FAA Aviation Mechanic Airframe (AMA)Airframe Electrical and InstrumentsMedium
During an inspection, a technician measures the spacing between support clamps on an unshielded electrical wire bundle routed through the fuselage. According to general aircraft wiring installation practices, wire bundles should typically be supported at intervals not exceeding what maximum spacing?
- A6 inches
- B24 inches
- C36 inches
- D12 inches
Show answer & explanationAnswer & explanation
Correct answer: B. 24 inches
General aircraft wiring practices (as referenced in FAA guidance such as AC 43.13-1B) call for wire bundles to be supported at intervals not exceeding 24 inches unless the manufacturer specifies otherwise, to prevent excessive sag, chafing, and fatigue from vibration.
Why the other options are wrong
- A. 6 inches is far tighter spacing than the general standard requires.
- C. 36 inches would allow excessive sag and vibration-induced chafing.
- D. 12 inches is closer but not the general maximum spacing standard.
Wire Bundle Support Spacing
The maximum distance allowed between clamps supporting an aircraft wire bundle to prevent sag, chafing, and vibration fatigue.
- General maximum spacing: 24 inches
- Closer spacing may be required near moving parts or high-vibration areas
- Improper spacing can cause chafing and eventual electrical shorts
Memory trick: 24 inches — two feet apart keeps wires from sagging like a hammock.