20001112038819A

(-23) Four miles from the avra valley airport at 4500 ft. MSL the engine RPM dropped from 2500 cruise to 1500 RPM. The pilot stated that advancing the throttle only further reduced engine RPM. The pilot tried carburetor heat without any success. The pilot made an off airport landing two miles southeast of the airport on rought terrain in the desert. The nose gear collapsed and the a/c came to rest inverted. The a/c sustained substantial daamge. The pilot and his passenger were not injured. -end- (.4) the airplane made a forced landing in an open desert area and came to rest inverted after colliding with desert brush. Earlier that morning, a 20-minute flight from home base to a local airport was conducted for the purpose of flight training for the pilot's son. Prior to the return flight, the son informed his father that during his flight the engine would balk, sputter, and cough every time he added power. When asked by his father if he was engaging the throttle too quickly, the son replied that he did not. The CFI was asked if he had noticed any problems with the engine. He replied that there was nothing unusual experienced with the engine. No discrepancies w ere noted during the taxi, takeoff roll, or initial climb out. About 15 minutes into the flight the pilot noted a drop in RPM. He made several unsuccessful attempts to troubleshoot the problem. When he applied carburetor heat, there was a further loss of RPM. The external examination of the engine disclosed no discrepancies. The engine was test run. The first engine start was unsuccessful. Ether was sprayed on the intake filter and several more attempts were made to start the engine. The engine would start, but would only run for 10 seconds during those attempts. The carburetor was removed and inspected. Fuel was observed in the bowl with unrestricted movement of the floats, and the main jet appeared free of debris. The carburetor was sent to the manufacturer for further examination. During the bench test when fuel was initially applied, it flooded the carburetor. When the outside of the carburetor was manually tapped the flooding stopped. No further discrepancies were noted with the bench test. An internal examination revealed that the float valve retractor clip was adjusted too loosely on the float and needle to ensure a positive retraction of the needle. This allowed for the clip clip to stick in the down position and allowed an increased amount of fuel to enter the carburetor. A blue silicone substance was found around the accelerator pump sump retainer and sump. The accelerator pump discharge check valve was leaking and not sealing properly. No further discrepancies were noted.