Nine elements about welding, and no welding

Thirty-six elements. Ten station elements and four artifact elements — the most hands-on subject in Airframe after landing gear. And a knowledge inventory that includes a technology you will never be asked to perform.

1. You must know welding. You will never weld.

K10 flame welding gases. K11 storage and handling. K12 flame welding practice. K13 inert-gas welding practice. K14 shielding gases. K15 steel tubing weld repairs. K16 weld repair procedures. Plus R4 compressed gas bottles and R5 electric welding equipment.

Nine elements about welding, and not one of the fourteen skill elements requires you to strike an arc. All fourteen are sheet metal.

Across the whole certificate the same holds: GEN-E covers weld characteristics as knowledge and S3 only inspects welds, by imagery.

So what are you actually being asked for? To know enough that you can:

• recognize an unacceptable weld when you inspect one (GEN-E Concepts);
• handle and store gas bottles safely, which is R4 and is a real hazard whether or not you weld;
• know when a repair needs welding, and therefore that it goes to someone qualified;
• know what welding does to the metal around it — the heat-affected zone, distortion, and why a welded repair on a heat-treated part changes its properties.

That last point is the one worth carrying. Heat changes metal. A weld is a local heat treatment you did not design, and it is why K15 treats steel tube repairs as a specified procedure rather than a matter of joining two things.

2. Rivet pattern is arithmetic with a reason

K7 and S11. Candidates learn edge distance and pitch as numbers to look up, and then cannot tell whether a pattern they are looking at is wrong.

Every number in a rivet pattern is preventing a specific failure:

• Edge distance too small — the rivet tears out through the edge of the sheet. The material between the hole and the edge is what carries the load, and below about two diameters there is not enough of it.
• Edge distance too large — the sheet can lift and buckle between the rivet and the edge, and the joint is not doing what it was designed to.
• Pitch too close — the sheet cracks between the holes, because the remaining material between them is a smaller section than the sheet itself.
• Pitch too far apart — the sheets separate between rivets, work, and fret.

So a pattern is a compromise between tearing out at the edge and cracking between the holes. Knowing that, you can look at an unfamiliar repair and form a view, which is what S14 needs.

GEN-H Concepts §6 is the other half: drill sizes are not interchangeable across series. A #30 hole and a 1/8 hole are different, and the difference is a correct rivet fit against a loose one.

3. The four artifact elements, and why rivets suit them

S1 install and remove solid rivets. S2 install and remove a blind rivet. S6 prepare and install a patch. S12 countersink rivet holes.

A riveted coupon displays its own quality permanently. Head formation, shop head dimensions, hole condition, countersink depth, smoking rivets, sheet marking — all of it is visible weeks later to anyone who knows what to look at.

You make them in the shop, at the structures and finishes bench, in the Airframe in-person course (AF-A Hands-on). Repetition spread over days builds the skill better than one long session, which is the same argument GEN-D Hands-on makes for flaring, so any practice you can do at home beforehand is worth doing, though it is optional.

S6, a patch, is the integrative one: layout, material selection, pattern, drilling, countersinking and installation in a single artifact.

4. Removing a rivet is a skill, and doing it badly costs a hole

S8 removes a repair that was installed with rivets, and it is where beginners do the damage.

The hole is the asset. A rivet removed carelessly leaves an oversized, oval or damaged hole, and the repair to that is a larger rivet — which changes the pattern, the edge distance and possibly the repairability of the whole panel.

The method is in AF-A Procedures Procedure 6. The principle: drill only the head, then break it off. Do not drill the shank out. The drill wants to wander into the sheet, and the sheet is what you are trying to keep.

5. S14 is where you stop executing and start judging

Determine extent of damage and decide if metallic structure is repairable.

Every other skill in this unit assumes that decision has been made. This is the one that makes it, and it is the same class of judgment as GEN-K Concepts §6 — getting it wrong produces a confident wrong answer rather than a visible failure.

The questions, in order:

1. What is the damage? Crack, dent, corrosion, deformation, missing material, a hole.
2. How far does it go? Extent is not the same as what you can see, and GEN-K Procedures Procedure 1 decides which method will tell you.
3. What does the SRM allow? Negligible damage, repairable damage, damage requiring replacement — most SRMs use those categories.
4. Is a repair permitted here? Repairs near other repairs, near edges, or in specified zones are frequently restricted.
5. Does a permitted repair exist, or does this need approved data? GEN-I Concepts §1 and §3.

S5, designing a repair from the SRM, is the companion. The SRM defines what is permitted; anything outside it is a major repair needing approved data, and that determination is GEN-I's.

6. What consumes this unit

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