AM Aircraft Maintenance Engine & System Repairs 2 — Questions and Answers
Question 1: When inspecting a turbine engine for hot section damage, which area is most susceptible to thermal cracking?
- Compressor inlet guide vanes
- Turbine nozzle guide vanes (Correct answer)
- Engine inlet lip
- Accessory gearbox housing
Correct answer: Turbine nozzle guide vanes
Turbine nozzle guide vanes are exposed to the highest gas temperatures in the engine and are most susceptible to thermal cracking and erosion.
Question 2: What is the correct method to check for internal cylinder cracking on a reciprocating engine cylinder barrel?
- Dye penetrant inspection
- Hydrostatic pressure test
- Magnetic particle inspection (Correct answer)
- Ultrasonic thickness testing
Correct answer: Magnetic particle inspection
Magnetic particle inspection (Magnaflux) is used on ferrous cylinder barrels to detect internal and surface cracks not visible to the naked eye.
Question 3: During engine run-up, oil pressure drops to zero but oil temperature remains normal. The most likely cause is:
- Clogged oil cooler
- Faulty oil pressure gauge or sending unit (Correct answer)
- Broken oil pump drive shaft
- Contaminated oil filter bypass valve stuck open
Correct answer: Faulty oil pressure gauge or sending unit
A sudden drop to zero with normal temperature and no engine distress usually indicates an instrument or sender failure rather than actual oil starvation.
Question 4: A turbojet engine compressor stall is best identified by which symptom during ground run?
- Gradual rise in EGT with stable RPM
- Loud banging or popping with RPM fluctuation (Correct answer)
- Smooth acceleration with decreasing fuel flow
- High pitched whine from accessory gearbox
Correct answer: Loud banging or popping with RPM fluctuation
Compressor stall produces a characteristic loud bang or series of pops accompanied by RPM fluctuation and a surge in exhaust gas temperature.
Question 5: What type of safety wire is required for aircraft engine oil drain plugs per FAA regulations?
- Copper wire of any gauge
- 0.020-inch stainless steel wire (Correct answer)
- Monel wire only
- Aluminum wire of equivalent strength
Correct answer: 0.020-inch stainless steel wire
FAA AC 43.13-1B specifies 0.020-inch diameter stainless steel safety wire for most engine hardware including oil drain plugs.
Question 6: A reciprocating engine shows low power output and rough running on one magneto. After replacing the magneto, the problem persists. The next inspection should focus on:
- Carburetor float level
- Spark plug condition and lead fouling
- Ignition harness insulation breakdown (Correct answer)
- Propeller blade angle
Correct answer: Ignition harness insulation breakdown
Persistent rough running after magneto replacement with one magneto suggests the ignition harness has high-resistance or insulation breakdown causing misfires.
Question 7: When reinstalling a turbine engine fuel nozzle, the torque value listed in the manufacturer's manual is considered:
- A minimum value only
- A maximum value only
- A specific value with defined tolerance (Correct answer)
- Advisory and may be adjusted by the mechanic
Correct answer: A specific value with defined tolerance
Manufacturer-specified torque values for fuel nozzles are specific values with tolerances that must be followed exactly to ensure proper seating and prevent leaks.
AM Aircraft Maintenance Engine & System Repairs 2
When inspecting a turbine engine for hot section damage, which area is most susceptible to thermal cracking?