Art of the Hunter
Orions scour the depths of the ocean from the heights of the clouds in search of modern warfare’s most elusive prey – the submarine. PTE John Wellfare learns how it’s done.

The lessons of history

CPL Daniel Bowden signals to the crew of an AP-3C on the flightline at RNZAF base Whnuapai during Exercise Tasmanex.

Photo by LACW Sonja Canty

A P-3C Orion, shown before recent modifications to the Air Force Orion fleet, passes over HMAS Cessnock at the beginning of a patrol.

Photo by PO Tracy Casteleijn

Search and Destroy

Click picture for a larger image of the Search and Destroy diagram

STEALTH is a submarine’s primary tool for both attack and defence, which makes the maritime patrol aircraft its number one enemy.

From high above the ocean surface, aircraft like the Air Force’s Orions can search for submarines using a variety of technologies from radar through to infrared sensors and deployed sonar buoys.

According to Squadron Leader Tim Creevey, XO of No. 11 Squadron, the keys to sub spotting are good intelligence support, good use of all the aircraft’s sensors and patience.

“Your intelligence needs to tell you, preferably, what type of submarine you’re looking for – nuclear or diesel – and that then will dictate the type of tactics that you will use to try and detect the submarine,” he says.

A conventional submarine runs on batteries while under the water, allowing it to be very quiet.

But a conventional submarine needs to “snorkel” several metres below the surface and take in air through a snort induction mast to run its diesel engines and recharge its batteries.

It’s during these periods of snorkelling that a diesel submarine is most vulnerable to detection.

“The tactics for [finding] diesel submarines are usually centred around trying to detect the periscope and snort mast while they’re above the water,” SQNLDR Creevey says.

“[Snorkelling] is usually done by the submarine at night time so it doesn’t allow a visual chance of detection, and it’s usually done when the ambient noise levels in the water are quite high to try to mask the noise generated by the engines.

We count on the fact that, from time to time, they’ll have to come near the surface to recharge their batteries.”

Maritime patrol aircraft lay sonar buoys, capable of picking up the sounds of a snorkelling submarine and reporting that information back to the aircraft, which helps an aircraft cover a much broader area.

Other sensors that can help detect a submarine are infrared and electro-optic sensors, which are usually mounted on the nose of the aircraft and allow it to scan a narrow arc to the front.

Nuclear submarines work differently to diesels, SQNLDR Creevey says, because they run permanently on their power plant and don’t need to surface to recharge batteries.

Although not as vulnerable to the tactics used to detect conventional submarines, the nuclear boats can still be located.

“[Nuclear submarines] are generally accepted to be slightly more noisy than a battery-powered boat, although modern day nuclear-powered submarines are also very quiet.

“We set up a sonar buoy field of a large number of sonar buoys to try to detect the noise made by the boat while underwater. That’s basically our primary means of detection.

“If we have intelligence that tells us exactly where it’s going to be tracking, then that’s even better, because we can set up a barrier [of sonar buoys] in front of it.”

But all these detection methods don’t render submarines helpless and ineffective. Most new subs have a number of tools and tricks to stay hidden and, in some cases, fight back.

“Modern-day submarines have sophisticated sensors that can detect a sonar buoy landing in the water,” SQNLDR Creevey says.

“Some of them are equipped with towed array sensors, which is basically an acoustic array that they tow behind them and they can pick up maritime patrol aircraft and ships and so on from a greater distance.

“There are new weapons coming onto the market now, which do have the capability to be launched from a submerged submarine. There are very few navies that actually employ that at the moment, but that’s an emerging threat.

“The risk is always of a submarine surfacing fully, with its sail out of the water, and having someone exit the conning tower and prepare a shoulderlaunched surface-to-air weapon. If we come across a surfaced submarine, that’s something we need to consider.”

The Orions, although usually unarmed, are capable of launching an individual attack or coordinating an attack by nearby allied forces if they are operating in direct support with surface vessels.

When operating in conjunction with other naval units, the detection of an enemy submarine means that its crew can expect to face a torpedo at any time. “Anti-submarine warfare helicopters can be tasked to come out at the same time [as an AP-3C],” SQNLDR Creevey says.

“So there could be us and two helicopters pursuing the same submarine at the same time. The helicopters are equipped with sonar buoys and so we’ll alternate – one aircraft will go down lower and one will go up higher – tagteam tracking the submarine and using helicopters to deploy weapons and so on.”

Like all things in war, it’s a two-way street – the hunter is also the hunted. New technologies for both sides of the battle are constantly being developed, which means that long into the future for both the submariner and the sub-hunter, winning will depend on skill, military intelligence and sometimes just plain luck.

 

The lessons of history

A captured German UB-133 in dock at the end of WWI.

A FORCE’S ability to find and destroy enemy submarines can decide the fate of thousands.

Although attempts to use submarines as weapons had been made as early as 1653, they weren’t particularly successful in war until WWI, in which German U-boats were particularly formidable, sinking between 300,000 and 600,000 tonnes of shipping per month from 1916-17.

During WWII, German U-boats sank more than 5000 merchant vessels and many Allied warships. Allied navies also employed the new boats with great success.

Submarines comprised only 1.6 per cent of the WWII US Naval fleet, but were responsible for sinking 30 per cent of the Japanese Imperial Navy by the end of the war.

 

 

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