Cessna 150F N8647G accident near Kalispell, Montana

Probable cause

A partial loss of engine power during initial climb due to fuel system contamination by a foreign substance. Contributing to the accident was the uneven terrain.

NTSB analysis

The certified flight instructor (CFI) and student took off for an instructional flight during which a series of touch-and-go landings were performed. During initial climb out for the 13th takeoff, the engine sputtered, regained power, and then lost power on the crosswind leg. The CFI took the controls and attempted a forced landing. The airplane impacted the uneven ground, collided into a fence, and was destroyed by fire. During the subsequent examination of the airframe and engine, no evidence of any preimpact mechanical malfunction was found. The engine's carburetor assembly was examined by the Safety Board Materials Laboratory. Granular material was found on the walls of the carburetor's throat and in the interior of the inlet duct. The idle jet was substantially blocked and the main jet was partially obstructed. Similar fine granular material and clumps of mixed fine and coarser granular material were also found inside the carburetor jets. Because the granular sand-like material was found in both the fuel and air sides of the carburetor, it is evident that the foreign substance entered the carburetor during flight. The airplane had a history of infrequent usage. During the 10-month period from April 2007 to February 2008, the airplane had been operated for only 8.8 hours.

Text from the NTSB. Open the NTSB docket for LAX08LA212 for the full record.