What happened
On June 14, 2004, an IranAir scheduled passenger flight, operating an Airbus A300-600 with registration EP-IBA, was taxiing toward runway 09 at Amsterdam Airport Schiphol. During the taxi sequence, an aircraft following the IranAir flight reported seeing smoke emanating from the left-side tires and brake area. While the flight crew initially reported no cockpit indications of trouble, they soon notified Air Traffic Control of heat detected on the left wheel brake.
Following a request from ATC, the engines were shut down to allow for a mechanical inspection. On-board mechanics and local ground personnel identified a misalignment in the fifth wheel. Upon towing the aircraft to a parking area and removing the wheel, investigators discovered that the axle and axle sleeve had completely sheared off. The incident resulted in substantial damage to the aircraft, though there were no injuries to the 250 passengers or crew.
The investigation
Technical examinations were conducted by several specialized laboratories, including Messier-Services Molsheim, Messier-Dowty, and Technofan. The investigation focused on the left main landing gear bogie, the wheel, the brake unit, and the brake cooling fan. Investigators analyzed the metallurgical state of the axle and the condition of the bearing components to determine why the structural failure occurred.
Findings
Technical analysis determined that the overheating of the external bearing zone was the primary driver of the failure. This intense heat caused cadmium embrittlement within the steel of the axle, creating a condition where the metal became fragile. This embrittlement led to crack initiation and intergranular propagation, ultimately resulting in a static rupture of the axle.
While the investigation confirmed that the brake cooling fan was not the source of the heat, and that the temperature had not reached the threshold required to melt the tire's fuse plugs, the overheating was traced directly to the bearing. However, because certain rollers and races were not recovered for study, the specific reason for the initial bearing failure—such as lubrication issues, corrosion, or excessive wear—could not be definitively established.