PISTOL CREEK, ID, USA
N206RA
Cessna TU-206G
After departing Pistol Creek Airstrip to the northeast, the pilot executed a course reversal, and continued his climb toward his destination. As he passed back over Pistol Creek, a witness heard a loud popping or sputtering sound, and then the engine went silent. The pilot entered a left hand pattern in an attempt to make it to the northeast end of the runway. Although the aircraft maneuvered in a very tight turn, the pilot was unable to reach the end of the runway, and the aircraft impacted coniferous trees about 50 feet short of the threshold. A post accident inspection of the engine revealed that the number two exhaust valve had failed, destroying a significant portion of the dome of the number two piston. Due to damage to the fracture area of the recovered portion of the valve, no determination could be made as to the initiation source or mode of failure.
HISTORY OF FLIGHT On July 25, 2000, approximately 1130 mountain daylight time, a Cessna TU-206G, N206RA, collided with trees while attempting an emergency landing at a remote airstrip about 40 miles east of McCall, Idaho. The airline transport pilot, who was the sole occupant, received fatal injuries, and the aircraft, which was owned and operated by Arnold Aviation, of Cascade, Idaho, was destroyed. The 14 CFR Part 135 cargo flight, which had just departed Pistol Creek Airstrip en route to Cascade, was being operated in visual meteorological conditions. The aircraft, which was being tracked by company flight following, was not on an FAA flight plan. There was no report of an ELT activation. According to witnesses, after the aircraft landed at Pistol Creek, it was loaded with approximately 500 to 600 pounds of trash/garbage that needed to be flown back to Cascade for disposal. After the engine was restarted, the aircraft was observed taxiing to the southwest end of the airstrip. There, the pilot increased the engine power for what appeared to witnesses to be a pre-takeoff engine check. This action was followed by the aircraft's departure to the northeast. Although this was opposite the direction of the intended flight, it constituted a down-river departure, which is standard procedure at Pistol Creek. After takeoff, the aircraft climbed to the northeast (down-river) for about one mile. The pilot then reversed course and climbed to the southwest (toward his destination of Cascade). As the aircraft passed back over Pistol Creek, witnesses heard a loud popping or sputtering sound, followed by an almost complete loss of any engine noise. The aircraft immediately turned onto what was described as a left downwind for landing on the northeast end of the Pistol Creek runway. As the aircraft continued on a downwind, base and final, it was seen trailing a bluish-white mist or smoke. Although the aircraft was seen banking very steeply during its turn from base to final, it overshot the extended centerline of the runway and angled back in toward the end of the runway from the north. About 200 feet prior to reaching the runway, the aircraft rolled wings-level just prior to impacting the top of several coniferous trees. After the initial impact, the aircraft collided with a number of other trees before coming to rest about 300 feet past the end of the runway and 225 feet to the west of the runway edge. A pilot who departed another airstrip about two miles northeast of Pistol Creek about the same time as the accident aircraft took off, heard the pilot of N206RA transmit "...engine out into Pistol Creek." A witness who worked in the area, and who was near the airstrip at the time the aircraft departed, said that in his opinion, the aircraft did not have enough altitude at the time of the engine failure to be able to maneuver to a point where it could successfully be aligned with the runway for landing. This individual is accustomed to seeing aircraft arrive and depart from this particular airstrip, and is familiar with the altitudes and flight paths usually associated with aircraft maneuvering to land. WRECKAGE AND IMPACT INFORMATION The forested area around the airstrip consists of a mixture of 80 to 100 foot high old growth timber along with younger trees in the 20 to 35 foot range. According to the Valley County Sheriff's Office, the aircraft initially collided with the top a couple of old growth trees approximately 50 feet short of the runway and 240 feet west of its centerline. From there it traveled another 200 feet through the lightly timbered forest on a magnetic track of 160 degrees. The aircraft came to rest at the base of an old growth tree, with the aft right side of the fuselage bent around the lower part of the 30 inch diameter trunk. Except for the most outboard portion of both wings and a small section of the empennage, the entire aircraft suffered extensive thermal damage. An inspection teardown of the engine revealed extensive mechanical impact damage within the number two cylinder. The top of the combustion chamber was extensively scarred, dented, and gouged, and approximately one-third of the dome of the associated piston had been broken away as the result of extensive repetitive impact forces. The head of the exhaust valve had separated from its stem, and was lodged sideways in the exhaust port. Although a portion of the head of the intake valve was still present on its stem, two large pieces of the head had separated and were located in the intake manifold. Both the intake and exhaust valve seats had been torn from their recesses. Most of the pieces of the intake valve seat were recovered. A small piece of the exhaust valve seat was recovered, but the majority of its structure was not located. Both the intake pushrod and the pushrod housing were bent, as was the intake valve stem. The exhaust valve guide had been broken off both above and below the cylinder head boss. Because the exhaust valve stem was missing, and the fracture on the head end of the exhaust valve stem was extensively damaged and distorted from the repetitive impact forces, failure mode and initiation point of the stem failure could not be determined. Therefore a second effort was made to locate the stem portion of the valve in the area of the impact site, but the missing stem could not be found. MEDICAL AND PATHOLOGICAL INFORMATION A toxicological examination of the pilot was conducted by the Federal Aviations Administration's Toxicology and Accident Research Laboratory. No carbon monoxide or cyanide was detected in the blood. No ethanol or drugs were detected in the urine. According to the Valley County Sheriff's Office, the coroner determined that due to the extent of the thermal injuries, an effective autopsy could not be performed. ADDITIONAL DATA AND INFORMATION The wreckage was released on 8/10/00 to Mr. Tracy Barrus, a claims representative for Phoenix Aviation Adjusters. The release of the wreckage took place at Boise, Idaho
A loss of engine power due to the fracture of the #2 cylinder intake valve stem and the puncturing of the #2 piston dome by the intake valve head. Factors include no suitable landing site within the maneuvering abilities of the aircraft, and coniferous trees in the area where the pilot attempted a forced landing.
Source: NTSB Aviation Accident Database
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