Bell BHT407 accident near Big Fork, Montana, April 25, 2013
On April 25, 2013 at about 4:16 pm local time, a 1998 Bell BHT407 (helicopter), registered N937GR, was substantially damaged in an accident during maneuvering near Big Fork, Montana (Kalispell City airport). It was a public-use flight (local) under public-use (government) rules. No one was hurt; 3 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The pilot’s failure to maintain helicopter control while maneuvering over mountainous terrain in strong up/downdrafts and possible mountain wave activity, which resulted in a loss of tail rotor effectiveness.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- April 25, 2013 · about 4:16 pm local time
- Place
- Big Fork, Montana · Kalispell City · map
- Type
- Accident
- Injuries
- No one was hurt; 3 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Bell BHT407, built 1998
- Registration
- N937GR · no longer on the register · serial 53282
- Damage
- Substantial damage
- Flight
- Public-use flight (local) · public-use (government) rules
The NTSB's narrative final · quoted from the NTSB record
The pilot reported that, while conducting a reconnaissance orbit over mountainous terrain, he crossed over a ridgeline and then lost directional control of the helicopter. He applied full left pedal and lowered the nose and collective in an attempt to regain control. The helicopter subsequently impacted the uneven snow-covered terrain and rolled onto its right side. Postaccident examination of the airframe and engine revealed no evidence of mechanical malfunction or failures that would have precluded normal operation. A weather study for the area around the accident site revealed that the temperature profile and windy environment supported strong up/downdrafts with the potential for mountain wave formation near the altitude at which the flight was maneuvering. It is likely that the pilot was unable to maintain control of the helicopter as a result of a loss of tail rotor effectiveness while operating in the high-altitude environment and in an area with strong up/downdrafts and possible mountain wave activity.
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
- Loss of tail rotor effectiveness during maneuvering defining event
- Loss of tail rotor effectiveness during emergency descent
- Off-field or emergency landing during landing
- Roll over during landing (flare/touchdown)
The NTSB's findings
- cause Aircraft › Aircraft oper/perf/capability › Performance/control parameters › Yaw control › Capability exceeded
- cause Personnel issues › Task performance › Use of equip/info › Aircraft control › Pilot
- Environmental issues › Physical environment › Terrain › Mountainous/hilly terrain › Contributed to outcome
- cause Environmental issues › Conditions/weather/phenomena › Turbulence › Terrain induced turbulence › Effect on operation
- cause Environmental issues › Conditions/weather/phenomena › Wind › Downdraft › Effect on operation
- cause Environmental issues › Conditions/weather/phenomena › Wind › Updraft › Effect on operation
Pilot
- Certificate: airline transport pilot, flight instructor
- Ratings: multi-engine land; single-engine land; single-engine sea; instructor: helicopter; instructor: instrument airplane; instrument: airplane; instrument: helicopter; rotorcraft: helicopter
- Flight time: 5,000 hours in all; 141 in this make and model; 61 in the last 90 days; 12 in the last 30 days; 4,000 as pilot in command; 200 on instruments
- Last flight review: March 18, 2013
- Medical certificate: Class 2 (with waivers/limitations)
- Seat: rgt
- Injury: no injuries
The aircraft
- Airframe total time: 1,308 hours
- Last inspection: continuous airworthiness programme, April 10, 2013; 6 hours since
- Maximum gross weight: 5,000 lb
- Seats: 7
- Landing gear: fixed
- Engine: Allison 250-C47B (turboshaft); 1,308 hours total
- Operator: Flathead County Sheriff'S Office
The flight
- Departed from: S27 Kalispell MT at 3:45 pm
- Destination: S27 Kalispell MT
Weather at the time
- Light: daylight
- Wind: from 170° at 9 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 52°F (11°C), dew point 30°F (-1°C)
- Altimeter: 29.88 inHg
- Observation at 3:55 pm from GPI, 18 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 | |||
| Passengers | 2 |
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.
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.