Primary finding
Probable cause
The certified flight instructor's inadequate compensation for the crosswind and delayed remedial action during landing, which resulted in a ground loop.
Investigator assessment
Analysis narrative
The certified flight instructor (CFI) stated that he was providing instruction to a student pilot in a glider. After a routine local instructional flight, they returned to the departure airport for landing. The student was flying the glider and the CFI was providing verbal instructions to him as they completed a standard traffic pattern to the dirt landing area. He reported that there was a crosswind at 12 knots, gusting to about 20 knots. The glider encountered a high sink rate and the CFI took authority over the controls. The glider ground looped, resulting in substantial damage to the tail. The CFI reported no preimpact mechanical malfunctions or failures with the glider that would have precluded normal operation.
Source record
Factual narrative
The certified flight instructor (CFI) was providing instruction to a student pilot in a glider. After a routine local instructional flight, they returned to the departure airport for landing. They flew a standard traffic pattern to runway 08R (dirt glider landing area) and the wind was from approximately 100 degrees at 12 knots, gusting to about 20 knots. The student was flying the glider, and the CFI was providing verbal instructions to him. The glider encountered a high sink rate, the CFI took the controls, and the glider ground looped. Post accident examination showed that the tail boom was fractured.