UNION leaders say operators need to give more assurances to offshore workers that North Sea helicopters are safe after the latest incident involving a Super Puma.

Two years ago, an Emergency Airworthiness Directive was issued over the EC225 and AS332 by the European Aviation Safety Authority over concerns about the fairing gutter, which protects the intermediate gearbox.

In May, a fleet was grounded after an EC225 operated by Bond Offshore Helicopters carried out an emergency landing in the North Sea.

An Air Accidents Investigation Branch (AAIB) later initially said a crack was found in the gearbox, but last week said there had been a false alert over failure of the main gearbox cooling and lubrication system.

The AAIB said Eurocopter, the manufacturers of the EC225, should be required by the European Aviation Safety Agency to review the design of the main gearbox lubrication system to ensure the crew was given an accurate indication of the system's status.