Electrical Cables & Connectors
Aircraft wire and AWG, circuit protection sized to the wire, crimped terminations, connectors and screening.
Electrical cables & connectors — summary notes
Free- Aircraft wire uses a copper (sometimes copper-alloy) conductor, often tinned, silver- or nickel-plated for corrosion and temperature resistance, with high-performance insulation (PTFE, ETFE/Tefzel, modern low-smoke types). Size is given in American Wire Gauge (AWG).
- AWG runs backwards: a SMALLER AWG number means a THICKER conductor that carries more current. Wire is selected for current-carrying capacity (ampacity, derated in bundles and at altitude), allowable voltage drop and mechanical strength.
- Circuit protection (circuit breaker or fuse) is sized to protect the WIRE, not the equipment — it must open before the wire overheats. This is why re-rating a breaker to stop nuisance trips is not permitted.
- Terminations: crimped terminals and splices made with a calibrated crimp tool and the correct barrel are preferred where there is vibration; soldered joints are avoided in high-vibration/high-heat areas. Connectors (circular MS bayonet/threaded, rack-and-panel, coaxial, fibre-optic) are keyed to prevent mis-mating and use pin/socket contacts with a backshell and strain relief.
- Screening/shielding and bonding control EMI; coaxial cable (with its characteristic impedance) feeds antennas and RF. Route and clamp wiring to avoid chafing, keep drip loops, and separate power from signal runs.
- ⚠ Exam trap: the circuit breaker/fuse protects the WIRE and is sized to the wire, not the load; and a LOWER AWG number is a THICKER wire (more current) — the numbering is reversed. Crimped joints are preferred to soldered where vibration is present.
A repeatedly tripping circuit breaker is 'fixed' by fitting a higher-rated breaker so it stops nuisance-tripping. Why is this dangerous?
The breaker is sized to protect the wire from overheating, not to suit the load. A higher-rated breaker lets more current flow through a wire that may not be rated for it, so a fault or overload can now overheat the insulation and start a fire before the breaker opens. The correct action is to find why it trips (short, overload, chafe) and rectify it, keeping the original wire-matched rating.
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