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ASN Wikibase Occurrence # 818
Last updated: 26 September 2018
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Type:Silhouette image of generic B772 model; specific model in this crash may look slightly different
Boeing 777-222
Owner/operator:United Airlines Inc
Registration: N220UA
C/n / msn: 30222
Fatalities:Fatalities: 0 / Occupants: 264
Aircraft damage: Minor
Location:O'Hare Int. Airport (ORD), Chicago, IL -   United States of America
Phase: Approach
Nature:International Scheduled Passenger
Departure airport:Shanghai, (PVG)
Destination airport:Chicago, IL (ORD)
Investigating agency: NTSB
On approach for landing, about 13 miles from the airport, the flight crew was informed that the cabin was filling with smoke. The cabin crew was unable to determine the source of the smoke. The captain declared an emergency in order to get the airplane on the ground as soon as possible. The first officer performed a normal landing and turned off on the first high-speed taxiway, at which time he noticed a low oil indication on the right engine. The engine was subsequently shut down. The captain elected to initiate an emergency evacuation due to the uncertainty of the situation and the possibility of a fire on-board. During the evacuation, one passenger sustained a fracture of a vertebra. Post accident examinations revealed a low oil quantity in the right engine, with metallic deposits on one of the engine chip detectors. A detailed teardown inspection of the right engine revealed the #2 bearing had failed. The compressor gas path exhibited oil deposits consistent with oil migration into the airplane's environmental system. The cabin pressurization system utilized 8th and 15th stage engine compressor bleed air. No evidence of an engine or cabin fire was observed. The engine manufacturer had released an improved bearing design prior to the accident. At that time, the operator began replacing the bearings on an attrition basis when the original bearings were no longer serviceable. However, the operator has revised that policy and is proactively replacing the original bearings, regardless of the condition, with the improved bearings.
Probable Cause: Emergency evacuation due to dense smoke in the cabin and the possibility of an on-board fire, which resulted in a serious injury to one of the 264 passengers and crew. An additional cause was the failure of an engine bearing, allowing oil to migrate into the environmental system, and resulted in the smoke in the cabin.



Revision history:

23-Jan-2008 00:41 JINX Added
24-Feb-2008 07:36 harro Updated
21-Dec-2016 19:13 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
21-Dec-2016 19:14 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
21-Dec-2016 19:16 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
21-Dec-2016 19:20 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
04-Dec-2017 19:03 ASN Update Bot Updated [Cn, Operator, Other fatalities, Departure airport, Destination airport, Source, Narrative]

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