Accident Overview
On July 8, 2008, at about 1240 mountain daylight time, a Cessna 150F, registration N8647G, suffered a partial loss of engine power during the initial climb after a touch-and-go landing at Kalispell City Airport, Kalispell, Montana. The certified flight instructor (CFI) and a student pilot were conducting an instructional flight under 14 Code of Federal Regulations Part 91. Visual meteorological conditions were present, and no flight plan had been filed. The airplane was destroyed by impact forces and a subsequent fire. Both the CFI and the student pilot sustained serious injuries.
Flight Narrative
According to the CFI's accident report, he and the student first flew to Glacier Park International Airport where they performed about 10 touch-and-go landings. They then returned to Kalispell and completed two more touch-and-goes. The accident occurred during the climb after the third takeoff. The CFI reported that the "engine sputtered" just before reaching the departure end of runway 13. He took control and manipulated the throttle; the airplane seemed to resume climbing. However, upon reaching between 400 and 500 feet above ground and turning onto the crosswind leg, the engine lost a significant amount of power. The airplane's pitch attitude decreased, and despite the CFI's efforts, it descended into terrain. The wreckage came to rest about 1,000 feet beyond the departure end of the runway.
Witness Observations
Several witnesses observed the accident. A mechanic located near the airport reported seeing the airplane take off and hearing the engine sputter and quit when it was about 30 feet above ground. He then heard the engine restart when the airplane was between 200 and 300 yards past the runway end and climbing. He observed the airplane begin a right turn, and the engine lost power again. The airplane quickly descended in a slight nose-down attitude. Buildings blocked his view of the actual crash, but he saw smoke rising from the site 2 to 3 minutes later. A bystander rescued the crew from the wreckage before the fire destroyed the airplane.
Examination of Aircraft and Components
Examiners from the Federal Aviation Administration (FAA), Cessna Aircraft Company, and Teledyne Continental Motors inspected the wreckage. The FAA noted that the carburetor's accelerator pump functioned and evidence of fuel was present. The residual fuel was field-tested: it lacked a blue tint consistent with 100LL aviation fuel and did not smell like avgas, according to the FAA's principal maintenance inspector. No preimpact internal engine or airframe component failures were reported.
The carburetor (Precision Model MA-3SPA, serial number BE02451), its air inlet ducting, air filter, and a fuel sample were sent to the NTSB's Materials Laboratory. Lab examination found granular material on the carburetor throat walls and inside the inlet duct. The material consisted of very fine dust-like particles and larger multi-colored rounded sand particles (0.020–0.040 inch diameter). The fine material was less than 0.001 inch. The idle jet was substantially blocked with the fine granular material, and the main jet was partially obstructed. The fuel sample contained plastic shavings and clumps of mixed fine and coarser granular material, similar to that found in the carburetor jets.
Maintenance and Fuel Records
The airplane owner reported that the aircraft was not frequently used. The logbook showed its most recent annual inspection on February 22, 2008, at a total time of 4,228.7 hours. About 10 months earlier, on April 24, 2007, the total time was 4,219.9 hours. The airplane had operated only 8.8 hours during that period. The FAA provided a fuel receipt dated July 3, 2008, bearing N8647G's registration, documenting acquisition of 18.54 gallons of aviation fuel at a Montana airport.