NEW concerns have surfaced over the North Sea Sikorsky S-92 fleet after a fatal crash involving a search and rescue helicopter off the coast of Ireland.

One crew member and three others were missing after the latest S-92 crash, just two months after the same aircraft was involved in an incident in the North Sea.

Captain Dara Fitzpatrick, a 45-year-old decorated Irish Coast Guard (IRCG) pilot, who had been with the search and rescue service for more than 20 years, was one of four crew members who went missing off the coast of Co Mayo, in Ireland, early Tuesday.

The Herald:

The Dublin-based Sikorsky S92 helicopter, which was providing cover for another helicopter involved in an early-morning rescue operation, lost contact at around 1am.

A spokesman for US-based Sikorsky, part of Lockheed Martin, said the firm was working with the helicopter's operator to gather information on the possible cause of the crash.

Eugene Clonan, acting director of the Irish Coast Guard, said it was a "dark day" for Ireland's emergency service.

In January, Sikorsky grounded all S-92 aircraft worldwide temporarily for safety checks including dozens in the North Sea following an incident involving the same make and model on the West Franklin Platform in the North Sea on December 28. It was making an emergency landing when it left significant gouge marks on the deck.

Operators were instructed to carry out the checks immediately, centred on tail rotors.

The Herald:

The decision caused widespread disruption to North Sea travel and paralysed the coastguard's search and rescue fleet.

It has emerged that three days later US and European issued an emergency airworthiness directive following what was described as three reports of S-92 operators losing tail rotor control caused by failed bearings.

They said Sikorsky S-92 helicopters must undergo inspections every 10 hours in the wake of North Sea crash.

Precautionary inspections were carried out on the five S-92s in rotation in Ireland (including a spare aircraft) after the US maker issued the alert.

The North Sea offshore industry has become almost entirely reliant on the S-92 after European regulators last year grounded certain Super Puma helicopters made by Airbus after an accident in which the rotor head separated from the helicopter.

The Herald: A Super Puma helicopter approaches the Sleipner A gas platform owned by StatoilHydro in the North Sea, of the coast of Norway

The Super Puma ban was conditionally lifted by the European safety agency but Britain and Norway have kept national restrictions in place.

Jake Molloy, Aberdeen-based regional organiser of the RMT union's offshore energy branch, said there was concern about the implications of the crash on operations in the North Sea.

"Of course there is concern. This is a tragedy. We await the outcome of investigations and hopefully the black box will give some early indications as to what put the aircraft in the sea. "I'd be concerned about any link to what happened in December as this is virtually the only aircraft we are using in the oil and gas sector as a consequence of the [Super Pumas] being on the ground," he said.

Capt Fitzpatrick was found alive in the waters off the County Mayo coast but later died in hospital, the IRCG said. She had been decorated for bravery in rescue missions and had appeared in an RTE television series about Ireland’s emergency services.

The Dublin-based crew had flown to provide cover for another IRCG helicopter carrying out a medical evacuation from a UK-registered fishing boat 150 miles off the Mayo coast.

A small amount of debris, including what is believed to be a helicopter fuel tank, was found on the shore near Blacksod in Mayo.

Gerard Flynn, the IRCG’s search and rescue operations manager said that no warning was given about the helicopter getting into difficulties in the area in the latest crash before it disappeared.

“This was a shock, the helicopter just simply disappeared. Communication was lost. Once communication was lost, an emergency procedure was initiated, a search was immediately initiated,” he said.

The latest crash came just two days after an eighth anniversary memorial service was held for the 17 who lost their lives after an S-92A, a civilian variant, crashed off the coast of Newfoundland.

A 2011 Transportation Safety Board report indicated that helicopter, which was en route to two offshore oil fields, crashed 11 minutes into its flight, moments after one of the two pilots reported the helicopter's gearbox was losing oil pressure.

In July 19, 2008, an S-92 carrying Rev Sun Myung Moon, the founder of the Unification Church, popularily known as the Moonies, crashed in South Korea. The 16 people aboard were slightly injured in the crash.