The Macau-bound helicopter which was forced to ditch in Victoria Harbour last weekend was the subject of a worldwide safety alert. Hong Kong Civil Aviation Department officials confirmed that the stricken Italian-made AgustaWestland AW139 - along with hundreds of the same model flying worldwide - was subject to an emergency airworthiness directive issued last October by European safety officials. The directive details a 'de-bonding' problem with panels on the 15-seater aircraft's tail boom and mandates rigorous daily checks on that section of the helicopter. Investigations into last weekend's incident continue, and official details are sketchy, but it is known that the AW139 helicopter - owned and operated by Macau-based company Sky Shuttle - suffered a 'tail rotor failure' seconds after take-off from the Shun Tak Centre helipad in Sheung Wan, forcing pilot Richard Moffatt to ditch in the harbour. The section of the tail that broke off and sank will form a key part of the investigation into what happened last Saturday. Aviation officials said it had yet to be retrieved from the harbour. The aircraft's 11 passengers were plucked to safety and suffered only slight injuries as a result of the efforts of Moffatt and his first officer, Fernando Sun Keng-pong, in bringing it safely down onto the surface of the harbour. Sky Shuttle operates a fleet of six AW139s, two of which are registered in Hong Kong and four in Macau. After being grounded in the immediate aftermath of the incident, the five remaining aircraft were cleared for take off last Wednesday. The emergency directive was issued by the European Aviation Safety Agency (EASA) on October 29 after the tail boom of a helicopter of the same model operated by Gulf Helicopters snapped off as it taxied along a runway in Qatar in August. Its issuance has split European and Hong Kong aviation officials. A spokeswoman for the Civil Aviation Department said it was aware of the de-bonding problem. 'However, the problem referred to by the emergency AD [the directive] was only on the section of the tail boom immediately behind the cabin, not on the vertical section at the tail. EASA did not specifically correlate the reason for the directive to the Qatar incident.' A spokeswoman for AgustaWestland also moved to play down any link between the Hong Kong and Qatar incidents. 'We can confirm that the airworthiness directive you reference relates to the same model as was involved in the Sky Shuttle incident, although we believe that the Qatar incident that preceded the directive's issuance and the incident here in Hong Kong are unrelated,' she said. However, EASA's Dominique Fouda said the directive applied to the whole tail boom and that the Qatar incident - among others - had been factored into the decision to issue the airworthiness directive. 'The directive was issued following a number of different incidents involving fuselage problems on the AW139. It covers the whole of the tail, including the section to which the tail rotor is attached. The Qatar incident was factored into the decision,' Fouda said. 'The directive remains in force but has not been updated in light of the Hong Kong incident because the investigation into that is still ongoing.' The directive mandates that inspections of the AW139 tail boom be made at more regular intervals as a result of potential tail boom problems. These include daily general visual inspections and frequent detailed inspections of the tail boom panels 'to detect bulging and/or deformations'. It goes on to say that these inspections should in some cases be carried out at intervals not exceeding 25 flight hours. Asked if this was being done prior to the ditching of the helicopter last weekend, the Civil Aviation Department spokeswoman said: 'The inspection records of the accident aircraft are being checked. All airworthiness directives issued by the state of manufacture are mandated by Hong Kong. 'Therefore, the two Hong Kong- registered AW139 of Sky Shuttle are in compliance with the requirement of the [directive] since it was issued. This includes daily general visual inspections, 25-flight-hour inspection and 50-flight-hour inspection.' The Hong Kong authorities are also aware of the Qatar incident and say they will liaise with the authorities in the Arab emirate if necessary. Despite several months having passed since the Qatar incident, details have not emerged as to what caused the tail boom to snap. There was initially speculation that a bird strike may have caused the helicopter pilot to lose control, but a former head of Hong Kong's Civil Aviation Department, Peter Lok, cast doubt on that theory. 'I never thought it was a bird strike. My feeling is that was an engine problem. These are not unheard of despite the fact that the way modern engines are designed enhances their safety quite considerably,' he said. The international investigation into the Victoria Harbour incident is being jointly undertaken by the Civil Aviation Departments of Hong Kong and Macau, the Italian Air Safety Board, AgustaWestland and the Transport Safety Board (TSB) of Canada - where the engines were manufactured. The Civil Aviation Department is expected to release a preliminary report into the incident in about three weeks' time.