# NTSB Accident SEA90LA137
> **SIKORSKY S-58BT** · 1990-07-16 · OVANDO, MT, USA · NONE
## Event
- **NTSB number:** SEA90LA137
- **Event ID:** 20001212X23835
- **Type:** Accident
- **Date:** 1990-07-16
- **Location:** OVANDO, MT, USA
- **Coordinates:** 47.069293, -113.040496
## Injuries
- **Highest injury:** NONE
- **Fatal:** 0
- **Serious:** 0
- **Minor:** 0
- **Uninjured:** 1
- **Total aboard:** 1
## Aircraft
- **Make:** SIKORSKY
- **Model:** S-58BT
- **Registration:** N439DS
- **FAR Part:** 133
- **Engines:** 2
- **Damage:** SUBS
## Conditions
- **Light:** DAYL
- **Weather:** VMC
## Probable cause

THE PILOT DID NOT MAINTAIN ROTOR RPM AFTER A COMPRESSOR ASSEMBLY BLADE FAILURE. A RELATED FACTOR WAS AN INADEQUATE AUTOROTATION RESULTING IN A HARD LANDING.

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*Source: [NTSB CAROL](https://data.ntsb.gov/carol-main-public/basic-search?source=ntsb&type=event&ntsb_number=SEA90LA137) · AI Analytics · CC0 1.0*