A loss of control accident involving a Bell 206 helicopter shortly after take-off was likely the result of a loss of tail rotor effectiveness due to proximity to a hangar, an ATSB investigation report details.
The helicopter was being used for a private flight from a property near Tumbarumba to Khancoban, NSW, on 16 July 2023.
Shortly after take-off from a helipad and while in a low hovering left turn, the helicopter yawed uncommanded to the right.
In response, the pilot lowered the collective to reduce height, then closed the throttle. The left skid then contacted the soft earth beside the pad, and broke off, and the helicopter rolled over, coming to rest on its left side.
The helicopter was substantially damaged but none of the occupants - the pilot and three passengers - were injured.
"The high all-up weight of the helicopter would have strengthened the recirculation of downwash from the main rotor blades generated by the helicopter's proximity to the hangar," ATSB Director Transport Safety Kerri Hughes said.
"The hovering left turn then brought the tail of the helicopter closer to the hangar, where recirculation would be greater. This likely disturbed the flow of air through the tail rotor, resulting in a loss of tail rotor effectiveness."
The accident is a reminder of the importance for pilots to remain cognisant of the factors that may induce unanticipated yaw (a loss of tail rotor effectiveness), Ms Hughes noted.
"Helicopter performance can be adversely affected by proximity to obstacles, including terrain, vegetation and buildings," she said.
"If unanticipated yaw is encountered, prompt and correct pilot response is essential."
While it was not found to have contributed to the accident, the ATSB investigation notes the helicopter was likely about 15 kg above its maximum take-off weight, due to errors during the weight and balance calculations for the flight.
Separately, while the ATSB's investigation was unable to quantify their contributions to survivability, the helmet worn by the pilot, and the use of 4- and 5-point restraints by the pilot and passengers, would have reduced the risk of injury.
"It is notable there were no injuries reported in this accident," Ms Hughes concluded.
You can find here the final report: Collision with terrain involving Bell 206B-1, VH-ZDI, 9.3 km south-south-east of Tumbarumba, New South Wales, on 16 July 2023
