Sikorsky has found a problem with this S-92 model that is used to ferry offshore workers in Newfoundland and Labrador. (Courtesy: Cougar Helicopters)

The European Aviation Safety Agency issued an emergency airworthiness directive Friday about the Sikorsky S-92 — the type of helicopter used by Newfoundland and Labrador's offshore oil industry — saying cracks have been found that could lead to loss of control of the chopper.

It's the second emergency airworthiness directive the agency has issued for Sikorsky S-92 helicopters.

Seventeen people died when a Sikorsky S-92 operated by Cougar Helicopters crashed into the ocean about 55 kilometres southeast of St. John's. As a result of the crash, an inquiry into helicopter safety is underway in St. John's.

The European agency's directive says cracks have reportedly been found in parts of the helicopter that attach the main gearbox to the fuselage. The main gearbox operates the main rotor blades on top of the helicopter.

"In one case, the mounting foot was completely severed from the main gearbox," the directive says. "This condition, if not detected and corrected, could lead to failure of the main gearbox attachment, possibly resulting in main gearbox detachment and consequent loss of control of the helicopter."

The aviation agency is recommending that Sikorsky S-92 operators carry out frequent inspections of the main gearbox mounting assembly.

"This emergency airworthiness directive requires repetitive inspections of the main gearbox mounting feet pad and foot ribs for cracks and if any cracks are found, the replacement of the main gearbox assembly with a serviceable unit."

In an email to CBC News, a Sikorsky official said his company is working to make its helicopters as safe as possible.

"The more attention on safety awareness, the better," wrote Sikorsky spokesman Paul Jackson. "We are continuing to work with the affected customers to determine root cause of this problem and correct it as quickly as possible. In the meantime, customers are flying and maintaining normal operations."

Jackson noted that the European Aviation Safety Agency doesn't have authority in Canada.

"Still, we're glad all operators are being reminded to focus on safety."

Friday's directive comes almost two weeks after Sikorsky sent a letter to its S-92 operators on Oct. 7, saying cracks have appeared in footing bolts that attach the main gearbox to the S-92s fuselage.

The reported cracks have occurred only on S-92s that ferry European offshore works to platforms in the North Sea.

On Oct. 8, the agency issued an emergency airworthiness directive explaining that there is an error in the Sikorsky S-92 helicopter's maintenance manual.

It said the error could lead to the installation of an incorrect part, and this could lead to a gearbox failure and a loss of oil pressure.

Gearbox failure and a loss of oil pressure have been cited as possible causes of the Cougar helicopter crash off Newfoundland.

In October, Sikorsky said it had been aware of the maintenance manual problem since July and notified customers at that time.