Module 6.11 Electrical cables and connectors

Knowledge levels

Sub-module	A	B1 / B3	B2 / B2L
6.11 Electrical cables and connectors	1	2	2

Content: cable types, construction and characteristics; high-tension and coaxial cables; crimping; connector types, pins, plugs, sockets, insulators, current and voltage rating, coupling, identification codes. (Installation and testing practices are in Module 7.7 EWIS.)

Cable construction

• Conductor: stranded copper (tinned, silver- or nickel-plated) for most wiring; aluminium for large feeders where weight saving matters (larger cross-section for the same current, special terminals). Stranding gives flexibility and fatigue resistance.
• Plating: tin (up to about 150 °C), silver (about 200 °C), nickel (about 260 °C and above, fire zones).
• Insulation: PVC (old, toxic smoke - not used in new pressurised aircraft), polyimide (Kapton - thin, tough, but prone to arc tracking and cracking when bent), PTFE (Teflon), ETFE (Tefzel), cross-linked ethylene (XL-ETFE), composite insulations (TKT: Teflon-Kapton-Teflon).
• Jacket and shield: braided or spiral copper shield against EMI; overall jacket protects the shield.

Wire size

• US: AWG (American Wire Gauge) - the larger the number, the smaller the wire (AWG 22 thin signal wire, AWG 0 or 0000 heavy battery/starter cable). Every 3 gauge numbers roughly halves the cross-sectional area.
• European/metric: cross-section in mm².
• Selection depends on current (heating), voltage drop over the run length, mechanical strength, ambient temperature, bundling (derating) and altitude.

Key fact: A smaller AWG number means a thicker wire that carries more current.