ATSB investigators have found that a Bell 206L Long Ranger broke up in flight after a collision with a wedge-tailed eagle. according to the final report released today.
VH-ZMF was traveliing from Cattai NSW to St Albans NSW on 9 July last year, when it crashed near Dargle Ridge Lookout. The only person on board, the pilot, died in the accident.
ATSB investigators subsequently found evidence of collision with a bird on the aircraft and remains of a wedge-tailed eagle in the vicinity.
The investigation revealed that the pilot probably didn't see the bird because the sun was coming directly through the windscreen, and was likely to have had their eyes inside the cockpit due to the need to change frequency approaching an ATC boundary.
According to the report, the subsequent break-up was caused when the main rotor severed the tail boom, most likely the result of excessive control movement.
“The pilot was likely startled by sighting the bird or the helicopter striking the bird, reacting via abrupt control inputs,” said ATSB Director Transport Safety Dr Stuart Godley.
“Unfortunately, these inputs led to the main rotor striking and severing the tail boom, and the helicopter breaking up in flight.”
The investigation reports states that the pilot's control inputs were likely an attempt to avoid the bird, but were abrupt enough for the rotor to strike the tail.
"Abrupt cyclic inputs and low to negative g rotor loading are a well-documented and accepted limitation of two-bladed teetering rotor head systems commonly used in light to medium helicopters," the final report states.
"Analysis of the impact marks on the tail boom of VH-ZMF and the separation of rotor blade tips, indicate that the tail boom was impacted and severed by contact with its own main rotor blades."
In the five years between 2018 and 2022, 212 birdstrikes involving helicopters were reported to the ATSB; however, VH-ZMF is the only one lost,
Over the 15 years between 2008 and 2022, 24,106 birdstrikes were reported to ATSB for all sectors of aviation.
“Birdstrike is sometimes an unavoidable and relatively common hazard for all aviation operations, one which is more prevalent at lower altitudes,” Godley said.
“A sound lookout and visual scanning processes, as well as avoidance of low-level flight and expected areas of large concentrations of birds are key to reducing the likelihood of birdstrike.”
The full report is on the ATSB website.