New hose lets subs go back to bottom
February 26, 2007
AUSTRALIA'S submarines could be prowling at deep ocean depths as early as next year, restoring a crucial combat capability lost after a near-catastrophe in 2003.
The plan would sharply boost the potency of the navy's six submarines, which have been banned from diving too deep because of safety concerns.
The depth restrictions were slapped on the fleet after a massive on-board flood almost sank the HMAS Dechaineux and its 55 crew off the coast of Perth in February 2003.
The Dechaineux was only 20 seconds from sinking to the ocean floor after a seawater hose broke while the submarine was at its deepest diving depth.
The accident, revealed in The Australian in July 2005, caused more than 12,000 litres of sea water to flood into the submarine in seven seconds, almost drowning sailor Geordie Bunting.
The navy responded to the near disaster by ordering all Collins-class submarines to cut their maximum operating depth -- known as "deep diving depth" -- by one-third to reduce the pressure on the seawater hoses.
But in doing so, it also curtailed the potency of its submarines, which are easier to detect and have more limited options for attack if they are subject to depth restrictions.
Defence last month contracted a Texas-based company, Oil States Industries, to design new flexible seawater hoses for the submarines that can absorb greater water pressure.
It hopes the new hoses will be ready as early as next year, allowing the Collins-class fleet to safely return to the diving depths it operated at before the Dechaineux accident.
"A prototype hose will be tested extensively in 2008 and certified for use before full production of replacement hoses occurs for fitting to submarines," a Defence spokesman told The Australian. "Advances in technology provides an opportunity to acquire replacement hoses that will assure effectiveness and safety of the seawater system."
Defence will not reveal how deep the Collins-class submarines can dive, saying the information is classified because it would help an enemy. The US and British navies publicly admit that their submarines can dive to more than 250m, but the real figure is believed to be more than three times this depth.
The Australian navy says the Collins-class submarines are safe, despite an exhaustive investigation failing to find why the seawater hose failed.
The hoses that ruptured on Dechaineux are still used, but the navy says the new hoses, which have more advanced technology, will provide extra "insurance" against floods.
The Dechaineux flood occurred while the submarine was testing systems under maximum pressure during training 40 nautical miles off the coast of Perth.
Able Seaman Bunting was in the lower motor when the hose broke behind him.
"There was a loud bang," said Seaman Bunting. "Then the water flooded in and I got tossed around like a washing machine. It was coming in so fast I thought it was all over."
The crew shut all external hull valves, halting the inflow of water. But the submarine had taken on so much water that it did not immediately respond to the commands to climb back towards the surface.
"It was pretty bloody close, mate ... there would have been a lot of people frozen in the moment," Seaman Bunting said. "I don't think there was anybody on our boat who wasn't ****-scared that day -- another five seconds and we would have been in big trouble. Another 10 and you have got to question whether we could have surfaced."