THE AUSTRALIAN Transport Safety Board has found the phenomenon of ground resonance probably caused a Flyon helicopter to crash while taking off from the bulk carrier Star Coral off Mackay in February.
The Augusta A109E, with two pilots on board, was heading back to base after dropping off a Torres Pilot to the inbound ship at the Blossom Bank boarding ground in Hydrographers Passage, about 200km north-east of Mackay on 25 February.
As the chopper – with a pilot flying in-command-under-supervision (ICUS) and a pilot supervising – lifted off the 93,251 DWT bulker’s hatch cover it developed severe vibrations, and although the take-off was aborted control was lost.
The helicopter came to rest upright on the helideck, more than 90° counterclockwise from its original position, having sustained substantial damage. No injuries were reported.
The ATSB found that the vibration was likely the result of the helicopter entering ground resonance, a phenomenon that dissipates when airborne, while it was in the process of departing from the ship.
“When the vibrations started, the pilot supervising perceived the pilot flying to be holding the cyclic in an abnormally aft position, and believed the main rotor may have struck the tail boom,” ATSB Director Transport Safety Stuart Macleod said.
In response, the pilot supervising, unannounced, took hold of the cyclic and collective in order to discontinue the take-off, while the pilot flying was still attempting to lift off.
“In isolation, the immediate responses taken by each pilot following the sudden onset of vibration were understandable,” Mr Macleod said. “But discontinuing the take-off after the onset of the vibration, with the rotor speed in the flight range, probably resulted in the loss of control and substantial damage to the helicopter.”
Mr Macleod noted the accident was a good example of the potentially catastrophic nature of ground resonance: “Typically, the onset of ground resonance is sudden and if the pilot does not take immediate corrective action, loss of control can occur rapidly.”
After the accident Flyon added new guidelines on ground resonance to its procedures, the Bureau reported.
Flyon has also developed an updated procedure for training and checking flight briefings that will include confirming the roles of each pilot, procedures for transferring aircraft control between pilots, and actions to be followed in the event of an actual emergency.
“Proper coordination between pilots is critical, particularly when responding to abnormal or emergency situations,” Mr Macleod said. “Pilot roles and responsibilities for emergency response and flying duties should be well established prior to each flight.”
Read the final report: Loss of control during marine pilot transfer operations involving Agusta A109E, VH-XUM and bulk carrier Star Coral, about 200 km north-east of Mackay, Queensland, on 25 February 2025.