HISTORY OF FLIGHT On December 14, 2011, about 0933 mountain standard time, a Robinson R22, N4052G, operating using the call sign “Velocity One,” experienced a total loss of engine power while maneuvering about 1.5 miles southwest of Tucson International Airport (TUS), Tucson, Arizona. The commercial pilot entered an autorotative descent that terminated in a hard touchdown. The pilot was seriously injured during the forced landing, and the helicopter was substantially damaged. The helicopter was registered to D3P3 Inc., Tucson, Arizona. The flight originated from TUS about 0841. The pilot was employed by Raytheon Missile Systems, Tucson, Arizona, which operated the helicopter in support of a company work project. The flight was performed under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and a company flight plan was filed. A participant in the test of a Raytheon ground-based proprietary system reported to the National Transportation Safety Board investigator that he was in radio contact with the pilot during the flight. Following prescribed procedures, the pilot was tasked to perform a series of specific maneuvers. The participant and the pilot reported that the maneuvers involved flying an orbital pattern at 2,000 feet with descents to 800 feet, above the ground, which was nearly level. Seconds prior to the crash, the pilot descended to 800 feet. During the descent, the pilot broadcasted the following statement to the local air traffic controller at TUS: “Engine failure, Velocity One engine failure.” No further communications from the pilot were recorded by TUS. The participant did not report hearing the pilot’s emergency transmission. A Raytheon employee witnessed the helicopter perform three descending flights. He reported that in the last descending flight the helicopter went from 2,000 feet above ground level (agl) to 800 feet agl where he hovered. He further stated that as the helicopter turned to head outbound it continued to descend. At about 150 feet agl the front end of the helicopter pitched up and continued to descend until it terminated in a hard landing. The pilot reported after a normal engine start and a couple of hover checks he departed TUS. He flew to the south entering the orbital test pattern and climbed to 4,500 feet mean sea level (MSL). After notifying the testing personnel on the ground that he was airborne he switched his frequency to the tower at TUS. He was instructed to report inbound and outbound on every pass. The pilot further reported after starting inbound on the second pass to waking up in the hospital 5 days later he does not remember anything of the event. He also stated that everything was normal with the flight up to the time of losing his memory. PERSONNEL INFORMATION At the time of the accident, the pilot, age 56, held a commercial pilot certificate with the following ratings; single and multiengine land airplanes, instrument airplane, rotorcraft-helicopter, and glider. He also held a certified flight instructor certificate (CFI) for single engine airplanes and a mechanic certificate with an airframe and powerplant rating. The CFI certificate had an expiration date of October 31, 2013. The pilot reported that the majority of his piloting experience had been in single engine airplanes, and he had accumulated about 967 hours of total flight time. Regarding helicopter experience, the pilot reported about 126 hours in the Robinson R22 helicopter. He had flown the R22 about 2 hours during the past 90-days. His last flight review was accomplished in the accident R22 on September 3, 2011. AIRCRAFT INFORMATION The accident Robinson R22 helicopter, serial number 1765, was manufactured on April 16, 1991 as a Beta model. It was originally equipped with a Lycoming O-320-B2C 160-horsepower engine. On June 28, 2006 a Lycoming O-360-J2A 145-horsepower engine was installed along with all of the equipment and placards required by the Type certificate Data sheet to convert the helicopter from a Beta to a Beta II. The helicopter held a Federal Aviation Administration (FAA) standard classification, normal category, airworthiness certificate. It was utilized by Raytheon without installation of any specialized equipment. The helicopter was also rented by its owner to the public for pleasure flights and flight instruction. MAINTENANCE HISTORY Maintenance logbook records indicate that the R22 was maintained on an annual and 100-hour inspection basis. Major airframe overhauls were performed in 1997, 1999, 2001, and in 2006, at approximate 2,000-hour intervals. The last maintenance entry listed in the aircraft logbook was dated November 25, 2011. On that date, an annual inspection was performed. The listed total time was 9,968.6 hours, at a Hobbs meter