Inspecting an engine

Six procedures, in the order the work happens.

Procedure 1 — Establish scope and inspect the records (S3, S5, S6, S11, S4)

1. Determine which inspection is due and under what rule (AF-D Procedures Procedure 1).
2. Read the scope — part 43 appendix D plus the engine manufacturer's program.
3. Establish engine time and cycles, and time since overhaul.
4. Check the engine TCDS: is this engine eligible for this airframe, in this configuration, with these accessories (S5, S6)?
5. Search ADs against engine, propeller and accessories, and check compliance history.
6. Check life-limited parts — by cycles as well as hours (PP-C Concepts §3).
7. Check service bulletins and ICA adopted or mandatory.

Check — can you account for the engine's history without gaps? A missing period is a finding to report, not an absence of maintenance.

Procedure 2 — Perform a differential compression check (S1, R1)

Read PP-C Concepts §1 and §2 first.

1. Warm the engine thoroughly and shut down. A cold check reads low.
2. Magnetos grounded (PP-H Procedure 0).
3. Remove one spark plug from each cylinder.
4. Bring the cylinder to top dead center on the compression stroke (PP-A Procedure 1).
5. Hold the propeller against rotation by the manual's method. Expect a kick when pressure is applied.
6. Apply the regulated pressure per the manufacturer's procedure, and read both gauges.
7. Listen — exhaust, induction, oil filler, adjacent cylinder (PP-C Concepts §1).
8. Record the reading and where the leakage was heard, for every cylinder.
9. For a low cylinder: re-run the engine, warm it, and re-check before condemning.

Check — record where the air went, not just the number. Two cylinders reading 60/80 with leakage at the exhaust valve and at the oil filler are two different engines.

Failure — a cold check, or a check with the propeller unrestrained.

Procedure 3 — Inspect the engine externally (S7, S9, S10, S8)

1. Clean sufficiently to inspect, without driving contamination into anything (AF-H Concepts §3 — no air lines into instruments).
2. Leaks (S9): oil, fuel, exhaust. Trace each to its source — the visible wet area is usually downstream of the leak.
3. Exhaust system (PP-L).
4. Baffling and cooling (PP-J how-to Procedure 4).
5. Engine controls (S8): full travel to both stops at the engine, correct rigging, no binding, secure.
6. Accessories (S10): security, condition, leakage, drive condition.
7. Wiring and plumbing (PP-F how-to Procedure 1).

Check — trace every leak to its source. Oil appears downstream of where it left, and cleaning it off and re-running is how you find the actual source.

Procedure 4 — Inspect the engine mount (S14, K8)

1. Clean the mount tubes enough to see the welds.
2. Inspect every weld with light and magnification — cracks start at the toe of the weld (GEN-K Procedures Procedure 2).
3. Inspect tubes for dents, corrosion, and distortion.
4. Inspect isolators: perished, collapsed, oil-contaminated, or delaminated rubber.
5. Check mounting hardware: correct type, security, torque.
6. Check alignment — an engine sitting off-center suggests a collapsed isolator or a bent mount.

Check — look at the welds specifically, not the tubes generally. Cracks are at the welds, and the welds are the least accessible part (PP-C Concepts §4).

Procedure 5 — Run the engine and check parameters (S12)

1. Everything in GEN-F Procedures Procedure 7.
2. Note ambient conditions and compute density altitude (GEN-J Procedures Procedure 3).
3. Record: oil pressure and temperature, cylinder head temperature, EGT, RPM, manifold pressure, fuel flow, magneto drop, idle speed and mixture rise.
4. Compare against book figures corrected for the day.
5. Check for leaks after shutdown — some only appear when hot and pressurized.

Check — before judging any figure, confirm the indication is real (PP-D how-to Procedure 1). Replacing engine parts because of a faulty gauge is the commonest wasted repair in Powerplant.

Procedure 6 — Record the inspection (S3, S13)

Per GEN-I Procedures Procedure 7:

1. Type and scope, with its reference.
2. Date, time in service, and cycles where applicable.
3. The determination — airworthy, or the discrepancy list provided.
4. Compression readings for every cylinder, with where the leakage was heard.
5. Signature, certificate number, kind of certificate.

Check — the compression figures belong in the record. They are the engine's condition history, and the next inspection's value depends on having the last one to compare against.

The checks, collected

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