What happened
On October 5, 2014, a Bücker Bü 133 C Jungmeister, registration HB-MIP, was performing a visual flight rules (VFR) flight at Lausanne-Blécherette Airport. After completing aerobatic maneuvers near the Villeneuve-Montreux region, the pilot returned to the airfield for landing on runway 18.
During the final approach, the pilot executed a leftward sideslip, which caused the aircraft's nose to point toward the right. The aircraft's airspeed was approximately 110 km/h. As the aircraft reached an altitude of only about 5 meters, it exhibited a high rate of descent, which increased the angle of attack. The aircraft struck the hard runway surface approximately 10 meters before the runway threshold with the right landing gear, and made a second contact roughly 75 meters further down the runway.
Upon impact, the right landing gear failed, causing the aircraft to veer left toward the edge of the runway. The aircraft subsequently overturned and came to rest on its back. The pilot was able to exit the wreckage without injury, and no fire occurred.
The investigation
SUST investigators utilized 3D reconstructions and webcam footage from the airfield to analyze the flight path. The investigation focused on the mechanical state of the landing gear and the aerodynamic parameters during the final moments of flight.
Technical examinations of the wreckage revealed significant damage to the right landing gear, including a deformed wheel rim and a broken grease bolt. The investigation found that the impact was so violent that it caused a "hydraulic lock" within the landing gear's shock absorber, transmitting extreme forces directly to the fuselage attachment points. Investigators also noted that the pilot had significant experience with Bücker aircraft but frequently flew the Bücker 131 Jungmann, which has a lower minimum approach speed than the 133 model, suggesting a potential confusion between the two types' performance characteristics.
Findings
- The primary cause of the accident was a hard landing resulting from a loss of control.
- The approach speed was too low, falling below the recommended limits for the aircraft type.
- The pilot completed the sideslip maneuver too late in the approach phase.
- The high rate of descent at low altitude led to an increased angle of attack, contributing to the instability.
- The failure of the landing gear was a direct result of the heavy impact on the hard runway surface.