# NTSB Accident SEA91LA077
> **BELL BH-47G2A** · 1991-03-31 · WAITSBURG, WA, USA · NONE
## Event
- **NTSB number:** SEA91LA077
- **Event ID:** 20001212X16707
- **Type:** Accident
- **Date:** 1991-03-31
- **Location:** WAITSBURG, WA, USA
- **Coordinates:** 46.219707, -118.14907
## Injuries
- **Highest injury:** NONE
- **Fatal:** 0
- **Serious:** 0
- **Minor:** 0
- **Uninjured:** 1
- **Total aboard:** 1
## Aircraft
- **Make:** BELL
- **Model:** BH-47G2A
- **Registration:** N38926
- **FAR Part:** 137
- **Engines:** 1
- **Damage:** SUBS
## Conditions
- **Light:** DAYL
- **Weather:** VMC
## Probable cause

THE IMPROPER INSTALLATION OF THE MAIN ROTOR MAST NUT AND LOCK WASHER BY MAINTENANCE PERSONNEL WHICH RESULTED IN THE SEPARATION OF THE MAIN ROTOR SYSTEM.

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*Source: [NTSB CAROL](https://data.ntsb.gov/carol-main-public/basic-search?source=ntsb&type=event&ntsb_number=SEA91LA077) · AI Analytics · CC0 1.0*