Delta B763 near Los Angeles on Jul 11th 2014, engine fire
Last Update: June 5, 2015 / 13:06:51 GMT/Zulu time
Incident Facts
Date of incident
Jul 11, 2014
Classification
Incident
Cause
Engine fire
Airline
Delta Airlines
Flight number
DL-101
Departure
Los Angeles, United States
Destination
Atlanta, United States
Aircraft Registration
N139DL
Aircraft Type
Boeing 767-300
ICAO Type Designator
B763
The NTSB released brief preliminary information on Oct 23rd 2014 stating, that maintenance found heat damage, scorching and sooting inside the engine. The NTSB is investigating the occurrence and had investigators travel for the investigation.
On My 29th 2015 the NTSB released their factual report reporting that a detailed examination of the engine revealed fire damage concentrated under the engine's heat shield from about 6:00 to 8:30 clock position (aft looking forward) forward of the accessory gear box. The NTSB wrote: "The fire and thermal distress included melted and consumed electric wire insulation, melted and consumed accessory gearbox fire loop isolators, melted and consumed tubing P-clamps, exposed electric wire conductors, and soot deposits."
Wet motoring of the engine revealed a fuel leak from the integrated drive generator's (IDG) fuel/oil heat exchanger main housing just aft of the forward weld. The unit, located just underneath the engine's heatshield, was removed from the engine. The NTSB wrote: "additional leak tests and a fluorescent penetrant inspection confirmed a circumferential through-wall crack in-line with where the inner core is brazed into the main housing, a second crack indication adjacent to the through-wall crack, and no internal leak between the fuel and oil sides of the inner core."
The NTSB continued:
Examination of post event engine photos (prior to the removal of any parts) and matching the arc damage on the IDG power feeder cables with the accessory drive lube and scavenge pump pressure line support bracket revealed that the IDG power feeder cables (below the engine heatshield) were not tight and straight along their support bracket but exhibited slack and dangling below the support bracket. A review of the installation drawing from the various aircraft and engine maintenance manuals, along with other exemplar DAL 767 CF6-80A powered airplanes, revealed that there should be no slack in the IDG cables; instead the cables should run straight and tight along its support bracket and gently bend upward towards the cutout hole in the engine heatshield. The DAL work specific cards for the installation and routing of the IDG power feeder cables at the time of the event included sketches that showed the proper routing along the support bracket with no slack.
Along with the observed arc damaged, the IDG power feeder cables also exhibited a considerable amount of orange tape to bundle all the cables together. This excessive slack in the IDG power feeder cables created the situation where the cables could get pinched/wedged between the inside of the thrust reverse cowl and the accessory drive lube and scavenge pump pressure (supply) line support bracket when the thrust cowl is closed and latched creating the environment for the IDG power feeder cables to chaff against the support bracket. The excessive amount of tape used on the IDG power feeder cables suggests that maintenance personnel may have noticed this chaffing and added extra tape without realizing that the chaffing was caused from the thrust reverser pressing the IDG power feeder cables against the bracket or that the slack was contributing to the chaffing.
The NTSB reported that the right hand engine installed on N139DL also showed misrouted IDG feeder cables.
The NTSB reported that as an immediate safety action the airline conducted a "once-through-the-fleet inspection for misrouted IDG power feeder cables" which found three more engines with misrouted IDG feeder cables, a total of 5 engines fleetwide were thus found with this incorrect wire installation. All of these installation were promptly corrected. The airline also updated their work cards to provide additional information and guidance on the correct installation of IDG feeder cables.
On Jun 5th 2015 the NTSB released their final report concluding the probable cause of the incident was:
The combination of fuel leaking from the integrated drive generator (IDG) fuel/oil heat exchanger and the coincident arcing of the IDG power feeder cables that ignited the leaking fuel. Contributing to the ignition of the fuel was the misrouting of the IDG power feeder cables, which resulted in chaffed cables that exposed the electrical wire that contacted a metal bracket, creating an arc.
Aircraft Registration Data
Incident Facts
Date of incident
Jul 11, 2014
Classification
Incident
Cause
Engine fire
Airline
Delta Airlines
Flight number
DL-101
Departure
Los Angeles, United States
Destination
Atlanta, United States
Aircraft Registration
N139DL
Aircraft Type
Boeing 767-300
ICAO Type Designator
B763
This article is published under license from Avherald.com. © of text by Avherald.com.
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