Incident
On 25 August 2017, at approximately 13:50 local time, a Maule M7-235 aircraft registered as HB-KDM was taxiing on Taxiway C at Grenchen Airport (LSZG). The pilot, holder of a commercial pilot license, was preparing to depart for Winterthur Airfield (LSPH) after maintenance work. While moving from the holding point toward Runway 24, the aircraft collided with a taxiway sign for Taxiway D. The right main landing gear was compressed and the propeller sustained heavy damage. The pilot was not injured.
Circumstances
The pilot, familiar with Taxiway C from previous flights, had consulted the aerodrome information (AD INFO) before taxiing. After receiving line-up clearance, he began moving slowly. He observed a portion of the holding line, a blue marker flag, and the paved Taxiway D to his left. To his right, he saw the Taxiway C sign. Believing Taxiway C continued straight, he rolled forward. The aircraft then struck the Taxiway D sign with the right main gear. The pilot immediately reduced power, but the tail wheel lifted and the propeller tips contacted the grass.
Investigation Findings
Taxiway C runs parallel to Taxiway D until the holding point, then turns right to join Runway 06-24 at a right angle. This turn is depicted on the LSZG AD INFO. The Taxiway D sign was positioned according to ICAO recommendations, with a distance of approximately 42 meters from the centerline of Taxiway D. The airport operator stated that Taxiway C is primarily used by local pilots and that no similar incidents had occurred in recent years. The taxiway, surfaced with plastic grid panels, is regularly mowed to improve visibility.
Analysis
The report noted that visibility of the lateral boundaries of a grass taxiway is generally poorer than that of a paved taxiway. Combined with the limited forward visibility from a tailwheel aircraft, this made it understandable that the pilot did not notice the right turn. Additionally, the clearly visible paved Taxiway D, which continues straight, created the impression that the pilot could proceed straight ahead. The report emphasized the importance of consulting the AD INFO during preflight and after any prolonged stop, such as waiting for clearance, to confirm the taxi route.