Spotlight on sub safety

Civilian visitors were at the controls of USS Greeneville

The BBC's Defence correspondent Jonathan Marcus looks at submarine safety issues after news that at least one civilian was at the helm of the USS Greeneville when it crashed into a Japanese trawler, sinking the vessel with the loss of nine crew.

The incident happened as the USS Greeneville was practising a rapid rise to the surface.

The US Navy confirms that civilian visitors were seated at two of the three main control positions of the submarine when it surfaced beneath the Japanese fishing boat.

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One was at the helmsman's position and the other at the ballast controls that help control the submarine's ascent or descent.

A former nuclear submarine captain says it is not unusual for civilians to vistit submarines, and to even man some control stations.

Captain Richard Sharpe, who served in the Royal British Navy, told the BBC that submarines are sometimes opened up for family days, VIPs and visits from contractors.

'Nothing to do with guests'

But Captain Sharpe says the activity of the civilians is totally irrelevant to the cause of the accident:

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"The accident was purely the fault of the command, who miscalculated were this fishing vessel was," said Capt Sharpe.

The USS Greeneville was conducting a drill in which the submarine dives to about 120 metres (400 feet) and then rapidly surfaces - known as an emergency main ballast blow.

Captain Sharpe says a person would have acted on an order when releasing the ballast, making the submarine shoot to the surface.

The real mistake, he says, was the decision to execute the manoeuvre in the first place.

"The [civilian] person would have been doing exactly what he was asked to do, which is to release the ballast tanks. Why they decided to surface when they did is the command's problem."

Unanswered questions

While it is not uncommon to have civilians in such positions during a visit, it is perhaps surprising that they should be in such positions during a critical manoeuvre.

Clearly the US Navy will want to be sure that their presence did not lead to any distraction of the crew.

The navy is already looking into why the submarine did not see the fishing vessel before it surfaced and lessons may be learnt for the future.

'No rescue effort'

But the Japanese authorities have also criticised the US for failing to give adequate help to the victims.

The USS Greeneville did not participate in the rescue operation

The US Navy has blamed the sea conditions, with waves breaking over the submarine, and stresses that a submarine's huge circular hull and poor sea-keeping qualities on the surface made any rescue effort impossible.

All of this may be technically correct, but it still leaves the question, despite the risks, about whether more could have been done.

Given the unpopularity of the US military in parts of Japan this is a highly charged issue.

The US Navy needs to be able to show that every care was taken in operating the submarine and that every effort was made to rescue survivors.

On both counts it still has to convince a sceptical Japanese public.

With additional reporting by BBC News Online's Lars Bevanger