The debris is the diagnosis

Twenty-four elements. This unit contains the most genuinely diagnostic reasoning in Powerplant, and it is not about the oil.

1. Oil is a sample, and the metal in it names the failing part

K5 chip detectors, K6 analysis, S6 filter and screen inspection, S13 identify the types of metal found in an oil filter, S14 chip detector removal and inspection.

Everything else in the certificate inspects a part in front of you. This infers the condition of parts you cannot see — bearings, gears, cam lobes, cylinder walls — from what they have shed into the oil.

What the material suggests:

But material is only one of four things to read, and the others matter as much:

• Quantity. A trace is normal wear; a measurable quantity is not.
• Size. Fine gray paste is normal; bright flakes are not.
• Shape. Slivers and curls suggest machining or scoring; spheres suggest fatigue.
• Trend. One sample means little. A rising trend across several is the finding.

A chip detector that has collected a fuzz of fine magnetic particles is telling you something different from one carrying a single bright flake, and the second is more serious than the first despite being smaller.

This is inference from evidence rather than inspection of a part, and GEN-K Concepts §1's technique-selection reasoning is its General-level parent.

2. Oil consumption tells you where the oil is going

K7. Three destinations, three different faults, and they are distinguishable.

• Past the rings — into the combustion chamber. Blue smoke, oily plugs on the affected cylinders, and it usually accompanies low compression (PP-C §1).
• Down the valve guides — also into the chamber, but typically worst after a period at idle or on start.
• Out of the engine — leakage. Visible, once you look properly, and the commonest cause of a sudden change in consumption.

A change in consumption is the finding, not the absolute figure. An engine that has used a quart every eight hours for two years and now uses one every four has told you something.

3. Mineral against ashless dispersant, and why break-in is different

K1, R1, S2.

Ashless dispersant oil holds contaminants in suspension so the filter can catch them and they do not settle as deposits. That is what you want for the life of the engine.

It is exactly what you do not want during break-in. New rings need to wear into the cylinder walls, and that requires a small amount of controlled abrasion. Straight mineral oil allows it; dispersant oil interferes with it, and rings that do not seat produce an engine that consumes oil for the rest of its life.

So a running-in engine gets mineral oil, for the period the manufacturer specifies, and topping it up with the wrong oil does invisible damage that is not recoverable without a top overhaul.

R1 — mixing oils — extends the point. Different oils are chemically different, and mixing types is not topping up.

4. Wet against dry sump, and where problems appear

K3, K4. A wet sump keeps the oil in the engine's own sump; a dry sump keeps it in a separate tank and scavenges it back.

Dry sump exists for aircraft that fly attitudes a sump cannot cope with, and for engines where oil temperature needs managing separately.

In both, the scavenge side is where problems appear. Pressure side faults are obvious — the gauge tells you. Scavenge faults are quiet: oil accumulating where it should not, foaming, rising temperature, and gradual loss from the tank with no external leak.

5. Oil pressure is resistance to flow, not quantity

S7, S11, S12. This is the reframe that makes pressure troubleshooting possible.

A pressure gauge reads the resistance the system offers to the pump's output. Low pressure can be:

• a worn pump — less flow;
• a relief valve stuck open or wrongly set;
• excessive bearing clearance — the oil escapes too easily, and this is the serious one;
• hot, thin oil — the same engine reads lower pressure hot than cold;
• low quantity, eventually.

So a pressure reading is meaningless without a temperature, and S12's temperature system is part of the same diagnosis rather than a separate one.

And adjusting the relief valve to restore pressure is a repair only if the relief valve was the fault. Otherwise it masks worn bearings, which is the failure this unit exists to catch early.

6. R3 — used oil is a regulated waste stream

Handling, storage and disposal of used lubricating oil.

Every engine servicing produces it, in volume, and it is a controlled waste with its own requirements.

GEN-G Concepts §6 covers the same obligation for solvents and chemical waste. Used oil is handled the same way: collected, stored and disposed of by the shop under its lease and local rules, never poured away or mixed with solvent.

7. What consumes this unit

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