What happened
On May 9, 2015, a Cessna TU-206G Mk I Turbo Stationair 6, registration SP-ASI, was performing skydiving operations at Krępa Słupska airport (EPSK). After successfully completing two prior jumps, the pilot prepared for a third landing following a jump from 4,000 meters. To save time and avoid unnecessary taxiing, the pilot decided to land further past the runway threshold than in previous approaches.
Upon touchdown on the main gear, the pilot noticed an unusual sound and an abnormal nose-down attitude of the engine cowling. Although the pilot attempted to pull back on the control column to lift the aircraft, the nose gear failed to maintain its proper position. The aircraft briefly lifted off the ground by approximately 0.5 meters before landing again. Despite the pilot's efforts, the nose gear collapsed, causing the propeller to strike the ground and bringing the aircraft to a halt on its nose.
The investigation
The PKBWL investigation focused on the structural integrity of the nose gear and the sequence of events leading to the failure. Investigators examined the aircraft's maintenance records, which showed the plane had recently undergone periodic work. The investigation also looked into the aircraft's center of gravity and the ground conditions at the landing site.
Crucially, the investigators examined the nose gear assembly and discovered that the components connecting the upper and lower parts of the gear legs had been disconnected. The search for the missing pin, washers, and nuts yielded no results at the accident site, indicating the hardware had detached prior to the landing. The investigation also reviewed the aircraft's movement prior to the flight, specifically a towing maneuver involving a service vehicle.
Findings
- The primary cause of the accident was the separation of the upper and lower nose gear legs due to the failure and loss of the connecting pin. This was triggered by an accidental impact with a tow bar during a recent towing maneuver by a service vehicle.
- The landing involved a slight bounce on the main gear without the main wheels leaving the ground, which caused maximum compression and loading of the already compromised nose gear.
- The aircraft was operating with a center of gravity near the extreme forward limit, which contributed to the nose-heavy behavior.
- The specific area of the runway where the nose gear collapsed had lower ground load-bearing capacity (softer ground) compared to previous landings, which exacerbated the gear's deflection and subsequent failure.
- The propeller strike was a direct consequence of the nose gear's inability to support the aircraft's weight following the structural failure.