Flights over the North Sea by Super Puma helicopters have resumed just one week after an AS332 L2 Super Puma crashed off the Shetlands in circumstances that remain unexplained.

Four workers―Sarah Darnley, George Allison, Gary McCrossan, and Duncan Munro―were killed on August 23, while one of 14 survivors of the crash remains in hospital with a broken back.

The decision to resume flights was taken by the offshore industry’s own Helicopter Safety Steering Group (HSSG), which includes the oil majors, support companies, the helicopter operators and the trade unions.

Flights were restarted only hours after the Air Accident Investigation Bureau (AAIB) received the aircraft’s “black box” flight recorder, with wreckage still being recovered from the sea off Sumburgh airport and before any but the most preliminary investigation into what happened had begun.

The HSSG decision was based on general expressions of confidence in the aircraft, rather than an assessment of the circumstances of the crash, from the European Aviation Safety Agency (EASA), Civil Aviation Authority (CAA), the pilots’ union BALPA, the Norwegian CAA, and the helicopter operators. The British CAA had previously supported the ban, stating that flights should not be authorised until it was “absolutely sure that it is safe to do so.” It suddenly did an about face, announcing in the absence of any new evidence, that it did not believe that accident was caused by an “airworthiness or technical problem”.

By contrast, an AAIB update issued at the same time as flights resumed stated, “investigation is ongoing and at this early stage it is not possible to identify the causal factors leading to the accident.” In terms of what actually happened, the AAIB merely confirmed that the aircraft suddenly reduced airspeed and descended rapidly. It was intact and upright when it entered the water. It then rapidly inverted.

Over the weekend an extraordinary dispute emerged between the AAIB and the CAA. An AAIB spokeswoman told the Herald, “The CAA have said what they have said, that is not what the AAIB or the Department for Transport has said. I can’t figure out why they have said what they have said. Our line is absolutely that it is an ongoing investigation and a cause has not yet been identified”.

Pressed by the Herald to explain if their decision could change again, a CAA spokesman conceded that the situation was “complicated” and “could change when we have more available information”.

The row makes clear that the original flight ban was solely intended to pacify oil workers.

The “timeout for safety”, was applied to all four Super Puma variants―L, L1, L2 and EC225―operating in the North Sea, despite these being significantly different aircraft. Moreover, having lifted the ban, the HSSG insisted that because of “understandable sensitivities” L2 aircraft would be restricted to “non-passenger carrying maintenance, positioning and training flights”.

Seeking to justify the ban’s lifting and a return to business as usual, Les Linklater of the HSSG said, “Four people tragically lost their lives... However there are almost 16,000 people offshore currently...there are 250 people who have spent more than 21 days offshore”. Linklater said that the helicopter operators should now offer “confidence building communication”.

The HSSG stance was backed up by the Rail, Maritime and Transport (RMT) union leader Bob Crow, who told the BBC, “At this moment there’s no reason [to think] the crash was mechanical”.

During the “timeout” Crow celebrated the fact the trade unions had made a “massive breakthrough in our core demand of workplace access”. The companies, fearing an industry-wide protest slipping out of the unions’ control, agreed to union officials remaining in contact with workers on the rigs.

The British sector of the North Sea has seen a string of incidents in recent years.

In 2009, an AS332 L2 disintegrated mid-air following a gearbox failure which detached the helicopter’s main rotor blades. Sixteen passengers and crew were killed. A Fatal Accident Inquiry into the disaster has repeatedly been delayed and is now scheduled for 2014, five years after the event.

Last year, two EC225 Super Pumas ditched, both of which were attributed to “potentially catastrophic” gearbox failures. The entire fleet of 16 EC225s was subsequently grounded pending remedial work by the three main helicopter operators. A blanket ban on the EC225s was only lifted in August this year.

The latest crash has once again focussed workers’ fears on the safety of the North Sea Super Pumas. A Facebook page Destroy the Super Pumas now has nearly 38,000 likes and features hundreds of comments from oil workers and their families.

Many commented on uncomfortable and dangerous seating arrangements in the Super Pumas. Workers have to put up with flights lasting two or three hours in a cramped cabin filled to capacity. In the event of a ditching, the passenger cabin can fill with water and the aircraft capsize in seconds, making evacuation very difficult.

This is exactly what happened August 23. One of the survivors, Martin Tosh, told the Shetland Times that the aircraft “banked to the left and was in the sea. The helicopter filled up extremely quickly. In less than 10 seconds the helicopter was full of water. I was one of the last survivors out”.

One worker said on Facebook he would only fly in future if he had a window seat. He went on, “We all feel the same about these conditions... all because the oil companies want to cram in as many as possible and transport them at as little cost as possible. Surely in this day and age an industry does not have the right to take away a person’s opportunity of having a clear escape route in order to save some petty cash”.

Surviving helicopter ditching has long been known to be problematic. Helicopter engines are necessarily on the top of the aircraft’s fuselage, therefore the aircraft tend to capsize and float, if they float at all, upside down. A 2005/6 report from the CAA, “Summary Report on Helicopter Ditching and Crashworthiness Research,” noted that “special consideration” was needed for the Northern North Sea with the long flight times and inhospitable sea conditions in the region.

The report, the latest of a long and highly technical series, concluded “The single most effective means of improving occupant survival in the event of a post-ditching capsize or a survivable water impact is through the provision of additional flotation devices to prevent total inversion following capsize”.

To date the CAA recommendations have not been implemented and no such upper fuselage flotation devices have been fitted to helicopters operating in the British sector of the North Sea, a fact which can be explained by the cost of these basic safety measures to the profit margins of the oil and helicopter industries.