What happened
On the approach to runway 06 at Jean-Lesage international airport, an Inter-Canadien Fokker F-28 was performing a landing following a flight from Sept-Îles. While the flight crew described the touchdown as soft, flight data recorder analysis indicated the aircraft touched down at 125 knots, which was higher than the reference speed. Shortly after contact with the runway, the aircraft began oscillating from side to side.
In an attempt to stabilize the aircraft, the captain applied heavy braking, but the oscillations persisted. During this period, the inboard wheel of the right main landing gear separated from the strut, followed shortly by the outboard wheel. The aircraft continued to travel down the runway on the remaining landing gear strut for several hundred feet before coming to a stop. The crew initiated an emergency evacuation via the wing exits and the service door. Although some passengers attempted to retrieve hand luggage during the process, the evacuation was completed without any 0 injuries.
The investigation
Investigators examined the mechanical condition of the landing gear and the flight data. Laboratory analysis revealed that the upper torque link had failed due to mechanical overload, with fatigue cracking identified at the site of the fracture. The investigation found that the clearances between several pins and bushes within the torque link assembly exceeded allowable in-service wear limits.
Additionally, the investigation established that the nitrogen pressure within the landing gear cylinder was higher than standard. This high pressure caused the landing gear strut to remain in an extended position for an extended duration. The investigation also noted that the lift dumpers were deployed late because the thrust levers had not been moved to the idle position quickly enough after touchdown. These factors, combined with the higher-than-normal landing speed, contributed to the intensity of the oscillations that led to the structural failure.
Findings
- The primary cause of the incident was the mechanical overload failure of the upper torque link.
- High nitrogen pressure in the main landing gear strut contributed to the failure.
- Late deployment of the lift dumpers and an increased landing speed exacerbated the oscillations.
- Excessive wear was present in the torque link pin and bush connections, exceeding service limits.
- The extended position of the strut due to high nitrogen pressure reduced the mechanical advantage of the torque links.