A ROW has blown up after oil industry representatives recommended that much of the Super Puma helicopter fleet should be cleared to fly, just six days after the Shetland crash that killed four oil workers.

The Helicopter Safety Steering Group (HSSG), consisting of oil and helicopter companies, trades unions and pilots, has called for an end to the voluntary suspension of many flights despite an initial investigation deciding it was too early to identify a cause for the crash.

But the HSSG has ­recommended that a ban on passenger flights involving the Super Puma AS332 L2, the type involved in the Shetland crash, should remain. There are 13 AS332 L2s, one AS332 L1 and 19 EC225 helicopters serving the UK oil and gas industry. AS355s have also recently been used.

In April 2009, 16 people died when an AS332 L2 Super Puma, the same type involved in the latest Shetland accident, returning to Aberdeen from the BP Miller platform plunged into the sea after a gearbox failure.

But the Civil Aviation ­Authority (CAA) has warned none of the Super Puma helicopters would be sanctioned to return into service, until it had given approval.

A CAA spokesman said: "We are the safety regulator and we have to be absolutely sure that recommendation can be safely put into effect.

"We need to be sure passenger operations on the Super Puma variants are safe and we are working with operators and HSSG to achieve that. They cannot begin passenger operations until we are absolutely sure that it is safe to do so."

Unite union leaders ­questioned the decision, saying the continued grounding of the AS332 L2 was the bare minimum the industry could be expected to do.

"Confidence has been shattered and the industry needs to provide substantive evidence - not ­opinion - to its workers demonstrating the airworthiness of the helicopters that are now returning to operations," said Unite Scottish Secretary Pat Rafferty.

"At the same time, Unite is demanding guarantees from employers that workers who feel unable to fly will not be subject to pressure or the threat of dismissal. The industry cannot merely expect the workforce to simply get their boots on and get back to work.

"Looking to the future and moving forward, the recovery of the helicopter's black box and the data held within will hopefully hold the key to establishing why this happened.

"Furthermore, particularly in light of the last 18 months where the UK offshore industry has been blighted by evacuations of offshore installations in addition to helicopter ditches, a forensic analysis into offshore health and safety must take place and an emergency Scottish Parliamentary debate should be the starting point for this."

Earlier, the missing flight data recorder from the crashed helicopter was recovered.

The Air Accidents Investigation Branch (AAIB) said the combined voice and flight data recorder would be taken to its Farnborough headquarters for analysis.

The AAIB said the Super Puma had appeared to show a reduction in airspeed accompanied by an increased rate of descent.

It said it appeared the helicopter had been intact and upright when it entered the water, but it was too early to identify a cause of the crash.

The AAIB update reported: "The evidence currently available suggests that the helicopter was intact and upright when it entered the water.

"It then rapidly inverted and drifted northwards. The helicopter was largely broken up by repeated contact with the rocky shoreline."

The HSSG said a campaign would be started to engage with the offshore workforce.

MP Frank Doran has called on Transport Secretary Patrick McLoughlin to establish a wide-ranging public inquiry into the safety of helicopters.