Let L 23 SUPER BLANIK accident near Moose, Wyoming, June 9, 2018
On June 9, 2018 at about 5:15 pm local time, a 1997 Let L 23 SUPER BLANIK (glider), registered N317BA, was destroyed in an accident during maneuvering (low-alt flying) near Moose, Wyoming. It was a business flight under general aviation rules (Part 91). 2 people were killed. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The pilot's encounter with atmospheric conditions that resulted in a loss of lift and a subsequent loss of control near terrain that precluded recovery. Contributing to the accident was the pilot's failure to follow the operator's published tour flight procedures regarding flight over the national park and minimum altitudes over and distance from terrain.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- June 9, 2018 · about 5:15 pm local time
- Place
- Moose, Wyoming · map
- Type
- Accident
- Injuries
- 2 people were killed.
- Weather
- visual conditions (good weather)
- Aircraft
- Let L 23 SUPER BLANIK NO SERIES, built 1997 · all L 23 SUPER BLANIKs on the register
- Registration
- N317BA · no longer on the register · serial 978406
- Damage
- Destroyed
- Flight
- Business flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot and one passenger departed on a sightseeing tour flight in the glider. After being released from the tow airplane about 13,800 ft mean sea level (msl), the glider pilot proceeded to fly over a national park near mountainous terrain. A video recording of the flight from the passenger's cell phone recorded the pilot state, "this is not good" twice and "I'm in trouble" as the glider neared the terrain. The glider impacted terrain between two mountain peaks (elevations about 12,800 ft msl and 12,500 ft msl) at an elevation about 11,000 ft msl. A review of weather data found upper level winds were from the south-southwest, which likely provided no significant orographic lift in the area of the accident site on the western side of the mountains and likely provided some downdraft activity due to the range immediately south. It is likely that the pilot maneuvered the glider close to terrain in an attempt to attain lift, but encountered atmospheric conditions that resulted in a loss of lift, a loss of control, and a subsequent impact with terrain. According to the operator's tour flight procedures, aircraft were not permitted to fly within the boundaries of the national park and were to maintain a minimum altitude of 2,000 ft above terrain. It is likely that compliance with the company's published procedures would have ensured terrain separation during the flight even in the event of an encounter with adverse wind conditions.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
What happened, in order
- Miscellaneous/other during prior to flight
- Other weather encounter during maneuvering (low-alt flying)
- Loss of control in flight during maneuvering (low-alt flying) defining event
- Attempted remediation/recovery during maneuvering (low-alt flying)
- Collision with terrain or object (not controlled flight into terrain) during maneuvering (low-alt flying)
The NTSB's findings
- cause Personnel issues › Action/decision › Info processing/decision › Decision making/judgment › Pilot
- cause Aircraft › Aircraft oper/perf/capability › Performance/control parameters › Altitude › Not attained/maintained
- cause Aircraft › Aircraft oper/perf/capability › Performance/control parameters › Heading/course › Not attained/maintained
- cause Environmental issues › Conditions/weather/phenomena › Wind › (general) › Effect on operation
- factor Personnel issues › Task performance › Use of equip/info › Use of policy/procedure › Pilot
- factor Personnel issues › Task performance › Planning/preparation › Flight planning/navigation › Pilot
Pilot
- Certificate: flight instructor, commercial pilot
- Ratings: single-engine land; instructor: glider; rotorcraft: glider
- Flight time: 1,200 hours in all
- Last flight review: April 30, 2017
- Medical certificate: Class 2 (with waivers/limitations)
- Seat: rear
- Injury: fatal
The aircraft
- Airframe total time: 3,782.9 hours
- Last inspection: annual inspection, February 23, 2018
- Maximum gross weight: 1,124 lb
- Seats: 2
- Landing gear: retractable
- Operator: Teton Avjet, LLC
The flight
- Departed from: DIJ Driggs ID at 3:50 pm
- Destination: DIJ Driggs ID
- Flight plan: none
Weather at the time
- Light: daylight
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 64°F (18°C), dew point 45°F (7°C)
- Altimeter: 30.04 inHg
- Observation at 4:56 pm from KJAC, 8 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 | |||
| Passengers | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
30 documents, released by the NTSB on July 20, 2020. View them here, or download them; the NTSB redacts some personal details before release, and this site shows the NTSB's own titles rather than its file names.
The same docket at the NTSB · documents without a copy here are fetched from the NTSB when you open them.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.