CHI95LA048

While en route the pilot heard a loud pop followed by engine vibrations and a partial loss of engine power. The pilot declared an emergency and was vectored toward a grass airstrip which he could not locate. En route to the grass strip a total loss of engine power was experienced. The airplane was landed in a plowed corn field. Post accident inspection revealed the crankshaft had separated between the no. 3 main bearing journal and the no. 5 cylinder crankpin due to fatigue cracking. Tcm service bulletin 92-16 addressing crankshafts made from non-vacuum arc remelted steel had not been complied with.

On November 29, 1994, about 1130 central standard time, a Piper PA-28R-201T, N1194H, sustained substantial damage in a forced landing near La Porte City, Iowa, following a total loss of engine power. The private pilot and one passenger aboard the airplane were not injured. A second passenger received minor injuries. The personal flight originated at the St. Paul Downtown Airport, St. Paul, Missouri, at 1000, with an intended destination of Walnut Ridge, Arkansas. A VFR flight plan was filed, and visual meteorological conditions prevailed at the time.

While at 7,500 feet above mean sea level, 18.7 miles south of Waterloo, Iowa, the pilot reported he heard a "pop" from the engine and it started vibrating violently. He stated that at this time he still had partial engine power. The pilot was given vectors to a grass strip near LaPorte City. En route to the airport a complete loss of engine power was experienced. The airplane was landed one mile short of the airport in a field.

The wreckage was inspected by a Federal Aviation Administration Inspector from the Des Moines, Iowa, Flight Standards District Office. This inspector determined that there was no engine continuity between the front of the engine and the accessory drive. There was no movement of the #5 and #6 cylinder pistons when the crankshaft was rotated. No other anomalies were found which would have resulted in the loss of engine power.

The crankshaft, s/n F940, was removed from the engine and was shipped to the NTSB Materials Laboratory, in Washington D.C. for further examination. Inspection of the crankshaft showed a separation between the No. 3 main bearing journal and the No. 5 cylinder crankpin. The fracture contained, "crack arrest features and a smooth fracture surface, typical of high cycle fatigue cracking." See attached Metallurgists Factual Report for more details.

On September 29, 1992, Teledyne Continental Motors issued Mandatory Service Bulletin 92-16 addressing the replacement of Non-VAR crankshafts. This crankshaft was not manufactured from vacuum arc remelted steel. The service bulletin states, "Sufficient field service data has now been accumulated to lead us to believe that it is prudent to require replacement of all non-VAR crankshafts in service with VAR crankshafts." This service bulletin had not been complied with on the accident engine.