WPR12LA140

During a solo instructional flight, the pilot reported that while on the downwind leg of the traffic pattern, just before turning to the base leg, the helicopter sustained a loss of rotor rpm. The pilot reported that he entered an autorotation and that the throttle was unresponsive. After landing in a marsh area, the helicopter rolled over. A postaccident examination of the helicopter and a successful engine run revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. The pilot's flight instructor related that the pilot had a documented history of inadvertently gripping the throttle on the collective which, while manipulating the collective, would result in overriding the governor and a low rotor condition.

On March 15, 2012, about 1645 Pacific daylight time (PDT), a Robinson helicopter R22 Beta, N290SH, made a hard landing at the Palo Alto Airport, Palo Alto, California, following a loss of engine power. The helicopter was registered to Parker Helicopter LLC, and operated by Sirius Flying, LLC, under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The pilot received a minor injury; the helicopter sustained substantial damage. The local instructional flight departed Palo Alto at 1640 PDT. Visual meteorological conditions prevailed, and no flight plan had been filed.The operator reported that the pilot stated that while on downwind, just prior to turning base, the helicopter experienced a loss of main rotor rpm. The pilot entered an autorotation and noticed that the throttle was unresponsive. During the forced landing into a marsh area, the helicopter rolled over. The pilot, with the assistance of legal counsel, submitted a Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2). The pilot stated that the helicopter and engine had no mechanical failures or malfunctions during the flight until the low rotor horn activated and the engine became unresponsive. The pilot's statement indicated that she had followed all of the procedures in the helicopter pilot operating handbook and utilized the proper checklists for the pre-flight and takeoff. PERSONNEL INFORMATION A review of Federal Aviation Administration (FAA) airman records revealed that the 50-year-old pilot held a commercial pilot certificate with ratings for airplane single-engine land, glider, and instrument airplane. She held a certified flight instructor (CFI) certificate with ratings for airplane single-engine land, and instrument airplane. She was operating the helicopter under a student pilot certificate. The pilot held a third-class medical certificate issued on March 21, 2011. It had the limitations that the pilot must wear corrective lenses. The pilot reported that she had accumulated a total helicopter time of 46 hours with 8 hours as pilot-in-command. Total time in all aircraft was reported as 750 hours. METEOROLOGICAL INFORMATION Weather at the time of the accident at 1647, was wind 270 at 10 knots; temperature 63 degrees Fahrenheit; dew point 55 degrees Fahrenheit. The carburetor icing probability chart from Federal Aviation Administration (FAA) Special Airworthiness Information Bulletin (SAIB): CE-09-35 Carburetor Icing Prevention, June 30, 2009, shows a probability of serious icing at glide power at the temperature and dew point reported at the time of the accident. TESTS AND RESEARCH Investigators examined the wreckage at Plain Parts, Sacramento, California, on April 25, 2012. The engine was started and run at idle until warm then run up to 100 percent. The magnetos were tested, and the right magneto had an excessive rpm drop. The left magneto was good. The engine was shut down, and the bottom spark plug from the number 4 cylinder was removed and cleaned andinstalled in number 3 cylinder bottom position. The number 3 bottom spark plug was moved to the number 4 bottom position. The engine was restarted and ran to 100 percent, and both magnetos tests were within limits. The postaccident examination of the helicopter and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. The pilot's instructor related that she had a history of inadvertently gripping the throttle on the collective which, while manipulating the collective, would result in overriding the governor and a low rotor condition. When this would happen the instructor would have to intervene to correct the low rotor condition. The instructor related that he thought the pilot had learned to correct the low rotor condition if it were to occur. On March 26, 2012, FAA inspectors from the San Jose Flight Standards District Office, met with the pilot and her attorney to discuss the accident. The pilot stated she was unable to furnish any information about the accident due to the event being too traumatic to recall. The attorney stated he had written the statement that the pilot submitted to the NTSB.