NTSB Identification: WPR09FA326
14 CFR Part 91: General Aviation
Accident occurred Sunday, July 05, 2009 in South Lake Tahoe, CA
Probable Cause Approval Date: 08/07/2012
Aircraft: CESSNA 150, registration: N51172
Injuries: 1 Fatal.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
Witnesses stated that the airplane lifted off and climbed to about 100 feet above the runway in an unusually high nose-up pitch attitude before turning left and descending into terrain. The pilot transmitted a "mayday" call on the Common Traffic Advisory Frequency just before the airplane entered the left turn. During postaccident testing of the engine, excessive vibration occurred as the rpm increased, and one of the spark plugs became excessively sooty, indicating an overly rich fuel/air mixture. The carburetor was then replaced and the engine ran normally at all power test points; the previously sooty spark plug was normal after this test. The accident carburetor was then examined, and a pin that secures the carburetor’s metal floats to their pivot point in the carburetor bowl was missing. Marks indicating contact on the edge of a float and on the side of the bowl were found, indicative of rubbing interference with the side of the bowl. The float-to-bowl contact likely altered the fuel quantity in the bowl, which likely created an overly rich mixture that would have further reduced available engine power at the high density altitude at which the airplane was being operated. The density altitude was calculated to be 8,708 feet. High density altitude adversely affects airplane climb performance and requires pilot vigilance to maintain adequate airspeed during takeoff and climb.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: A partial loss of engine power due to a malfunctioning carburetor and the pilot’s failure to maintain adequate airspeed while maneuvering to return to the runway. Contributing to the accident was the high density altitude. Full narrative available
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