Forty-six elements, nine of them Risk Management — the most of any Airframe subject — and twenty skills.
The title says Aircraft Electrical Systems. Twelve elements are about wire.
1. Generation is six elements; wire is twelve
K7 wire sizes, types, selection and installation. K9 shielding. K15 connectors, splices,
terminals and switches. R5 routing and securing. R6 wire sizing. R7 terminal selection.
S1 inspect routing. S2 terminate and splice. S3 assemble a connector. S7 install wiring
and protective devices. S8 secure bundles. S10 bonding jumpers.
Generators, alternators, inverters and CSDs occupy six knowledge elements and produce two imagery skills between them.
That emphasis is correct and it should shape how you study. A mechanic's electrical work is overwhelmingly conductors, terminations, routing and protection. The generation theory exists so those decisions are informed — you need to know what is supplying the circuit to size and protect it — but you will spend your career on the wire.
2. R8 — soldering, and the thing candidates get backwards
Effects of soldering.
Most people arrive believing a soldered joint is the good one and a crimp is the compromise. In an airframe it is the other way round.
Solder wicks up between the strands and makes the conductor rigid where it meets the flexible part. That transition is a stress riser, and airframe vibration breaks wires there. The joint itself is fine; the wire snaps just behind it.
A crimp, by contrast, is a controlled cold weld — a specified deformation, made with a calibrated tool, verified by a gauge. It stays flexible right up to the terminal, and its quality is measurable rather than judged.
That is the same idea as torque in GEN-E Concepts §1: a specified mechanical result verified by a tool, not by appearance.
So S5, solder aircraft wiring, is bounded rather than general — used where the approved data
calls for it, not as a default. And K14, R8 and R9 should be learned as one idea rather than
three: what soldering does, why it is restricted, and how to do it when it is called for.
3. Nine risk elements, and four of them are one rule
R1 testing and troubleshooting. R2 connecting and disconnecting external power. R3
maintenance on energized circuits. R4 maintenance in areas containing wiring.
De-energize first. The ACS states it four ways because it is broken four ways.
R3 is the explicit case. R4 is the subtle one, and it is the one that produces most of the
work in this unit: working near wiring, where the hazard is not shock but damaging a conductor
you were not thinking about — a drill through a loom, a panel edge on a bundle, a tool dropped
into a bay.
That damage surfaces later as an intermittent, which is the hardest fault class to find, and
it is why S1's routing inspection matters after any work in a bay.
4. S9 — the one place you size something
Determine an electrical load in a given aircraft system.
With R6 wire sizing and K8 switch derating, this is the closest Airframe comes to asking you
to design rather than to inspect or install.
Current capacity sets a floor. Acceptable voltage drop usually sets the actual size. A wire that will carry the current without overheating may still be too small, because the drop over a long run leaves the load with insufficient voltage. Candidates size on current alone and get it wrong on long runs.
The inputs: load current, run length, allowable voltage drop, whether the load is continuous or intermittent, conductor bundle size and ambient temperature.
And the protective device protects the wire, not the equipment. A breaker is sized so the wire cannot overheat; sizing it to the load and ignoring the wire produces a circuit where the wire is the fuse.
Adding equipment to an aircraft is an electrical load analysis before it is anything else — and GEN-I Concepts §1's major-or-minor judgment is waiting at the other end of it.
5. Shielding, bonding and lightning are one idea
K9 shielding, K10 lightning protection, S10 bonding jumpers — and
AF-I §2 and AF-H K23. Bonding
appears in four subjects.
A bond is a low-impedance path so that current has somewhere to go that is not through something delicate. Lightning, static and fault current all need that path. The airframe is the path, and anything mounted on rubber or through paint is not connected to it until it is bonded.
Shielding is the same idea applied to a conductor: a screen intercepts interference and carries it to ground. A shield grounded at the wrong end, or at both ends where the design calls for one, can be worse than none — it becomes an antenna or a ground loop.
Bonding is measured, not judged. A specified milliohm value, taken with a meter, against the manufacturer's limit — which makes it one of the most objective checks in Airframe and connects straight to GEN-A Procedures Procedure 4.
6. Routing is where the delayed failures come from
R5, S1, S8. Chafe is the mechanism, and it is slow.
The rules that prevent it: support at the specified intervals, maintain separation from moving parts, control cables, hot sections and fluid lines, respect bend radius, and provide drip loops so fluid runs away from connectors rather than into them.
Never route wiring below a fluid line where a leak can drip onto it — and GEN-D Concepts §6 states the same rule from the fluid side. Two units, one rule, one consequence.
7. What consumes this unit
| This unit | Is consumed by |
|---|---|
| Ohm's law, voltage drop, measurement | Arrives from GEN-A |
| Terminals, crimping, torque discipline | Arrives from GEN-E |
| Bonding | AF-I §2, AF-H |
| Load analysis and sizing | GEN-I Concepts §1 — major or minor |
| Routing near fluid lines | GEN-D Concepts §6 |
| Engine-bay wiring | PP-F §1 — the same rules, hotter |
License
CC BY-SA 4.0 (Licensing).