CEN16LA213

The commercial pilot reported that, while conducting a spray pass, he pulled on the helicopter's collective, and the rotor speed dropped. He lowered the collective, applied maximum throttle, and pulled on the collective again, but the rotor speed continued to drop. He then attempted to land in a nearby yard, but the tailboom struck a tree, and the helicopter then flipped on its right side. A witness, who was an experienced agricultural helicopter pilot, reported that he had flown with the accident pilot for about 12 hours in the accident helicopter, which was a piston engine-powered helicopter that did not have a throttle governor, to familiarize him with managing the throttle. He stated that the accident pilot's previous experience was in turbine-powered helicopters that had a throttle governor. The witness stated that he was in the field watching the accident pilot perform spraying operations. The pilot made a downwind pass in the field in a tight area. He said that, when the pilot pulled up to climb above the trees at the end of the pass, he heard the engine "bog down" and that he thought that the pilot had pulled the collective without adding throttle. A postaccident examination of the helicopter and a test run of the engine revealed no preaccident mechanical malfunctions or failures that would have prevented normal operation. Based on this evidence, it is likely that the pilot failed to apply engine power when he applied collective input, which resulted in a loss of rotor speed and an exceedance of the helicopter's performance capability.

On June 9, 2016, about 1630 central daylight time, a Bell 47G-5 helicopter, N6203N, was substantially damaged during a loss of control while performing agricultural spraying operations near Laurels, Texas. The pilot received minor injuries. The helicopter impacted a tree and the ground and sustained damage to the fuselage, landing gear, and main rotor system. The aircraft was registered to and operated by Hendrickson Flying Service, Inc. under the provisions of 14 Code of Federal Regulations Part 137 as an aerial application flight. Visual meteorological conditions prevailed for the flight, which was not on a flight plan. The local flight originated at an unconfirmed time. The pilot reported that while conducting a spray pass, he pulled on the collective and the rotor speed dropped. He said that he lowered the collective, applied maximum throttle and pulled on the collective again but the rotor speed continued to drop. He then attempted a landing in a yard next to a house where the tail boom struck a tree and the helicopter came to rest on its right side. A witness, who was an experienced agricultural helicopter pilot reported that he had flown with the accident pilot for about 12 hours in the accident helicopter. He stated that the accident pilot's previous experience was in turbine powered helicopters with governed throttle. He flew with him to familiarize him with managing throttle on the piston engine powered Bell 47 that did not have a throttle governor. The witness stated that he was in the field watching the accident pilot perform spraying operations. The pilot made a downwind pass in the field in a tight area where the helicopter was in and out of the field quickly. He said that when the pilot pulled up for the trees at the end of the pass he heard the engine "bog down." He said that he thought that the pilot had pulled collective without adding throttle. A postaccident examination of the helicopter and a satisfactory test run of the engine disclosed no preaccident mechanical malfunctions or anomalies that would have prevented normal operations.