AM Aircraft Maintenance Engine & System Repairs 3 — Questions and Answers
Question 1: Hydraulic fluid is found contaminated with engine oil in an aircraft system. The correct maintenance action is:
- Add hydraulic fluid to dilute the contamination
- Flush the entire hydraulic system and replace all seals (Correct answer)
- Operate the system to blend the fluids
- Replace only the hydraulic reservoir
Correct answer: Flush the entire hydraulic system and replace all seals
Cross-contamination of hydraulic fluid with engine oil requires a complete system flush and seal replacement because petroleum oil degrades MIL-PRF-5606 or Skydrol seals.
Question 2: Which NDT method is most effective for detecting subsurface fatigue cracks in aluminum aircraft structures?
- Dye penetrant inspection
- Eddy current inspection (Correct answer)
- Magnetic particle inspection
- Visual inspection with 10x magnifier
Correct answer: Eddy current inspection
Eddy current inspection detects subsurface cracks in non-ferrous materials like aluminum without requiring the surface to be bare metal.
Question 3: When replacing a fuel control unit (FCU) on a turboprop engine, the first step after installation is to:
- Perform a full-power engine run
- Perform a fuel system leak check
- Calibrate the FCU to the engine using trimming procedures (Correct answer)
- Fill the fuel system and check for air locks
Correct answer: Calibrate the FCU to the engine using trimming procedures
After FCU replacement, the unit must be calibrated to the specific engine through the manufacturer's trimming procedure before any engine run.
Question 4: An aircraft piston engine develops excessive blow-by past the piston rings. This condition is most reliably detected by:
- Oil consumption check only
- Differential compression test (Correct answer)
- Cylinder head temperature monitoring
- Magneto timing check
Correct answer: Differential compression test
A differential compression test directly measures the ability of each cylinder to hold pressure, identifying worn or damaged rings causing blow-by.
Question 5: The purpose of compressor washing on a turbine engine is primarily to:
- Remove carbon deposits from the turbine section
- Restore lost performance caused by compressor fouling (Correct answer)
- Clean fuel nozzle internal passages
- Reduce metal fatigue in compressor blades
Correct answer: Restore lost performance caused by compressor fouling
Compressor washing removes salt, dust, and contamination fouling the blades to restore aerodynamic efficiency and lost thrust or power.
Question 6: During engine teardown, a turbine blade is found with tip rub marks. Per typical maintenance manuals, this blade should be:
- Polished smooth and reinstalled
- Replaced if rub depth exceeds the serviceable limit (Correct answer)
- Inspected visually only and approved if no cracks found
- Replaced automatically regardless of depth
Correct answer: Replaced if rub depth exceeds the serviceable limit
Tip rub is evaluated against published serviceable limits; blades within limits may be returned to service, but those exceeding limits must be replaced.
Question 7: What is the primary reason for performing a borescope inspection of a turbine engine between overhauls?
- To check fuel nozzle spray pattern
- To assess internal hot section condition without disassembly (Correct answer)
- To verify compressor blade count
- To inspect oil system passages
Correct answer: To assess internal hot section condition without disassembly
Borescope inspections allow technicians to visually assess turbine blades, combustors, and nozzle vanes for cracks, erosion, or distress without engine removal or teardown.
AM Aircraft Maintenance Engine & System Repairs 3
Hydraulic fluid is found contaminated with engine oil in an aircraft system.
The correct maintenance action is: