Bell BHT407 N937GR

Summary

On 25 April 2013 at about 16:16 local time, a Bell BHT407 registered N937GR, operated by Flathead County Sheriff's Office, was involved in an accident near Big Fork, Montana, United States. 3 people were on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

25 April 2013 at 16:16

Classification

Accident

Location

Big Fork, Montana, United States

Nearest airport

Kalispell City (S27)

Coordinates

48.1531, -113.9239

Aircraft

Bell BHT407

Registration

N937GR

Category

Helicopter

Year built

1998

Engines

1

Operator

Flathead County Sheriff's Office

Operating rule

Public Use

Phase of flight

Not recorded

Route

Kalispell → Kalispell

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR13TA205

Nobody was injured.

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.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

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.

Quoted verbatim from the NTSB record.