A Robinson R44 dynamic rollover accident highlights to helicopter pilots the importance of carefully examining landing sites before take-off, and maintaining smooth and controlled flight inputs during critical phases of flight.

The helicopter was conducting a sightseeing flight on 7 August 2023 with a pilot and three passengers on board in the Northern Territory’s Limmen National Park.

During take-off, the helicopter rolled to the right and collided with the ground. The helicopter was substantially damaged and one passenger sustained serious injuries. The pilot and a second passenger sustained minor injuries, while the third passenger was uninjured.

The ATSB’s investigation found that during take-off, unknown to the pilot, the helicopter’s left skid had been pressed against a tree root that was partially obscured by sand.

“The helicopter began to roll to the left, against the tree root, as the pilot applied control inputs to raise the helicopter into a hover,” ATSB Director Transport Safety Stuart Macleod explained.

The pilot responded to this unexpected movement by applying right cyclic, and then lowering the collective in an attempt to settle the helicopter on its skids.

“However, the pilot was not aware that while the right cyclic input freed the skid from the tree root, it also led to the helicopter drifting to the right. As such, when the pilot lowered the collective, the helicopter dynamically rolled over to the right.”

Mr Macleod said the accident highlights the importance of smooth and controlled flight inputs in the critical phases of flight.

“While a helicopter is in contact with the ground, it is subject to various influences which could result in a dynamic rollover,” he said.

The ATSB investigation also highlights the importance of helicopter pilots and operators conducting thorough visual inspections of all landing sites to identify potential hazards, prior to take-off.

“Bush landing sites and paddocks can also be prone to concealed hazards,” Mr Macleod concluded.

Read the final report: Collision with terrain involving Robinson R44, registration VH-HRB, 95 km west-north-west of Borroloola, Northern Territory, on 7 August 2023.

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