# NTSB WPR20LA245: Cessna 337, N337V, Ennis, MT, July 30, 2020 - Type: NTSB accident investigation - Classification: Accident · Fatal · Class 3 · Limited · Final report - Date: July 30, 2020, 09:38 local (15:38 UTC) - Place: Ennis, MT - Coordinates: 45.389999, -111.558052 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=45.3900&lon=-111.5581&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering: Loss of control in flight](https://openairdocs.org/ntsb-events/240) - Highest injury: Fatal - Injuries: 1 fatal, 2 serious - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: Aviation Safety Inspector, Textron Aviation - NTSB case key (mKey): 101709 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR20LA245 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/101709/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=101709 - Page: https://openairdocs.org/ntsb/WPR20LA245 ## Probable cause 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. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Performance/control parameters: airspeed](https://openairdocs.org/ntsb-findings/01062010): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Cessna 337F, 1 case](https://openairdocs.org/ntsb-findings/01062010/cases.md?model=2075725), [All aircraft, 1,681 cases](https://openairdocs.org/ntsb-findings/01062010/cases.md) - [Performance/control parameters: angle of attack](https://openairdocs.org/ntsb-findings/01062042): Aircraft › Aircraft oper/perf/capability · Capability exceeded (probable cause); cases with it: [Cessna 337F, 1 case](https://openairdocs.org/ntsb-findings/01062042/cases.md?model=2075725), [All aircraft, 990 cases](https://openairdocs.org/ntsb-findings/01062042/cases.md) - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Cessna 337F, 3 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=2075725), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md) - [Attention/monitoring: monitoring environment](https://openairdocs.org/ntsb-findings/02021545): Personnel issues › Psychological · Pilot (probable cause); cases with it: [Cessna 337F, 1 case](https://openairdocs.org/ntsb-findings/02021545/cases.md?model=2075725), [All aircraft, 809 cases](https://openairdocs.org/ntsb-findings/02021545/cases.md) - [Terrain: mountainous/hilly terrain](https://openairdocs.org/ntsb-findings/03021010): Environmental issues › Physical environment · Effect on operation; cases with it: [Cessna 337F, 1 case](https://openairdocs.org/ntsb-findings/03021010/cases.md?model=2075725), [All aircraft, 329 cases](https://openairdocs.org/ntsb-findings/03021010/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering: Loss of control in flight](https://openairdocs.org/ntsb-events/240) (defining event); cases with it: [Cessna 337F, 1 case](https://openairdocs.org/ntsb-events/240/sequence.md?model=2075725), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) - [Maneuvering: Aerodynamic stall/spin](https://openairdocs.org/ntsb-events/241); cases with it: [Cessna 337F, 1 case](https://openairdocs.org/ntsb-events/241/sequence.md?model=2075725), [All aircraft, 1,529 cases](https://openairdocs.org/ntsb-events/241/sequence.md) - [Uncontrolled descent: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Cessna 337F, 5 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=2075725), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis 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. ## Factual narrative On July 30, 2020, about 0938 mountain daylight time, a Cessna 337F, N337V, was substantially damaged when it was involved in an accident near Ennis, Montana. The right-front seat student pilot was fatally injured, and the left-front seat commercial pilot-in-command (PIC) and rear-seat passenger were seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations (CFR) Part 91 personal cross-country flight. According to the PIC, he planned a route of flight from Helena, Montana, to Jackson Hole, Wyoming. The PIC further reported that the right seat student pilot was flying the airplane about 3,000 ft above ground level. When they decided to fly over a ski resort at Big Bear, Montana, the flying right-seat student pilot turned the airplane to the southeast in the direction of mountainous terrain. The airplane subsequently entered a boxed canyon, and with a ridge now in the airplane’s flightpath that could not be cleared, the PIC took control of the airplane and attempted an evasive maneuver to exit the boxed canyon. However, the evasive maneuver, which was unsuccessful, resulted in a stall/spin and subsequent impact with remote mountainous terrain. The PIC opined that the accident should have been easily avoided by having more than sufficient altitude before entering mountainous terrain. Additionally, the PIC reported no mechanical anomalies with the airplane or engine prior to the accident that would have precluded