What happened
On 4 May 2011, a Rans S7 Courier, registration G-OJKM, was conducting a private flight near Glenforsa, Isle of Mull. As the pilot approached the airfield, the airfield manager warned of downdrafts and turbulent crosswinds at the start of Runway 07. Seeking to assess the conditions personally, the pilot proceeded with the approach, flying with the right wing down into the crosswind. While attempting to maintain this attitude to wait for a lull in the turbulence, the aircraft suddenly dropped, causing the right wheel to strike the runway.
Although the pilot maintained directional control and completed the landing, the aircraft suffered damage to the right landing gear, airframe, and propeller. During the sequence, the propeller struck the ground, resulting in the detachment of a portion of one blade. The pilot was initially unaware that the right mainwheel and axle assembly had actually broken away from the undercarriage leg during the impact.
The investigation
Investigators examined the detached wheel and axle assembly following the incident. Upon inspection of the fractured end of the attachment tube, a pre-existing crack was identified. The investigation established that while the landing was firm, the impact was not sufficiently heavy to have caused the tube to break in the absence of this prior structural weakness.