Pilot Debrief

BOMBARDIER CRJ700 near Hodeida — 2014-09-13

Final reportENG14IA029
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Date
2014-09-13
Location
Hodeida, YE
Aircraft
BOMBARDIER CRJ700
Registration
7O-FAB
Category
Airplane
Fatalities
0
Phase of flight
Takeoff roll

Probable cause

The probable cause of the undercowl engine fire was the burn-through of the combustion chamber inner liner from the accumulation of dust that became molten during operating and infiltrated the combustion chamber thermal barrier coating causing it to spall off and accelerate normal thermal distress. The burn-though of the combustion chamber caused downstream hardware to experience higher than designed temperatures that resulted in mechanical and thermal distress to the point that the low pressure turbine case began to melt. Contributing to the combustion chamber failure was the operators' failure to do recommended borescope inspections that would have detected the combustion chamber distress and hence the removal of the engine before it was allowed to progress to the point that the combustion and turbine sections of the engine failed.

NTSB narrative

On September 13, 2014, at about 06:02 UTC, Airways Bombardier (formerly Canadair) CRJ702ER Next Generation (NG), registration number 7O-FAB, powered by two General Electric (GE) CF34-8C5B1 turbofan engines, experienced a No. 1 (left) engine failure just after takeoff from the Hodeida International Airport (HOD), Yemen. The flight crew received a No. 1 engine fire warning indication along with high N2 vibrations and performed an inflight shutdown (IFSD) of the engine and made an uneventful air turn back (ATB) and landing at HOD. External examination of the No. 1 engine revealed a 26½ inches circumferential breach in the low pressure turbine case. Disassembly of the engine revealed a 10 inch burn-through hole in the combustion chamber inner liner. No anomalies were noted to any of the hardware upstream of the combustion chamber. Downstream of the combustion chamber, thermal distress and impact damage was noted throughout the high pressure and low pressure turbines. Debris that looked and felt like a brown soft talc was collected from the HPT aft shaft and HPT stage 2 blade retainers and sent to GE for analysis. Although the samples were similar, the HPT stage 2 blade debris was enriched with calcium sulfate (CaSO4). According to GE, the dust forms a calcium-magnesium-aluminum-silica (CMAS) that melts and infiltrates the structure on the thermal barrier coating (TBC) of the combustion liner surfaces causing the TBC to spall and accelerate thermal deterioration of the liner. Engine trend data for the event engine showed that starting in early May 2014 that there was an anomaly with the engine's interstage turbine temperature. GE recommended that the engine should be borescope inspected and to troubleshoot the temperatue indication system. Review of the engine logbook for the event engine found no mention of a borescope inspection or troubleshooting of the temperature indication system after May 2014. A review of other CF34-8C5/8E engines operating in a similar harsh enviroment found the event engine found had remained on wing and operated almost 2.5 longer than the average engine.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Failure to inspect engine temperature indications after May 2014.

NTSB coding

  • Fire/smoke (non-impact) · Takeoff

Evidence available

  • 10 docket documents
View NTSB final reportView NTSB docket

Docket documents10

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