What happened
On 18 June 2023, a Boeing 787-9, registration 9V-OJF, was operating a scheduled flight from Incheon International Airport in South Korea to Singapore via Taipei. During the initial pushback from the parking bay, the ground crew noted unusual resistance, though the flight crew proceeded after confirming the parking brakes were released. As the aircraft taxied toward the runway, the crew experienced intermittent vibrations during several turns.
During the flight, the crew observed a status message indicating a tire pressure system issue and noted that pressure readings for both nose tires were no longer displaying. While the crew was unaware of the structural damage, airport authorities at Incheon discovered a nose wheel, tire debris, and other components scattered along the taxiways.
Upon arrival at Taoyran International Airport, the crew performed a landing without further vibration. However, once the aircraft reached its parking bay, ground personnel discovered that the left-hand nose wheel and a portion of the axle were missing.
The investigation
An investigation conducted by the TSIB, in coordination with the Korean authorities, focused on the structural failure of the nose landing gear. Metallurgical examinations of the recovered components revealed that the left axle had sheared at the inboard location.
Laboratory analysis performed by the aircraft manufacturer identified significant heat damage on the axle, including melted cadmium plating and discolored primer. Scanning Electron Microscopy (SEM) confirmed that the fracture was an intergranular fracture caused by cadmium embrittlement. Additionally, the examination of the inboard bearing showed significant deformation, including brinelling marks, suggesting the bearing had been subjected to forces exceeding design limits.
Findings
- The primary cause of the axle failure was cadmium embrittlement, which led to an intergranular fracture of the metal.
- The inboard bearing experienced extreme heat and high point loading, likely due to rollers becoming skewed and seizing during operation.
- Evidence of corrosion was found on the outboard bearing cup, potentially resulting from improper storage or maintenance conditions.
- The shearing of the axle caused the loss of the left-hand nose wheel and the severance of the tire pressure sensor wiring.