Amateur-built FISHER DAK accident near Bozeman, Montana, October 3, 2009
On October 3, 2009 at about 3:48 pm local time, a amateur-built FISHER DAK, registered N359JM, was substantially damaged in an accident during enroute (cruise) near Bozeman, Montana (Gallatin Field). It was a personal flight under general aviation rules (Part 91). 1 person had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
A loss of engine power due to shearing of the crankshaft gear cluster bolts. Contributing to the accident was the lack of regular overhaul periods as recommended by the engine manufacturer.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- October 3, 2009 · about 3:48 pm local time
- Place
- Bozeman, Montana · Gallatin Field · map
- Type
- Accident
- Injuries
- 1 person had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Amateur-built FISHER DAK
- Registration
- N359JM · no longer on the register · serial DH38
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot was departing on a local flight when the engine lost power; the pilot force-landed the airplane in a field. Post accident examination of the engine showed that the bolts securing the crankshaft gear cluster to the crankshaft were sheared. The crankshaft gear cluster is geared to the camshaft gear and rotates as the engine operates. Examination of the bolts showed that all four bolts had sheared between the crankshaft gear cluster and the attach point to the crankshaft. Two bolt heads, including a portion of the bolts’ lengths, were missing. The other portions of these bolts remained threaded to the crankshaft attach points. The two remaining bolt heads were still safety-wired and in place; however, they had sheared from the crankshaft. The lower threaded portions of all four bolts remained threaded at the crankshaft attach points. No pieces of the missing bolt heads or bolt portions were identified in the accessory case or the oil sump. Examination of the fracture surfaces on the threaded bolt portions showed that the surfaces of the sheared bolts with the missing heads appeared battered. The portions of the bolts still threaded in the crankshaft that belonged to the remaining bolt heads were not battered. The engine had not undergone a complete overhaul of the type that would have exposed the accessory gear section to inspection for over 35 years. According to Teledyne Continental Motors Service Instruction Letter 98-9A, the C-85 engine should be overhauled every 12 years or 1,800 hours.
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
What happened, in order
- Loss of engine power (total) during enroute (cruise) defining event
- Off-field or emergency landing during landing
The NTSB's findings
- cause Aircraft › Aircraft power plant › Engine (reciprocating) › Recip engine power section › Fatigue/wear/corrosion
- factor Aircraft › Aircraft power plant › Engine (reciprocating) › (general) › Not serviced/maintained
Pilot
- Certificate: private
- Ratings: single-engine land
- Flight time: 193 hours in all; 141 in this make and model; 10 in the last 90 days; 3 in the last 30 days
- Last flight review: July 15, 2008
- Medical certificate: Sport Pilot
- Seat: left
- Injury: minor injuries
The aircraft
- Airframe total time: 141 hours
- Last inspection: condition inspection, October 23, 2008; 25 hours since
- Maximum gross weight: 1,150 lb
- Seats: 2
- Landing gear: fixed
- Engine: Cont Motor C85 SERIES (piston); 0 hours total
The flight
- Departed from: BZN Bozeman MT at 3:45 pm
- Destination: BZN Bozeman MT
- Flight plan: none
Weather at the time
- Light: daylight
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 43°F (6°C), dew point 30°F (-1°C)
- Altimeter: 29.90 inHg
- Observation at 3:56 pm from BZN, 4 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight 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.