What happened
On November 16, 2012, an Airbus A300-B4, registration EI-EAC, operated by Air Contractors, was performing an international cargo flight from Leipzig, Germany, to Bratislava, Slovakia. The flight proceeded normally until the landing phase on runway 22. Following touchdown, the crew deployed thrust reversers and configured the aircraft for deceleration.
Approximately six seconds after the nose wheel made contact with the runway, the crew experienced intense vibrations that intensified as the aircraft slowed. At approximately 85 kt, the thrust reversers were stowed, at which point the aircraft began to veer sharply to the left. The pilot flying attempted to correct the deviation using heavy braking, rudder inputs, and nose gear steering, but the aircraft could not be maintained on the centerline. The aircraft exited the runway to the left at roughly 45 kt, at which point the nose gear struck a concrete utility cover, causing the gear to collapse. The aircraft slid for several dozen meters before coming to a complete stop. There were no fatalities or injuries among the crew.
The investigation
The investigation focused on the mechanical integrity of the nose gear steering linkage and the maintenance history of the aircraft. Investigators examined the central axis (apex pin) of the nose gear torque links. Analysis of the components revealed that the assembly had been incorrectly reinstalled during a maintenance procedure performed 26 days prior to the accident. Specifically, the investigation found that a washer had been improperly positioned, creating a gap that prevented the locking washer from fully engaging the splines on the axis. This allowed the nut to unscrew during flight operations.
Investigators also examined the site of the excursion, noting that the nose gear failure was caused by the impact with a concrete manhole cover located within the runway strip. The investigation reviewed the Aircraft Maintenance Manual (AMM) and found that while diagrams were provided, the text lacked explicit instructions regarding the orientation of the washers, which contributed to the error.
Findings
- The primary cause of the runway excursion was the incorrect reinstallation of the nose gear torque link assembly, which led to the unscrewing of the central axis nut during operation.
- The loss of steering control triggered a shimmy motion in the nose gear bogie, causing the aircraft to deviate from the runway centerline.
- The collapse of the nose gear was caused by the collision with a concrete obstacle (a utility cover) located in the runway strip.
- The maintenance error was facilitated by a lack of clear, unambiguous instructions in the manufacturer's maintenance manual regarding the specific orientation of the washers during reassembly.
- The presence of a non-frangible concrete obstacle in the runway strip contributed to the severity of the damage.