What happened
On 19 January 2004, an Airbus aircraft operated by Air Canada experienced a failure of the right nosewheel assembly during operations. The incident involved the failure of the nosewheel's right inboard roller bearing. While the flight data recorder showed no abnormalities during the landing or the preceding eight landings, the mechanical failure resulted in a fractured nosewheel axle, which remained partially lodged within the right nosewheel assembly.
The investigation
TSB engineers performed a detailed examination of the fractured nosewheel axle, the nose landing gear sliding rod, and both nosewheels involved. The investigation also included a review of the flight data recorder (FHD) to assess the aircraft's performance during the landing sequence.
Technical analysis focused on the components of the nose landing gear, manufactured by Liebherr, and the specific roller bearing produced by the Timken Company. The investigation sought to understand why the bearing failed and how that failure impacted the structural integrity of the axle.
Findings
Investigators determined that the right inboard roller bearing in the nosewheel failed. A primary contributing factor was the dislodgement of the grease dam, which allowed lubricant to migrate away from the bearing and into the wider nosewheel assembly. This loss of lubrication increased loads on the bearing cage.
As the bearing failed, the resulting friction generated temperatures high enough to reach the melting point of cadmium. This molten cadmium penetrated the nose landing gear axle, causing liquid metal embrittlement of the intergranular structure, which ultimately led to the axle fracture.
Safety action
Following the incident, Air Canada implemented several measures, including coating nose landing gear axles with SermeTel, an inorganic anti-corrosive base, to mitigate the risks of cadmium infusion. The airline also updated its maintenance alerts and wheel installation procedures to emphasize the necessity of inspecting grease dams and using correct installation tools.
Industry-wide responses included a Goodrich service letter recommending the use of Mobil SHC-100 grease for its superior adhesion and lubrication properties, alongside new inspection procedures for bearing grease seals on A318, A319, A320, and A321 aircraft. Additionally, Airbus began testing a new integrated retaining ring and seal design intended to better protect bearings from contaminants.