Terminating, routing, protecting

Eight procedures. Guided first attempts are in AF-K Hands-on.

Measurement procedures are in GEN-A Procedures and are not repeated here.

Procedure 0 — De-energize, and know what is near you (R1–R4)

1. Identify the circuit from the wiring diagram.
2. De-energize: pull the breaker, disconnect the battery where the work requires it, disconnect external power.
3. Confirm dead with a meter, at the point you will be working.
4. Look at what else is in the bay. R4 — the hazard is damaging a conductor you were not thinking about (AF-K Concepts §3).
5. Protect adjacent looms before drilling, cutting or levering anything.

Check — confirm dead at the point of work, not at the panel. Two circuits can share a bay and only one of them is the one you pulled.

Procedure 1 — Determine the electrical load, and size the wire from it (S9, R6)

S9 is the load; R6 is the wire. The procedure was previously titled for the wire size alone, which named it after R6's output rather than after the element it assesses.

1. Establish the load current. Sum the connected loads on the circuit or bus, and establish for each whether it is continuous or intermittent — only continuous load counts against the continuous-duty limit. Compare the total against the generator or bus rating and against the percentage of rating the manual allows continuously; the margin that remains is what any added equipment has to fit inside.
2. Measure the run length, out and back.
3. Find the allowable voltage drop for that system from the manual or AC 43.13-1B.
4. Select from the chart, using both current capacity and voltage drop — take the larger size the two give (AF-K Concepts §4).
5. Adjust for bundle size and ambient temperature, which reduce capacity.
6. Size the protective device to protect the wire.

Check — compute the voltage drop for the size you chose and compare against the limit. Sizing on current alone is the standard error, and on a long run it fails the drop check.

Failure — sizing the breaker to the load. The breaker exists to stop the wire overheating; if it is larger than the wire can stand, the wire is the fuse.

Procedure 2 — Strip and terminate (S2)

1. Select the correct terminal for wire gauge and stud size.
2. Strip to the length the terminal requires — no more. Exposed conductor beyond the barrel is a short waiting to happen.
3. Do not nick the strands. A nicked conductor fails at the nick, later, from vibration.
4. Crimp with the correct tool and the correct die, fully cycled.
5. Inspect: insulation not in the conductor barrel, conductor visible at the inspection window where the terminal has one, no strands outside the barrel.
6. Pull-test to the specified value where required.

Check — give it a firm pull. A correct crimp does not move. This takes a second and it catches the crimp made with the wrong die.

Failure — a crimp made with pliers or the wrong die. It holds on the bench and releases under vibration.

Procedure 3 — Splice (S2)

1. Confirm a splice is permitted here — the manual and AC 43.13-1B limit how many splices a run may have and where they may be.
2. Stagger splices in a bundle so they do not form a bulge.
3. Use the approved splice for the gauge, crimped with the correct tool.
4. Insulate and seal per the approved method.
5. Support the splice — it must not carry load or sit at a flexing point.

Check — a splice must be supported and staggered. A bundle with several splices at the same point is stiff, bulky and chafes.

Procedure 4 — Assemble a connector (S3)

1. Identify the connector and its contact type — pin, socket, size, and whether crimp or solder.
2. Check the wiring diagram for pin assignment, and mark the wires before starting.
3. Crimp contacts with the correct tool and positioner.
4. Insert contacts with the insertion tool until they click home, and confirm with the removal tool's resistance or a gentle pull.
5. Fit sealing plugs in unused cavities — an unplugged cavity admits moisture.
6. Assemble the backshell, supporting and clamping the cable so strain is taken by the shell, not the contacts.

Check — tug each wire gently at the back of the connector. A contact that has not latched comes back out, and it will do so in service if it does not do so now.

Failure — a contact not fully seated. It works on test and backs out under vibration, producing an intermittent that is very hard to find.

Procedure 5 — Solder, where it is called for (S5, R8, R9)

First confirm soldering is what the approved data calls for (AF-K Concepts §2).

1. Clean the conductor and the joint.
2. Use the specified solder and flux — and never acid flux on electrical work; it corrodes the joint from the inside.
3. Heat the work, not the solder. Solder should melt on the joint, not be dripped onto it.
4. Use just enough solder to wet the joint. Excess wicks up the strands and extends the rigid section.
5. Do not move the joint while it cools. A disturbed joint looks dull and grainy and is weak.
6. Clean off flux residue.
7. Support the wire so the joint is not a flex point — this is the whole point of R8.

Check — the joint should be shiny and smooth, with the wire outline visible through it. Dull, grainy or blobby means it was disturbed, too cold, or over-soldered.

Failure — an unsupported solder joint at a flex point. It is a designed-in fatigue failure.

Procedure 6 — Route and secure a bundle (S8, R5)

1. Follow the routing the drawing specifies, and the existing route where you are replacing.
2. Clamp at the specified intervals with the specified clamps — correct size, cushioned, not over-tightened.
3. Maintain separation: from control cables, moving parts, hot sections, and fluid lines. Never below a fluid line (AF-K Concepts §6).
4. Respect bend radius, and leave service loops at connectors.
5. Provide drip loops so fluid runs away from connectors.
6. Check for chafe points through full travel of anything that moves.

Check — move everything that moves, through full travel, and watch the bundle. Controls, gear, flaps, doors. Chafe is found this way and not by looking at a static aircraft.

Procedure 7 — Install a bonding jumper (S10)

1. Prepare both surfaces: remove paint, anodizing and corrosion products to bare, clean metal at the contact area only.
2. Fit the jumper with the specified hardware, metal to metal at the contact faces.
3. Torque per the manual.
4. Measure the resistance across the bond and compare against the manufacturer's limit.
5. Restore corrosion protection around the joint without insulating the contact faces (GEN-G Concepts §3).

Check — measure it. Bonding is the one thing in this unit with an objective numerical pass criterion, and a bond that looks fine and reads high is doing nothing.

Failure — bonding through paint or anodizing. It looks like a bond and is an insulator.

The checks, collected

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