Serious incident Lockheed L-1011-385-1 N735D,
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ASN Wikibase Occurrence # 370520
 
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Date:Friday 29 December 2000
Time:23:15 LT
Type:Silhouette image of generic L101 model; specific model in this crash may look slightly different    
Lockheed L-1011-385-1
Owner/operator:Delta Air Lines
Registration: N735D
MSN: 193C-1226
Total airframe hrs:58217 hours
Engine model:Rolls-Royce RB211-22B
Fatalities:Fatalities: 0 / Occupants: 300
Aircraft damage: Minor
Category:Serious incident
Location:Honolulu, HI -   United States of America
Phase: En route
Nature:Passenger - Scheduled
Departure airport:San Francisco International Airport, CA (SFO/KSFO)
Destination airport:Honolulu-Daniel K. Inouye International Airport, HI (HNL/PHNL)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
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.


Probable Cause: the electrical wire arcing and burning as result of insulation degradation, which more than likely resulted from improper clamping.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: LAX01IA066
Status: Investigation completed
Duration: 2 years and 11 months
Download report: Final report

Sources:

NTSB LAX01IA066

Location

Revision history:

Date/timeContributorUpdates
25-Mar-2024 11:33 ASN Update Bot Added

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