Incident Overview

Description
Air Canada flight AC901, an Airbus A330-343, suffered a right main landing gear failure while landing on runway 06L at Montreal International Airport, Canada. A few seconds after touchdown on Runway 06L, the bogie beam failed on the right main landing gear. At the same time, indications of a right main landing gear malfunction were displayed in the cockpit. The aircraft continued its landing roll, with the right gear shock strut scraping the runway, and came to rest on the runway. The crew requested assistance from aircraft rescue and firefighting services. Significant landing gear damage, which made towing the aircraft impossible, was observed. Findings as to causes and contributing factors: 1. On 17 December 2021, while the aircraft was taxiing for takeoff, for an undetermined reason, one of the bearings on the No. 4 wheel seized and caused the protective sleeve to rub against the bogie beam bushing, causing localized overheating of the bogie beam base metal. 2. Given that the overheat indicator strip closest to the beam at the No. 4 wheel on the axle was its original colour, applicable procedures allowed for the replacement of the axle and the bogie beam bushing without a thorough damage assessment. 3. Given that the component maintenance manual does not provide any specific repair for a bushing replacement, the Disassembly and Assembly sections were used as references. Consequently, the inspection criteria during bushing replacement focused on ensuring the correct dimensions rather than detecting damage, which eliminated the requirement for non-destructive tests. 4. Given the intact indicator strip, the clear transition between the blackened area and the adjacent protective layer, and the intact paint on the beam around the bushing, the technicians who performed the visual inspection during the replacement of the damaged bushing concluded that the beam was in good condition, even though the bogie beam base metal had overheated. 5. Two cracks emanated from a previously undetected area of overheating under the bogie beam bushing. One of the 2 cracks spread and caused a fracture of the No. 4 wheel bore. 6. Upon landing on 25 December 2021, the fracture emanating from the No. 4 wheel bore spread rapidly and resulted in the bogie beam breaking into several pieces. No longer supported by the wheels, the shock strut scraped the runway until the aircraft came to rest.
Primary Cause
1. A localized overheating issue within the No. 4 wheel bearing bushing, caused by a seized bearing, resulted in excessive bogie beam base metal heat. 2. The lack of a specific repair procedure for bushing replacements, relying solely on visual inspection criteria, led to the omission of non-destructive testing and the failure to detect the underlying overheating issue.1. A localized overheating issue within the No. 4 wheel bearing bushing, caused by a seized bearing, resulted in excessive bogie beam base metal heat. 2. The lack of a specific repair procedure for bushing replacements, relying solely on visual inspection criteria, led to the omission of non-destructive testing and the failure to detect the underlying overheating issue.Share on: