and any points where water could have entered to prevent recurrence.
Question 5: A mechanic notices an aircraft's compass reads 10 degrees off during a compass swing. What is the appropriate corrective action?
- Replace the compass immediately
- Adjust the compensation screws and update the compass correction card (Correct answer)
- Declare the compass unserviceable if error exceeds 5 degrees
- File a maintenance discrepancy and allow the pilot to compensate mentally
Correct answer: Adjust the compensation screws and update the compass correction card
Compass deviation within allowable limits can be corrected by adjusting the compensating magnets and must be documented on an updated compass correction card.
Question 6: When inspecting control cable tension, you find the elevator cable is at 40 lbs when the maintenance manual specifies 50-70 lbs. What is required?
- The cable tension is acceptable as long as it is above 30 lbs
- Adjust cable tension to within the specified range using the cable turnbuckles (Correct answer)
- Replace the cables as worn cables cause low tension
- Document the finding and re-check at the next 100-hour inspection
Correct answer: Adjust cable tension to within the specified range using the cable turnbuckles
Flight control cables must be adjusted to within the manufacturer's specified tension range using the turnbuckles before the aircraft is returned to service.
Question 7: Which NDT method is most appropriate for detecting internal voids and delaminations in composite aircraft structures?
- Magnetic particle inspection
- Dye penetrant inspection
- Ultrasonic inspection or tap testing (Correct answer)
- Eddy current inspection
Correct answer: Ultrasonic inspection or tap testing
Ultrasonic testing and tap testing are the primary methods for detecting internal defects such as voids and delaminations in composite structures.
ACS Troubleshooting Techniques & Inspection Standards 3
When using a dial indicator to check crankshaft runout, the total indicated reading (TIR) is 0.006 inches.
If the maximum allowable runout is 0.004 inches, what action is required?