What happened
On September 11, 2017, a Piper PA-18 (Super Cub), registration HB-PLQ, was engaged in a training flight at Birrfeld Airport (LSZF). The flight was intended to train a pilot, who was also a Class Rating Instructor (CRI(A)), on the tendency of tailwheel aircraft to swing or veer during ground maneuvers.
The training session consisted of a series of touch-and-go landings designed to systematically build experience. The initial phases involved standard landings on a grass runway, followed by maneuvers involving slalom turns on the main gear to feel the aircraft's swerve tendency. Later stages of the flight involved the instructor intentionally disrupting the aircraft's longitudinal alignment on the runway, requiring the pilot to correct the heading. The final phase of the training moved to the paved runway to compare the aircraft's behavior on hard surfaces versus grass.
During the 15th landing on the paved runway, the pilot was unable to maintain the aircraft's alignment with the runway centerline. The aircraft veered off taxiway Echo, crossed the northern taxiway, and struck the airport's northern perimeter fence.
The investigation
SUST examined the flight sequence and the specific training objectives. The investigation focused on the maneuvers performed during the touch-and-go sequence, specifically the transition from grass to paved surfaces and the intentional directional disturbances introduced by the instructor. Investigators also reviewed local meteorological data recorded at Birrfeld during the time of the incident.
Findings
- The aircraft sustained heavy damage to its left wing and left landing gear.
- The airport's perimeter fence was also damaged during the collision.
- There were no injuries to the two occupants of the aircraft.
- Wind measurements at the time of the incident indicated ground winds between 8 and 15 km/h, with gusts reaching up to 22 km/h and shifting directions between 230 and 270 degrees. Fluctuations in wind strength may have contributed to the loss of directional control during the final landing.
- The investigation raised questions regarding the effectiveness and safety of using intentional directional disturbances as a method for teaching tailwheel swerve tendencies.