Accident Overview
On December 2, 2010, at approximately 0430 central standard time, a Cessna 180, registration N3246D, operated by the pilot, sustained substantial damage following a forced landing after the engine lost power during the approach to Eppley Airfield (OMA) in Omaha, Nebraska. The pilot, who was the sole occupant, was not injured. Visual meteorological conditions prevailed at the time of the accident. The flight was conducted under 14 CFR Part 91 without a flight plan. The cross-country flight originated in Butte, Montana, with a refueling stop in Philip, South Dakota, and was destined for London, Kentucky.
Sequence of Events
According to Federal Aviation Administration (FAA) inspectors, the pilot was on landing approach and approximately half a mile from runway 14L when the engine lost power. During the forced landing, the airplane impacted a small tree and terrain, coming to rest with the nose facing south and the left wing tip in water. The right wing was compressed, and the horizontal stabilizer was torn off. Damage also occurred to the engine cowling, both elevators, both ailerons, and both wing tips. Fuel leaked from the compromised fuel tanks.
Examination and Findings
The aircraft was moved to a nearby airport hangar and examined on December 3 and 7, 2010. Inspectors found both wing fuel sumps, the engine fuel sump, fuel bowl, and carburetor fuel and inlet screens clear of contamination. Both magnetos turned and all spark plugs fired. No leaks were present in the intake system, and all cylinders had satisfactory compression. Valve train continuity was established.
On December 9, a bench propeller was installed for functional testing. During testing, the engine lost power when the throttle was quickly moved from low to high power, with the issue becoming more pronounced as the engine warmed. A roughness was felt in the accelerator pump while manually moving the control at the carburetor, and very little fuel flow came from the pump. The carburetor (model MA-4-5, serial number 3986073-R MF-V) was removed, disassembled, and cleaned of all check valves, ports, vents, venturi, nozzle bleed holes, carburetor bowl vent channels, and float assembly. After reassembly, much higher fuel output was achieved, and the carburetor and accelerator pump were reinstalled. All functional checks then returned to normal.
Probable Cause
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.