N445HSRobinson Helicopter R44 II

On August 22, 2015, about 1742 central daylight time, a Robinson R44 II helicopter, N445HS, was substantially damaged after impact with terrain near Carlos, Texas. The pilot and passenger were seriously injured. The helicopter was registered to and operated by Perfect Filler LLC under the provisions of 14 Code of Federal Regulations Part 91 as a business flight. Day visual meteorological conditions prevailed for the flight, with no flight plan filed. The local flight departed from Coulter Field Airport (CFD), Bryan, Texas, about 1630.

The pilot stated the purpose of the flight was to film a second (lead) helicopter while hunters onboard utilized rifles to hunt wild hogs. At the filming location, the lead pilot radioed to the accident pilot that he was flying much too high. Based on this feedback from the more experienced pilot, the accident pilot descended from about 400 feet agl to 200 feet agl, which was about 100 feet above the lead helicopter. The accident pilot stated his descent made it more challenging for him to keep the lead helicopter in sight while facing into the headwind, which was about 20 knots. The accident pilot initiated a right pedal turn to keep the lead helicopter in sight and the accident helicopter entered into a descending right spin, which the pilot was not able to arrest. The helicopter subsequently impacted trees, which damaged the main rotor, tail rotor, and fuselage.

Federal Aviation Administration (FAA) personnel responded to the accident site and located the wreckage in a rural, wooded area, with no evidence of a post-crash fire. The helicopter came to rest on its right side, with both main and tail rotor blades attached. The main and tail rotor blades were observed to have damage consistent with impact. Flight control continuity was established to all flight controls and the tail rotor system was intact, with no anomalies noted. Examination of the helicopter revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.

A recording was recovered from the passenger's video camera and evaluated by the NTSB Recorder Laboratory. The passenger was seated in the back right seat of the helicopter and was filming the lead helicopter as it engaged in aerial hog hunting. Because the recording did not capture any part of the accident helicopter during the accident sequence, it was difficult to judge the camera's orientation as compared to the accident helicopter's orientation.

The video began with the camera view pointed downward towards the lead helicopter and captured trees being blown by the rotor wash of the lead helicopter. This rotor wash was northwest of the lead helicopter's position. The camera view was shaky and occasionally zoomed toward the lead helicopter.

At 00:28 into the recording, both helicopters appeared to have lessened their groundspeed. At 00:36, the camera's view zoomed in tight to two individuals holding rifles leaning out of the lead helicopter. Between 00:36 and 00:57, both helicopters appeared to be stationary and facing southeast. Around 00:58, the lead helicopter appeared to move away from its stationary hunting position and at 01:09, the lead helicopter moved over a clear area in the surrounding vegetation.

At 01:10, the accident helicopter entered a yaw to the right, which quickly developed into a rapid spin. The camera's view began to blur within the first second of the onset of the spin. The accident helicopter completed at least seven continuous spin rotations as it descended and subsequently impacted into trees at about 01:45.

According to the FAA Helicopter Handbook, a loss of tail rotor effectiveness (LTE) is caused by aerodynamic conditions resulting in a tail rotor control margin deficiency and is not caused by a mechanical failure in the tail rotor system. Certain factors can exacerbate LTE, such as slow forward airspeed (a higher power demand from the main and tail rotor), high gross weight, and relative winds that may result in a disruption of airflow through the tail rotor or the lateral stability of the helicopter. In a LTE situation, once an adverse yaw rate has sufficiently developed, it may be impossible to correct it with full pedal in the opposite direction.

The Robinson R44 II has a main rotor system that rotates counter-clockwise (when viewed from above), which requires a tail rotor system to yaw the helicopter left in order to provide main rotor anti-torque. In a LTE situation where there is insufficient tail rotor thrust to maintain directional control, the R44 II yaws to the right.

Robinson Helicopter Corporation (RHC) Safety Notice No. SN-34 titled "Aerial Survey and Photo Flights – Very High Risk", issued in March 1999 and revised in April 2009, discusses the safety risks associated with such flights performed by inexperienced pilots. The accident pilot did not meet the RHC safety notice recommendation of 500 hours of pilot in command in helicopters and 100 hours in the model flown. Additionally, the accident pilot had never conducted a commercial operation or a flight requiring him to maintain a hover while in close proximity to another helicopter. Neither the accident pilot nor the lead pilot was aware of the Robinson SN-34. The RHC safety notice also recommends that photo flights "should only be conducted by experienced pilots who are willing to say no to the photographer and only fly at speeds, altitudes, and wind angles that are safe and allow good escape routes."

Prior to the flight, the lead pilot recognized and was concerned with the inexperience of the accident pilot relative to the flight profile. He stated that a conversation with the accident pilot "raised many red flags" regarding the flight's safety. He considered not using the accident pilot for the filming, but decided to proceed "because of the value of the footage."