The pilot was carrying out an initial flight test of the microlight. The weather was fine, with calm wind and good visibility. Five minutes after takeoff from Perth Airport, the pilot flew an approach to Runway 09, a 609 m asphalt runway. After touchdown, the pilot was unable to prevent the microlight veering to the right and the right mainwheel ran onto the adjacent grass. He reported that the runway excursion caused a jolt through the airframe which resulted in the fracture of a ‘D’ shackle in the rear drag link tension cable assembly. This in turn caused the right landing gear to collapse (it was designed to fold for de-rigging, once the ‘D’ shackle was unfastened).