ANC05LA018

The commercial certificated pilot reported that while the airplane was in level cruise flight at 5,000 msl, he noted a rough running engine and a slight reduction in engine rpm, which was followed by a rapid loss of engine power, and subsequent loss of altitude. He was unable to restore adequate engine power to maintain level flight, and selected a snow-covered area as a forced landing site. During the landing roll, the airplane's nose landing gear collapsed, and the airplane nosed over. The airplane sustained structural damage to the wings and fuselage. An FAA inspector reported that during his inspection of the accident airplane's engine, he discovered that a significant portion of the exhaust valve had broken free from the exhaust valve stem in the number 1 cylinder. He stated that the broken portion of the valve subsequently entered the number 1 cylinder combustion chamber and damaged the piston.

On December 14, 2004, about 1600 Alaska standard time, a wheel-equipped Piper PA-28-140 airplane, N801FS, sustained substantial damage during an off airport forced landing following a loss of engine power, about 35 miles southeast of Sleetmute, Alaska. The airplane was being operated as a visual flight rules (VFR) cross-country personal flight under Title 14, CFR Part 91, when the accident occurred. The commercial certificated pilot and the two passengers sustained minor injuries. Visual meteorological conditions prevailed, and a VFR flight plan was in effect. The flight originated about 1335, from the Lake Hood Airstrip, Anchorage, Alaska, and was en route to Bethel, Alaska, when the accident occurred.

During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on December 19, 2004, the pilot related that he had to alter his intended flight path slightly due to low weather conditions along his route. He said that while the airplane was in level cruise flight at 5,000 msl, he noted a rough running engine and a slight reduction in engine rpm. He said that emergency procedures did not remedy the engine roughness, which was followed by a rapid loss of engine power, and subsequent loss of altitude. The pilot said that he was unable to restore adequate engine power to maintain level flight, and he selected a snow-covered area as a forced landing site. During the landing roll on the soft, snow-covered terrain, the airplane's nose landing gear collapsed, and the airplane nosed over. The airplane sustained structural damage to the wings and fuselage.

A Federal Aviation Administration (FAA) airworthiness inspector from the Anchorage Flight Standards District Office (FSDO), traveled to Bethel after the airplane had been recovered from the remote accident site. During a telephone conversation with the NTSB IIC on September 7, 2005, the FAA inspector reported that during his inspection of the accident airplane's engine, and after removing the number 1 cylinder from the engine crankcase, he discovered that a significant portion of the exhaust valve had broken free from the exhaust valve stem. He stated that the broken portion of the valve subsequently entered the number 1 cylinder combustion chamber. The number 1 piston sustained significant amount of damage, including a large hole in the top portion of the piston assembly.