What happened
On June 7, 1968, a Wassmer WA 40, registration HB-DCA, was conducting a local pleasure flight from Grenchen Airport with a pilot and three passengers. During the landing phase, the pilot encountered a crosswind from the Jura mountains and elected to maintain a higher approach speed of 80 mph to counteract the wind.
As the aircraft crossed the runway threshold, it remained approximately 2 meters airborne, resulting in a touchdown roughly 320 meters down the 580-meter grass runway. This left only about 260 meters of runway remaining for the rollout. To stop the aircraft within this limited distance, the pilot applied heavy braking. While traversing uneven sections of the grass strip, the aircraft experienced jolts that caused the nose gear to collapse. The aircraft subsequently pitched forward onto its nose, coming to a halt approximately 60 meters before the end of the runway. There were no injuries among the four occupants.
The investigation
The investigation examined the aircraft's technical condition, the pilot's experience, and the runway environment. The Wassmer WA 40 was found to be in an airworthy condition, and no evidence of pre-existing material fatigue or defects in the nose gear strut was discovered. The investigation also reviewed the manufacturer's recommended landing procedures, which suggest lower approach speeds and a shorter landing distance than what was experienced during this event. The physical condition of the grass runway, specifically the presence of undulations and waves, was also evaluated.
Findings
- The pilot performed a landing with an excess of speed due to the decision to counteract crosswind conditions.
- The touchdown occurred too far down the runway, significantly reducing the available rollout distance.
- The necessity of heavy braking on a short remaining distance placed extreme stress on the landing gear.
- The uneven surface of the grass runway contributed to additional mechanical shocks during the rollout.
- The primary cause was the structural overstress of the nose gear strut, leading to its failure.