On October 8, 1994, about 1340 hours Pacific daylight time, N51MB, a Bony MB-1 home built airplane, operated by the owner/pilot, impacted terrain during an uncontrolled descent and was destroyed in Madras, Oregon. There was fire. The uncontrolled descent was precipitated by a flight control malfunction while climbing. The certificated recreational pilot, the sole occupant, received minor injuries. Visual meteorological conditions prevailed and a flight plan was not filed. The personal flight departed from Madras and was conducted under 14 CFR 91. According to the pilot: After passing end of runway 16 at [about] 500 [feet above the ground,] I made slight power reduction and lowered the nose. At this point, the plane started a right turn without my input to do so. I attempted to straighten out but could not obtain left rudder. I continued to fly the airplane and made 2 complete right turns while trying to figure things out and free the controls. On the third turn I saw a powerline and in order to pass over it added power and leveled the wings.... This application of left aileron created a cross controlled situation and I probably spun in from near powerline height. I cleared the line but impacted the ground shortly beyond. According to an FAA Aviation Safety Inspector from Hillsboro, Oregon, the airplane impacted a field located about 1/2 mile southwest of the departure airport. A ground fire had engulfed the wreckage. A determination of pre-impact mechanical malfunctions could not be made due to impact and thermal damage. The FAA inspector also stated that the "pilot's statement is consistent with findings."