20060825018819A

(-23) Carburetor float stuck in full rich during acrobatic maneuvers. Manual rotation of engine was smooth with no mechanical resistance. No other mechanical engine or related system malfunction noted. Please see attached airman narratives for additional information regarding conduct of flight and pilot situational responses. Pilot-in-command statement: at approximately 13:10 PDT, stearman N58980 departed runway 13L at rhv, California for a local VFR flight. I, the pilot-in-command, privacy data omitted was the pilot operating the controls during the incident. I occupied the front cockpit during the flight. Purpose of the flight was to check the Boeing's aerobatic performance parameters due to it being equipped with long span stall strips on all four wings and to familiarize the owner to determine if he would like to learn some mild maneuvers to perform. After some power on and power off stalls, to determine speeds, two wingover maneuvers (l&r) were satisfactory as well as an aileron roll to the left. At approximately 5000 feet, I attempted a loop at 145 mph. Full throttle was applied at about 30-40 deg. Above the horizon. It was quickly apparent that the loop wasn't going to followa rounded trajectory as the airspeed bled off too rapidly. This was an observed 3 g pull up. At the apex, I decided to allow the aircraft nose to drop and did a half roll to upright on an approximate 30-40 degree down line. I checked in the mirror to see if the rear seat pilot was agreeable to continue and he gave me a thumbs-up sign of approval. I was still on the down line when we both noticed the flames from the exhaust, apparently, blazing full length of the fuselage beyond the rear cockpit. I yawed the airplane right to observe if the flames would separate. They did not. The engine didn't respond to throttle and I determined that the engine had quit. Mixture was shut off and the fire went out. Then a re-start was attempted which only resulted in white smoke coming out the exhaust. I had already diverted toward the valley as we were some 8 or 9 miles nw from E16 airport and two ridge lines of hills e of highway 101. Seconds after the fire went out I indicated to the rear seat pilot the field I had chosen parallel to highway 101. He indicated agreement with a head nod. It was a very suitable field for an off airport landing but had electric or phone lines and some trees near theedge. A slight turn was required to become aligned with the landing area. Mixture was at idle cutoff and fuel and magnetos were turned off after the air start attempt and the rear seat pilot turned off all electrical. I had been conserving altitude to clear the obstacles and was very near stall when we cleared. I released some back pressure in an attempt to gain some more momentum for a flare. When I brought the airplane level it stalled at some height. The right wing started to drop just at the stall break. The aircraft pitched forward and, with no power and no momentum for elevator control, continued over onto its back using the stopped prop for a fulcrum. The aircraft came to rest inverted.