Electrical Cables and Connectors
Core concepts
Aircraft wire is selected by conductor size (AWG), strand count, insulation type and temperature rating, and by the current it must carry with acceptable voltage drop. Insulations include PVC, PTFE, ETFE/Tefzel, silicone and fibreglass; specifications such as MIL-W-22759 define the wire. Shielded and coaxial cables carry sensitive or high-frequency signals and need correct termination and grounding at the specified end only.
Connectors are circular or rectangular with pin and socket contacts, keyways to prevent mis-mating and positive contact retention. Crimping is the preferred termination, using the correct tool and a pull test; solder joints must be supported and never used as the mechanical joint. Bonding and grounding paths carry fault and static current and must be clean, protected and within resistance limits. Route bundles clear of fuel, oxygen and hydraulic lines, hot areas and control runs, supported at regular intervals and protected against chafing.
Traps in questions
Aluminium wire is prohibited in aircraft electrical systems. A bundle carrying many currents must be derated - bundled wires run hotter than single wires. Over-tightened clamps cut insulation; too small a bend radius damages conductors; wrong insertion tools spread or damage contacts. Mixing power and low-level signal wires in one bundle invites interference.
Rule of thumb
Allow a bend radius of at least ten times the bundle diameter, support the run at roughly 24 in intervals and near connectors, and leave a service loop at each termination.