What happened
At approximately 1505 Atlantic daylight time, a Schemlipp-Hirth KG Cirrus glider, registration C-GUIL, was prepared for a winch-assisted takeoff on the grass adjacent to Runway 20 at Stanley Airport. The wind was blowing from the west-northwest at roughly eight knots, creating a slight quartering tailwind. Following the club's operational procedures, the winch operator initiated a "full-out" launch to account for these wind conditions.
The aircraft lifted off and maintained level flight for less than five seconds before experiencing an abrupt, steep pitch upward to an altitude of approximately 200 feet. During this climb, the glider rolled into an inverted position to the right. In an attempt to prevent a perceived stall, the winch operator increased power, but the tow cable released automatically as the aircraft overflew the cable. The glider subsequently descended and struck the ground while inverted. The pilot sustained one fatality, and the aircraft was destroyed.
The investigation
The investigation focused on the mechanical integrity of the aircraft and the environmental conditions at the time of the launch. The pilot, an experienced instructor with significant flight time, was found to have been operating under variable wind conditions. Because the airfield's windsock was too distant to be clearly seen from the takeoff position, the pilot had been estimating wind speed and direction using a signal flag and plastic tape.
Investigators examined the aircraft's seat assembly, a cloth hammock design. They discovered that the forward attachment bolts, which secure the seat to the floor, had failed. Specifically, the right and center bolts had pulled out of their anchor nuts. While the threads on the right anchor nut appeared shiny—suggesting they had torn out—the investigation revealed that these threads had been previously damaged by cross-threading, which likely prevented the assembly from achieving full clamping strength.
Findings
- The seat failure was caused by the combined effect of previously cross-threaded anchor nuts, the likelihood that the bolts were not fully engaged, and the high acceleration forces experienced during the launch.
- When the seat bolts pulled free, the pilot was thrown downward and rearward, away from the flight controls. This sudden movement caused the control stick to move rearward, triggering the extreme pitch-up and subsequent loss of control.
- The pilot was unable to reach the manual cable release due to the sudden displacement caused by the seat failure.
- The method used to estimate wind conditions—observing a signal flag or plastic tape—was insufficient for providing the accuracy required during light and variable winds.
- In a normally reclined position, the tow hook release handle in this specific aircraft model is difficult for shorter pilots to reach.