What happened
On 2 October 2022, a Robinson R22 Beta II, registration VH-RAS, departed Koorda, Western Australia, intending to fly to Jandakot via Northam. The flight proceeded normally until the aircraft reached cruise altitude, at which point it departed from controlled flight. Data analysis indicates the helicopter entered a rapid, nearly vertical descent, eventually impacting the terrain in an inverted position. The accident resulted in 2 fatalities and the total destruction of the aircraft.
The investigation
The ATSB examined the wreckage and flight data to determine the cause of the structural failure. Investigators identified evidence of extreme teetering and mast bumping, noting fractures in the spindle tusks, teeter stops, and pitch links, as well as rotor blade impact on the fuselage.
While the exact sequence of events remains unclear, the investigation focused on whether the aircraft entered a low-g condition or a low rotor RPM/rotor stall state. Although the tachometer showed low engine and rotor RPM at the moment of impact, it was difficult to confirm the exact operational state immediately preceding the loss of control. The investigation also considered various potential triggers, such as turbulence, engine power loss, or pilot inputs, but the lack of onboard cockpit imagery prevented a definitive conclusion on the initial cause.
Findings
- The aircraft likely entered a low-g and/or low rotor RPM condition, which, combined with potentially delayed or improper control inputs, led to extreme rotor teetering and subsequent in-flight break-up.
- The installation of quick-disconnect dual flight controls in a passenger seat increased the risk of accidental or improper control inputs by a passenger.
- The pilot had not disclosed the use of prescription medication for a medical condition to the Civil Aviation Safety Authority, preventing a proper medical risk assessment.