Lebanon, ME, USA
N8777Q
Cessna U206G
While en route to his destination the private pilot began experiencing a rough running engine with a subsequent total loss of engine power. Unable to make the nearest airfield the pilot elected to land in a farm field. During landing roll the nosewheel contacted a burrow resulting in the separation of the nosewheel assembly and a loss of control. The airplane came to rest in the upright position and the pilot was able to egress without assistance. During the engine examination a sub-surface fatigue fracture was discovered on the number 5 crankshaft cheek resulting in the failure of the crankshaft and loss of engine power. The engine was last overhauled approximately 17 years prior to the accident. The engine manufacturer stated that the engine should be overhauled every 12 years. On January 23, 1998, the Federal Aviation Administration released guidance for the replacement of the crankshaft at the next overhaul or the next time the crankshaft was removed. At the time of the accident, compliance with the service bulletin and airworthiness was not accomplished, nor required.
On October 18, 2007, at 1340 eastern daylight time (EDT), a single-engine Cessna U206G airplane, N8777Q, was substantially damaged during a forced landing following a loss of engine power near Lebanon, Maine. The instrument rated private pilot, who was also the owner and operator, was not injured. The airplane departed Ticonderoga Municipal Airport (4B6), Ticonderoga, New York, at approximately 1235 EDT on a 121-nautical mile cross-country flight destined for the Sanford Regional Airport (SFM), Sanford, Maine. Visual meteorological conditions prevailed and an instrument flight plan was filed for the 14 Code of Federal Regulations Part 91 personal flight. According to a statement provided by the pilot, during en route descent to SFM at 3,500 feet mean sea level (MSL) the engine began to run rough with an associated partial loss of engine power. The pilot declared an emergency with the Boston Center approach controller who also assisted the pilot in locating the nearest airfield. The engine then experienced a complete loss of engine power and the propeller "froze." After establishing the airplane's best glide speed, the pilot determined the nearest airfield could not be made and located a field for a forced landing. The pilot landed the airplane in the field and began applying the brakes. The nosewheel hit a burrow resulting in the nosewheel assembly separating from the airplane. Directional control was lost and damage was sustained by both wings when they impacted the ground. The airplane came to rest in the upright position and the pilot egressed the airplane without assistance. A field examination was conducted on the engine by a technical representative from Teledyne Continental Motors (TCM) under the supervision from the Federal Aviation Administration (FAA). The number 5 connecting rod was found separated from the crankshaft. The crankshaft was separated forward of the number 3 bearing. The engine was shipped to TCM for a more extensive examination. The engine was examined by technical representatives from TCM under the supervision of the NTSB. During the examination a sub-surface fatigue fracture was found on the number 5 bearing cheek of the airmelt or non-vacuum air remelted (VAR) manufactured crankshaft. A review of the engine logbook revealed the last engine overhaul occurred on May 1, 1990. This is the last time that the crankshaft was documented to have been removed from the crankcase. The last annual inspection occurred on April 26, 2007. The pilot reported no mechanical malfunctions prior to the accident. On June 25, 1996, TCM released Critical Service Bulletin (CSB) 96-8 requiring the replacement of non-VAR crankshafts with a new or serviceable VAR crankshaft at "engine overhaul or whenever the crankshaft is removed or made accessible by crankcase disassembly." According to the CSB, "In 1978 TCM began using VAR process steel in the forging of crankshafts for use in a number of its engines. The VAR process produces a forging with fewer impurities providing the greatest reliability and resistance to unusual operating circumstances." The FAA released an Airworthiness Directive 97-26-17 on January 23, 1998 stating the non-VAR crankshafts should be removed "at the next engine overhaul or whenever the crankshaft is next removed from the engine." TCM Service Information letter (SIL) 98-9A, states that the engine should be overhauled at least every twelve years, or on the accumulation of 1,700 hours for an IO-520-F engine. At the time of the accident the engine had accumulated over 17 years and 1,138.9 hour since major overhaul. Compliance with the SIL is not mandatory for Part 91 operators. At 1351 EDT, an automated weather reporting facility located approximately 8 nautical miles east of the accident site reported winds from 200 degrees at 4 knots, visibility 10 miles, temperature 69 degrees Fahrenheit, dew point 52 degrees Fahrenheit, skies clear and a barometric pressure of 29.94 inches of Mercury.
Failure of the crankshaft resulting in the total loss of engine power.
Source: NTSB Aviation Accident Database
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