# NTSB Accident WPR13TA205
> **BELL BHT407** · 2013-04-25 · Big Fork, MT, USA · NONE
## Event
- **NTSB number:** WPR13TA205
- **Event ID:** 20130423X65502
- **Type:** Accident
- **Date:** 2013-04-25
- **Location:** Big Fork, MT, USA
- **Coordinates:** 48.153057, -113.923889
## Injuries
- **Highest injury:** NONE
- **Fatal:** 0
- **Serious:** 0
- **Minor:** 0
- **Uninjured:** 3
- **Total aboard:** 3
## Aircraft
- **Make:** BELL
- **Model:** BHT407
- **Registration:** N937GR
- **FAR Part:** PUBU
- **Engines:** 1
- **Damage:** SUBS
## Conditions
- **Light:** DAYL
- **Weather:** VMC
## Probable cause

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.

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*Source: [NTSB CAROL](https://data.ntsb.gov/carol-main-public/basic-search?source=ntsb&type=event&ntsb_number=WPR13TA205) · AI Analytics · CC0 1.0*