Maintenance practices, inspection, troubleshooting, ground running and preservation
Maintenance practices, inspection, troubleshooting, ground running and preservation
This section covers the practical AME tasks that verify engine condition and return an engine to service. The exam tests inspection methods, compression testing, run-up limits and preservation.
Core rules and concepts
- Inspections include visual checks, torque and safetying, oil and filter analysis, borescope examination and differential compression testing.
- A differential compression test compares regulated air pressure with cylinder pressure. Leakage heard at the exhaust indicates an exhaust valve; at the intake, an intake valve; at the crankcase breather, rings or piston.
- Ground running requires tie-down or chocks, fire extinguisher, correct oil and fuel, and a run-up to check magnetos, carburettor heat, idle and oil pressure. Limits and warm-up must follow the manual.
- Troubleshooting is systematic: confirm the symptom, check the simplest cause, isolate the system, then repair and retest.
- Preservation for storage includes inhibiting cylinders and fuel system, sealing openings, controlling humidity and rotating or tagging according to instructions.
Worked example
A differential test with 80 psi applied shows 60 psi on the cylinder gauge. Leakage = (80 − 60) ÷ 80 = 25%. The engine is not automatically unserviceable; compare with the manufacturer’s limit, commonly 60/80 minimum, and locate the leak. Air at the exhaust would condemn an exhaust valve, while air at the breather suggests rings.
Traps
Do not pass a cylinder solely because it starts; do not ignore a mag drop or high oil temperature on run-up; and do not store an engine without inhibiting it.