On April 27, 2017, about 0945 mountain standard time, a Schweizer 269C, N521AR, was substantially damaged subsequent to a hard landing near Coolidge, Arizona. The helicopter was operated by Canyon State Aero, LLC under the provisions of 14 Code of Federal Regulations Part 91. The private pilot, the sole occupant, sustained minor injuries. The cross-country instructional flight departed Falcon Field Airport (FFZ), Mesa, Arizona, about 0915 with a planned destination of Coolidge, Arizona. Visual meteorological conditions prevailed and no flight plan had been filed. The pilot reported that the purpose of the flight was training in preparation towards a commercial certificate. While traveling south about 2,000 to 2,100 ft mean sea level, and 65 to 70 knots airspeed, he scanned manifold pressure, altitude, airspeed and engine/rotor rpm. Everything appeared normal. Shortly thereafter, he noticed a change in the sound of the engine, and that the rpm gauge indicated a drop. The pilot checked the throttle to make sure it had not rolled back out of the friction. He then rolled the throttle further, however there was no response. He rolled it slightly off and again there was no response. The helicopter was close to the ground at this time, so he chose a spot to land on the open desert floor. Just before touchdown, he flared and the helicopter impacted the ground hard and rolled over onto its right side. During the postaccident engine examination, the bottom spark plugs were removed. According to the Champion Spark Plugs Check-A-Plug Chart AV-27, the spark plug electrodes displayed coloration consistent with normal wear. The crankshaft was rotated by hand with no binding noted. Thumb compression was observed in each cylinder. Mechanical continuity was established to the accessory section. During the engine control continuity check, the throttle arm at the fuel injector servo would not move when a corresponding input was applied at the collective throttle grip. Further examination revealed that the throttle cable was found to have separated within the cable housing, and in an area where the cable housing was slightly bent. The cable housing was securely mounted at each end and exhibited no visual evidence that it had been damaged during the accident sequence. The cable was removed from the housing. There was no kinking or evidence of binding observed. The cable was found worn and had separated near the servo end about 1 inch from where it swaged to the rigid portion. The engine was then prepared for an engine run. The engine was started with the starter using standard procedures. Once the engine was at operating temperature, the throttle was advanced to an rpm to facilitate a magneto check utilizing the cockpit mounted ignition switch. Both magnetos operated at each of their respective switch detents and within manufacturers specifications. The engine ran smoothly throughout the operational check. The engine manufacturer participant reported that the subject cable is not controlled by any hourly or calendar life limits, and there was no way to disassemble the cable from the housing to facilitate an internal examination. Further examination of the helicopter maintenance logbooks did not provide a history for the subject cable.