Accident Summary
On August 19, 2010, at 1130 eastern daylight time, a Cessna 310F, registration N6762X, sustained substantial damage upon impact with terrain during a forced landing to a pasture near LaGrange, Indiana. Visual meteorological conditions prevailed at the time. The flight was operating under 14 CFR Part 91 as a personal flight without a flight plan. The pilot and passenger were uninjured; a horse was injured when struck by the airplane and later euthanized.
Sequence of Events
According to the pilot, the airplane was in cruise flight at 3,500 feet above mean sea level (MSL) at an airspeed of 155 knots when he 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 might be a stall or gear warning. He believed the vibration came from the left engine or propeller, so he shut down the left engine and feathered the left propeller. Advancing the right engine to full power did not change the vibration. The airplane continued to lose altitude while flown at the single-engine best rate of climb speed. The pilot performed a forced landing to a pasture, where the airplane struck a wire fence and a horse. A post-crash fire ensued.
Examination
The on-scene Federal Aviation Administration inspector reported that the pilot initially stated the vibration was emanating from the tail. No ground scars consistent with the landing gear being extended were found; only fuselage scars were present. The landing gear handle was in the up (retracted) position, and the flaps were extended.
Examination of the airplane revealed that all control surfaces were attached, with no evidence of repetitive contact to adjacent surfaces. 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, while the left propeller blades were relatively straight. Substantial damage included a left wing separation and a buckled empennage. No anomalies were found that would have induced an aircraft vibration.
Engine Test
The right engine, a Continental Motors IO-470-D (serial number CS105283-D-R), had its last major overhaul on March 26, 1998, at a Hobbs time of 1,504.1 hours. Its last inspection was a 100-hour inspection on April 8, 2010, at an airplane total time of 2,153 hours, engine total time of 5,519.8 hours, and time since major overhaul of 648.9 hours.
The engine was removed and shipped to Teledyne Continental Motors in Mobile, Alabama, for an engine run supervised by the National Transportation Safety Board investigator-in-charge. Prior to the test, the fuel control unit screen showed contaminants consistent with cloth or fabric fibers; the screen was reinstalled without removing these contaminants. A test club propeller was installed. During the test, the engine was run at throttle settings of 1,260 rpm, 1,630 rpm, 2,100 rpm, and 2,450 rpm for 5-minute intervals each, then advanced to full open for 5 minutes and cycled from idle to full throttle six times. No interruption or hesitation in power was noted.
Weather and Performance
The Kirsch Municipal Airport (IRS) in Sturgis, Michigan, about 12 miles north of the accident site at an elevation of about 924 feet MSL, recorded a temperature of 81°F and an altimeter setting of 29.98 inches of mercury.
The pilot reported the airplane weight at the time of the accident as 4,000 pounds. The Cessna 310F Owner's Manual climb data (flaps and gear retracted, inoperative propeller feathered, wing banked 5° toward operating engine, full throttle, propeller speed 2,625 rpm, mixture leaned) indicates that at 2,500 feet and 50°F, the rate of climb is 545 feet per minute at a best climb speed of 106 knots indicated airspeed, with a decrease of 10 feet per minute for each 10°F above standard temperature.