NTSB Identification: LAX01IA066.
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Scheduled 14 CFR Delta Airlines Inc.
Incident occurred Friday, December 29, 2000 in Honolulu, HI
Probable Cause Approval Date: 11/25/2003
Aircraft: Lockheed L-1011-385-1, registration: N735D
Injuries: 300 Uninjured.
NTSB investigators used data provided by various sources and may have traveled in support of this investigation to prepare this aircraft incident report.
The air transport aircraft was cruising 2 hours after departure at 32,000 feet in clouds when it experienced an electrical discharge near the co-pilot's over window panel. Just prior to the discharge event, the flight crew observed a phenomenon known as St. Elmo's Fire, during which time loud popping noises were heard in the radios. After the discharge, sparks, smoke, and a strong acrid smell of electrical burning were noted from near the co-pilot's over window panel. The smoke and fume checklist was performed, halon was applied on two separate occasions, and the relative circuit breakers and electrical switches were opened. The flight landed uneventfully 45 minutes later. Post incident examination of the affected wires revealed that electrical arcing and shorting had occurred between the airplane structure, a clamp, and a 30-wire bundle. The affected wire bundle passed behind the flight engineer's station and overhead to the heated windshields. The wire bundle and its clamps were examined and it was noted that the wires were insulated with aromatic polyimide, which is susceptible to arc tracking and insulation flashover. Though the insulation did not display complete insulation breaches, it was noted that the arcing event initiated near a clamp, which was destroyed by the event. The clamp aft of the burned area was of normal size, while the clamp forward of the destroyed one was too small. It is plausible the insulation was either chafed or crimped by the damaged clamp, allowing the arcing event to take place. In turn, the arc tracking and insulation flashover then consumed the surrounding wires.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: the electrical wire arcing and burning as result of insulation degradation, which more than likely resulted from improper clamping. Full narrative available
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