What happened
On September 30, 2010, a Piper PA-18-150 Super Cub, registration D-ELVR, was involved in an accident at Aosta Airport during a dual-instruction flight. The aircraft was being used for a transition training mission, intended to qualify a pilot for tailwheel-type aircraft.
Immediately following landing, the aircraft began to drift slightly to the left of the runway centerline. In an attempt to correct this deviation, the pilot applied excessive right rudder. This maneuver triggered a significant yaw to the right, initiating a circular trajectory known as a ground loop.
The instructor attempted to intervene by taking control, applying left rudder, and increasing engine power to regain directional control. However, the aircraft continued its rightward rotation, causing the right main gear to lift and the left tire to skid. As the aircraft exited the paved runway onto the grass, the uneven terrain caused the aircraft to bounce. Upon landing, the left landing gear collapsed, resulting in the aircraft sliding on its left wing, fuselage, and propeller. The aircraft eventually came to a stop on the grass, facing the opposite direction of the initial landing.
Both occupants, a pilot and an instructor, escaped the aircraft without injury. The aircraft sustained substantial damage to the engine, propeller, left wing, fuselage, and main landing gear.
The investigation
The ANSV investigation examined the flight dynamics, the aircraft's mechanical characteristics, and the training program provided by the Aero Club Valle d'Aosta. Investigators analyzed the specific handling properties of tailwheel aircraft, noting that the narrow track of the Piper PA-18-150 Super Cub and its reinforced shock absorbers can exacerbate rolling moments during sudden directional changes.
The investigation also reviewed the training curriculum. It was noted that while the club provided a theoretical program for tailwheel transition, the specific instructional materials regarding the aircraft's peculiarities were largely left to the instructor's discretion. Furthermore, there was no documented evidence of the results of the theoretical examination required by the training manual.
Findings
- The primary cause of the accident was the pilot's loss of directional control during the deceleration phase following landing.
- The pilot's excessive use of right rudder to correct a leftward drift initiated the destabilizing ground loop.
- A lack of complete familiarity with the specific directional control characteristics of this aircraft, particularly on asphalt surfaces, contributed to the event.
- The physical characteristics of the aircraft, including its narrow wheel track and high-resistance shock absorbers, contributed to the severity of the ground loop and the subsequent tendency to overturn.