time of 1,577.2 hours. On June 28, 2006, a Lycoming O-360-J2A engine, serial number L-31895-36A, was installed in the helicopter following its Lycoming factory overhaul that was completed on May 30, 2006. At installation, the engine’s total time was 4,431.7 hours, and the time since overhaul (and tachometer/Hobbs time) was 0.0 hours. The last maintenance entry in the R22’s engine logbook was dated November 25, 2011. On this date, a 100-hour inspection was performed at a total time since new of 6,008.9 hours. The listed tachometer/Hobbs, and the time since overhaul, was 1,577.2 hours. At the commencement of the accident flight, the Hobbs meter registered 1,595.8 hours. An FAA airworthiness inspector reviewed the maintenance records. The FAA inspector reported that pertinent service bulletins and airworthiness directives were found to have been complied with. No unresolved squawks were listed on the “Aircraft Discrepancy Log.” METEOROLOGICAL INFORMATION Tucson International Airport’s field elevation is 2,641 feet mean sea level. At 0853, TUS reported the following weather conditions: wind calm, 10 miles visibility, scattered clouds at 4,100 feet above ground level, temperature 8 degrees Celsius, dew point 4 degrees Celsius, and altimeter 30.18 inches of Mercury. At 0953, TUS reported the following weather conditions: wind calm, 10 miles visibility, broken ceiling at 4,600 feet above ground level, temperature 9 degrees Celsius, dew point 4 degrees Celsius, and altimeter 30.20 inches of Mercury. A review of the carburetor icing chart located in the FAA Special Airworthiness Bulletin CE-09-35 "Carburetor Icing Prevention" revealed that the helicopter was operating in conditions conducive for serious icing at cruise power. WRECKAGE AND IMPACT INFORMATION FAA inspectors responded to the accident site and performed an initial examination of the wreckage. The accident site was located about 2,570 feet mean sea level at the following approximate coordinates: 32 degrees 6.12 minutes north latitude by 110 degrees 57.43 minutes west longitude. Based upon the National Transportation Safety Board investigator and Robinson participants’ review of accident site photographs, the ground scar signatures of disturbed soil and broken branches appear consistent with the accident helicopter impacting the ground in a nose high attitude such that the aft portion of the tail boom and the lower vertical stabilizer touched the ground first. Thereafter, the skids impacted the ground and both cross tubes broke. The right skid’s toe was found imbedded in the soil and broke off from the remainder of the skid. Several yards further away, additional disturbed vegetation and depressions in the soil were noted. The helicopter was found resting on its right side, with its Plexiglas bubble shattered and its tail boom broken off, but with all rotor blades attached. The helicopter was initially examined on scene by the responding FAA coordinator. The FAA reported observing fuel in the gascolator and fuel tanks. He also stated the air filter was clean of debris and oil was observed leaking from a broken line from the oil cooler. MEDICAL AND PATHOLOGICAL INFORMATION In February, 2011, the pilot was issued his most recent aviation medical certificate as a second class. The certificate was issued with a limitation that required the pilot to wear corrective lenses and possess glasses for near and interim vision. TESTS AND RESEARCH During the helicopter’s subsequent airframe and engine examination, the following was noted: The main rotor blades exhibited upward bending (coning signatures) with no apparent leading edge damage. The continuity of the flight and engine control systems was confirmed. The pilot’s right seat support structure was collapsed in a vertically downward direction. The tail rotor drive shaft was torsionally twisted and broken. The v-belts were observed intact and seated, and all engine accessories appeared undamaged. The gascolator screen was devoid of foreign material, and fuel was observed in the fuel tanks. The engine was started without removing it from the airframe. It was operated over a range of power settings, from idle to full power. After several minutes of normal operation, the engine was shut down. The test run was concluded without evidence of any anomalies. All of the filaments in the instrument panel annunciator lights were visually examined. None were found broken. The aural low rotor warning horn was energized, and it activated. The carburetor heat control knob was found in the down or “OFF” position. The latch which locks the carburetor control knob in the down position was found engaged around the shaft of the control knob. The latch and its attachment bracket were bent upward.