CEN11LA089

During the landing approach and 1/2-mile from the runway, the engine lost power. During the ensuing forced landing, the airplane impacted a tree and terrain. During postaccident functional testing of the engine, it lost power when the throttle was moved quickly from a low power setting to a high power setting, and became more pronounced as the engine got warmer. The carburetor was removed from the engine and a visual inspection was conducted. A roughness was felt in the accelerator pump while manually moving the control at the carburetor, and very little fuel flow came from the accelerator pump. The carburetor was disassembled and all check valves, ports and vents, the venturi, nozzle bleed holes, carburetor bowl vent channels, and float assembly were cleaned. After reassembly, a much higher fuel output was achieved. The carburetor and accelerator pump were reinstalled on the engine, and all functional checks were normal.

On December 2, 2010, approximately 0430 central standard time, a Cessna 180, N3246D, registered to and operated by the pilot, was substantially damaged when the pilot made a forced landing and impacted terrain after the engine lost power on landing approach to Eppley Airfield (OMA), Omaha, Nebraska. Visual meteorological conditions (VMC) prevailed at the time of the accident. The personal flight was being conducted under the provisions of 14 Code of Federal Regulations (CFR) Part 91 without a flight plan. The pilot, the sole occupant on board. was not injured. The cross-country flight originated in Butte, Montana, with a refueling stop in Philip (PHP), South Dakota, and was ultimately destined for London (LOZ), Kentucky. According to Federal Aviation Administration (FAA) inspectors, the pilot was on landing approach and 1/2-mile from runway 14L when the engine lost power. During the ensuing forced landing, the airplane impacted a small tree and terrain, and came to rest with the nose facing south and the left wing tip in the water. The right wing was compressed, and the horizontal stabilizer was torn off. The engine cowling, both elevators, both ailerons, and both wing tips were damaged. Fuel was seen leaking from the compromised fuel tanks. The airplane was removed to a nearby airport hangar. It was examined on December 3 and 7, 2010. During the examinations, both wing fuel sumps, the engine fuel sump, fuel bowl and carburetor fuel and inlet screens were found clear of contamination. Both magnetos were turned and all spark plugs fired. There were no leaks in the intake system, and all cylinders had satisfactory compression. Valve train continuity was established. On December 9, a bench propeller was installed. During functional testing, the engine lost power when the throttle was quickly moved from a low power setting to a high power setting, and became more pronounced as the engine got warmer. A roughness was felt in the accelerator pump while manually moving the control at the carburetor. Very little fuel flow came from accelerator pump. The carburetor (model number MA-4-5, serial number 3986073-R MF-V) was removed, disassembled, and all check valves, ports and vents, the venturi, nozzle bleed holes, carburetor bowl vent channels, and float assembly were cleaned. After reassembly, a much higher fuel output was achieved. The carburetor and accelerator pump were reinstalled on the engine. All functional checks were normal. The inspectors concluded that the carburetor acceleration pump or the check valve below it had become stuck, resulting in an improper fuel mixture when the pilot attempted to add power, causing the engine to lose power.