SZD 55-1 N551DR accident near Channahon, Illinois

Probable cause

The glider pilot's failure to maintain adequate pitch control while being towed and his subsequent failure to maintain adequate airspeed control after releasing from the towline, which resulted in the glider exceeding its critical angle of attack and an aerodynamic stall/spin at a low altitude.

NTSB analysis

The single-seat glider, flown by a private pilot, was being towed into the air by a tow airplane. During the takeoff ground run, the glider's right wing dropped and contacted the ground after the wing-runner let go of the right wing. The wings leveled momentarily, and then the left wing contacted the ground while the glider was veering slightly to the left. The pilot again leveled the wings briefly before the glider pitched up about 30° to 40° and became airborne. The tow airplane was still on its takeoff ground run when the glider pitched-up. As the glider climbed in a 30° to 40° nose-up attitude, the tow airplane took off, and, shortly thereafter, the glider released from the towline. The glider's pitch attitude leveled out, and it briefly entered a right turn before it entered an aerodynamic stall/spin about 150 ft above the ground. The tow airplane subsequently landed uneventfully with the towline still attached to its tail clasp mechanism.

A postaccident examination of the glider's airframe revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. The complete span of towline and tow ring remained attached to the tow airplane and appeared undamaged, consistent with the glider pilot having intentionally released the towline. There was no evidence of a medical condition or substance use that contributed to the accident. The pilot likely was distracted by the wings contacting the ground during the takeoff run and allowed the glider to pitch-up into a rapid climb. After the pilot released the glider from the towline, he likely did not recognize that the glider was approaching stall speed and allowed the glider to exceed its critical angle of attack, which resulted in an aerodynamic stall at a low altitude.

Text from the NTSB. Open the NTSB docket for CEN16FA308 for the full record.