- Date
- September 7, 2009, 21:00 local (Sep 8, 2009, 01:00 UTC)
- Place
- St. Johns, Canada
- Damage
- Minor damage
- Phase of flight
- Enroute
- Aircraft
- N840MHBoeing 767 432ER
- Defining event
- Enroute-cruise: Electrical system malf/failure
- Weather
- Not reported
- Status
- Completed · report November 13, 2014
- Report
- Approved by Office Director
- NTSB office
- Aviation Engineering Division
- Case key
- 74697
From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the incident.
On this page
Probable cause
The NTSB’s determination of the probable cause, and any contributing factors.
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.
Findings · 1
NTSB’s coded findings. Those marked are part of the probable cause; the rest are factors or other findings.
Analysis
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.
Factual narrative
On September 7, 2009 at approximately 2100 EDT a Delta Air Lines (DAL) 767, N840MH, operating as flight 186, 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. There were 206 passengers, 8 cabin crew and three flight crew and no injuries were reported. DAL maintenance crews examined the area above the forward lavatory on the left side and found a wire bundle which had numerous fractured and melted wires, with soot on the bundle and immediate area. There were also signs of chaffing on a piece of support structure near the cable routing. A review of the Boeing wire installation drawings revealed that the damaged wire bundle was routed incorrectly and not properly secured. DAL performed a fleet inspection and found one other airplane with this wire bundle incorrectly routed. It was not damaged and they corrected the installation. The investigation did not determine if the incorrect routing occurred during manufacturing, maintenance, or modifications. A review of the wires in the bundle confirmed that oxygen system, passenger address system, and lavatory power wires were included in the bundle.
Sequence of events
The events NTSB coded, in order, by phase of flight. The defining event is the one that best describes the accident.
Aircraft
- Registration
- N840MH
- Reported as
- Boeing 767 432ER (432ER)
- Category
- Airplane
- Serial number
- 29718
- Built
- 2001
- Damage
- Minor damage
- Fire
- In-Flight
- Flight
- Part 121
- Operator
- Delta Air Lines Inc
- Registered owner
- Delta Air Lines Inc
- Airworthiness certificate
- Unknown
- Departed
- JFK · New York, NY
- Destination
- VCE · Venice
- Flight plan
- Unknown
Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.
Weather
- Conditions
- Not reported
Docket · 1
The files NTSB released with the investigation on November 13, 2014, on NTSB’s docket system: statements, records, photos and specialists’ reports. 1.6 MB in all.