CEN24LA313

The improper overhaul of the carburetor and the malfunction of left magneto which resulted in a partial loss of engine power.

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.

On August 9, 2024, about 1600 central daylight time, a Grumman G-164A, N6569, was substantially damaged when it was involved in an accident near Dyess, Arkansas. The pilot was seriously injured. The flight operated under the provisions of Title 14 Code of Federal Regulations Part 137 as an aerial application flight. The pilot stated that when he departed the strip, the engine was performing normally. About ½ mile from the grass strip, the airplane had climbed to 120 ft above ground level, when the pilot could no longer climb or maintain level flight. The pilot maneuvered the airplane below power lines and the airplane’s landing gear contacted a rice field. The airplane settled into the rice and abruptly nosed over which resulted in substantial damage to the fuselage and wings. 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 engine had accumulated 9,652 hours total time in service, and about 1,338 hours since overhaul. 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 actions were recorded following this event. A postaccident examination of the engine at a radial engine repair facility found that carburetor was seized and the left magneto would not produce spark when rotated, but the right magneto did produce spark. The left magneto malfunction to produce spart was not determined. The carburetor was sent to an accessory shop for examination. Disassembly of the carburetor revealed the economizer needle was the incorrect part. In addition, the graphite packing was excessively tight, which affected the needle spring’s ability to properly seat the needle in a downward position. The needle being allowed to remain in an upward position would result in overly rich mixture. A review of the maintenance logbooks found that the carburetor was overhauled and installed back on the engine on August 22, 2023, at a tachometer time of 1,271 hours. The most recent inspection was a combined annual and 100-hour inspection which was logged on December 10, 2023, and the airplane had flown about 38 hours since those inspections.