SEA05LA110

After flying in the local area for about 20 minutes, the pilot entered the VFR traffic pattern, and after turning on base leg the aircraft's engine suddenly lost all power. He was therefore forced to execute a power-off landing in an open field, where the aircraft's nose gear encountered some soft terrain and collapsed. A post-accident inspection determined that there was sufficient uncontaminated 100LL fuel on board. During a series of test runs, the engine ran extremely rough at rpm's below 1,500, and it quit a number of times during the run. The engine smoothed out some when the fuel boost pump was turned on to the low position, and smoothed out even more when the pump was turned to the high position. The un-metered fuel pressure was measured, and although it was lower than the specification directed, it was not low enough to account for the very rough running engine. At the end of the series of test runs, the spark plugs were removed, and their white ashy color confirmed that the engine was running extremely lean. Further flow tests and inspections were performed on the fuel system components after they were removed from the aircraft, but the results of these tests did not reveal any anomalies that would be expected to cause the engine to run rough or quit while on a reduced power approach. In addition, the fuel pump was tested to ensure that there was no air leaking past the shaft seal, and the results of that test was negative. At the completion of the testing/inspection process, it could not be clearly determined what was causing the engine's fuel system to run so lean.

On May 30, 2005, approximately 2015 Pacific daylight time, a Beechcraft A-36, N9017V, experienced a nose gear collapse during a forced landing off the north end of Runway 17 at Tacoma Narrows Airport, Tacoma, Washington. The private pilot and his passenger were not injured, but the aircraft, which is owned and operated by the pilot, sustained substantial damage. The 14 CFR Part 91 personal pleasure flight, which departed Tacoma Narrows Airport about 20 minutes prior to the accident, was being operated in visual meteorological conditions. No flight plan had been filed.

According to the pilot, after flying in the local area for about 20 minutes, he had reentered the VFR traffic pattern, and after turning on base leg the aircraft's engine suddenly lost all power. The pilot briefly tried to get the engine restarted, but because of the low altitude, he soon turned his attention to making a forced landing in an open area short of the runway. He touched down in a grassy area off the north end of the runway, and although the flare and touchdown were uneventful, during the landing roll, the aircraft's nose gear encountered some soft terrain and collapsed. When the gear collapsed, the aircraft's wing contacted the terrain.

A post accident inspection of the aircraft revealed that the left fuel tank was about 1/16 full, and the right tank was about 5/8 full, and that the fuel was 100LL that appeared to be uncontaminated. The engine was then started and test run. During the test it ran extremely rough at rpm's below 1,500, and it quit a number of times during the run. The engine smoothed out some when the fuel boost pump was turned on to the low position, and smoothed out even more when the pump was turned to the high position. The un-metered fuel pressure was measured, and although it was lower than the specification directed, it was not low enough to account for the very rough running engine. At the end of the series of test runs, the spark plugs were removed, and their white ashy color confirmed that the engine was running extremely lean.

Because no clear determination could be made as to the source of the rough running, the entire fuel system was removed from the aircraft and taken to Flightcraft, Inc., located in Portland, Oregon, for further testing and inspection. The results of these tests indicated that several of the flow rates for the components were slightly out of specification limits, but according to the Flightcraft technicians, none of the tests indicated any deviation from the specification that was sufficient enough to cause the engine to run rough or quit while on a reduced power approach. In addition, the fuel pump was tested to ensure that there was no air leaking past the shaft seal, and the results of that test was negative.

At the completion of the testing/inspection process, it could not be clearly determined what was causing the engine's fuel system to run so lean.