NTSB Identification: ENG09IA016
Scheduled 14 CFR Part 121: Air Carrier operation of DELTA AIR LINES INC
Incident occurred Monday, September 07, 2009 in St. Johns, Canada
Probable Cause Approval Date: 11/13/2014
Aircraft: BOEING 767 432ER, registration: N840MH
NTSB investigators traveled in support of this investigation and used data obtained from various sources to prepare this aircraft incident report.
The Delta Airlines 767 was two hours enroute from John F. Kennedy International Airport (JFK) to Venice Marco Polo Airport (VCE), when the cabin lights flickered, the passenger address system was intermittent and then inop, the left side oxygen masks deployed and a sulphur smell was observed, but no smoke. The flight diverted to ATL and landed without incident.
Examination of the area above the forward lavatory on the left side revealed fractured wires, sooted equipment, and chafed structure. Drawings showed the wire bundle was incorrectly routed. These findings indicated that the incorrect routing allowed the wires to chafe over time. This chafe eventually exposed the conductor(s) and either two wires or a wire to grounded structure resulted in a electrical short with arcing.
A review of the wire functions within the bundle showed wires related to oxygen system, passenger address system, and lavatory power. This is consistent with the reported anomalies.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: Incorrect installation of a wire bundle, which contained wires for oxygen system, passenger address system and lavatory power, led to chafing of the wires on structure. The chafing eventually exposed the wire conductors and resulted in electrical arcing, malfunction of the affected systems and a sulfur odor. Full narrative available
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