What happened
On November 27, 196 and at approximately 15:30 CET, a Bücker 131, registration HB-URB, was involved in a ground collision at Pruntrut airfield. While taxiing from the parking area toward the runway, the pilot attempted to maneuver the aircraft through a gap between two parked planes. To assist with steering on the slippery surface, the pilot applied the wheel brake to initiate a leftward correction. However, the brake responded with excessive force, causing the aircraft to pivot approximately 45 degrees. Due to the wet and partially frozen ground conditions, the pilot was unable to stop the aircraft in time, resulting in the nose of the HB-URB striking the right wingtip of a parked Piper Cub, registration HB-ODG.
The investigation
The investigation established that the HB-URB was airworthy and possessed a valid registration at the time of the event. The pilot was a highly experienced private pilot with approximately 3,300 flight hours. The surface conditions at the airfield were noted as being wet and partially frozen, which contributed to reduced traction. The investigation examined the mechanical behavior of the braking system and the interaction between the steerable tailwheel and the ground surface during the taxiing maneuver.
Findings
- The primary cause of the collision was the unintended and heavy application of the wheel brake, which caused the aircraft to deviate sharply from its intended path.
- The braking system on this model of Bücker 131 is known to be prone to irregular and heavy engagement.
- The slippery, wet, and partially frozen ground reduced the effectiveness of the steerable tailwheel and prevented the pilot from regaining control or stopping the aircraft once the sudden pivot occurred.
- The collision resulted in damage to the propeller, canopy, and left wing of the HB-URB, as well as significant damage to the left wingtip of the HB-ODG.