Engine Inspection, Run-Up and Maintenance Records

Isolate rough running in a fixed order, because the order follows how likely each cause is: ignition first — magnetos, plugs, and the high-tension harness — then induction leaks, then fuel supply and contamination, then mechanical compression. A systematic order reaches the common causes first and avoids the classic error of replacing a magneto when the fouled plug was the fault.

Differential compression testing quantifies cylinder health against the value in the engine manual. Listen at the exhaust port for a leaking exhaust valve, at the intake for a leaking intake valve, at the breather for worn rings, and at the neighbouring spark plug hole for a head gasket leak. Compare the highest reading with the lowest: a large spread indicates uneven wear, and a uniformly low result indicates a ring, bore or valve-train problem rather than one bad cylinder.

The run-up is a fixed ritual. Check oil temperature and pressure in the green, perform the magneto check and confirm the drops are even and within limits, verify suction or manifold pressure, cycle the propeller to flush the hub and confirm governor operation, exercise and check the flight controls, check the flight instruments respond, and lean for the field elevation. Each step is recorded with the values obtained.

Before return to service, confirm the engine and propeller airworthiness directives, life-limited part status and overhaul status against the records, and close the job with an entry that states the work done, the data it was done to, the parts fitted, the time in service, the date and your signature within your authorisations.