Accident Overview
On September 6, 2013, about 0925 central daylight time, a Continental Copters Inc., OH13-H Tomcat agricultural helicopter, registration N9005T, operated by Scotts Helicopter Service Inc. of LeSueur, Minnesota, struck the ground during an aerial application flight. The pilot was not injured. Visual meteorological conditions prevailed, and no flight plan was filed. The flight was conducted under 14 CFR Part 137. The helicopter departed from a private location near Gaylord, Minnesota, approximately 0920.
Flight Sequence
The pilot reported to work after a scheduled day off. The first aerial application flight of the morning was uneventful, after which the helicopter landed to reload pesticides. The pilot then took off and applied about 75 gallons of pesticide to a field. En route to the next field at an altitude of 300-400 feet above ground level, the pilot attempted to contact his truck driver via two-way radio. The radio connection to his helmet was unplugged, so he reached to plug it in with his right hand while transferring his left hand from the collective to the cyclic. The pilot estimated this process took 5 to 8 seconds. Immediately after plugging in the radio, the collective control moved to the full down position, causing the pilot's notebook to fly around the cabin.
Response and Landing
The pilot quickly grabbed the collective and raised it. He then noticed the helicopter losing altitude and the main rotor RPM decreasing, with the engine and rotor RPM needles separated. He twisted the throttle control back and forth without effect and attempted an autorotation. The helicopter touched down hard, sustaining substantial damage to the tailboom.
Investigation Findings
An FAA inspector conducted an on-site inspection and reported no mechanical or environmental anomalies. The pilot stated in his NTSB form recommendation that he could have chosen not to unplug his helmet and keep his hand on the collective at all times, which would have prevented the collective from slamming down while he connected the radio cables. Review of maintenance logs showed no prior entries regarding collective control malfunctions, and the helicopter had operated normally during the first flight. Notably, this helicopter model lacks a friction control mechanism on the collective, meaning it could move if not held in place by the pilot.