The information on what happened on Wednesday (April 21) was given by Indonesian navy chief Yudo Margono at a news conference on Thursday.
All are in Central Indonesian Time (WITA), the same time logged in Bali and Singapore.
Wednesday, April 21
Nanggala-402 requests permission to dive at a depth of 13m and prepares to fire a torpedo. In line with procedure, the submarine is accompanied by a searider.
The submarine’s bow is visible to the searider from a 50m distance.
Other navy vessels get into position to launch the torpedo.
Searider monitors the periscope and Nanggala-402’s identification light slowly dims and disappears.
Nanggala-402 fails to respond to several calls. The periscope, which should have been visible, vanishes. Communication with Nanggala-402 is cut off.
A helicopter is dispatched to try to locate it visually but yields no result.
The submarine is scheduled to resurface, but does not appear. The navy then conducts procedures when a submarine loses contact or experiences problems.
The navy sends out a “submiss” signal, launches a search effort to look for the Nanggala-402 and training is postponed.
Thursday, April 22
Indonesia deploys six military vessels and a helicopter in its search effort at the last known position of the submarine in waters of north Bali. The ships include underwater oceanographic vessel Rigel.
Indonesia later says it is deploying 14 more vessels to join the search.
The Republic of Singapore’s submarine rescue vessel MV Swift Rescue vessel is expected to arrive in Bali waters on Saturday, said an Indonesian military spokesman.
A submarine rescue ship of the Royal Malaysian Navy, Rescue Mega Bakti is expected to arrive on Monday.
Indonesia’s defence ministry says Australia is sending HMAS Balarat and HMAS Sirius, India is sending one vessel and the United States a Poseidon aircraft.
Offers of assistance also come from Germany, France, Turkey, South Korea and Russia.
THE STRAITS TIMES