ERA09LA284

The pilot stated that during the downwind leg for a practice autorotative landing while flying at 600 to 625 feet mean sea level with the governor on, he applied carburetor heat and five seconds later he perceived by sound that the engine lost power. He turned onto base leg, and attempted to restart the engine but allowed the main rotor rpm to decrease to 87 percent. He stopped his restart attempts and initiated descent for an autorotative landing. He maintained 65 knots during the descent and when the flight was at 40 feet with obstacles ahead (mobile homes), he intentionally slowed the helicopter. At 20 feet above ground level he pulled collective which activated the main rotor rpm warning and resulted in a hard landing. Postaccident examination of the helicopter revealed the throttle, mixture, and carburetor heat control rigging were correct. No contaminants of the fuel system were noted. Following recovery of the helicopter with the main rotor blades removed, an FAA inspector observed the engine start and operate to idle rpm. The conditions (temperature and dew point) were favorable for serious carburetor icing at only glide power.

On May 7, 2009, about 0800 eastern daylight time, a Robinson R22 Beta, N456SH, registered to November Alpha LLC, operated by a private individual, was landed hard during an autorotative landing near Winter Haven, Florida. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 Code of Federal Regulations (CFR) Part 91 personal flight from Winter Haven’s Gilbert Airport (GIF), Winter Haven, Florida. The helicopter was substantially damaged and the certificated private pilot was not injured. The flight originated from GIF about 0745. The pilot stated that after takeoff he remained in the traffic pattern for runway 11 and executed practice autorotative landings with a power recovery. During the downwind leg for another practice autorotative landing while flying at 600 to 625 feet mean sea level with the governor on, he applied carburetor heat and five seconds later he perceived by sound that the engine quit. He turned onto base leg, and attempted to restart the engine but allowed the main rotor rpm to decrease to 87 percent. He stopped his restart attempts and initiated descent for an autorotative landing. He maintained 65 knots during the descent and when the flight was at 40 feet with obstacles ahead (mobile homes), he intentionally slowed the helicopter. At 20 feet above ground level he pulled collective which activated the main rotor rpm warning and resulted in a hard landing. Examination of the accident site by a Federal Aviation Administration (FAA) airworthiness inspector revealed the helicopter landed 100 yards short of the mobile homes. A portion of the tailboom was separated and the main rotor blades were bent and wrinkled. The throttle, mixture, and carburetor heat control rigging was found to be correct. The fuel gascolator and bowl were clean. Following recovery of the helicopter with the main rotor blades removed, an FAA inspector observed the engine start and operate to idle rpm. According to a FAA Special Airworthiness Information Bulletin, based on the temperature and dew point (75 and 66 degrees Fahrenheit respectively), the conditions were favorable for serious carburetor icing while at glide power.