GAA17CA251

The pilot of the experimental amateur-built helicopter, which had a clockwise rotating main rotor blade, reported that he took off from private property with a right crosswind. He added that, when the helicopter reached 20 to 30 knots, about 50 ft above the ground, he turned southwest, which resulted in a right quartering tailwind. He further added that, as he made the turn, he applied right antitorque pedal, but "nothing was there." The pilot reported that he subsequently decided to "set it down" in a field ahead and that, about 3 to 5 ft above the ground, the "tail started to come around counter-clockwise." During the touchdown, the right skid caught on a hidden car muffler, and the helicopter rolled onto its right side and impacted terrain. During a postaccident interview, the pilot reported that he "lost tail rotor effectiveness," and he encountered "too much wind for this aircraft [helicopter]." The main rotor and tailboom sustained substantial damage. The pilot reported that there were no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation. The pilot reported that the wind was from the north and about 15 knots. The nearest automated weather observation station (AWOS), 41 nautical miles (nm) from the accident site, recorded that, about the time of the accident, the wind was from 350° at 14 knots, gusting to 26 knots. About 20 minutes before the accident, the AWOS recorded a peak wind from 340° at 30 knots. The density altitude at the AWOS location was 5,332 ft. The Federal Aviation Administration Helicopter Flying Handbook stated, in part: "Loss of tail rotor effectiveness (LTE) or an unanticipated yaw is defined as an uncommanded, rapid yaw towards the advancing blade which does not subside of its own accord. It can result in the loss of the aircraft if left unchecked." The handbook further stated, in part: "At higher altitudes where the air is thinner, tail rotor thrust and efficiency are reduced. Because of the high density altitude, powerplants may be much slower to respond to power changes. When operating at high altitudes and high gross weights, especially while hovering, the tail rotor thrust may not be sufficient to maintain directional control, and LTE can occur." It is likely that the high-density altitude and the pilot's positioning of the helicopter such that it resulted in a right quartering tailwind reduced the tail rotor effectiveness of the helicopter and contributed to the pilot's inability to maintain helicopter control during the hover to landing.

The pilot of an experimental amateur-built helicopter, which had a clockwise rotating main rotor blade, reported that he took off from private property with a right crosswind. He added that when the helicopter reached 20-30 knots, about 50 ft. above ground, he turned southwest, which resulted in a right quartering tailwind. He further added that as he made the turn, he applied right anti-torque pedal, but "nothing was there." Subsequently, the pilot reported that he decided to "set it down" in a field ahead, and about 3-5 ft. above the ground the "tail started to come around counter-clockwise." During the touchdown, the right skid caught on a hidden car muffler and the helicopter rolled onto its right side and impacted terrain. During a postaccident interview, the pilot reported that he "lost tail rotor effectiveness," and he encountered "too much wind for this aircraft [helicopter]." The main rotor and tail boom sustained substantial damage. The pilot reported that there were no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation. In an interview with the National Transportation Safety Board investigator-in-charge, the pilot reported that the wind was from the north, about 15 knots. An automated weather observation station (AWOS), 41 nautical miles (NM) from the accident site, about the time of the accident, recorded wind 350° at 14 knots, gusting to 26 knots. The AWOS recorded a peak wind, about 20 minutes before the accident, 340° at 30 knots. The density altitude, at the nearest airport with a recorded AWOS, 41 NM from the accident site, was 5,332 ft. The Federal Aviation Administration Helicopter Flying Handbook stated in part: Loss of tail rotor effectiveness (LTE) or an unanticipated yaw is defined as an uncommanded, rapid yaw towards the advancing blade which does not subside of its own accord. It can result in the loss of the aircraft if left unchecked." The handbook further stated in part: "At higher altitudes where the air is thinner, tail rotor thrust and efficiency are reduced. Because of the high density altitude, powerplants may be much slower to respond to power changes. When operating at high altitudes and high gross weights, especially while hovering, the tail rotor thrust may not be sufficient to maintain directional control, and LTE can occur."