Pilot Debrief

BOEING 767 432ER near St. Johns — 2009-09-08

Final reportENG09IA016
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Date
2009-09-08
Location
St. Johns, CA
Aircraft
BOEING 767 432ER
Registration
N840MH
Category
Airplane
Fatalities
0
Phase of flight
Cruise

Probable cause

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.

NTSB narrative

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.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Properly securing and routing the wire bundle during installation or maintenance.

NTSB coding

  • Electrical system malf/failure · Enroute-cruise

Evidence available

  • 1 docket document
View NTSB final reportView NTSB docket

Docket documents1

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