Colgan DH8D near Pittsburgh on Mar 17th 2011, engine shut down in flight because of engine fire
Last Update: June 5, 2015 / 11:39:19 GMT/Zulu time
The FAA reported the aircraft received "unknown damage".
The NTSB reported on Jun 30th 2011 that the crew received a #1 engine oil master warning while in cruise at FL230 about 60nm from Pittsburgh. The crew noticed the engine #1 oil pressure display showed just white dashes and interpreted this to have no oil pressure indication with all other engine parameters normal. However a rapid rise of engine oil temperature followed, the #1 engine fire warning activated and the engine began to lose power. The crew discharged one fire bottle, 30 seconds later discharged the second fire bottle, the fire indication however remained. The crew declared emergency and diverted to Pittsburgh. The passengers deplaned through the R2 door onto the runway. Emergency services determined the fire was extinguished, the fire warning however still remained active. A post flight inspection reveleased the #1 engine had received severe thermal damage to its turbine section with an approximate 4 by 4 inch (10 x 10 cm) hole burnt through the bottom of the gas generator case.
On Jun 5th 2015 the NTSB released their final report concluding the probable cause of the incident was:
the flight crew's delay in shutting down the left engine following an engine oil pressure master warning, which led to a hard rub inside the engine that served as an ignition point for a titanium fire. Contributing to the event was a PW150 No. 5 seal design vulnerability to titanium ignition that can occur with continued engine operation following an engine oil pressure loss event.
The NTSB reported that post event analysis of the engine showed the engine oil was seriously contaminated with metallic particles. The left oil pump was found seized, internal examination showed a vane, that scavenges oil from the engine bearing 2/2.5 had not fully retracted due to metallic contamination. The NTSB wrote: "The protruding vane struck the element rotor and arrested pump rotation, causing torsional overload separation of the pump driveshaft and cut-off of oil supply to the engine."
The NTSB reported, the engine bearings' 4 and 5 cavities were found dry showing "wear damage characteristic of operation without adequate lubrication". Both bearings showed dull gray discolouration. The other engine bearings were found intact.
The NTSB reported regarding the engine bearing number 5: "The No. 5 bearing area was extensively damaged. The No. 5 bearing housing assembly was thermally destroyed. The No. 5 bearing (titanium alloy) flexible support housing and the No. 5 bearing front carbon seal and cover were partially consumed/melted together and were no longer recognizable. The No. 5 bearing front air seal runner was scorched and the runner section was eroded/missing. The No. 5 bearing oil nozzle housing, housing outer cover, rear carbon seal, and outer race were severely heat damaged. The No. 5 bearing IR, OR, and cage were intact but were thermally damaged, and the rollers were disintegrated. The No. 5 bearing pressure and scavenge oil tubes were largely consumed. The integral diaphragm section of the gas generator diffuser assembly, a thin-walled titanium-alloy structure linking the No. 5 bearing support housing diameter with the gas generator shield at the diffuser apex diameter, was entirely consumed. Large sections of the combustion section large exit support duct (LESD) inner and outer walls were thermally consumed/melted. The thermal damage exposed the back face of the (titanium-alloy) impeller, which showed a rough and eroded surface texture and exducer vane tip erosion, but was otherwise intact. The three diffuser exit ducts located bearing at 6 to 7 o'clock and immediately inboard of the gas generator case burn-through hole were thermally consumed/melted. Diffuser ring bore inside surfaces exposed at the apex end of two of the melted exit ducts were in good condition. The remaining 20 diffuser exit ducts located around the circumference of the gas generator case were intact. The HPT front cover was partially oxidized and the HPT airfoil tips and leading edges were eroded. The gas generator case exhibited no significant thermal damage other than the burn-through hole at 6 to 7 o'clock. Re-solidified metal splatter was fused to the diffuser, diffuser exit ducts, LESD outer wall, combustion chamber inner liner and small exit duct, HPT disk nozzle housing assembly, HPT disk bore, HPT shroud segments, LPT airfoils and LPT shroud segments. The engine exhibited no circumferential melting damage or other evidence of high-velocity, 360 degree distribution of molten particles."
This article is published under license from Avherald.com. © of text by Avherald.com.
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