'THIS CASE WAS MODIFIED APRIL 8, 2008." On October 8, 2006, about 1312 Pacific daylight time, a Robinson R22 Beta, N821SH, experienced a loss of engine power during initial climb from the Cable Airport, Upland, California. The certified flight instructor (CFI) took the flight controls from his private pilot student. The CFI autorotated into a gravel pit adjacent to runway 24. The touchdown was hard, and the helicopter was substantially damaged. Neither the CFI nor student was injured during the instructional flight. The helicopter was owned and operated by Silver State Helicopters, LLC., North Las Vegas, Nevada. Visual meteorological conditions prevailed, and no flight plan had been filed. The flight was performed under the provisions of 14 Code of Federal Regulations Part 91, and it originated from Chino, California, about 1230. The CFI reported to the National Transportation Safety Board investigator that during the first portion of the flight no evidence of any mechanical malfunction was apparent. Upon arriving at Chino they made an approach to the southeast helicopter pads and then departed. During the subsequent climb out from the Cable Airport, the engine and main rotor rpm decreased. The CFI reported that an effort was made to correct for the low engine/rotor rpm by rolling on (increasing) throttle and lowering the collective, but there was no response from the throttle control. Thereafter, the CFI took the controls from his student and initiated an autorotative descent. Touchdown was hard, and the main rotor blades severed the tail boom. After securing the helicopter the CFI stated that he inspected the throttle linkage. He reported that something appeared disconnected behind the firewall. "When rotating the throttle from full open to full close, the push/pull tube that connects to the carburetor does not move." Under the direction of the Safety Board, the helicopter was examined by the Federal Aviation Administration (FAA) coordinator. The FAA coordinator reported that he examined the helicopter's throttle over travel spring assembly. He observed evidence that it had been removed and reinstalled improperly on a previous occasion. The helicopter's maintenance records did not reflect this maintenance, or any maintenance in this area. The FAA coordinator additionally reported that the specific examination finding was that the upper rod end bearing was separated from the lower portion of the rod because it had not been safety wired as required. He opined that following this disconnection, all throttle control capability was lost.