Schempp-Hirth STANDARD CIRRUS N352D accident near Prescott Valley, Arizona

Probable cause

The pilot’s failure to maintain adequate airspeed and his exceedance of the glider’s critical angleofattack during the initial climb after a ground-tow launch, which resulted in an aerodynamic stall/spin.

NTSB analysis

A glider club member reported that the accident glider had been flown twice earlier in the day with no anomalies noted. He added that, before the accident flight, he advised the pilot that the glider had a "touchy elevator" and that things seemed to happen fast in a fiberglass glider. He observed the glider launch and noted that the glider appeared to be moving slowly with an increased angle-of-attack. When the glider reached about 800 ft above ground level, he observed it enter a left stall/spin before impact.

The ground-tow winch operator stated that the accident pilot made a standard radio call that he was ready to launch and that he requested a reference speed of 65 mph. The operator then added power and saw what appeared to be a normal takeoff and initial climbout, during which the pilot called his speed as "65," which indicated that the winch power setting was as desired for the tow. The operator added that he heard the pilot call what sounded like "more power," which is not a standard call; a normal call would be one that indicated power needs, such as needed airspeed above or below the desired reference speed. The operator began to add additional power, but almost immediately thereafter, he saw the glider's nose drop as the glider entered a spin. Several other witnesses at the airport reported similar accounts of the accident sequence.

Postaccident examination of the glider and the tow winch system revealed no anomalies that would have precluded normal operation. Therefore, based on the witness statements, it is likely that the pilot failed to maintain adequate airspeed during the initial climb and exceeded the glider's critical angle-of-attack, which resulted in an aerodynamic stall/spin and subsequent impact with terrain in a steep nose-down attitude.

Text from the NTSB. Open the NTSB docket for WPR15FA144 for the full record.