NTSB Factual Report

On June 9, 2018, about 1115 mountain daylight time, a retractable tandem-geared LET L-23 (Super Blaník) glider, N317BA, collided with remote mountainous terrain while en route about 7 miles northwest of Moose, Wyoming after departing from the Driggs-Reed Memorial Airport (DIJ), Driggs, Idaho. The commercial pilot and the passenger sustained fatal injuries. The glider was destroyed. The glider was registered to Teton AvJet, LLC, Driggs, and was operated by Teton Aviation Center, Driggs, under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91 as a visual flight rules sightseeing tour flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed. The flight originated from DIJ at 0950 and was released from the tow airplane at 1037.

Teton Aviation Center based at DIJ, conducts Title 14 CFR Part 91 sightseeing tour flights to the public in both airplanes and gliders, staying within a 25-statue mile radius of DIJ. DIJ is located at an elevation of 6,231 feet mean sea level (MSL). The purpose of the sightseeing tour flight was to facilitate viewing of the Teton Range mountains for the passenger. A friend of the passenger purchased the sightseeing tour flight as a gift for the passenger.

The operator reported that a sightseeing tour flight typically is about 1 hour in duration, with the first thirty minutes for the tow operation, with the remaining thirty minutes gliding back to DIJ. The glider typical spends about 15 minutes at the altitude it was released at before it begins the descent. The sightseeing tour flight predominately flies over the Caribou-Targhee National Forest, encompassing both Idaho and Wyoming.

The tow pilot, employed by Teton Aviation Center who flew a tailwheel-equipped Aviat A-1 airplane, reported he and the glider pilot discussed the planned route of flight prior to takeoff. The planned route after departure from DIJ was to head south toward Darby Canyon, then proceed north along the ridges near the Grand Targhee Resort, Alta, Wyoming, and then along the ridges of Teton Canyon toward the Grand Teton National Park. The tow pilot further reported that he and the glider pilot briefed safe altitudes for the route of flight, and then completed the preflight duties for the glider together.

After departing from DIJ, the tow airplane and glider reached 10,000 feet MSL. The two aircraft proceeded south and climbed to 11,000 feet MSL and turned west toward Darby Canyon. Both aircraft arrived at the foothills of Darby Canyon at 11,500 feet MSL and the tow pilot reported "there wasn't much lift." Both aircraft then flew east toward the boundary of Grand Teton National Park. Prior to reaching the boundary, both aircraft flew north, paralleling the Teton Range and were "slowly climbing." Upon reaching a point 3 miles west of the South Teton peak, at an altitude of 13,800 feet MSL, the glider pilot released the glider at 1037. The tow pilot reported that he obtained visual confirmation of the release in his rear-view mirror and departed back to DIJ without further incident, landing at about 1045.

During the tow operation, the tow pilot reported that he maintained radio communication with the glider pilot throughout the entire flight and they worked together to find lift to gain sufficient altitude for release. The glider pilot did not report any mechanical malfunctions or failures with the glider during the tow operation.

The front desk manager for Teton Aviation Center was expecting the glider to return to DIJ between 1115 to 1130. Starting at 1130, the front desk manager attempted to make multiple radio calls on a universal communications frequency (commonly referred to as "UNICOM") to the glider with no success. At 1220, the glider was reported overdue to the Federal Aviation Administration (FAA). At 1240, an Alert Notice (commonly referred to as an "ALNOT") was issued by the FAA.

A National Park Service (NPS) search and rescue team consisting of NPS Rangers from Jenny Lake Rescue, working in conjunction with Teton County (Wyoming) Search and Rescue, utilized data acquired from a cellular phone onboard the glider to determine the last known coordinates. The owner of Teton Aviation departed from DIJ at about 1435 in a private helicopter and flew to the area of the last known coordinates. The owner was able to obtain visual confirmation of the wreckage at about 1450. No emergency locator transmitter was onboard the glider, nor was one required to be.

The wreckage was in steep mountainous terrain, about 11,000 feet MSL between the Middle Teton peak (12,809 feet MSL) and the South Teton peak (12,519 feet MSL), near the frozen Icefloe Lake, in the Teton Range, located in the Grand Teton National Park. The accident site was classified as technical mountaineering terrain. The NPS search and rescue team was inserted to the accident site via a NPS-contracted helicopter for recovery and documentation purposes at about 1530. Photographs provided by the NPS showed both wings and an impact crater located on a west facing snow and ice-covered saddle. The photographs further showed the fuselage, empennage, and miscellaneous debris located near the base of the saddle, by Icefloe Lake. The saddle originates at the South Teton Peak and extends to the northeast culminating at the Middle Teton peak.

The wreckage was extracted via external load with a NPS-contracted helicopter to a secure location in the Grand Teton National Park for a wreckage layout and examination. On June 13, the NTSB investigator-in-charge (IIC), along with an aviation safety inspector (ASI) from the FAA Salt Lake City Flight Standards District Office traveled to the operator in Driggs to tour the company facilities and conduct interviews with company personnel. On June 14, the NTSB IIC, the FAA ASI, and two representatives from Teton Aviation Center traveled to the Grand Teton National Park to conduct a wreckage layout and examination. During the examination, no preimpact mechanical malfunctions or failures with the glider were noted. All major structural components of the glider were accounted for. The glider was found to be assembled correctly for flight operations. An examination of the maintenance records revealed no evidence of uncorrected mechanical discrepancies with the glider.

The two-seat capacity non-motorized glider, serial number 978406, was manufactured in 1997 in the Czech Republic.