Why should solid, round conductor wire be avoided in aircraft use?

• A. It is too expensive
• B. It cannot carry high current
• C. It is too flexible
• D. It is prone to fatigue breakage

Answer: (D)

In aircraft wiring, vibration and repeated bending are constant realities, so the ability to withstand fatigue is crucial. A solid, round conductor is stiff and doesn’t flex with the airframe as well as stranded conductors do. This causes stresses from vibration to concentrate at bends, terminations, and clamp points. Over many vibration cycles, microcracks develop on the conductor surface and propagate, leading to fatigue breakage and potential loss of electrical continuity. Stranded conductors, made of many small strands, can flex more easily and distribute bending stresses, making them far more resistant to fatigue in a vibrating aircraft environment. Proper bend radii and support are still important for both types, but the fatigue resistance of stranded wire is why solid round conductors are avoided.