What happened
On April 6, 2017, a Piper PA-19 Army Cub, registration LN-ACG, was performing landing practice at Skien Airport Geiteryggen. The flight, operated by Grenland Flyklubb, began with a landing that resulted in several bounces. During this initial touchdown, the aircraft's direction control was lost, initiating a groundloop toward the right. The pilot applied full throttle in an attempt to recover directional control, which briefly lifted the aircraft back into the air.
During the subsequent attempt to stabilize the flight, the pilot executed a sharp turn to the left to return to the runway centerline. However, this maneuver was performed at a low airspeed and with excessive bank angle. Consequently, the aircraft lost lift and the left wing struck the runway. The impact caused the aircraft to skid toward the left, eventually coming to rest on its side with the right wing heavily damaged and the nose pointing toward the ground.
The investigation
The Norwegian Safety Investigation Authority (NSIA) examined the aircraft's mechanical condition and the pilot's flight history. The investigation confirmed that the tailwheel steering system was in good working order and that the aircraft had recently undergone maintenance with no technical defects noted.
Investigators also reviewed the pilot's experience, noting that while the pilot had recently completed a checkout on tailwheel aircraft, they had limited total time on this specific type. The investigation utilized eyewitness accounts from an instructor and a controller, as well as airport webcam footage, to reconstruct the sequence of the groundloop and the subsequent wing strike.
Findings
- The initial landing was unstable, characterized by high speed and an improper touchdown point, which led to multiple bounces.
- The pilot's attempt to recover from the groundloop by applying full throttle was complicated by the fact that the carburetor heat was left on, which reduced available engine power.
- The loss of directional control during the groundloop was exacerbated by the inherent physics of tailwheel aircraft, where the center of gravity is located behind the main gear.
- The final wing strike was caused by an aggressive left-hand turn performed at insufficient airspeed and with an excessive bank angle, leading to an aerodynamic stall.