Induction and cooling

Six procedures. Most of this unit is inspection, and inspection with a specific thing to look for.

Procedure 1 — Inspect a carburetor heat system (S1, S2)

1. Inspect the heat muff and the exhaust component inside it for cracks (AF-G Procedures Procedure 4). This is a carbon monoxide inspection as well as a heat one.
2. Check the shroud sealing and the ducting for holes, collapse and security.
3. Operate the control through full travel and confirm the valve reaches full hot and full cold at the airbox, not just at the cockpit knob.
4. Check the alternate air valve for free operation and correct seating.
5. Where the manual specifies, check the heat rise — a temperature or an RPM drop.

Check — check the valve at the airbox, not the knob. A control that reaches its cockpit stop without moving the valve fully is the commonest carburetor-heat defect and it is invisible from the cockpit.

Failure — passing a cracked heat muff. It puts exhaust gas into the cabin (PP-J Concepts §1).

Procedure 2 — Service an induction air filter (S5)

1. Remove per the manual, noting orientation.
2. Inspect the filter: holes, damage, collapse, and the sealing face.
3. Clean or replace by the approved method — some filters must not be blown out with compressed air, which drives dirt through.
4. Inspect the airbox and ducting behind the filter, which is where anything that got past it will be.
5. Install with the correct sealing and orientation.

Check — look behind the filter. Debris downstream of a filter means the filter has been bypassed or holed, and cleaning the filter does not address that.

Procedure 3 — Inspect the induction system (S3, S8, S9, S14, S15)

1. Trace the whole path from inlet to cylinder, naming components.
2. Inspect for obstruction — nests, debris, ice damage, collapsed ducting.
3. Check manifold and intake pipe joints for leaks: staining, soot, loose clamps, hardened or cracked hoses.
4. Check drains clear and functioning.
5. Check the inlet duct and its security.

Check — an induction leak leans the cylinder it feeds. If one cylinder runs hot or rough, inspect its intake joint before anything else.

Procedure 4 — Inspect baffling and cooling (S17, S19, S18)

Read PP-J Concepts §2 first: you are inspecting a pressure seal, not a sheet metal panel.

1. Inspect every baffle for cracks — especially at bends and fastener holes — and for security.
2. Inspect every seal for hardening, tears, and correct direction. A seal folded the wrong way lets air through, and the correct direction is toward the pressure.
3. Look for gaps at the cowling, between baffles, and around cylinders.
4. Inspect cooling fins for breakage and bending, and measure any missing area against the limit.
5. Check cowl flaps: rigging, full travel, security, and that they seat closed.

Check — look for daylight. With the cowling fitted, any gap you can see through is air that is not cooling a cylinder. This is the fastest and most reliable baffling check there is.

Procedure 5 — Repair a cylinder baffle (S16)

1. Assess the damage and confirm a repair is permitted (AF-A Procedures Procedure 1).
2. Fabricate and fit per AF-A Procedures Procedures 3–7 — layout, drill, cleco, rivet.
3. Restore the seal. The repair must reproduce the original sealing arrangement, or it has fixed the panel and not the cooling.
4. Refit and check for gaps (Procedure 4).

Check — the repair is judged on whether the seal is restored, not on whether the sheet metal is neat.

Procedure 6 — Inspect a turbocharger and waste gate (S6, S7, R1)

1. Allow it to cool. A turbocharger runs extremely hot.
2. Inspect for leaks: exhaust leaks at the turbine housing show as soot; oil leaks at either end suggest seal failure.
3. Check security of mounting and of all connections.
4. Check the waste gate: free movement through full travel, linkage condition, actuator condition, no binding.
5. Inspect the compressor and turbine wheels where accessible for damage and rubbing.
6. Check for shaft play per the manual's limits.
7. Inspect the intercooler where fitted for blockage and leaks.

Check — move the waste gate through full travel by hand. A waste gate that sticks closed is an overboost, and overboost is detonation (PP-J Concepts §3).

Failure — shutting the engine down immediately after high-power running. The oil in the hot bearing cokes, and the turbocharger fails later.

The checks, collected

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