Primary finding
Probable cause
The flight instructor’s failure to maintain adequate airspeed and his exceedance of the glider’s critical angle of attack, leading to an aerodynamic stall during the off-field landing.
Investigator assessment
Analysis narrative
The student pilot reported that he was flying the glider until about 10 minutes before the accident, when the flight instructor took over control and started looking for thermals to gain altitude. He said the flight instructor was mostly quiet until he said they were going to perform an off-field landing. The glider flew across a tree line about 150 ft above ground level and turned to land in a bean field. Neither the student nor the flight instructor had any recollection of the accident. Postaccident examination showed that the forward fuselage was crushed upward, and rearward and the outboard 6 ft of the left wing was separated. The separation point had signatures indicating upward bending of the tip. The damage to the glider was consistent with a nose-low, left-wing-low impact. Flight control continuity was verified from the cockpit to all control surfaces. No anomalies were detected. Based on the available information, the glider likely had insufficient altitude to return to the departure airstrip and the flight instructor attempted an off-field landing. The nose-low, left-wing-low impact suggested that the instructor likely exceeded the glider’s critical angle of attack and encountered an aerodynamic stall at low altitude during the landing attempt.
Source record
Factual narrative
On June 21, 2023, about 1530 eastern daylight time, a Let L-23 Super Blanik, N10BR, was substantially damaged when it was involved in an accident near Richmond Field Airport (69G), Gregory, Michigan. The flight instructor was seriously injured, and the student pilot received minor injuries. The glider was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The glider came to rest about 3,500 ft northwest of the north end of the runway at 69G. The student pilot reported that he was flying the glider until about 10 minutes before the accident when the flight instructor took over control and started looking for thermals to gain altitude. He said the flight instructor was mostly quiet until he said they were going to perform an off-field landing. The glider flew across a tree line about 150 ft above ground level and turned to land in a bean field. The student had no further recollection of the accident. The flight instructor also reported that he had no recollection of the flight. The glider sustained substantial damage to the fuselage and both wings. Postaccident examination showed that the forward fuselage was crushed upward, and rearward and the outboard 6 ft of the left wing was separated. The separation point had signatures indicating upward bending of the tip. The damage to the glider was consistent with a nose-low, left-wing -ow impact. Flight control continuity was verified from the cockpit to all control surfaces. No preimpact anomalies were detected.