SEA94LA196

The pilot reported that the engine lost power while in cruise flight. A forced landing was made to an open field where during the landing roll, the airplane nosed over. During the engine inspection, it was found that the crankshaft broke at the number 2 journal. Testing revealed a fatigue crack emanating from the radius inward, and the presence of score marks indicate that the bearing inserts shifted aft during engine operation and were rubbing against the journal radius.

On July 25, 1994 at 1757 Pacific daylight time, a Cessna T210M, N761TK, experienced a loss of engine power while in cruise flight. The pilot initiated a forced landing to an open field near Rathdrum, Idaho. During the landing roll, the nose gear collapsed and the airplane nosed over. Visual meteorological conditions prevailed at the time and a U.S. Forest Service flight following flight plan was filed. The airplane was substantially damaged and the commercial pilot was not injured. The flight had departed from Bonners Ferry, Idaho, on July 25, 1994 at 1730 and was en route to Spokane, Washington.

The pilot reported that while cruising at 1,000 feet above ground level, the engine lost power. The pilot initiated a forced landing to an open field. During the landing roll, the nose gear collapsed and the airplane nosed over.

During an engine inspection, it was found that the crankshaft was broken at the aft radius of the number two main journal. The crankshaft was removed and sent to the National Transportation Safety Board Materials Laboratory for a metallurgical examination. The specialist reported that the fatigue crack emanated from multiple origins at the radius between the number two main journal and the crankcheek. Most of the number two main journal bearing surface contained rotational wear marks and ladder cracking. Evidence of bearing insert metal had transferred onto the journal surface. Heat discoloration, circumferential scoring damage, and ladder cracking were also visible at the aft radius of this journal.

The specialist reported that evidence on the other bearing journals indicated light to moderate scoring and heat damage on the surfaces of all six rod journals and main journals. The number three main bearing journal was severely overheated and scored. All of the rod journals bearing inserts indicated evidence of excessive rubbing and circumferential scoring.