On May 28, 1996, about 0711 hours Pacific daylight time a McDonnell Douglas MD-600 helicopter, N600RN, was destroyed during flight tests at Thermal, California. The pilot was not injured. The helicopter was in a flight test program for FAA certification under 14 CFR Part 27. The specific test point at the time of the mishap was part of a flight strain survey and involved cyclic control reversals. The pilot set the parameters and executed the cyclic inputs as planned. Almost simultaneous with the aft movement of the cyclic there was a loud noise and immediate vibrations in the aircraft and controls. There was a chase aircraft for the mission and the chase pilot advised that the tail boom had been struck by a main rotor blade and had separated from the airframe. The pilot of the mishap aircraft then experimented with powered flight, but found that the right yaw was not controllable. He elected to continue the power off autorotation with a controllable left yaw. The autorotation was continued to a vacant field with some piles of brush and other desert debris. The pilot used available rotor rpm, cyclic, and collective control to execute a modified autorotation landing. The resultant landing was onto a brush pile with some skid and main rotor blade damage. The engine exhaust was adjacent to dry brush and grass which resulted in a grass fire. The ground fire destroyed the helicopter.