Sikorsky S-58BT accident near Ovando, Montana, July 16, 1990
On July 16, 1990 at about 4:30 pm local time, a Sikorsky S-58BT (helicopter), registered N439DS, was substantially damaged in an accident near Ovando, Montana. It was an other work-use flight under external-load helicopter rules (Part 133). No one was hurt; 1 person was on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
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.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- July 16, 1990 · about 4:30 pm local time
- Place
- Ovando, Montana · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Sikorsky S-58BT · all S-58BTs on the register
- Registration
- N439DS · registry record · serial 58-658
- Damage
- Substantial damage
- Flight
- Other work-use flight · external-load helicopter rules (Part 133)
The NTSB's narrative final · quoted from the NTSB record
DURING AN EXTERNAL LOAD LOGGING OPERATION, THE PILOT HAD JUST TAKEN OFF FROM REFUELING AND WAS PREPARING FOR ANOTHER LOAD PICK- UP WHEN THE NUMBER ONE ENGINE LOST POWER AND FLAMES WERE OBSERVED SHOTTING OUT FROM THE EXHAUST. THE PILOT TRIED TO FLY THE HELICOPTER ON ONE ENGINE TO A LANDING AREA, HOWEVER, RPM WAS DROPPING. THE PILOT INITIATED AN AUTOROTATION WHICH RESULTED IN A HARD LANDING.
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
Pilot
- Certificate: commercial pilot
- Ratings: multi-engine land; single-engine land; instrument: airplane; instrument: helicopter; rotorcraft: helicopter
- Flight time: 6,298 hours in all; 1,248 in this make and model; 6,000 as pilot in command
- Medical certificate: Class 2 (valid medical--no waivers/lim.)
- Seat: unk
The aircraft
- Last inspection: inspection type not recorded; 0 hours since
- Maximum gross weight: 12,500 lb
- Seats: 2
- Landing gear: fixed
- Engine: P&W T400-CP-400 (turboshaft); 0 hours total
The flight
- Departed from: Canyon Creek MT at 4:15 pm
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Visibility: 50 statute miles
- Sky: clear
- Temperature: 86°F (30°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 |
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.