What happened
On April 26, 2009, a flight instructor and a student were conducting a local flight in a LET L-23 Super Blanik, registration N238SB. Prior to the flight, the instructor noted approaching adverse weather from the south and intended to demonstrate a crosswind landing before terminating glider operations for the day.
The glider released from its tow aircraft at approximately 1,000 feet above ground level and transitioned to a downwind pattern for runway 29. During the final approach, the instructor struggled to maintain alignment with the runway due to strong, gusting crosswinds and limited forward visibility caused by heavy rain. The instructor subsequently chose to land the aircraft in a grassy area located immediately north of the runway. During the landing, the glider struck a taxiway sign, resulting in substantial damage to the left wing. There were no injuries resulting from the accident.
The investigation
An analysis of weather radar and surface observations revealed that a thunderstorm moved into the airport area shortly after the flight departed. This thunderstorm brought lightning, heavy rain, and intense winds. The airport's automated surface observing system recorded a peak wind of 42 knots from 220 degrees magnetic. The maximum demonstrated crosswind component for the LET L-23 Super Blanik for safe aerotow launching, approach, and landing was 16 knots.