What happened
On September 2, 197 and, a pilot was conducting a dual-instruction flight at the Porrentruy aerodrome. This flight was intended to be the final session under the supervision of an instructor before the pilot would begin flying the Bücker Lerche HB-URB solo.
During the approach to the grass runway 07, the pilot attempted a shorter flight duration than the previous session. While on final approach, the aircraft entered a right slip. This maneuver resulted in the aircraft landing slightly offset to the right, touching down in a mown field adjacent to the landing area. After approximately 35 meters of ground roll, the right wheel struck a metallic airfield marker located at the front right corner of the aerodrome. The impact partially tore the landing gear from the aircraft, causing the plane to collapse and slide on its belly for about 40 meters before coming to a halt. The occupants of the aircraft were unharmed.
The investigation
The investigation established that the pilot held a valid private pilot license with limited experience on this specific type, while the instructor was a professional pilot. The aircraft's airworthiness and registration documents were found to be valid.
Investigators examined the airfield's marking system and found that the metallic posts used for the corner markers were incomplete. Specifically, the posts marking the front left corner had been removed a few days prior to allow for grass mowing and had not yet been replaced. The pilots reported that they did not see the remaining obstacle. The investigation also noted that the incomplete markings likely made it more difficult to identify the threshold of runway 07.
Findings
- The primary cause of the accident was imprecision in maintaining the approach centerline.
- The landing was performed without a certain identification of the runway threshold due to the incomplete airfield markings.