N275BMBeech V35 · 1966

On September 18, 2011, about 1035 eastern daylight time, a Beech V35, N275BM, operated by a commercial pilot, sustained minor damage during a forced landing, following a total loss of engine power shortly after takeoff from the Tweed-New Haven Airport (HVN), New Haven, Connecticut. The certificated commercial pilot and a passenger were not injured. Visual meteorological conditions prevailed and an instrument flight rules flight plan was filed for the personal flight that was conducted under the provisions of 14 Code of Federal Regulations Part 91.

According to the pilot, the airplane departed HVN and began to climb without incident. As the airplane approached 6,000 feet mean sea level, the pilot felt a shutter and slight change in engine rpm. A few seconds later, he experienced oil on the windscreen, smoke, and engine roughness, followed by a total loss of engine power. The pilot declared an emergency and was able to return to HVN to perform a forced landing to runway 14. During the landing, the airplane sustained minor nose gear damage when it overran the runway about 50 feet, and came to rest in weeds.

The airplane was powered by a Teledyne Continental Motors IO-550-B83, 300-horsepower engine, equipped with a three-bladed Hartzell constant-speed propeller.

Examination of the airplane by a Federal Aviation Administration inspector revealed that the propeller and forward portion of the crankshaft, aft of the propeller mounting flange, separated inflight and was subsequently located in a wooded area. The engine and the separated portion of the crankshaft were retained for further examination.

A teardown of the engine conducted at Continental Motors Inc., Mobile, Alabama, under the supervision of an NTSB investigator, revealed that the crankshaft and counterweight assembly exhibited lubrication distress, thermal damage, and mechanical damage on all six connecting rod journals. The crankshaft was fractured in two-pieces across the No. 4 main journal. The crankcase main bearing supports adjacent to the fracture exhibited fretting signatures and lock-slot elongation. The No. 4 main bearing was extruded, with portions found in the oil sump. Metallurgical examination of the fractured crankshaft revealed cracks initiated on the bearing surface near an oil transfer tube and propagated in fatigue. Cracks were also identified on the bearing fillet radius.

At the time of the incident, the airplane had been operated for about 5,470 total hours, and 14 hours since its most recent annual inspection, which was performed on August 11, 2011. The engine was manufactured during November 2006, and had been operated for about 910 total hours. In addition, the engine had been operated for about 500 hours since maintenance was performed that included the reinstallation of the Nos. 2 and 4 cylinders after repair, on February 17, 2009.