WPR09LA025

On October 26, 2008 about 1230 Pacific daylight time, a Naval Aircraft Factory N3N-3, N44848, experienced a total loss of engine power seconds after takeoff from runway 24 at the Rialto Municipal Airport, Rialto, California. The airplane collided with vegetation during the forced landing in an open field about 1/2-mile southwest of the airport. The airplane was substantially damaged. The commercial certificated pilot was not injured. Visual meteorological conditions prevailed during the personal flight, and no flight plan was filed. The flight was performed under the provisions of 14 Code of Federal Regulations Part 91. The pilot reported to the National Transportation Safety Board investigator that the planned round-robin flight originated about 1205 from the Flabob Airport in Riverside. In pertinent part, the pilot reported to the Safety Board investigator that he performed a preflight inspection of the airplane, which was followed by a pretakeoff inspection. The single fuselage fuel tank was full of fuel. All systems appeared to function normally, and he initiated the planned hour-long local area flight. The pilot flew to the Rialto Municipal Airport, landed, and taxied back for takeoff. The accident occurred during the pilot's attempted return flight to Flabob. According to the pilot, during the ensuing takeoff, the "engine power output and acceleration were normal." However, upon climbing about 150 feet above the runway, "the engine smoothly lost power....The power loss felt like the throttle lever [was] being smoothly closed from takeoff power to idle. There was no engine roughness, vibration, or perceived reduced power output preceding the loss of power, and no backfiring or sputtering [was] associated with the power loss." The pilot made a forced landing in a nearby field. Seconds prior to landing, the engine "momentarily and smoothly regained power" for 5 to 7 seconds. Then, it "smoothly lost power a second time, again without roughness, backfiring, or sputtering." During rollout in the field, the airplane collided with a tree, which resulted in impact damage to the wings. Several hours later, the pilot recovered the airplane from the accident site under a police escort. The pilot reported that no fuel was added to the airplane's fuel tank. The pilot reported that he started the engine following normal procedures, and he taxied the airplane for about 15 minutes from the accident landing site to the airport, whereupon its engine was shut down. A company mechanic for the airplane's owner reported to the Safety Board investigator that when the owner purchased the airplane, it was equipped with the accident carburetor. Since the company's acquisition of the airplane, no maintenance had been performed to the carburetor. The Federal Aviation Administration coordinator reported to the Safety Board investigator that the airplane's engine was externally examined, and no evidence of any mechanical malfunction was apparent. Thereafter, theairplane's carburetor was removed and a teardown examination was performed by Aero Engines, Los Angeles, California. During the teardown examination, internal assembly anomalies were found. The owner's mechanic reported that the carburetor's "main jets were [found] too small for the engine application." This model carburetor may be installed on different models of engines. Also, the accident carburetor had been improperly assembled. The mixture shaft was improperly keyed and/or out of alignment with its respective track. This anomaly may result in unreliable mixture settings.