Accident Overview
On August 22, 2015, at approximately 1742 central daylight time, a Robinson R44 II helicopter (registration N445HS) was substantially damaged after colliding with terrain near Carlos, Texas. The helicopter was operated by Perfect Filler LLC under 14 CFR Part 91 as a business flight. Day visual meteorological conditions prevailed, and no flight plan was filed. The flight had departed Coulter Field Airport (CFD) in Bryan, Texas, about 1630.
Flight Sequence
The pilot reported the flight's purpose was to film a second (lead) helicopter while hunters onboard used rifles to hunt wild hogs. At the filming location, the lead pilot advised the accident pilot that he was flying too high. In response, the accident pilot descended from about 400 feet agl to 200 feet agl, roughly 100 feet above the lead helicopter. The accident pilot noted that the descent made it more difficult to keep the lead helicopter in sight while facing a headwind of about 20 knots. He initiated a right pedal turn to maintain visual contact, and the helicopter entered a descending right spin that he could not arrest. The helicopter subsequently struck trees, damaging the main rotor, tail rotor, and fuselage.
Wreckage Examination
FAA personnel arrived at the rural, wooded accident site. No post-crash fire occurred. The helicopter came to rest on its right side with main and tail rotor blades still attached, showing impact damage. Flight control continuity was established to all controls, and the tail rotor system was intact with no anomalies. Examination revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.
Video Recording Analysis
A video recording from the passenger's camera was analyzed by the NTSB Recorder Laboratory. The passenger, seated in the back right seat, had been filming the lead helicopter. The recording did not capture the accident helicopter during the accident sequence, making orientation judgments difficult. The video initially showed the camera pointed downward at the lead helicopter, capturing trees blown by its rotor wash. At 00:28, both helicopters appeared to reduce groundspeed. Between 00:36 and 00:57, they seemed stationary, facing southeast. Around 00:58, the lead helicopter moved away. At 01:10, the accident helicopter began a right yaw that quickly became a rapid spin. The view blurred within one second. The helicopter completed at least seven continuous spin rotations before impacting trees at about 01:45.
Additional Information
The FAA Helicopter Handbook describes loss of tail rotor effectiveness (LTE) as an aerodynamic condition causing insufficient tail rotor control margin, not a mechanical failure. Factors exacerbating LTE include slow forward airspeed, high gross weight, and relative winds disrupting tail rotor airflow. Once an adverse yaw rate develops, full opposite pedal may not correct it. The Robinson R44 II's main rotor rotates counter-clockwise, requiring left yaw for anti-torque; in LTE, the helicopter yaws right.
Robinson Helicopter Corporation Safety Notice SN-34 (revised April 2009) addresses risks of aerial survey and photo flights for inexperienced pilots. The accident pilot did not meet the recommendation of 500 hours pilot-in-command in helicopters and 100 hours in the model. He had never conducted a commercial operation or a flight requiring hovering near another helicopter. Neither pilot was aware of SN-34. The safety notice recommends such flights be conducted only by experienced pilots willing to refuse unsafe requests.
Before the flight, the lead pilot recognized concerns about the accident pilot's inexperience. He considered not using him but proceeded due to the value of the footage.