Cessna U206G accident near Leverett, Massachusetts, December 5, 2010
On December 5, 2010 at about 8:30 pm local time, a Cessna U206G, registered N9742Z, was substantially damaged in an accident during enroute (cruise) near Leverett, Massachusetts. It was a personal flight under general aviation rules (Part 91). 2 people were killed and 2 people were seriously injured. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
A total loss of engine power due to the fatigue failure of the crankshaft, which resulted from improper tightening of the cylinder hold-down nuts.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- December 5, 2010 · about 8:30 pm local time
- Place
- Leverett, Massachusetts · map
- Type
- Accident
- Injuries
- 2 people were killed and 2 people were seriously injured.
- Weather
- visual conditions (good weather)
- Aircraft
- Cessna U206G · all U206Gs on the register
- Registration
- N9742Z · no longer on the register · serial U20606636
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The airplane was in cruise flight at 3,000 feet above ground level when the engine developed vibrations and, shortly after, lost total power. The pilot conducted a forced landing in an open field. The pilot cleared the trees adjacent to the field but did not see the electrical wires on the other side. The airplane’s main landing gear contacted the wires, and the airplane flipped and impacted the ground inverted. Examination of the engine revealed that several incorrect nuts for the cylinder hold-down studs were installed, and the breakaway torque values measured for the cylinder hold-down nuts were consistent with improper torque having been applied. Metallurgical examination revealed that the engine’s crankshaft fractured due to fatigue cracks that developed as a result of the No. 2 main bearing shifting in the crankcase saddle. The through-bolts that clamp the No. 2 crankcase saddle faces are secured with the hold-down nuts for the Nos. 2 and 3 cylinders. The engine had a reported total time in service of 6,629 hours with 1,475 hours since major overhaul. All six cylinders had been replaced since the overhaul, with the Nos. 2 and 3 cylinders having been replaced 692 and 549 hours before the accident, respectively.
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 emergency descent
- Collision with terrain or object (not controlled flight into terrain) during emergency descent
- Collision with terrain or object (not controlled flight into terrain) during uncontrolled descent
The NTSB's findings
- cause Aircraft › Aircraft power plant › Engine (reciprocating) › Recip eng cyl section › Incorrect service/maintenance
- cause Personnel issues › Action/decision › Action › Incorrect action performance › Maintenance personnel
- Environmental issues › Physical environment › Object/animal/substance › Wire › Contributed to outcome
Pilot
- Certificate: commercial pilot, private
- Ratings: multi-engine land; single-engine land; instrument: airplane
- Flight time: 390 hours in all; 90 in this make and model; 172 in the last 90 days; 47 in the last 30 days; 200 as pilot in command
- Medical certificate: Class 1 (without waivers/limitations)
- Seat: left
- Injury: serious injuries
Other crew
- Certificate: commercial pilot, private
- Ratings: single-engine land; instructor: helicopter; rotorcraft: helicopter
- Flight time: 10,000 hours in all
- Medical certificate: Class 2 (with waivers/limitations)
- Seat: rgt
- Injury: fatal
The aircraft
- Airframe total time: 6,572 hours
- Last inspection: 100-hour inspection, October 25, 2010; 15 hours since
- Maximum gross weight: 3,600 lb
- Seats: 6
- Landing gear: fixed
- Engine: Cont Motor IO 520 SERIES (piston); 0 hours total
The flight
- Departed from: EEN Keene NH at 7:15 pm
- Destination: ISP Islip NY
- Flight plan: VFR
- A second pilot was aboard
Weather at the time
- Light: daylight
- Wind: from 310° at 9 knots, gusting 15
- Visibility: 10 statute miles
- Sky: overcast at 4,200 ft; not recorded
- Temperature: 28°F (-2°C), dew point 14°F (-10°C)
- Altimeter: 29.52 inHg
- Observation at 7:52 pm from ORE, 13 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 | 1 | ||
| Passengers | 1 | 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.