What happened
On 14 June 2017, a Piper PA 16 Clipper, registration EI-AEL, was conducting a private flight from Letterkenny to Abbeyshrule Airfield. After a normal landing on runway 29, the pilot began taxiing toward the club apron. As the aircraft approached the first taxiway intersection on the right, it was struck by a strong gust of wind from the left.
This wind gust caused the aircraft to veer sharply. During the excursion, the left wingtip made contact with the runway, leading to the collapse of the left undercarriage leg. The aircraft then traveled through long grass and entered an adjacent field, which sat lower than the runway surface. The impact caused the aircraft to nose-down, resulting in substantial damage to the propeller, engine bearer, cowling, and wing structure. There were no injuries to the pilot or the passenger.
The investigation
The AAIU examined the aircraft's mechanical condition, the meteorological data, and the inherent handling characteristics of tail-wheel aircraft. The investigation noted that the aircraft had been upgraded with a more powerful Lycoming engine in 2014. Meteorological reports for the time of the accident indicated a moderate to fresh southerly flow with the potential for turbulence due to mountain waves.
Investigators also reviewed the physics of tail-wheel operations. Unlike tricycle-gear aircraft, tail-wheel configurations are naturally directionally unstable on the ground because the center of gravity is located behind the main wheels. This makes them highly susceptible to "weathervaning" into the wind and prone to "ground-loops" when subjected to crosswinds.
Findings
- The aircraft was operating in a crosswind environment at the time of the incident.
- A sudden gust from the left side caused an initial directional upset.
- The application of right rudder to counteract the initial gust likely caused the aircraft to swing in the opposite direction, a common phenomenon in tail-wheel aircraft where excessive correction leads to a rapid swerve.
- The resulting tight turn caused the left wingtip to strike the runway and the landing gear to fail.
- The terrain, specifically the drop into the adjacent field and the long grass, contributed to the aircraft nosed-over during the excursion.