What happened
On March 14, 1970, an Air Canada Douglas DC-8-53, registration CF-TIH, was involved in a ground accident at Zurich Airport. The aircraft was performing a charter flight from Zurich to Toronto. While taxiing toward the threshold of runway 16, the pilot initiated a 180-degree right turn to align with the takeoff direction. During this maneuver, approximately 45 degrees into the turn, the nose gear suddenly collapsed. The aircraft's nose struck the runway, resulting in a 4-meter scrape mark on the pavement. The crew and passengers were able to evacuate the aircraft immediately without difficulty.
The investigation
Investigators examined the aircraft's nose gear assembly and the runway conditions. The investigation found that the landing gear lever was in the extended position and that the runway surface was dry and free of ice or snow. Analysis of the wreckage revealed fragments of an aluminum casting, identified as the support bracket for the locking cylinder, at the site of the nose strike. Examination of the nose gear mechanism revealed that the piston within the cylinder was unable to rotate freely, as it had become jammed with the perforated tube. This jamming was caused by a damaged lower sealing ring. Furthermore, a dimensional deviation of approximately 9.9 mm was discovered on the inner wall of the piston, which prevented the internal components from reaching a proper stop.
Findings
- The primary cause of the accident was the collapse of the nose gear due to a failure in the locking system.
- The support bracket for the locking cylinder fractured because the steering movement was transmitted directly into the bracket during the turn.
- A dimensional error in the piston's inner wall caused abnormal interaction and jamming between the perforated tube and the piston.
- The nose gear was turned sharply to the right prior to the collapse, and the resulting mechanical stress led to the structural failure of the locking mechanism.
Safety action
No specific safety recommendations or subsequent actions were recorded in the final report.