On October 30, 2009, at 1130 mountain standard time, a Sauer KR-2S experimental homebuilt airplane, N811RJ, sustained substantial damage during a forced landing following a loss of engine power near Glendale, Arizona. The commercial pilot, the sole occupant, received minor injuries. The pilot was operating the airplane under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed for the aircraft’s first flight, which was originating at the time of the accident. A flight plan had not been filed. The pilot said that immediately after takeoff, at approximately 300 feet above ground level, the airspeed began to decrease. He lowered the airplane’s nose to maintain airspeed. He then noticed that the engine’s rpm was decreasing. The pilot performed a forced landing straight ahead, and during the rollout, the airplane impacted a berm. Both wings were displaced aft and the bottom of the fuselage was broken. The owner/builder of the airplane reported that the airplane’s 20-gallon fuel tank was located between the firewall and the instrument panel. There were eight gallons of fuel in it at the time of the accident. The fuel system was gravity feed to the carburetor. The fuel tank’s vent line passed through the firewall into the engine compartment and terminated near the bottom of the aircraft. The owner/builder reported that the engine’s cooling air flow exited the engine compartment at the same location as the fuel tank’s vent line. He further reported that he believed the exiting airflow may have created a negative pressure in the tank, which reduced the fuel flow to the engine during flight. Two Federal Aviation Administration inspectors examined the experimental Corvair 164 CID engine with the builder. They found no anomalies that would have prevented normal engine operation.