Inspecting

Five procedures. Procedure 1 runs before the others and is the one this unit is built on.

Measurement procedures are in GEN-E Procedures and are not repeated here (GEN-K Quick reference).

Procedure 1 — Select an inspection technique (R4)

Given — a part, and a reason to inspect it. Sought — a method that could actually find what you are looking for.

Method

1. Name what you are looking for. A fatigue crack. Corrosion under a lap. A disbond. Wear beyond a limit. "Anything wrong" is not an answer and does not lead to a method.
2. Say where it would be. Surface or subsurface. At a hole, a radius, an edge, a bond line.
3. Name the material. Ferrous, non-ferrous, composite, porous.
4. Choose the method that can see there, in that material (GEN-K Concepts §1).
5. Check what the approved data requires. If the manufacturer specifies a method, that governs — your reasoning confirms it rather than replaces it.
6. State the method's blind spot and decide whether it matters.

Check — complete this sentence: "If the defect were present, this method would find it, because …" If you cannot, you have chosen a method rather than selected one.

Failure — dye penetrant on a subsurface crack, magnetic particle on aluminum, a tap test on solid laminate. Each returns clean. Each is recorded as an inspection.

Procedure 2 — Perform a visual inspection (S4)

Method

1. Establish the scope from approved data — what area, what you are looking for, what the limits are.
2. Clean the area. Much of what is found is found while cleaning.
3. Arrange lighting, including raking light across the surface.
4. Work a pattern — a defined start, a defined route, a defined end.
5. Use aided vision: magnifier, mirror, borescope where access requires it.
6. Concentrate on stress concentrations: holes, radii, edges, fastener heads, weld toes, changes of section.
7. Measure anything you find, against the limit in approved data.
8. Record what you inspected, what you found, and the disposition.

Check — can you describe your coverage pattern? If you cannot say where you started and where you finished, you did not cover it — you looked at it.

Failure — inspecting only what is easy to see. Failures concentrate where access is worst, because that is where inspection is least often done.

Procedure 3 — Perform a dye penetrant inspection (S5)

Confirm first that the material is non-porous and the defect would be surface-breaking (Procedure 1).

Method

1. Clean thoroughly and dry. Penetrant cannot enter a defect filled with oil, paint or corrosion product. This step decides the result.
2. Apply penetrant and observe the dwell time in the kit's instructions. Too short and it has not entered; too long and it dries in place.
3. Remove surface penetrant by the specified means — and no more. Over-cleaning pulls penetrant back out of the defect and the indication disappears.
4. Apply developer thinly and evenly.
5. Observe over time. Indications develop and grow; a bleed-out that widens is a real defect, a spot that appears at once and does not change may be surface contamination.
6. Evaluate against the acceptance criteria, and clean the part afterwards.

Check — an inspection that finds nothing on a part you know to be cracked has failed, not passed. Process a known-defective reference specimen alongside the work to confirm the technique and materials are working.

Failure — inadequate pre-cleaning. The commonest cause of a false clean result, and it looks exactly like a good inspection.

Procedure 4 — Perform a tap test (S8)

Confirm first that the structure is thin skin over core, not solid laminate (Procedure 1).

Method

1. Use the specified tapper — a coin-sized tap hammer, not a screwdriver handle.
2. Establish the sound of good structure by tapping a known-sound area first.
3. Tap in a grid pattern, consistent force, moving systematically.
4. Listen for a change — a dull, flat or dead response against the sharp response of bonded structure.
5. Mark the boundary of any suspect area and map its extent.
6. Confirm by another method where the approved data requires it.

Check — step 2 is the check. Without a known-good reference, "dull" has no meaning. If you have not established the good sound, you cannot recognize the bad one.

Failure — tapping too hard, which damages the structure, or too inconsistently, which makes every response sound different.

Procedure 5 — Inspect for AD compliance (S6)

Method

1. Establish which ADs apply (GEN-I Procedures Procedure 3).
2. Read what the AD requires you to inspect, by what method, at what interval, to what criteria.
3. Perform it — by the specified method. An AD that calls for eddy current is not satisfied by a visual inspection.
4. Record compliance: the AD number and revision, the method, the finding, the date and time in service, and the next due point if recurring (GEN-I Procedures Procedure 6).

Check — read your record back against the AD's compliance paragraph. Every requirement it states should be answered in your entry.

Failure — substituting a method. If the AD specifies a technique, an alternative needs an AMOC, not a judgment.

The checks, collected

Four of the five checks are about proving the method could have found it. That is what separates an inspection from a look, and it is why GEN-K Concepts §6 treats a clean result as a claim rather than an observation.

License

CC BY-SA 4.0 (Licensing).