On April 7, 2010, about 1622 eastern daylight time, an amateur-built Revolution Mini 500, N118NR, impacted the ground during a precautionary landing near Middleboro, Massachusetts. The certificated commercial pilot was uninjured, and the helicopter sustained substantial damage. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight conducted in accordance with 14 Code of Federal Regulations Part 91. The flight originated at Plymouth Municipal Airport (PYM), Plymouth, Massachusetts, at 1540. The pilot stated that while he was in cruise flight, he noticed that the water coolant temperature began to increase, followed by an increasing exhaust gas temperature. He elected to perform a precautionary landing in a field, and as he "pulled pitch to cushion the landing," the engine lost power due to overheating. The helicopter then landed hard and rolled over. Examination of the helicopter by a Federal Aviation Administration inspector revealed that it came to rest in a field. The right skid was buckled and the tail boom was severed from the fuselage. Flight control continuity was confirmed from the cockpit through the tail rotor system and from the cockpit cyclic and collective controls. Examination of the engine compartment revealed that a coolant hose leading from the coolant expansion tank to the engine block was disconnected. The water pump housing was removed from the engine and there was no coolant observed or liquid residue in the water pump housing. No traces or stains of coolant were observed in engine compartment or on the outside of the fuselage, however corrosion was observed on the radiator fins. The helicopter was stored in a hanger and previously flown on December 18, 2009, for 1.4 hours and again on March 27, 2010, for 1.3 hours with no mechanical anomalies indicated in the aircraft logbooks.