On February 15, 1990, a Boeing 747-446B (registration UNREG) was involved in an aviation accident near Everett, WA. Investigators recorded the probable cause as: The trunnion fractured as a result of pre-existing intergranular cracks. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 8 related events involving the same aircraft type or operator are linked below.
During the landing roll, the pilot received caution messages for hydraulic pressure and gear door, and noted the airplane listing to the right. Post-flight inspection revealed a fractured right wing landing gear trunnion caused by pre-existing intergranular cracks.
Event Description
During the landing roll at the end of a flight, the pilot reported that the Engine Indication and Crew Alerting System (EICAS) displayed caution messages for hydraulic pressure and quantity, and gear door. The pilot also noted that the airplane was listing to the right.
Inspection and Findings
Subsequent inspection revealed that the right wing landing gear outer cylinder aft trunnion arm had broken. The part was subjected to metallurgical testing to determine the cause of the fracture.
Metallurgical Analysis
Metallurgical testing determined that the trunnion fractured as a result of pre-existing intergranular cracks. No other contributing factors were identified.
Probable cause
The trunnion fractured as a result of pre-existing intergranular cracks.
