19990304013749A

(.19) On March 4, 1999, at 1453 Alaska standard time, an interstate S-1B1 Arctic tern, tail wheel equipped airplane, N48027, was substantially damaged during a forced landing about 1/2 mile short of runway 33 at Merrill field, Anchorage, Alaska. The solo private pilot sustained minor injuries. The airplane was being operated as a local, personal flight under 14 CFR part 91. The flight departed Merrill field at 1315. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed. The NTSB investigator-in-charge (iic) interviewed the pilot at the scene at 1530 on March 4. The pilot indicated that as he was returning to Merrill field, the engine began to run rough, and the engine speed dropped to about 600 RPM. He applied carburetor heat, but did not notice a change in RPM. During the emergency descent, while in a wings level attitude, engine power momentarily returned to normal, then dropped off again. The pilot said he confirmed his fuel selector was on the left tank, which had more fuel. He stated that he realized he was not going to reach the runway, and completed a forced landing at slow speed into a snow covered area with small trees. The pilot told the iic that during his flight, he exhausted the fuel in the right tank, and was returning to Merrill on the left tank. Initial inspection of the airplane revealed about five gallons of fuel in the left tank, and a small amount in the right tank. A steady stream of clear, blue fluid flowed out of each wing tank sump drain. The cables connecting the throttle,mixture, and carburetor heat controls to the engine were connected, and the carburetor control arms were able to be moved. There was no indication of rotational scratching or bending visible on the propeller. (.4) while approaching the airport, the airplane's engine lost power. The pilot applied carburetor heat with no response. He intentionally ensured the fuel valve was selected to the 'left main' position, because he knew there was about five gallons of fuel in that tank. The right tank was empty. The fuel system in the left tank has two outlet standpipes. The 'left main' loses suction with about five gallons remaining. The 'reserve' standpipe allows these remaining five gallons to flow out of the tank when 'reserve' is selected on the fuel valve. The pilot told the NTSB investigator-in-charge (iic) he did not understand the plumbing for the fuel system. The pilot performed a forced landing at an off airport site. The NTSB iic confirmed that there was fuel in the left tank, and only a trace of fuel in the right tank.