Accident Narrative
Shortly after takeoff, as the airplane reached an altitude of 300 to 400 feet above ground level, the engine rapidly lost power. The pilot maneuvered the airplane into a gliding configuration and, determining that the airplane could not reach the airport, opted to perform a forced landing in a dry riverbed. During the landing flare, the airplane collided with vegetation and came to an abrupt stop after impacting a large bush.
Maintenance History
A review of the airplane's maintenance records revealed a history of ongoing problems with the idle mixture. In an effort to address these problems, the operator had the carburetor overhauled approximately one week before the accident. However, the mixture discrepancy recurred after the overhaul.
Engine Examination
Following the accident, an examination of the engine disclosed that spark plugs from the number one cylinder, as well as the top number two plug, appeared dark and sooty, with the bottom number two plug being oily. Additionally, the bottom number three and four plugs were covered in lead deposits. Investigators performed an engine run, during which the engine accelerated to 1,600 revolutions per minute (rpm) and ran smoothly, although black smoke emitted from the exhaust stack. After leaning out the mixture, the engine accelerated to 2,100 rpm and the exhaust cleared. A detailed examination of the carburetor revealed no mechanical malfunctions or anomalies other than an excessively low idle fuel flow.