Serious incident Boeing 777-222ER N206UA,
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ASN Wikibase Occurrence # 173445
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Date:Monday 31 December 2012
Type:Silhouette image of generic B772 model; specific model in this crash may look slightly different    
Boeing 777-222ER
Owner/operator:United Airlines
Registration: N206UA
MSN: 30212/216
Year of manufacture:1999
Fatalities:Fatalities: 0 / Occupants: 258
Aircraft damage: Minor
Category:Serious incident
Location:45 km South of Incheon Int'l Airport -   South Korea
Phase: En route
Nature:Passenger - Scheduled
Departure airport:Seoul-Incheon International Airport (ICN/RKSI)
Destination airport:Tokyo-Narita Airport (NRT/RJAA)
Investigating agency: ARAIB
Confidence Rating: Accident investigation report completed and information captured
A B777-200 airplane, N206UA, operated as United Airlines flight 890, which took off from Incheon International Airport, Republic of Korea, bound for Narita International Airport, Japan, experienced a pop sound accompanied with a yaw to the left while climbing through about 28,000 ft after takeoff. At this time, the IDG) tripped off, and No.1 engine fail EICAS message appeared, followed by fault messages for surge, N2, IDG and FMU. As the engine flamed out, in-flight restart was attempted but unsuccessful. The flight crew who decided to return declared an emergency
to air traffic control (ATC), descended, and landed safely at Incheon International Airport, point of departure, about 13:05.
Aboard the airplane were 2 flight crew, 10 cabin crew, and 246 passengers, but there was no personal injury.
The Aviation and Railway Accident Investigation Board (ARAIB) determines the cause of this serious incident was that the mechanical breakdown of the MB-7 bearing, which supports the front part of the gearbox drive gear shaft at the No. 1 engine MGB, stopped the transmission of the N2 rotor's rotational power to the MGB through the layshaft, which shut down all engine components mounted on the MGB, thereby resulting in the IFSD.
Contributing to this serious incident was that, during the last engine assembly, when the MB-7 bearing was mounted on the MGB driveshaft, the PMA drive retaining nut was tightened with a less torque than that prescribed by the EM, which caused its failure to support the MB-7 bearing inner race, thereby resulting in the mechanical damage of the MB-7 bearing.

Accident investigation:
Investigating agency: ARAIB
Report number: 
Status: Investigation completed
Download report: Final report


Revision history:

30-Jan-2015 20:08 harro Added

Corrections or additions? ... Edit this accident description

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