On August 17, 1993, at 1515 hours Pacific daylight time, a Pilatus B4-PC11AF glider, N205AS, collided with the runway surface at the Truckee Tahoe Airport, Truckee, California, after experiencing an inflight loss of control during an aero tow. The pilot was beginning a local visual flight rules personal flight. The glider, operated by Ames Soaring Club, Livermore, California, sustained substantial damage. The certificated private pilot, the sole occupant, received serious injuries. Visual meteorological conditions prevailed. The glider was being towed behind an airplane. Witnesses observed some erratic movement by the glider, followed by a tow line release by the glider. The pilot tried to make a 180 degree turn back to the runway. The glider then lost control and collided with the runway in a nose down, right wing low attitude. The glider was transported to J.J. Glider Repair, Placerville California, for examination. The tow release cable was inspected by the FAA Aviation Safety Inspector from the Reno Flight Standards District Office. The inspector reported he found that the cable was frayed and 50 percent of the strands were broken where the cable exits the instrument panel. He stated that the frayed and broken strands allowed the cable to bind in the housing which prevented complete locking of the tow hook.