Indonesia navy says missing submarine likely sank but holds hope for crew survival; Indonesia thanks Australia for help

Indonesia’s navy has confirmed a missing submarine has likely cracked and sunk but insists crew members may be alive.

Indonesian Navy submarine KRI Alugoro sailing on a search mission for KRI Nanggala, a Navy submarine that went missing during a naval exercise, in the waters off Bali on April 22. Picture: AFP

Indonesian navy officials have confirmed a missing submarine, KRI Nanggala, has likely cracked and sunk in waters up to 850 metres deep north of Bali — far lower than its capacity depth — with 53 people on board, but insist there is still a chance of finding crew members alive.

Navy chief Yudo Margono said debris recovered within about a 16km radius from where the 44-year-old vessel first submerged at 3am Wednesday and lost contact — including pieces from the torpedo tank, periscope grease and prayer mats — suggest the 44-year-old vessel’s torpedo tank had cracked during the dive, causing it to flood and sink.

But Admiral Margono said the search for surviving submariners would continue — despite previously saying the Nanggala’s air supply would run out at 3am Saturday (AEST 0600) — because if the vessel had not lost power it might still have more than a day’s air left.

“We cannot estimate the condition of the crew because we have not found even one of them. Our hope is that we will know after evacuation,” he said on Saturday afternoon.

“In the last few days we found pieces and items in the waters in the last known location of the submarine. We believe these components were attached to the submarine and would not have detached if it was not facing external pressure or a crack in the torpedo launcher.

“With these authentic proofs, which we believe came from the Nanggala, we have been advised to declare the submarine sunk. Now we will prepare for technical evacuation for the crew members who may be alive.”

Admiral Margono said the submarine had likely cracked under pressure then flooded, but that it was possible that there were cabins that the water could not enter.

Asked about oxygen supply, he replied: “Like I said, [there would be] 72 hours oxygen if the sub blacked out, but if it has electricity then it is five days. We have no way to establish whether they are blacked out or not. When they dove all their lights were on.”

The sinking of the Nanggala marks the maritime nation’s first ever submarine disaster, but comes just three months after 62 people died when an Air Sriwijaya passenger plane plunged into the Java Sea just minutes after take-off from Jakarta airport.

Admiral Margono said the Nanggala is believed to have sunk into a sea trough up to 850m deep, far below its capacity of 500m.

Many experts believe the 1395-tonne, diesel electric vessel would have begun to break up at such depths.

Search vessels in the area had already located an oil spill suspected to mark the point where the submarine submerged and then lost contact around 3am Wednesday during a torpedo exercise, as well as a “high magnetic point”, possibly an object, floating about 50m to 100m below the water’s surface.

But it was only on Friday that the first sonar equipment capable of identifying the object — aboard Australia’s HMAS Ballarat — arrived on the scene. Indonesia’s own hydrographic survey vessel, KRI Rigel, arrived on Friday evening, joining a fleet of more than 25 search ships.

Singapore’s submarine rescue vessel MV Swift Rescue reached the area on Saturday, while two more deep sea search and rescue vessels were on route from Malaysia and India. A US P8 Poseidon surveillance aircraft also arrived in Bali yesterday.

Admiral Margono conceded the submarine’s likely depth would make any evacuation difficult and that it was likely that the vessel would need to be refloated first, but added; “With these difficulties, we will still try our best”.

Singapore’s MV Swift vessel is equipped with a Deep Search and Rescue Six (DSAR 6) submersible craft that can attach itself to a crippled submarine and rescue up to 17 occupants at a time, but is only built to sustain depths of up to 500 metres. A remote operated vehicle on board can reach depths of up to 1000 metres however.

Admiral Margono added the crew on board Australian naval frigate HMAS Ballarat had been working “non-stop since last night” to locate the missing submarine.

Late on Friday Indonesian Defence Minister Prabowo Subianto expressed his “tremendous gratitude” to Australia for its assistance in the search for the Nanggala.

“On behalf of the Ministry of Defence of the Republic of Indonesia, I’d like to express my tremendous gratitude for the help given by the Australian Government in the tragedy of the loss of contact KRI Nanggala 402 through the Minister of Defence His Excellency @PetterDutton_MP,” General Prabowo tweeted.

Retired Australian Navy rear admiral Peter Clarke told The Weekend Australian that if the submarine had sunk to 700m or more there was little chance anyone would have survived.

“I think the amount of time that people might have been able to survive has been grossly overestimated,” said Mr Clarke, who has previously commanded both nuclear-power and conventional submarines.

“If you look back to things like the Kursk (the Russian submarine that sunk in 2000) we were all thinking then that people might survive for five to 10 days when actually we were talking hours, not days.

“The thing that would be most catastrophic in a situation like this is a submarine sinking well below operating depth, to a depth where a weak point in the hull fails — such as torpedo tubes or access hatches — and then the water comes in very quickly.

“The more water comes in, the faster the submarine sinks, eventually equalising the pressure inside at which point it would be unlikely for people to survive.”