ERA25LA062

The pilot, who was also a repairman who had recently completed maintenance on the airplane, reported that the recently installed engine had been running poorly and had previously experienced a loss of power during ground operations. While troubleshooting, the pilot discovered that the carburetor floats were improperly installed, so he replaced the carburetor floats and spark plugs. Maintenance records indicated that the carburetors were repaired three days before the accident, and the engine was reported to have operated satisfactorily following the maintenance. Additional ground runs and high-speed taxi tests were completed without reported anomalies. On the day of the accident, the pilot planned to perform a functional test flight and reported that all engine indications were normal during the takeoff roll and initial climb. While climbing through about 200 ft msl, the engine lost power without warning. The pilot initiated a left turn in an attempt to remain near the airport and maintain glide speed; however, the airplane descended into trees. The pilot was seriously injured and the airplane’s fuselage was substantially damaged during the accident sequence. A postaccident examination of the engine revealed continuity throughout the crankshaft and valve train, normal compression on all cylinders, and no evidence of lubrication deficiencies, overheating, detonation, preignition, or other internal mechanical malfunctions. Examination of the carburetor for the engine’s number 2 and 4 cylinders revealed that its piston slide had seized due to a buildup of oxides in the chamber top cavity where the piston slide shank moved. No contamination was observed within the carburetor, and no other anomalies were revealed during the examination of the engine or fuel system. The engine manufacturer stated that a seized piston slide could result in reduced engine performance, rough engine operation, or improper fuel delivery to the cylinders. Given this information, it is likely that oxide buildup in the carburetor was not identified and remediated during the recent maintenance of the carburetors that had occurred just before the accident, which resulted in the seizure of its piston slide, and the subsequent total loss of engine power during the accident flight.

On November 27, 2024, about 1319 eastern standard time, an experimental amateur-built Bot Journey airplane, N814B, was substantially damaged when it was involved in an accident near Ocean Isle Beach, Norh Carolina. The pilot received serious injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 test flight. The test flight occurred at Odell Williamson Municipal Airport (60J), Ocean Isle Beach, North Carolina. According to the pilot, who was also a light sport aircraft repairman, the airplane had recently been equipped with a used Rotax 912ULS engine that had been running poorly. A few days before the accident, the engine experienced a total loss of power during ground operations while a flight instructor was conducting ground runs, which included takeoff accelerations on the runway. During troubleshooting, the pilot discovered damaged and improperly installed carburetor floats. The pilot subsequently replaced the carburetor floats, replaced all eight spark plugs, and performed additional maintenance. The pilot and flight instructor then conducted several ground runs and high-speed taxi tests over a two-day period without reported anomalies. On the day of the accident, the pilot initiated a functional test flight from runway 06 at 60J. The pilot reported that all engine indications were normal during the takeoff roll and initial climb. While climbing through about 200 ft msl, the engine lost power without warning. The pilot initiated a left turn in an attempt to remain near the airport and maintain glide speed; however, the airplane descended into trees. Postaccident examination of the airplane revealed impact damage to the engine and firewall assembly. The propeller sustained damage, with two blades separated at the hub and the third blade fractured near the hub. Examination of the engine revealed continuity throughout the crankshaft, valve train, and accessory systems. Thumb compression was obtained on all cylinders during manual rotation of the propeller shaft. Internal engine components exhibited evidence of normal lubrication and no indications of overheating, scoring, detonation, preignition, or other mechanical malfunctions. The fuel system was examined, and the fuel lines were secure and free of obstructions. Both carburetors were removed and inspected. The carburetor for cylinders 1 and 3 contained a small amount of fuel and no anomalies were noted. The floats were of the updated design, were within weight limits, and the carburetor slide, diaphragm, and throttle components operated normally. Examination of the carburetor for cylinders 2 and 4 revealed that the piston slide was seized in the fully down position and did not move freely within the carburetor body. After disassembly, the piston slide remained seized within the chamber top and could neither be separated nor rotated. The diaphragm was undamaged, and the throttle plate rotated normally throughout its full range of motion. No contamination wasobserved within the carburetor float bowl, and the floats were of the updated design and within allowable weight limits. The NTSB Materials Laboratory examined the carburetor for cylinder 2 and 4 and found that the piston slide was seized due to a buildup of oxides in the chamber top cavity where the piston slide shank moved in and out. A review of the maintenance records revealed that, three days before the accident, the carburetors were repaired in accordance with the Rotax maintenance manual, and the carburetor floats were replaced with the updated Rotax float design. The maintenance entry further stated that the engine was operated satisfactorily after the maintenance was completed.