On November 12, 2006, at 1228 Pacific standard time, a Ryan Navion B, N5348K, experienced a loss of engine power during the takeoff initial climb from runway 6 and made a forced landing in an open field near Flabob Airport (RIR), Riverside, California. The commercial pilot/owner operated the airplane under the provisions of 14 CFR Part 91 as a personal flight. The airplane sustained structural damage to the fuselage and wings. The pilot and a private pilot passenger were not injured. Visual meteorological conditions prevailed for the local area flight, and no flight plan had been filed. The flight was destined for El Monte Airport (EMT), El Monte, California. The National Transportation Safety Board investigator-in-charge (IIC) interviewed the pilot. The pilot reported that the day before the accident he had flown from EMT to Corona Municipal Airport (AJO), Corona, California, and refueled the airplane. He then flew back to EMT. On the day of the accident, they had departed for EMT earlier that morning to attend an airshow at RIR. There were no problems encountered with the flight the day before or the earlier flight to RIR. The pilot reported that the run-up at RIR for the return flight to EMT was normal. About 50-100 feet above ground level (agl), with no remaining runway, the engine started to sputter. The pilot stated that he had already retracted the landing gear before the engine began to run rough. Shortly after the engine began to sputter it lost all power; the pilot placed the landing gear in the down position and noted that they were losing altitude. He chose an open field to make the emergency landing, and reported that the landing gear was only partially extended when the airplane touched down in the open field. The landing gear collapsed after touchdown, which caused damage to the wings and fuselage; the airplane came to rest upright and was lying on one of its wings. The propeller also struck the ground. A Federal Aviation Administration inspector performed a post accident examination of the airplane on December 5, 2006. The examination revealed that an excessive amount of air was leaking into the fuel system through worn seals in fuel selector valve. The investigator also observed air leaking into the fuel system through the gascolator gasket. Service Bulletin No. 101A, dated August 23, 2005, was issued by the type certificate holder, Sierra Hotel Aero, Inc., regarding the fuel system fuel selector valve, serial number NAV-4-002 thru NAV-4-2561. The Service Bulletin states: "Previous design has a history of wear, causing internal leakage, valve step air ingestion and improper valve selector positioning. Internal leakage of the valve is suspected in several cases resulting in inadvertent fuel transfer between main and auxiliary tanks. Improper valve selector positioning and air ingestion has been implicated in several crashes - some fatal. The improper positioning is more likely to occur as detents in the original body wear, making positive tank selection less obvious." According to the airframe logbook, the airplane had a total time of 4,839.2 hours. An annual inspection had been completed on November 1, 2006, and the airplane had flown approximately 4 hours since the inspection. There was no indication in the logbook that the service bulletin had been performed. ADDITIONAL INFORMATION Sierra Hotel Aero, Inc., issued mandatory Service Bulletin No. 106A on May 1, 2007, which addressed an inspection of the fuel selector valve at every annual inspection unless terminating action had been accomplished through compliance of Navion Service Bulletin No. 101A. (http://www.navion.com/servicebulletins/SB%20106A.pdf)