A shipboard helicopter accident likely due to ground resonance emphasises the importance of proper pilot coordination in responding to abnormal situations, an ATSB investigation outlines.
On 25 February 2025, the Agusta A109E helicopter with two pilots on board - a pilot flying in‑command‑under‑supervision (ICUS) and a pilot supervising - was taking off from a bulk carrier about 200 km north‑east of Mackay, Queensland, after dropping off a marine pilot.
As it was lifting off from the ship's helideck, the helicopter developed severe vibrations. The take‑off was discontinued but control of the helicopter 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, the helicopter operator added new guidelines on ground resonance to its procedures.
It 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."
You can find here 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
