History of Flight
On December 5, 2010, about 1530 eastern standard time, a Cessna U206G, registration N9742Z, crashed in an open field in Leverett, Massachusetts. The airplane was operated by an individual and registered to Airborne Maintenance Incorporated. The flight, conducted under visual flight rules and 14 CFR Part 91 as a personal flight, originated from Dillant-Hopkins Airport (EEN) in Keene, New Hampshire, destined for Long Island Mac Arthur Airport (KISP) in Islip, New York. Visual meteorological conditions prevailed, and flight following was activated. The aircraft departed EEN about 1505.
Five minutes before the accident, the flight was handed off from FAA Boston Air Route Traffic Control Center to FAA Bradley Approach. Shortly after, the flight was lost from radar. Last radar contact was at 1528, at an altitude of 1,900 feet msl and a ground speed of 87 knots. No distress calls were received.
The pilot stated the flight was in cruise at 3,000 feet msl when the engine developed a vibration, then stopped producing power. To assist troubleshooting, the occupant in the right front seat switched places with a passenger who was a pilot and mechanic. The pilot saw an open field and elected an off-field landing. The airplane cleared adjacent trees, but the pilot did not see electrical wires behind the trees. He recalled clearing the trees and lowering flaps, then unbuckling his seat belt and calling 911.
Personnel Information
The left-seat pilot held a commercial pilot certificate with single-engine land, multiengine land, and instrument ratings. He was issued a first-class medical certificate on April 20, 2010, with no limitations. He reported 390 total hours, with 90 in the accident airplane.
The right-seat passenger, age 62, held a commercial pilot certificate (rotorcraft-helicopter), a private pilot certificate (single-engine land), and a flight instructor certificate (rotorcraft-helicopter). He held a second-class medical certificate issued August 11, 2010, with limitations requiring glasses for near vision. He had 10,000 total hours and held an airframe and powerplant mechanic certificate.
Aircraft Information
The Cessna U206G, serial number U20606636, was a six-place, all-metal, high-wing, single-engine airplane with fixed landing gear and a variable-pitch propeller. Manufactured in 1982, it had a standard airworthiness certificate in the normal category. It was powered by a Continental IO-520-DCF 300-horsepower engine with a Hartzell three-bladed propeller. The engine was overhauled in April 2004. Its last inspection was October 25, 2010, at 1,459.2 hours since major overhaul. The airframe's last inspection was also October 25, 2010, at 6,556.8 hours total time. At the accident, total time was 6,572.1 hours.
Meteorological Information
The closest official weather observation was at Orange Municipal Airport (ORE), Massachusetts, about 13 miles northeast of the accident site. The 1552 METAR reported wind from 310 degrees at 9 knots gusting to 15 knots; visibility 10 statute miles; overcast clouds at 4,200 feet; temperature -2°C; dew point -10°C; altimeter 29.52 inches of mercury.
Wreckage and Impact Information
The main wreckage was located at 42°26.391'N, 072°29.317'W, about 105 feet from electrical transmission wires. The top wire was frayed but intact, drooped above the ground. The airplane, on an estimated heading of 210 degrees, caught the top wire with its main landing gear at an estimated height of 72 feet above ground. The wire separated from its attachment points, and the airplane became inverted, impacting the ground right wing first in a near-inverted attitude, coming to rest facing about 360 degrees.
The left main gear spring detached from its securing bracket but remained attached; the left wheel assembly separated. The right main gear separated from the fuselage attachment, coming to rest about 35 feet northeast. The right wing tip was crushed, bent, and curled downward (upward due to inverted attitude). The right wing strut separated from the fuselage, ripped into the cabin, and folded inside. The right side of the fuselage was crushed and buckled outward; the right roof area was crushed into the glare shield. The left fuselage did not buckle. The left wing and strut remained intact, with impact damage. The windshield was shattered. The vertical stabilizer was bent and curled left.
The lower engine cowl separated, exposing the engine bottom. The engine separated from its mounts and rested on the upper cowling. The lower engine bay and cowl flap and belly had engine oil streaking. The propeller and engine remained attached; one blade was stuck in the soil. The spinner and blades had no damage; blades were in low pitch.
All flight control surfaces were attached. Control cable continuity was established. The flap actuator was in the full extended position; the control rod to the right flap had separated. Both wing fuel tanks were breached; fuel was observed at the site. The fuel selector was in the left tank position. The fuel system from tanks to gascolator had no discrepancies; fuel was in the gascolator. The auxiliary electric fuel pump operated when powered.
Engine control cable continuity was established. The engine had impact damage to the intake manifold and vacuum pump. The oil sump and crankcase were damaged but not breached. The oil cap and dipstick were installed and secured. Borescope inspection of cylinders revealed no discrepancies. Spark plugs had no discrepancies. Both magnetos were in place; several ignition wires were cut by impact. The fuel pump had impact damage but was safety wired; fuel flowed when the outlet line was disconnected. The fuel pump drive shaft rotated by hand; the coupling was intact. The bolt securing the alternator belt adjustment brace to the engine was missing; the alternator belt was loose.
Medical and Pathological Information
The Medical Examiner's Office in Holyoke, Massachusetts, conducted a postmortem examination of the pilot-rated passenger. The cause of death was blunt force trauma. The FAA Civil Aeromedical Institute conducted toxicology testing; no ethanol or drugs were detected.
The passenger seated in the middle row, right seat, succumbed to his injuries 7 days after the accident.
Test and Research
An engine teardown examination was conducted at Continental Motors Incorporated with NTSB oversight. External examination revealed that seven stud flange nuts between cylinders were not self-aligning and had flat seats; others were self-aligning with beveled seats. Several nuts were not at required torque. Internal examination showed the crankshaft fractured forward of the number 2 connecting rod and journal. The number 2 connecting rod bolt and nut were found in the oil sump. The number 2 main bearing was damaged, with sections missing, and shifted on the crankcase saddle. Fretting damage was observed on the saddle contact surfaces. The number 2 main bearing journal exhibited scoring consistent with bearing rotation. The crankcase, bearings, crankshaft, and number 2 connecting rod assembly were retained for metallurgical examination.
Metallurgical examination revealed the crankshaft fractured through the cheek at the aft end of the number 2 main journal. The fracture surface was relatively smooth with curving crack arrest lines, consistent with fatigue. Fatigue features emanated from multiple origins at the crankshaft surface in the radius between the number 2 main journal and the cheek. Circumferential scoring and metal transfer were observed on adjacent surfaces. Fatigue features extended through nearly the entire thickness of the cheek. The number 2 main bearing was fractured into pieces; one piece was shifted with an outward curve. Other pieces were in the oil sump. The bearings had an orange color consistent with a copper-lead layer. The number 2 main journal surface was tinted gold-brown, consistent with elevated temperatures. Circumferential scoring was also on the journal. Examination of the crankcase halves revealed damaged saddles for number 1 and number 2 main bearings, with fretting on contact faces.
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 between 420.9 and 728.5 hours before the accident. The number 2 cylinder was replaced 692.0 hours before the accident; number 3 cylinder was replaced 549.3 hours before.