Southbury, CT, USA
N3810X
Beech A36TC
During taxi, runup, and takeoff, the pilot did not notice any anomalies with the engine, and the flight progressed without incident until about 90 miles short of the intended destination when the engine started to run rough for a few seconds before it stopped producing power. The windscreen became covered with oil, and the pilot executed an off airport forced landing, substantially damaging the airplane. External examination of the engine revealed three holes in the top of the engine case, and a crankshaft counter weight pin resting on top of the engine. Internal examination of the engine revealed heavy mechanical damage on the No. 5 counter weight, and the engine case in the vicinity of the No. 3 and No. 4 cylinders. Examination of the No. 5 counter weight assembly revealed that one of the two aft snap rings, plates, and pins were missing. The pin was located on top of the engine during the external examination, but neither the snap ring nor plate could be located. The fact that the engine was operated for approximately 16 hours since overhaul, along with the witness mark on the surface of the counter weight, suggested that the snap ring, plate, and pin were installed; however, it could not be determined if the snap ring was properly seated. A review of engine overhaul records revealed that on February 5, 2005, the counterweights, along with the pins, plates, and snap rings were installed on the crankshaft.
On April 20, 2005, at 1603 eastern daylight time, a Beech A36TC, N3810X, was substantially damaged during a forced landing to an open field after experiencing a total loss of engine power near Southbury, Connecticut. The certificated private pilot received minor injuries. Visual meteorological conditions prevailed for the business flight that departed Cuyahoga County Airport (CGF), Cleveland, Ohio, destined for the Theodore Francis Green State Airport (PVD), Providence, Rhode Island. An instrument flight rules flight plan was filed and activated for the flight conducted under 14 CFR Part 91. According to the pilot, he arrived at the airport, preflighted the airplane, and then boarded. During taxi, runup, and takeoff, he noticed no anomalies with the engine, and the flight progressed without incident until about 90 miles southwest of Providence. While in cruise flight at 9,000 feet msl, the pilot felt the engine start to "shake and then shudder." About 5 seconds later, the engine lost power, and the windscreen became covered with oil. The pilot advised air traffic control (ATC) of his situation, and declared an emergency. The air traffic controller advised the pilot that the Waterbury-Oxford Airport (OXC), Oxford, Connecticut, was the closest airport, and recommended a heading of 150 degrees. The pilot thought he saw an airport at 130 degrees, which he turned the airplane towards. The controller radioed the pilot that he was no longer headed towards the closest airport, and once again, recommended a heading of 150 degrees. The pilot acknowledged the transmission, and turned the airplane back towards the Waterbury-Oxford Airport. After passing 5,000 feet msl, the pilot felt he might not reach the airport, so he started looking for an alternate forced landing location. After descending through 2,500 feet, the pilot was confident he would not make the airport. He identified an open field, and maneuvered to land, but impacted trees and wires just short of his intended forced landing area. The airplane came to rest about 4.5 miles west of the Waterbury-Oxford Airport, and the pilot egressed unassisted. The pilot added that the engine had been overhauled approximately 16 hours before the accident, so he closely monitored engine instruments during the flight, and did not notice any anomalies with the engine oil pressure, engine oil temperature, or cylinder head temperature. The engine was removed from the airframe, and sent to a maintenance facility in Mattituck, New York, for further examination. On May 19, 2005, the engine was examined under the supervision of the Safety Board. External examination of the engine revealed three holes in the top of the engine case, and a crankshaft counter weight pin resting above the No. 2 cylinder deck area. Internal examination of the engine revealed heavy mechanical damage on the No. 5 counter weight, and the case in the vicinity of the No. 3 and No. 4 cylinders, along with the associated pistons. The No. 3 and No. 4 connecting rod links had separated, and the associated fracture surfaces were consistent with overload. Examination of the No. 5 counter weight assembly revealed that one of the two aft snap rings, plates, and pins were missing. The pin was located on top of the engine during the external examination, but neither the snap ring nor plate could be located in or around the engine. An impression on the surface of the No. 5 counter weight was identified. The impression started on the surface of the counter weight and angled into the hole where the No. 5 aft snap ring, plate, and pin should have been located. The impression had an average depth of approximately 1/8 inch, was about 1 inch long, and had approximately the same diameter as the pin that was found on top of the engine. A review of engine overhaul records revealed that on February 5, 2005, the counterweights, along with the pins, plates, and snap rings, were installed on the crankshaft. The engine and wreckage were released to a representative of the owner on May 20, 2005.
The failure of the counter weight aft snap ring to hold the associated plate and pin in place, which resulted in a total loss of engine power.
Source: NTSB Aviation Accident Database
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