ANC99LA009

The certificated commercial pilot and two passengers departed a remote airport on an air taxi flight. After takeoff, the pilot climbed the airplane to about 1,000 feet msl. The engine began to run rough. Emergency engine procedures did not remedy the roughness. The airplane began losing altitude, and the pilot selected a forced landing area in a slough. The airplane collided with trees, and received damage to the wings, fuselage, and empennage. A sample of fuel from the left reservoir tank was murky and silty, and contained a small amount of water. Laboratory analysis of the fuel sample revealed the fuel met the standards for aviation fuel. Contamination in the fuel sample consisted of silt and dust, microscopic fibers, and paint chips. After recovery, examination of the engine did not find any mechanical malfunction. The engine produced full power on a test stand.

On October 26, 1998, about 1735 Alaska standard time, a wheel equipped Cessna 207A airplane, N73533, sustained substantial damage during a forced landing, about 3 miles west of Aniak, Alaska. The airplane was being operated as a visual flight rules (VFR) on-demand passenger flight under Title 14 CFR Part 135 when the accident occurred. The airplane was operated by Arctic Circle Air Inc., Anchorage, Alaska. The certificated commercial pilot, and the two passengers, received minor injuries. Visual meteorological conditions prevailed. VFR company flight following procedures were in effect. The flight originated at the Aniak Airport, about 1732.

The director of operations for the operator reported the flight was a charter flight to Kalskag, Alaska, which is located about 22 miles west of Aniak. After takeoff, the pilot climbed the airplane to about 1,000 feet msl. The engine began to run rough, and emergency procedures did not remedy the roughness. In the NTSB Pilot/Operator report (NTSB form 6120.1/2) filed by the operator, the pilot included a written statement. The pilot said that after performing the engine emergency procedures, the engine began slowing down, and he knew the airplane would not remain airborne. The pilot selected a forced landing area in a slough that contained trees. The airplane collided with trees, and received extensive damage to the wings and fuselage. The empennage was torn from the fuselage.

A Federal Aviation Administration (FAA) airworthiness inspector from the Anchorage Flight Standards District Office, traveled to the accident scene on October 27, 1998, and examined the airplane. The inspector reported the left wing fuel tank was extensively damaged and breached. He obtained about 160 milliliters of fuel, primarily from the left reservoir tank, and included a small amount gathered from the gascolator. The fuel sample was murky and silty, and contained a small amount of water. Examination of the fuel from the right wing revealed it was clean and bright, and did not contain any visible contaminants.

The fuel sample gathered by the FAA inspector was examined at a laboratory in Anchorage, Alaska. The fuel sample met the specifications for aviation fuel. Analysis of the visible contaminants in the fuel sample revealed that 85 percent of the contaminants were silt and dust, 10 percent were white translucent fibers, and 5 percent were paint chips.

The engine remained attached to the airframe at the accident site, until the wreckage was recovered in February, 1999. The engine was examined in Anchorage on February 24, 1999. The examination revealed the magnetos were timed within specification and produced spark at all leads. The massive electrode spark plugs were dry and had a gray appearance. Valve train continuity was established, and thumb compression was present in all cylinders. The oil filter was free of any visible metal. The fuel control inlet filter screen was free of contaminants. The fuel manifold assembly had been opened, and examined by FAA inspectors during their initial visit to the airplane at the accident scene. The screen was free of contaminants.

On February 25, 1998, the engine was placed on an engine test stand and started. The engine produced full power.