normal operation. The rear seat passenger reported that they departed Helena at 0845 and that the “entirety of the flight was flown by the front left-seat pilot.” He further stated that the PIC was climbing in an attempt to clear a ridge when the airplane stalled and impacted terrain in a nose-down attitude. The Montana State Medical Examiner, Missoula, Montana, performed an autopsy on the student pilot and noted the cause of death as multiple blunt force injuries. Right Seat Student Pilot Medical Review Toxicology testing performed at the Federal Aviation Administration Forensic Sciences Laboratory identified 11-hydroxy-delta-9-THC [tetrahydrocannabinol] in the urine and its metabolite, carboxy-delta-9-THC was detected in the blood and urine. Levels of 11-hydroxy-delta-9-THC were 26.4 ng/mL and levels of carboxy-delta-9-THC were 3.1 ng/mL and 1225 ng/mL, respectively. Delta-9-THC (the primary psychoactive component in cannabis) was not detected. The cannabis plant contains chemicals called cannabinoids. Significant performance impairments are usually observed for at least 1-2 hours following cannabis use, and residual effects have been reported up to 24 hours. However, it is difficult to relate blood levels of delta-9-THC to effects, and there is no mechanism for relating levels in any other specimens to psychoactive effects. ## Aircraft - Registration: [N337V](https://openairdocs.org/aircraft/N337V), registered now, S/N 33701369, built 1971 (OpenAirDocs) - Reported make and model: Cessna 337 (F) - Registry model: [Cessna 337F](https://openairdocs.org/model/cessna-337f) (registry code 2075725) (OpenAirDocs) - Registry engine: [Continental IO-360 series](https://openairdocs.org/engine/continental-io-360-series) (registry code 17025, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 33701369 - Year built: 1971 - Airframe hours: 2028 - Engines: Continental TSIO-360-C 210 horsepower reciprocating; Continental TSIO-360-C 210 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, April 1, 2020, 43 hours before - Departed: HLN, Helena, MT - Destination: JAC, Jackson Hole, WY - Equipment: Stall warning system ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 27; injuries: serious; flight instructor, commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review July 22, 2020; seat: left; restraint: lap only; flight hours: 671 total, 37 in this make and model, 653 as pilot in command, 200 in the last 90 days, 89 in the last 30 days, 1 in the last 24 hours - Student pilot; injuries: fatal; student; medical: class 3, with waivers/limitations; seat: right; toxicology performed; flight hours: 200 total ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Lowest ceiling: none - Temperature: 66 °F, dew point 46 °F - Altimeter: 30.37 inHg - Observed at: EKS, 8 nm away ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20200730006719A](https://openairdocs.org/incident/20200730006719A), Jul 30, 2020: Cessna 337F, Destroyed, 1 fatal. The PIC planned the route of flight the day prior to departure. He stated that they stayed relatively low, 3000 AGL, so that they could take in the sights… ## Docket (8 files) The files NTSB released with the investigation on June 9, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=101709. 6.5 MB in all. - Medical factual report (item 1, PDF, 3 pages, 226 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13448410&FileExtension=pdf&FileName=WPR20LA245_MedicalFactualReport-Rel.pdf - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 2, PDF, 9 pages, 3.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13934883&FileExtension=pdf&FileName=WPR20LA245%20Pilot%20Report_Redacted-Rel.pdf - Maps or charts of accident area (item 3, PDF, 6 pages, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12662858&FileExtension=pdf&FileName=Accident%20site%20maps-Rel.pdf - Record of conversation (item 4, PDF, 2 pages, 27 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12663506&FileExtension=pdf&FileName=Record%20of%20Conversation-Rel.pdf - Statement of party representatives to NTSB investigation (item 5, PDF, 1 page, 136 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12662016&FileExtension=pdf&FileName=NTSB%20party%20form_Redacted-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 6, PDF, 1 page, 194 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12663294&FileExtension=pdf&FileName=NTSB%20Release%20of%20Wreckage%20Form_Redacted-Rel.pdf - FAA toxicology report (student pilot) (item 7, PDF, 1 page, 384 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13857584&FileExtension=pdf&FileName=faa%20tox%201_Redacted-Rel.pdf - Photo array of accident site (item 8, PDF, 5 pages, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12662656&FileExtension=pdf&FileName=Photo%20array%20of%20accident%20site-Rel.pdf From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.