Monday, May 1, 2017

Rotorway Exec 162F, N164JB: Accident occurred April 30, 2017 in Wheatland, Platte County, Wyoming

Additional Participating Entity:
Federal Aviation Administration / Flight Standards District Office; Denver, Colorado

Aviation Accident Final Report - National Transportation Safety Board: https://app.ntsb.gov/pdf

Aviation Accident Data Summary - National Transportation Safety Board:  https://app.ntsb.gov/pdf

Investigation Docket - National Transportation Safety Board: https://dms.ntsb.gov/pubdms

http://registry.faa.gov/N164JB


NTSB Identification: GAA17CA251
14 CFR Part 91: General Aviation
Accident occurred Sunday, April 30, 2017 in Wheatland, WY
Probable Cause Approval Date: 07/20/2017
Aircraft: BENDER JOSEPH KIT ROTOWAY, registration: N164JB
Injuries: 1 Uninjured.

NTSB investigators used data provided by various entities, including, but not limited to, the Federal Aviation Administration and/or the operator and did not travel in support of this investigation to prepare this aircraft accident report.

The pilot of the experimental amateur-built helicopter, which had a clockwise rotating main rotor blade, reported that he took off from private property with a right crosswind. He added that, when the helicopter reached 20 to 30 knots, about 50 ft above the ground, he turned southwest, which resulted in a right quartering tailwind. He further added that, as he made the turn, he applied right antitorque pedal, but “nothing was there.” The pilot reported that he subsequently decided to “set it down” in a field ahead and that, about 3 to 5 ft above the ground, the “tail started to come around counter-clockwise.” During the touchdown, the right skid caught on a hidden car muffler, and the helicopter rolled onto its right side and impacted terrain. 

During a postaccident interview, the pilot reported that he “lost tail rotor effectiveness,” and he encountered “too much wind for this aircraft [helicopter].”  
The main rotor and tailboom sustained substantial damage.

The pilot reported that there were no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation.

The pilot reported that the wind was from the north and about 15 knots. The nearest automated weather observation station (AWOS), 41 nautical miles (nm) from the accident site, recorded that, about the time of the accident, the wind was from 350° at 14 knots, gusting to 26 knots. About 20 minutes before the accident, the AWOS recorded a peak wind from 340° at 30 knots. The density altitude at the AWOS location was 5,332 ft. 

The Federal Aviation Administration Helicopter Flying Handbook stated, in part: “Loss of tail rotor effectiveness (LTE) or an unanticipated yaw is defined as an uncommanded, rapid yaw towards the advancing blade which does not subside of its own accord. It can result in the loss of the aircraft if left unchecked.” The handbook further stated, in part: “At higher altitudes where the air is thinner, tail rotor thrust and efficiency are reduced. Because of the high density altitude, powerplants may be much slower to respond to power changes. When operating at high altitudes and high gross weights, especially while hovering, the tail rotor thrust may not be sufficient to maintain directional control, and LTE can occur.”

It is likely that the high-density altitude and the pilot’s positioning of the helicopter such that it resulted in a right quartering tailwind reduced the tail rotor effectiveness of the helicopter and contributed to the pilot’s inability to maintain helicopter control during the hover to landing. 

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
The pilot's decision to operate the helicopter in gusting wind and high-density altitude conditions and his positioning of the helicopter such that it resulted in a right quartering tailwind, which resulted in a loss of helicopter control due to a loss of tail rotor effectiveness.

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