The eagle collided with the Bell 206L-1 LongRanger helicopter below its front left windscreen about nine minutes into a planned flight from Cattai to St Albans on July 9 last year flight, the Australian Safety Transport Bureau said in its final report on Friday.
The collision happened about 152 metres above ground, as the helicopter crossed the Dargle Ridge.
The pilot was likely unable to see the bird due to glare from the sun, and may have been changing radio frequencies at the time it hit the aircraft, the report found.
"The pilot was likely startled by sighting the bird or the helicopter striking the bird, reacting via abrupt control inputs," the bureau's director of transport safety Stuart Godley said.
"Unfortunately, these inputs led to the main rotor striking and severing the tail boom, and the helicopter breaking up in flight."
Witnesses said they saw the helicopter enter a rapid banking turn to the right as it pitched upwards. They also heard the rotor beats change tone, before the helicopter rolled as it descended.
One person said they saw the main rotor blades separate from the helicopter during the descent.
The pilot was fatally injured after the main fuselage hit the ground in open farmland below the ridge.
The helicopter was destroyed in a fire after impact.
The pilot had recently travelled to Adelaide where they had been helping with flood recovery efforts, and returned to their home in Cattai to secure it from flooding.
A media helicopter in the area filming flooding stopped to offer help, and footage from the scene captured biological matter on the left nose cowl of the wreckage, before the helicopter was consumed by the flames.
A local landowner also found more bird matter and biological tissue, which was taken from the accident site by investigators, and found to be from a wedge-tailed eagle.
Assessors believe the helicopter was flying directly into the sun at the time of the collision, and the size and shape of the craft's windscreen put the sun in the top of the pilot's view.
The pilot was also approaching the control boundary for Richmond, requiring they shift their vision as they changed radio frequencies.
"It was unlikely that the pilot saw or had time to avoid the wedgetail eagle due to sun glare and the required radio frequency change," Dr Godley said.
This is despite the weather conditions being fair at the time of the crash.
Birdstrikes are common in aviation, with 212 collisions involving helicopters reported to the safety bureau between 2018 and 2022, Dr Goldey said.
This was the first in that five-year period resulting in a fatal crash.
Across all areas of aviation more than 24,000 birdstrikes have been reported to the bureau between 2008 and 2022.
