What happened
On August 3, 1965, a Piper PA-18-150 Super-Cub, registration HB-OVZ, was performing glider towing operations at Grenchen Airport. Following the release of a sailplane during the third tow of the series, the pilot initiated a landing approach at a speed of approximately 70 to 80 mph. To mitigate the impact of moderate, gusty winds from the west-northwest, the pilot set the flaps to position 1.
Upon touchdown, the aircraft encountered a large puddle on the runway, which caused significant deceleration. As the aircraft continued to roll for approximately 20 meters, the tail lifted, causing the propeller to strike the ground. The pilot promptly turned off the ignition to prevent a potential nose-over. The aircraft eventually came to a complete stop without further incident.
The investigation
The investigation examined the landing conditions and the pilot's decision-making regarding the runway selection. It was noted that the pilot landed on the glider runway (South runway 25), despite an agreement with a flight instructor to avoid certain landing zones. The pilot stated he was unaware of this specific agreement and noted that the motor glider runway was closed by two crosses, while the North runway was avoided due to active motor aircraft traffic.
Investigators also reviewed the configuration of the aircraft during the landing roll. While the pilot had moved the flap lever during the flare to prepare for retraction, the investigation concluded that maintaining the flaps in position 1 would not have significantly increased the risk of the accident.
Findings
- The primary cause of the accident was the aircraft striking a large puddle on the runway surface.
- The water caused intense braking forces that led to the sudden lifting of the aircraft's tail.
- The resulting pitch change caused the propeller to impact the ground.
- There were no injuries to the pilot, and damage to the HB-OVZ was limited to a bent propeller and dented skin panels.