The European Aviation Safety Agency has issued an emergency airworthiness directive affecting a number of Eurocopter types following "a serious incident" that almost led to a helicopter rolling off an oil rig's helideck.
The directive, issued on 4 April, affects the Eurocopter SA330J, all AS332 variants and the EC225LP.
EASA says following extension of its landing gear, the helicopter displayed a cockpit amber alarm indicating low fluid levels in its left-hand hydraulic system.
"After landing, the helicopter started to roll towards the edge of the helideck as the flight crew was not aware that wheel-brake capability was affected and relied only on the effectiveness of the helicopter's ancillary hydraulic accumulator," says EASA.
An investigation showed the cockpit alarm was caused by hydraulic fluid leakage resulting from the failure of one hydraulic union connector in the left-hand hydraulic circuit.
"This condition, if not detected and correctly assessed by the flight crew, could result in reduced control of the helicopter after landing," it adds.
The airworthiness directive requires amendment of the rotorcraft flight manuals' emergency procedures section by inserting relevant revisions, and ensuring that all crews who operate to raised platforms are aware of the risk.