What happened
On the afternoon of March 19, 2016, a Bücker Fan Club aircraft, registration HB-UUD, was performing a seasonal inspection flight at Thun Airport (LSZW). The flight was being conducted as a training operation under visual flight rules (VFR) by a pilot accompanied by a flight instructor.
While taxiing toward the holding point for runway 32, the aircraft struck a taxiway marker. The pilot felt a physical jar, which he initially interpreted as having rolled over a concrete shaft. Following the impact, the crew continued with the planned flight, noting no changes in the aircraft's handling characteristics. However, upon landing, the crew discovered damage to the aircraft.
The investigation
The investigation focused on the positioning of the taxiway marking and the resulting impact. It was noted that earlier that same morning, participants at a club general assembly had been specifically alerted to the presence of the taxiway markers.
Upon inspecting the site, investigators measured the actual width of the taxiway, which was found to be approximately 10.50 meters. The investigation also reviewed the Federal Office of Civil Aviation (BAZL) guidelines regarding optical aids for unpaved runways and taxiways. These guidelines specify that for aircraft with a wingspan between 15 and 24 meters, the taxiway width is defined as 10.5 meters, and edge markers should ideally be placed at a maximum distance of 3 meters from the taxiway edge.
Findings
- The Bücker aircraft sustained minor damage, specifically the tearing of the fabric covering on the underside of the horizontal stabilizer.
- The collision was caused by the improper positioning of the taxiway marker relative to the taxiway width.
- There were no injuries to the crew or any third parties.