CEN17LA192

The commercial pilot reported that, after completing the local air tour flight in the helicopter, he approached the private helipad location from the south. On approach and about 50-60 kts, the pilot began to arrest the helicopter's descent to view the windsock and determine the proper approach to the helipad. The pilot reported that the wind was from the south, so he decided to make the final approach from the north. About 200 ft above ground level and west of the helipad, the pilot initiated a left turn, and the helicopter started an uncommanded descent. The pilot applied power to stop the descent, but the helicopter continued sinking toward terrain. Due to the low altitude, the pilot committed to land and leveled the helicopter. During the landing, the back of the landing gear skids struck the terrain, which resulted in the main rotor blades contacting and severing the tail boom. Postaccident examination did not reveal any anomalies with the airframe or engine that would have precluded normal operation, and both the pilot and the operator reported that there were no mechanical malfunctions or failures. The pilot's calculated weight and balance was within limits at the time of the accident. A video of the accident sequence was consistent with the pilot's statement. It is likely that, during the descent to land, the helicopter encountered a vortex ring state (settling with power) condition, which resulted in a rapid descent and hard landing.

On May 20, 2017, about 1340 mountain daylight time, a Robinson Helicopter Company R66 helicopter, N778TL, impacted terrain following a loss of control on approach to landing near Canon City, Colorado. The commercial pilot and four passengers were not injured, and the helicopter sustained substantial damage. The helicopter was registered to Hynes Aviation Industries, Inc, and operated by Colorado Vertical under provisions of Title 14 Code of Federal Regulations Part 91 as a local air tour flight. Day visual meteorological conditions prevailed and a company visual flight rules flight plan was filed for the local flight. The flight originated from a private helipad near Canon City about 1335. The pilot reported to the National Transportation Safety Board (NTSB) investigator-in-charge that after completing the local air tour flight, the helicopter approached the private helipad location from the south near highway route 50. After crossing over route 50 on approach about 50-60 kts, the pilot began to arrest the descent to view the wind sock and determine the proper approach to the helipad. The pilot reported the winds were from the south, so he decided to make the final approach from the north. About 200 ft above ground level and west of the helipad, the pilot initiated a left turn, and the helicopter started an uncommanded descent. The pilot applied power to stop the descent, but the helicopter continued sinking towards the terrain. Due to the low altitude, the pilot then committed to land and leveled the helicopter. During the landing, the back of the landing gear skids struck the terrain, which resulted in the main rotor blades contacting and severing in the tail boom. The helicopter came to rest upright and the occupants exited the helicopter. Postaccident examination of the helicopter airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. The pilot reported that the helicopter weight was 2,580 lbs at the time of the accident, and the pilot's calculated center of gravity was 92.92 inches. A GoPro HERO3 Silver Edition camera was mounted on the helicopter windshield facing inward into the cabin. The camera was installed on the helicopter to provide passengers a video of their air tour flight. A copy of the accident flight video was recovered by the operator and provided to the NTSB. The video was reviewed by the NTSB's Office of Research and Engineering and a video study was completed. The study goal was to estimate the forward and vertical speeds of the helicopter before the hard landing. The analysis of the video was based on a mathematical model of the camera. Four parameters, yaw, pitch, roll, and horizontal field of view angle, were estimated from video frames recorded before takeoff, when the helicopter was on the departure helipad. Parameter estimation was based on several reference points, which were visible through the helicopter windows and aerial images of the accidentarea. According to the study calculations, the forward speed was estimated at 34+3 knots, and the highest estimated vertical descent speed was 570+60 ft/min. In addition, the helicopter experienced an elevated level of vibrations during a time interval of approximately seven seconds that ended just before ground impact.