What happened
On a flight from Delaronde Lake to Swan Lake, Saskatchewan, a Cessna 180J, registration C-GRPR, encountered deteriorating weather conditions. As the pilot and one passenger progressed through their 80-nautical-mile route, falling snow and lowering cloud ceilings reduced visibility. While the pilot was evaluating whether to divert to a nearby road or return to base, the aircraft began to yaw to the right during a left turn at approximately 500 feet above ground level.
During this maneuver, the aircraft experienced airframe buffeting, and the pilot struggled to maintain pitch control. Despite applying full engine power and elevator input, the aircraft descended into a wooded area. The impact, which occurred during daylight, destroyed the aircraft. The two occupants sustained serious injuries and were airlifted to a hospital.
The investigation
The investigation examined the aircraft's mechanical condition, the weather environment, and the landing gear configuration. Investigators found that the aircraft's weight and center of gravity were within approved limits, and no pre-impact engine anomalies or structural defects were found. While the aircraft had been modified with skis, no evidence of airframe icing was detected.
Technical analysis focused on the ski attachment components. The left ski link had been previously modified with an unapproved weld repair, reducing its strength to approximately 74% of the original specification. The right ski link contained a pre-existing fatigue crack that had reduced its strength to roughly 31%. Additionally, the forward bungee cords used in the ski rigging were found to provide only about half of the required resistance to stretching.
Findings
- The aircraft may have encountered air turbulence of sufficient strength to cause the descent.
- The forward rigging bungees for both skis lacked the required stretching resistance, which may have permitted the skis to oscillate or vibrate.
- The right main ski attachment link failed upon impact due to a pre-existing fatigue crack.
- The left main ski attachment link failed upon impact at the site of an unapproved repair.