CEN17LA267

The commercial pilot was conducting an agricultural aerial application flight. The pilot reported that the helicopter made an uncommanded right yaw during a turn. The pilot stated that he applied full left pedal to counter the yaw and that the helicopter centered briefly, but then the right yaw started again, which continued as the helicopter descended and impacted the ground. Because the helicopter was likely operating out of ground effect at a high power setting, the uncommanded right yaw was likely the result of a loss of tail rotor effectiveness (LTE). According to Federal Aviation Administration guidance, the procedures to recover from LTE are early detection followed by applying forward cyclic to regain airspeed, applying right (not left) pedal to maintain rotor rpm, and reducing collective to reduce the high power demand on the tail rotor. On the basis of the available information, the pilot lost control of the helicopter when he responded improperly to the LTE by adding left pedal rather than by applying forward cyclic and right pedal and reducing collective.

On July 8, 2017, about 1040 eastern daylight time, a Robinson R44 helicopter, N7224U, impacted the ground following a loss of control while conducting an aerial application flight near Ireland, Indiana. Following the impact with the ground, a fire erupted and the helicopter was destroyed. The pilot received serious injuries. The aircraft was registered to and operated by JR Aviation , Inc., under the provisions of Title 14 Code of Federal Regulations Part 137 as an aerial application flight. Visual meteorological conditions prevailed for the flight, which was not operated on a flight plan. The local flight originated from an unknown location at an unknown time. The pilot reported that he was spraying a field and when making a spray turn he felt a vibration or shuddering of the whole helicopter accompanied by an uncommanded right yaw. He applied full left pedal and the helicopter centered briefly, but then the right yaw started again and continued to impact. The pilot extricated himself and crawled about 20 ft from the wreckage when a fire erupted and consumed the helicopter. When asked if he felt the event was related to a mechanical or an aerodynamic event, he replied that he thought it was an aerodynamic event. He commented that he was a flight instructor and that he had never felt the kind of vibration that occurred during the accident flight. Examination of the helicopter was limited due to the extensive fire damage, but no anomalies could be found with components that were able to be examined. Federal Aviation Administration's Helicopter Flying Handbook, FAA-H-8083-21A, contains a section titled "Loss of Tail Rotor Effectiveness (LTE)" which states: 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. It is very important for pilots to understand that LTE is caused by an aerodynamic interaction between the main rotor and tail rotor and not caused from a mechanical failure. Some helicopter types are more likely to encounter LTE due to the normal certification thrust produced by having a tail rotor that, although meeting certification standards, is not always able to produce the additional thrust demanded by the pilot. FAA-H-8083-21A further stated that early detection followed by application of forward cyclic, right pedal, not left, and reducing collective to reduce the high power demand is the key to recovery. The weather conditions reported at a nearby airport included variable wind at 4 kts.