NTSB Factual Report

On August 19, 2010, at 1130 eastern daylight time, a Cessna 310F, N6762X, received substantial damage on impact with terrain during a forced landing to a pasture near LaGrange, Indiana. Visual meteorological conditions prevailed at the time of the accident. The 14 CFR Part 91 personal flight was not operating on a flight plan. The pilot and passenger were uninjured. A horse was injured when it was struck by the airplane and later euthanized. The flight originated from Wauseon, Ohio, at 1100 and was en route to Wahpeton, North Dakota.

The airplane was in cruise flight at 3,500 feet above mean sea level (MSL)(LaGrange, Indiana, is about 932 feet MSL) and at an airspeed of 155 knots when the pilot reportedly noticed a sudden vibration, decreased controllability, and a loss of altitude. Both sets of engine instruments indicated normal manifold pressure, engine speed, and temperature. The pilot also heard a repetitive loud beeping, which he thought was either a stall or gear warning. The pilot thought that the vibration was from the left engine/propeller so he decided to shut down the left engine and feather the left propeller. He advanced the right engine to full power but did not notice a change in the vibration. The pilot stated the airplane continued to lose altitude while at the airplane's single-engine best rate of climb speed. The pilot then performed a forced landing to a pasture where the airplane struck a wire fence and a horse. A post crash fire ensued. The horse was later euthanized due to its injuries.

According to the on-scene Federal Aviation Administration inspector, the pilot initially stated that the vibration was emanating from the tail. There were no ground scars in the pasture consistent with the landing gear being extended but only of the fuselage. The landing gear handle was in the up or retracted position. The flaps were extended.

The inspector's examination of the airplane noted that all of the control surfaces were attached and there was no evidence of repetitive contact of the control surfaces to any of the adjacent surfaces. The control surfaces were attached and control continuity from the control surfaces to the cockpit controls was confirmed. The fuel selector was positioned to the right fuel tank. The left fuel tank contained fuel. The right propeller blades exhibited S-shaped bending and twisting consistent with engine power, and the left propeller blades were relatively straight. The airplane sustained substantial damage, which included a left wing separation and a buckled empennage. Examination of the airplane revealed no anomalies that would have induced an aircraft vibration.

The right engine was a Continental Motors IO-470-D, serial number CS105283-D-R. The engine's last major overhaul was dated March 26, 1998, at a Hobbs time of 1,504.1 hours. The engine underwent its last inspection during a 100-hour inspection dated April 8, 2010, at an airplane total time of 2,153 hours, an engine total time of 5,519.8 hours, and a time since major overhaul of 648.9 hours.

The right engine was removed from the airplane and shipped to Teledyne Continental Motors, Mobile, Alabama, where it underwent an engine run under the supervision of the National Transportation Safety Board Investigator-in-Charge for the accident investigation. Prior to the engine run, the fuel control unit screen was removed and noted to contain contaminants that were consistent with cloth/fabric fibers. The fuel servo screen was reinstalled without removal of the fuel control unit screen contaminants. A test club propeller was installed onto the engine for the test.

During the test, the engine throttle was set to the following speeds for 5-minute intervals: 1,260 rpm, 1,630 rpm, 2,100 rpm, and 2,450 rpm. The throttle was then advanced to the full open position for 5 minutes and advanced 6 times from idle to full throttle. No interruption or hesitation in power was noted.

The pilot reported that the airplane weight at the time of the accident was 4,000 pounds.

The Kirsch Municipal Airport (IRS) Sturgis, Michigan, automated weather observing system, located about 12 miles north of the accident site and at an elevation of about 924 feet MSL, recorded: temperature - 81 degrees Fahrenheit(F) and an altimeter setting - 29.98 inches of mercury.

The Cessna 310F Owner's Manual provides the following climb data based upon the flaps and landing gear retracted, the inoperative propeller feathered, wing banked 5 degrees toward the operating engine, full throttle, propeller speed at 2,625 rpm, and the mixture leaned at the recommended leaning schedule. The rate of climb is to be decreased 10 feet/minute for each 10 degrees F above standard temperature for the particular altitude. At a gross weight of 4,000 pounds, at 2,500 feet and 50 degrees F, the rate of climb is 545 feet at a best climb speed of 106 knots indicated airspeed.

NTSB Probable Cause

The pilot did not maintain altitude due to his distracted attention to a vibration of unknown origin.