Kaman HH-43B accident near Mullan, Idaho, June 26, 2001
On June 26, 2001 at about 3:45 pm local time, a Kaman HH-43B (helicopter), registered N556D, was substantially damaged in an accident near Mullan, Idaho. It was an other work-use flight under external-load helicopter rules (Part 133). 1 person had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The development of multiple fatigue cracks which ultimately resulted in the fracture of the 1st stage gas producer turbine rotor sealing disc. Factors contributing to the accident were mountainous/hilly and unsuitable terrain conditions.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- June 26, 2001 · about 3:45 pm local time
- Place
- Mullan, Idaho · map
- Type
- Accident
- Injuries
- 1 person had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Kaman HH-43B
- Registration
- N556D · no longer on the register · serial 59-1556
- 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 pilot was preparing to lift a load of logs from a 150-foot hover in the Kaman HH-43B helicopter when a total loss of power occurred. He transitioned into an autorotation colliding with the steeply sloped, tree covered terrain. A partial disassembly of the ex-military Lycoming T53-L-13B turboshaft engine revealed that the 1st stage gas producer turbine rotor sealing disc was fractured and had broken into three approximately equal sized segments. Metallurgical examination of the disc fragments revealed fatigue cracks through three of the six cooling holes, and examination of the fracture faces for all three cooling holes by scanning electron microscope revealed multiple fatigue striations at each fracture face.
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: flight instructor, commercial pilot
- Ratings: multi-engine land; single-engine land; instructor: helicopter; rotorcraft: helicopter
- Flight time: 13,300 hours in all; 4,200 in this make and model; 230 in the last 90 days; 90 in the last 30 days; 13,000 as pilot in command
- Last flight review: July 6, 2000
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: left
- Injury: minor injuries
The aircraft
- Airframe total time: 11,811 hours
- Last inspection: annual inspection, June 22, 2001; 12 hours since
- Maximum gross weight: 9,150 lb
- Seats: 2
- Landing gear: fixed
- Engine: Lycoming T53-L-13B (turboshaft); 0 hours total
- Operator: Precision Helicopters LLC.
The flight
- Departed from: Mullan ID at 2:15 pm
- Flight plan: none
Weather at the time
- Light: daylight
- Wind: from 350° at 11 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 57°F (14°C), dew point 48°F (9°C)
- Altimeter: 29.95 inHg
- Observation at 3:55 pm from COE, 48 miles away
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.