SINGAPORE: A two-storey structure resembling part of a submarine stands tall and imposing at a Republic of Singapore Navy (RSN) training centre, tucked away at Changi Naval Base in Tanah Merah. 

Here, engineers squeeze through a tiny gap to get to the base of the "submarine". Lying flat on their bellies, they then practise basic maintenance tasks such as refuelling batteries. 

Known as the maintenance trainer, this is one of two simulators for Singapore's new Invincible-class submarines.

The other is a virtual procedural trainer which crew members can use to familiarise themselves with the vessel and operate certain machinery - without physically stepping into a submarine.

The navy's first and second Invincible-class submarines became fully operational after a commissioning ceremony on Tuesday (Sep 24), officiated by Prime Minister Lawrence Wong. 

The first of the submarines, named Invincible, was launched in 2019. The second and third - Impeccable and Illustrious - followed suit in 2022. The fourth, Inimitable, was launched earlier in April. The development of Illustrious and Inimitable is "progressing well" in Germany and the submarines are expected to return to Singapore by 2028, the Defence Ministry said on Tuesday. 

Designed and customised for operations in Singapore's shallow and busy tropical waters, the Invincible-class submarine features an X-shaped stern rudder for more precise manoeuvres.

Propulsion systems based on fuel cell technology allow it to stay submerged for about 50 per cent longer than older Archer-class submarines.

The 70m-long submarine also has a higher payload of eight torpedo tubes, and can travel at a surface speed of more than 10 knots - about 19kmh - or more than 15 knots when submerged.

Each boat is manned by a crew of 28, and built with customised operator consoles to suit the smaller frames of Singapore naval personnel. 

The Invincible-class submarines were conceptualised and engineered by the RSN, Singapore's Defence Science and Technology Agency (DSTA) and German naval company thyssenkrupp Marine Systems.

Other simulators used by the Singapore Navy include the Invincible-class submarine dive trainer, where crew can learn and practice piloting a vessel. 

The dive trainer tilts back and forth to mimic the descent and ascent of a submarine as it ducks underwater and resurfaces to "escape" from threats.

For the older Archer-class submarines, a command team trainer also lets naval personnel practise operating in a command centre.

Here, navy personnel at a sonar console will listen out for and identify potential targets, before those manning a weapon control console assign weapons for firing.

To become a RSN submariner, candidates undergo a nine-month qualification course.

It starts with a basic training phase where they learn about submarines as well as how they dive and surface. 

They then move on to vocational or specific training: For example, those part of the sonar team will learn how to listen for sounds at sea; while engineers learn about the engines of a submarine. 

Candidates finish off the course with hands-on harbour practical training before a wrap-up assessment of everything they've learnt.

A recent graduate of the submarine qualification course, Military Expert 1 (ME1) Axell Lim, is now an underwater operator of the Invincible submarine. 

The 24-year-old works with a team to help maintain the vessel and keep it operationally ready.

"Onboard the submarine, we are like the ears of the boat. We are trained to listen to the different vessels so that we can identify their type and their direction in order to navigate safely through the waters," ME1 Lim said. 

"It's like walking through a room blindfolded and then trying to listen out to the different voices in the room, and then trying to get from point A to point B."

Ahead of Tuesday's submarine commissioning ceremony, commander of the seventh flotilla fleet Colonel Fong Chi Onn told reporters the navy "definitely wants" to shorten the nine-month duration of the qualification course.

"Submarines are small. You can't bring a lot of people for training on board," he said, adding that trainees would have to compete with existing crew for time on the vessel.

But this has changed with virtual training.

Marine engineer ME4 Toon Wei Kiat, who works to keep the Impeccable submarine's machinery running smoothly, explained the significance of simulators as part of training.

"If I put myself in the (shoes) of the learners, the trainer provided me a safe environment, a place to practise, a place to stress-test my competency, my skills, before (I'm even) required to work onboard a submarine," he said.

Here, submariners will be able to correct themselves if they've made a mistake or followed a wrong procedure, the 48-year-old noted. 

Such that when they're actually performing a real task onboard the submarinemafabet, ME4 Toon added, it "will not cause any unwanted scenarios to happen".

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