INS Betwa mishap: Navy orders probe, uneven weight balance suspected to be cause of accident

Two sailors were killed and a frontline naval warship was put out of action when the INS Betwa capsized in a dry dock in Mumbai yesterday. The INS Betwa, a 3800-tonne Brahmaputra class frigate was being undocked at the naval dockyard at about 1.50 pm on December 5 when it slipped off the dock blocks and keeled over in the dry dock.

REGULAR OCCURRENCE

The incident adds to the Navy's worrying record of losing warships in peacetime accidents. Since 2004, the navy has lost a submarine, a frigate and two corvettes in accidents. The most catastrophic of these was the August 14, 2013 loss of the INS Sindhurakshak which exploded and sank in the naval dockyard killing 18 crew members.

Yesterday's incident is the first of its kind in the Indian Navy's history. A near-miss occurred in 1998 when a Type 1500 submarine INS Shishumar listed during dry docking. The Shishumar did not topple but remained at a 17 degree list till the next high tide when she was refloated. "The incident occurred during a misalignment in the dock plan where two or three sets of the 16-odd dock blocks were displaced," one officer recalls.

A dry dock is a narrow basin which can be flooded and a ship brought in, then drained to allow the vessel to sit on a dry platform. This is called docking. Vessels that are docked are usually brought to rest on a series of 'dock blocks' or keel blocks. Vessels are dry docked to allow their underwater surfaces to be repaired and painted.

Docking and undocking of a ship is a precise plan called the 'dock plan' drawn out well in advance. Blocks are arranged in the dock prior to the docking based on the underwater profile of the ship.

DEDUCING THE REASON BEHIND THE ACCIDENT

"We will need to know the Betwa's dock plan. Also, did it happen when the ship lifted off the blocks and then due to some improper calculation of trim, the ship being heavier on the port side, pivoted off the blocks?" says a warship captain.

Loading and weight balance is a very elaborately done with the warship's Captain certifying its correctness.

"Based on these photographs, it would appear that the warship was unevenly loaded," one naval officer says. "The predominant weight was on the port side resulting in more weight being generated on the dock blocks which would have either shifted or given way, thus leading to the ship to turn turtle."

It is too early to say whether the 126-metre-long warship is a total write-off, naval officials say. That can only be decided after the ship is made upright in a massive salvage exercise. The Betwa will have to be lifted and canted over before the internal damage can be studied. A capsize of this nature could result in heavy internal damage, dislodgement of internal equipment and disturbance of the ship's centre of gravity.

A navy spokesperson said that the technical evaluation for making the ship upright is in progress and an inquiry has been ordered into the incident.

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