An emergency airworthiness directive for several Eurocopter types has been issued by the European Aviation Safety Agency after an AS332 Super Puma helicopter suffered brake failure when landing on the helideck of a North Sea offshore oil rig, and "started to roll toward the edge of deck", the agency reported.
There have now been three EASA emergency ADs in the last two months relating to Eurocopter helicopters, but they are unrelated to each other.
After extending the landing gear on approach to the rig, the crew witnessed a cockpit amber alarm indicating a low level of hydraulic fluid in the left hand side hydraulic system.
The EASA emergency AD said: "After landing, the helicopter started to roll towards the edge of the helideck as the flightcrew was not aware that wheel brake capability was affected and relied only on the effectiveness of the helicopter's ancillary hydraulic accumulator."
This AD requires the insertion of a "rush revision" into the emergency procedures section of each applicable rotorcraft flight manual.
The report continued: "The results of the following investigation showed that this alarm was due to hydraulic fluid leakage, caused by the failure of one hydraulic union connector in the LH hydraulic circuit."
EASA has issued AD 2012-0059-E to address this "potential unsafe condition", which, it says, can affect Eurocopter SA330, AS332 and EC225 helicopters, requiring an immediate rotorcraft flight manual revision to cover any other cause of leakage from the emergency/auxiliary hydraulic circuit that could result in an empty accumulator.
EASA says that this situation could affect other Eurocopter helicopters that are fitted with an emergency accumulator. This includes the SA365N (as an option) and in basic configuration for the SA365N1, AS365N2, N3 and the EC155. The agency says a "potential leak could, in certain operational conditions, lead to the same consequences".