Univair Aircraft Corporation 108-1 accident near Tuftonboro, New Hampshire, July 17, 2013
On July 17, 2013 at about 7:50 pm local time, a Univair Aircraft Corporation 108-1, registered N8721K, was substantially damaged in an accident during enroute (cruise) near Tuftonboro, New Hampshire. It was a personal flight under general aviation rules (Part 91). 2 people had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
Maintenance personnel’s failure to remove circumferential gouges in the aft radius of the R2 rod journal on the crankshaft during its last engine overhaul, which resulted in the fatigue failure of the crankshaft and a subsequent total loss of engine power.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- July 17, 2013 · about 7:50 pm local time
- Place
- Tuftonboro, New Hampshire · map
- Type
- Accident
- Injuries
- 2 people had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Univair Aircraft Corporation 108-1
- Registration
- N8721K · no longer on the register · serial 108-1721
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
About 7 minutes after takeoff and while leveling off the airplane at 1,800 ft, the pilot leaned the fuel-to-air mixture, and the engine immediately began to run roughly. The more experienced right-seat pilot took control of the airplane and attempted to restore power, but his attempts were unsuccessful. The propeller continued to rotate briefly but then stopped. The pilot maneuvered the airplane for a forced landing in a field, and the airplane subsequently impacted a raised concrete culvert. Postaccident examination of the engine revealed that the crankshaft was fractured. Metallurgical examination of the crankshaft revealed evidence of fatigue cracking that had originated from circumferential gouges at the aft radius of the R2 rod journal. A review of engine records revealed that, about 45 years before the accident, the crankshaft was replaced during an engine overhaul and that the main and connecting rod bearing journals were ground 0.010-inch undersize. About 7 years before the accident, the engine was overhauled again, and the crankshaft main and connecting rod bearing journals were polished. The engine was installed in the accident airplane about 3 years before the accident; the engine failure occurred about 115 hours after the engine's last overhaul. It is likely that, if maintenance personnel had detected and removed the circumferential gouges at the aft radius of the R2 rod journal during the engine's last overhaul, the fatigue cracking would not have started and the crankshaft would not have failed.
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
- Aircraft maintenance event during prior to flight
- 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 landing (landing roll)
The NTSB's findings
- cause Personnel issues › Action/decision › Action › Lack of action › Maintenance personnel
- cause Aircraft › Aircraft power plant › Engine (reciprocating) › Recip engine power section › Fatigue/wear/corrosion
- cause Aircraft › Aircraft power plant › Engine (reciprocating) › Recip engine power section › Failure
Pilot-Rated Passenger
- Certificate: private
- Ratings: single-engine land
- Flight time: 82 hours in all; 26.7 in this make and model; 4.4 in the last 90 days; 2.9 in the last 30 days; 27.8 as pilot in command
- Last flight review: August 24, 2012
- Medical certificate: Class 3 (with waivers/limitations)
- Seat: left
- Injury: minor injuries
Pilot
- Certificate: airline transport pilot, flight instructor, commercial pilot
- Ratings: multi-engine land; single-engine land; single-engine sea; instructor: airplane multi-engine; instructor: airplane single-engine; instructor: glider; instructor: instrument airplane; instrument: airplane; rotorcraft: glider
- Flight time: 11,303 hours in all; 90 in this make and model; 29 in the last 90 days; 22 in the last 30 days; 8,230 as pilot in command; 2,073 on instruments
- Last flight review: December 17, 2011
- Medical certificate: Class 3 (with waivers/limitations)
- Seat: rgt
- Injury: minor injuries
The aircraft
- Airframe total time: 1,523 hours
- Last inspection: annual inspection, January 14, 2013; 10 hours since
- Maximum gross weight: 2,230 lb
- Seats: 4
- Landing gear: fixed
- Engine: Franklin 6A4150 SERIES (piston); 0 hours total
The flight
- Departed from: 5M3 Moultonboro NH at 7:43 pm
- Destination: NH31 Wolfeboro NH
- Flight plan: none
- A second pilot was aboard
Weather at the time
- Light: daylight
- Wind: from 230° at 10 knots
- Visibility: 10 statute miles
- Sky: scat at 7,000 ft
- Temperature: 91°F (33°C), dew point 66°F (19°C)
- Altimeter: 30.03 inHg
- Observation at 7:55 pm from LCI, 11 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 | |||
| Passengers | 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.