Cessna 337 accident near Ennis, Montana, July 30, 2020
On July 30, 2020 at about 3:38 pm local time, a 1971 Cessna 337, registered N337V, was substantially damaged in an accident during maneuvering near Ennis, Montana. It was a personal flight under general aviation rules (Part 91). 1 person was killed and 2 people were seriously injured. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The pilot-in-command’s failure to maintain sufficient airspeed while attempting an evasive maneuver from a boxed canyon, which resulted in an aerodynamic stall/spin and impact with mountainous terrain. Contributing to the accident was the pilot-in-command’s failure to monitor the environment before flying into mountainous terrain.
Source: NTSB aviation accident database, copy made October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- July 30, 2020 · about 3:38 pm local time
- Place
- Ennis, Montana · map
- Type
- Accident
- Injuries
- 1 person was killed and 2 people were seriously injured.
- Weather
- visual conditions (good weather)
- Aircraft
- Cessna 337 F, built 1971 · all 337s on the register
- Registration
- N337V · registry record · serial 33701369
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The left seat pilot-in-command (PIC) reported that, he passed the controls to the right seat student pilot once they were en route on the accident flight. The rear seat passenger’s postaccident statement indicated that the left seat pilot was at the controls for the duration of the flight; however, he may not have seen the exchange of the flight controls as he was seated behind both pilots at the time. As they were flying southbound on the cross-country flight over a valley about 3,000 ft above ground level, they agreed that they wanted to view a resort in the area. The student pilot then turned the airplane to the southeast towards higher mountainous terrain. After the airplane had entered a boxed canyon, and with a ridge in the airplane’s flightpath that it could not clear, the PIC took control of the airplane and attempted an evasive maneuver to reverse course to exit the canyon. However, during the maneuver, the PIC likely did not maintain sufficient airspeed, which resulted in an aerodynamic stall/spin and subsequent impact with remote mountainous terrain. The PIC reported no mechanical anomalies with the airplane that would have precluded normal operation. Toxicology results indicated that the student pilot had used cannabis, but likely had metabolized it such that no detectable psychoactive chemicals remained in his blood. The toxicology results and the student pilot’s limited role in the accident flight suggest that the effects of cannabis use were unlikely to have contributed to the accident.
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
- Collision with terrain or object (not controlled flight into terrain) during uncontrolled descent
- Loss of control in flight during maneuvering defining event
- Aerodynamic stall/spin during maneuvering
The NTSB's findings
- Aircraft › Aircraft oper/perf/capability › Performance/control parameters › Airspeed › Not attained/maintained
- Aircraft › Aircraft oper/perf/capability › Performance/control parameters › Angle of attack › Capability exceeded
- Personnel issues › Task performance › Use of equip/info › Aircraft control › Pilot
- Personnel issues › Psychological › Attention/monitoring › Monitoring environment › Pilot
- Environmental issues › Physical environment › Terrain › Mountainous/hilly terrain › Effect on operation
Pilot
- Certificate: flight instructor, commercial pilot
- Ratings: multi-engine land; single-engine land; instructor: airplane multi-engine; instructor: airplane single-engine; instructor: instrument airplane; instrument: airplane
- Flight time: 671 hours in all; 37 in this make and model; 200 in the last 90 days; 89 in the last 30 days; 653 as pilot in command; 325 on instruments
- Last flight review: July 22, 2020
- Medical certificate: Class 2 (with waivers/limitations)
- Seat: left
- Injury: serious injuries
Dual student
- Certificate: student
- Flight time: 200 hours in all
- Medical certificate: Class 3 (with waivers/limitations)
- Seat: rgt
- Injury: fatal
The aircraft
- Airframe total time: 2,028 hours
- Last inspection: annual inspection, April 1, 2020; 43 hours since
- Maximum gross weight: 4,630 lb
- Seats: 2
- Landing gear: retractable
- Engine 1: Continental TSIO-360-C (piston); 2,027 hours total
- Engine 2: Continental TSIO-360-C (piston); 2,031 hours total
The flight
- Departed from: HLN Helena MT at 3:00 pm
- Destination: JAC Jackson Hole WY
- Flight plan: none
Weather at the time
- Light: daylight
- Sky: clear
- Temperature: 66°F (19°C), dew point 46°F (8°C)
- Altimeter: 30.37 inHg
- Observation at 3:55 pm from EKS, 8 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 | |||
| Passengers | 1 | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
About this page
Everything above comes from the NTSB's public accident database: the narrative, probable cause and findings are the NTSB's own words, and the coded tables behind its report (pilot, aircraft, flight, weather, injuries, sequence of events) are written out in plain English. Pilots' ages, home towns and medical details are left out on purpose. The documents and photographs are the NTSB's docket, the folder of records gathered during the investigation, shown as the NTSB released them (the NTSB redacts some personal details first) and listed under the NTSB's own titles. This site's own text never names pilots, passengers or anyone else involved. A preliminary report describes what is known soon after the event and can change; the final report, with the probable cause, usually follows one to two years later and this page is refreshed when it does. Case number WPR20LA245.