What happened
On June 4, 2006, during a regional gliding competition at Hausen am Albis, a Maule M-7-235 tug aircraft, registered HB-KDM, was performing a takeoff tow of an ASW 27 glider, registered HB-3269. During the preparation for departure, the glider pilot had retracted the airbrake flaps, which inadvertently deactivated the aircraft's wheel brakes.
As the tug aircraft began to taxi forward to extend the tow rope, the tension from the rope caused the unbraked glider to roll forward, resulting in the glider's wheel running over the slack rope. The tug pilot briefly stopped the aircraft to wait for another glider to clear the runway, but then proceeded with the takeoff after receiving a radio signal from the start coordinator stating the rope was taut.
Noticing the rope had been rolled over, two ground assistants moved to the front of the glider's wings with the intention of pushing the aircraft back to re-tension the rope. The start coordinator, positioned with an obstructed view, attempted to issue a "Stop" command via radio, but the command was not heard by either pilot. As the Maule M-7-235 accelerated, the wings of the ASW 27 struck the two assistants, causing one serious injury.