Schweizer SGS 2 32 N17970 accident near Morrisville, Vermont

Probable cause

The pilot's exceedance of the glider's critical angle of attack while maneuvering, which resulted in an aerodynamic stall/spin and impact with terrain. Contributing to the accident was the pilot's decision to operate the glider outside of its published weight limitations.

NTSB analysis

The commercial pilot of the glider departed on a 30-minute local sightseeing flight with two passengers seated in the rear seat. The pilot of the tow plane reported that during the tow to the glider's 4,500-ft mean sea level (msl) release altitude, he had to "weave around the clouds" and stated that the mountaintops were obscured by clouds. A witness who saw the glider release from tow stated that, following release, the glider flew away and "disappeared" into clouds. When the glider did not return as expected, the tow pilot initiated an aerial search; the glider was subsequently located in trees at an elevation of 3,673 ft msl about 7 miles west of the departure airport. The glider impacted terrain in a near-vertical, nose-down attitude; the forward cockpit was crushed, but the rear cockpit was largely intact. Examination of the glider revealed no evidence of preimpact mechanical malfunctions or anomalies that would have precluded normal operation.

The relatively low-energy, vertical impact attitude of the glider was consistent with an aerodynamic stall/spin. Weight and balance calculations revealed that the glider was likely about 50 lbs over its maximum gross weight at the time of the accident, but remained within its published center of gravity limits. The glider's increased gross weight would have resulted in an increased stall speed. Given the low clouds in the area, it is possible that the pilot inadvertently entered an area of reduced visibility and subsequently exceeded the glider's critical angle of attack, resulting in an aerodynamic stall and spin. It is also likely that the glider's increased gross weight and stall speed increased the glider's susceptibility to a stall/spin situation.

Although lap belts and shoulder harnesses were required for each occupant of the glider, the accident glider was equipped with only a single lap restraint for the front pilot's seat, and a single lap restraint for both rear seat occupants. The combined weight of the rear seat occupants likely resulted in the failure of the single lap belt's mounting hardware in overload.

Text from the NTSB. Open the NTSB docket for ERA18FA238 for the full record.