Kaman HH-43 B/F accident near Troy, Montana, September 23, 1996
On September 23, 1996 at about 11:00 pm local time, a Kaman HH-43 B/F (helicopter), registered N4069R, was substantially damaged in an accident near Troy, Montana. It was a positioning flight under general aviation rules (Part 91). 2 people had minor injuries; 4 others were unhurt. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
failure of the freewheeling sprag unit bearings for undetermined reasons.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- September 23, 1996 · about 11:00 pm local time
- Place
- Troy, Montana · map
- Type
- Accident
- Injuries
- 2 people had minor injuries; 4 others were unhurt.
- Weather
- visual conditions (good weather)
- Aircraft
- Kaman HH-43 B/F
- Registration
- N4069R · registry record · serial 64-17558
- Damage
- Substantial damage
- Flight
- Positioning flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot reported that while in cruise flight, the internal autorotation cockpit gauge needles split, and the helicopter lost altitude. The rotor rpm was decreasing, and the pilot initiated an autorotation. During the descent, the pilot noted that the N1 gauge indicated that the engine was running, but there was no power to the rotor. The helicopter landed hard, which drove the landing gear through the belly and separated the tail boom. A postaccident investigation revealed that bearings in the one-way freewheeling sprag clutch had failed. The one-way clutch was not a time-retireable item, and determining total time of the assembly from the maintenance records was not possible.
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: 10,000 hours in all; 3,500 in this make and model; 9,500 as pilot in command
- Medical certificate: Class 2 (valid medical--no waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 7,587 hours
- Last inspection: annual inspection, September 15, 1996; 40 hours since
- Maximum gross weight: 9,150 lb
- Seats: 7
- Landing gear: fixed
- Engine: Lycoming T53-L13B (turboshaft); 0 hours total
The flight
- Departed from: MT at 2:00 pm
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Visibility: 30 statute miles
- Sky: clear
- Temperature: 64°F (18°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 | |||
| Passengers | 2 | 3 |
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.
Other NTSB records under N4069R the same tail number, which may have belonged to a different aircraft at the time
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.