CEN24LA313 · Grumman G164 A

Shortly after departure for the aerial application flight, the engine was operating but was not producing adequate horsepower, and the airplane was unable to maintain altitude. The pilot then maneuvered under power lines and executed a forced landing to a rice field. The airplane nosed over in the rice crop and sustained substantial damage to the wings and fuselage. According to the pilot’s weight and balance calculation, at the time of the accident, the airplane was about 350 pounds under the maximum gross weight. The pilot reported that he experienced a similar partial loss of engine power about a week before, but he was able to continue flight by jettisoning the load. No maintenance was performed following that flight. Postaccident examination of the engine found that left magneto would not produce spark, and the carburetor throttle shaft was seized due to foreign material inside a bushing. The reason for the left magneto not able to produce spark was not determined. Disassembly of the carburetor found that the economizer needle was incorrect part. In addition, the graphite packing on the economizer needle was excessively tight, which affected the needle spring’s ability to properly seat the needle in a downward position. It was likely that the economizer needle being allowed to remain in an upward position would result in overly rich fuel mixture. The carburetor was overhauled about 23 hours prior to the accident. The combination of an overly rich fuel mixture and a problem with the ignition system could then result in a loss of engine power.

Verbatim NTSB analysis and probable cause from the NTSB dataset