Sikorsky S-58JT accident near Marblemount, Washington, February 13, 1995
On February 13, 1995 at about 6:20 pm local time, a Sikorsky S-58JT (helicopter), registered N1099T, was substantially damaged in an accident near Marblemount, Washington. It was an other work-use flight under external-load helicopter rules (Part 133). 1 person was seriously injured. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
FATIGUE FAILURE OF THE MAIN ROTOR DRIVESHAFT.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- February 13, 1995 · about 6:20 pm local time
- Place
- Marblemount, Washington · map
- Type
- Accident
- Injuries
- 1 person was seriously injured.
- Weather
- visual conditions (good weather)
- Aircraft
- Sikorsky S-58JT · all S-58JTs on the register
- Registration
- N1099T · no longer on the register · serial 58-1646
- Damage
- Substantial damage
- Flight
- Other work-use flight · external-load helicopter rules (Part 133)
The NTSB's narrative final · quoted from the NTSB record
THE MAIN ROTOR DRIVESHAFT FAILED DUE TO FATIGUE FAILURE WHILE THE PILOT WAS CONDUCTING HELICOPTER LOGGING OPERATIONS. THE MAIN ROTOR DRIVESHAFT HAD 952 HOURS SINCE NEW, AND HAD BEEN INSTALLED NEW AT THE MOST RECENT GEARBOX OVERHAUL. OVERHAUL PERIOD AND MAIN ROTOR DRIVESHAFT RETIREMENT TIME ARE 2500 HOURS. THE PILOT WAS NOT AT AN ALTITUDE OR AIRSPEED WHERE A SUCCESSFUL AUTOROTATION COULD BE ACCOMPLISHED.
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: single-engine land; instrument: airplane; rotorcraft: helicopter
- Flight time: 11,389 hours in all; 3,139 in this make and model; 95 in the last 90 days; 53 in the last 30 days; 11,389 as pilot in command
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 9,776 hours
- Last inspection: continuous airworthiness programme, February 9, 1995; 14 hours since
- Maximum gross weight: 12,500 lb
- Seats: 2
- Landing gear: fixed
- Engine: P&W PT6-T3 (turboshaft); 0 hours total
The flight
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 045° at 5 knots, gusting 8
- Visibility: 75 statute miles
- Sky: clear
- Temperature: 28°F (-2°C), dew point 0°F (-18°C)
- Altimeter: 29.00 inHg
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.