Accident Overview
On June 9, 2018, at about 1115 mountain daylight time, a LET L-23 Super Blaník glider, registration N317BA, was destroyed in an accident near Moose, Wyoming. The pilot and passenger sustained fatal injuries. The glider was operated by Teton Aviation Center (TAC) under Title 14 Code of Federal Regulations Part 91 as a sightseeing flight.
Flight History
The glider departed Driggs-Reed Memorial Airport (DIJ) in Driggs, Idaho, under tow. The tow pilot and glider pilot discussed the planned route and briefed safe altitudes before departure. The flight proceeded south and climbed to 11,000 ft mean sea level (msl), then turned west toward Darby Canyon. The aircraft reached the foothills of Darby Canyon at 11,500 ft msl. The tow pilot reported minimal lift. They flew east toward Grand Teton National Park boundary, gaining some lift from ridgelines, then north paralleling the Teton Range, slowly climbing. About 3 miles west of South Teton peak, at 13,800 ft msl, the glider released from tow at 1037. The tow pilot confirmed the release and returned to DIJ, landing about 1045. Radio communication was maintained throughout the tow; no anomalies were reported.
Video Evidence
A video recorded by the passenger on a cell phone showed the glider near the Teton Range, flying over Grand Teton National Park. The footage indicated the glider was nearly level with the top of Middle Teton. The pilot was heard stating "this is not good." The glider banked right parallel to the ridgeline. The last visible airspeed indication was about 42 knots. The ridgeline appeared above the glider. The glider then entered a steep descent, with the pilot again stating "this is not good." The glider briefly recovered but then entered another steep descent, with the pilot stating "I'm in trouble." The glider returned to a neutral pitch but continued descending. As it descended, it turned right toward the ridgeline. In the final frame, the yaw string was hanging about 45° to the right.
Wreckage and Examination
When the flight did not return as expected, TAC personnel attempted radio contact. At 1220, the glider was reported overdue to the FAA. A search using cell phone data located the wreckage between Middle Teton peak (12,809 ft msl) and South Teton peak (12,519 ft msl) near frozen Icefloe Lake, at about 11,000 ft msl. The wreckage was found in steep mountainous terrain. Examination revealed that all major structural components were accounted for, flight control continuity was established, and no preimpact mechanical malfunctions or failures were noted.
Personnel Information
The pilot had previously held a second-class medical certificate that expired in 2016, but glider operations under Part 91 do not require a medical certificate. Hired by TAC in March 2001, she had logged 650 hours of glider instruction and 559 sightseeing tour flights. Her most recent recurrency flight was on April 27, 2018. TAC personnel described her as safety-conscious and thorough. Autopsy attributed the cause of death to multiple blunt force injuries, with no significant natural disease. Toxicology tests were negative for ethanol and drugs.
Weather Conditions
The National Weather Service forecast indicated southwesterly winds increasing with height, with AIRMET Tango current for moderate turbulence below 16,000 ft in the area. Sounding data suggested the glider likely encountered southerly winds of 25 to 27 knots at altitude, with potential light turbulence. The wind direction would not generate significant orographic lift on the western slopes of the Teton Range. It could not be determined what weather information the pilot reviewed before departure; no record of a preflight briefing was found.
Additional Information
The Teton Aviation Center standard operating procedures specified that scenic flights to view the Teton Range were not authorized to overfly Grand Teton National Park, were to remain at least half a mile outside park boundaries, and were to maintain a minimum altitude of 2,000 ft above ground level (AGL) over mountainous terrain. The day before the accident, the pilot had conducted a similar sightseeing flight with another passenger, who described her as a very competent pilot with smooth flying skills. That flight included passes on the backside of the Teton range.