Specials

Special Eighteen Hours of Perisher

The Trade, November 2002.

 

Lieutenant Commanders Gary Lawton and Mark Potter successfully completed the Netherlands Submarine Command Course held between March and July of this year. The final sea phase of the course lasts for 28 days and is conducted off the West Coast of the United Kingdom and Ireland. The following piece covers an eighteen-hour period towards the end of the course.

"All round look, raise attack". Silence fell quickly in the control room as the periscope rose to a height half a metre above the choppy, grey waters. Spray, whipped up by the strengthening norwester, flew onto the periscope window obscuring the Duty Commanding Officer’s view out to the west. With a silent curse, he ordered the attack periscope to be lowered after a single, slow sweep of the horizon. He knew that he would have to raise the periscope again within four minutes to see if the ‘SOMERSET’ was still within engagement range. Sonar had reported that the Type 23 frigate had faded on sonar two minutes ago. This information was unsurprising as the DCO knew from experience that the 23’s were extremely quiet below 10 knots when they used their diesel-electric propulsion. The warship could still be as close as 4000 yards away. The DCO murmured to his Attack Coordinator "If that contact is not visible after the next look we will carry on with the approach".

British Royal Navy type 23 frigate. (Photo: © DCC Navy).¹

ORCA (According to P. van den Broek code names for SMCC boats are not normal so the reporters probably made a mistake since ORCA is the name of the GIPSY trainer) had spent the last three days approaching the North Channel from the west coast of Ireland. The crew had threaded their way through a NATO task group that was, and still known to be, supported by Nimrod and P3 Orion maritime patrol aircraft. The poor weather had helped mask their presence, especially during the transit of the treacherous Orsay Gap. The Gap lies 25 miles to the north of Ireland; one mile wide and 100 metres deep, it follows an Shaped groove that cuts through granite reef 20 metres deep. Countering the tidal currents that reach speeds of 5 knots ORCA had navigated her way through using the stream to assist in conserving the battery. The echo sounder provided the necessary clues to determine where the boat was from her expected track.

The Gap was effectively the gateway to the North Channel and then the Clyde Approaches, home of the ORCA’s target – a Ballistic Missile Submarine based at Faslane, Scotland. Intelligence had reported the imminent departure of one of the ‘bombers’ to her patrol areas deep in the Atlantic Ocean. The tasking was explicit and direct – destroy the SSBN before it entered the Atlantic. The DCO and his team had thought long and hard on how to achieve this aim and knew their best course of action to achieve their goal was to penetrate the coastal waters and gain contact on the target before it submerged. Once it had dived the target would be a hole in the ocean and virtually impossible to detect.

Royal Netherlands Navy type P3 Orion maritime patrol aircraft (Photo Marco P.J. Borst).¹

"Bearing that! Down". The DCO stepped back from the descending periscope and off the viewing platform that dominated the centre of the control room. Pacing over to the chart table he examined the detail of the island that he considered offered the best opportunity of a safe snorting haven. Yes, he had just identified the ruins of the castle that dominated the skyline of the ridge that ran through the centre of the island. Following a brief exchange with the AC and navigator he briefed the control room. "Right team, during that last all-round look there was no sign of the SOMERSET. I believe she has continued to open out to the west. I saw the castle ruins of the large island – the bearing and the echo-sounder depth indicate we are just to the north of the 40 metre patch where we will await our target. Standby bearings for a fix".

The fix placed ORCA 2 miles north of the island. The island was some 5 miles by 2 miles in size and its north coast was dominated by a series of cliffs and granite outcrops, battered by Atlantic gales for millennia. The chart revealed that the water was deep enough close inshore for ORCA to safely operate. The DCO believed he also had a good chance of being able to snort without detection from patrolling ASW aircraft due to the sheer face of the cliffs and the abundance of rocks and reef protruding through the waves.

"Standby to snort on three diesel engines!" The two engine room watch keepers made their way aft through the crew mess to monitor their compartment as the snort was prepared from the Control Room. The sun had set ninety minutes ago and only one P3 racket was held at low levels. The previous DCO had not snorted for the duration of his watch. The battery was now at 17% and the atmosphere needed to be changed. Additionally, the crew were already on edge as smoking had not been permitted for over 5 hours and the DCO knew the team performed better when they could smoke. The DCO briefed the oncoming watch leader of his intentions; snort (snort and snort again) and remain undetected from the MPA and use the island to minimise their radar capability.

"Danger, danger, danger!" After just 20 minutes the snort was stopped and all masts lowered as the P3 radar signal strength increased suddenly. The DCO returned to the Control Room quickly scanning the plots and sensor displays. Following a short situation report from the Watch Leader he checked ship control and conducted an all round look on the attack periscope. As he looked out into the night two lights, one red the other green, traced arcs in the darkness. It was the P3 – had ORCA been detected or was the aircraft conducting a search in the vicinity of the island? The P3 had been on station for over four hours. The DCO knew the aircraft would have to return to its base to refuel and change crews within the next two hours – what aircraft, if one was available, would replace it? Checking the battery capacity and reducing speed he ordered the submarine to a new course to stem the tidal stream so that the boat maintained its position over the 40 metre patch. After seven minutes the DCO conducted another all round look. The aircraft revealed itself as a single, strobe light flying low at a range of five miles. Waiting a further seven minutes the Watch Leader conducted the next visual sweep simultaneously checking the intercept strength of the P3 radar. The radar strength had decreased and the aircraft was no longer visible.

For the remainder of the night ORCA continued to snort at intermittent periods clearing the atmosphere and improving the battery capacity to 65%. The DCO slept soundly until "Danger, danger, danger!" woke him with a start. Upon entering the Control Room he managed to hear the last part of the report from the radar intercept operator "…classified Searchwater". So, the new dangerous racket was from a British Nimrod aircraft. This radar had the potential to detect a single periscope head at great range. The DCO questioned the Watch Leader about the new racket. The intercepted bearing was to the north-east of ORCA; this meant the aircraft was likely to be arriving within its, and ORCA’s, patrol area from its home airfield in the north of Scotland. The first wisps of light were apparent in the east as the Watch Leader conducted an all round look. The sun would rise in another 45 minutes. The Nimrod wasn’t seen during that single, slow sweep of the horizon.

RAF type Nimrod R1 maritime patrol aircraft (Photo: © DCC RAF).¹

The DCO checked the chart with the Watch Leader. They had calculated that the SSBN would arrive to the northeast of their position in a further eight hours. ORCA had a further 25 miles to go to close towards that point. Intelligence traffic received overnight reported that Sea King helicopters, fitted with dipping active sonar, would be supporting the egress of their target. They, in addition to the warships, would make it very hard to get to an attacking position without being detected. He knew that he would have to use ORCA’s inherent stealth to get to that position.

"Biiinnnggg". The underwater telephone loudspeaker turned everyone’s head as it relayed the first transmission of a sonobuoy. The sonar operators quickly classified it as a British sonobuoy at a level that suggested it may gain contact on ORCA. "I have the submarine" ordered the DCO, "Set revolutions for 2 knots". Had ORCA been detected by the Nimrod’s radar or was this the first part of a pre-planned acoustic search by the aircraft. Assume nothing, the DCO thought to himself as he conducted the next all-round look. There it was – the Nimrod looped around to the north of ORCA. Feeling very exposed, as though all the eyes of Nimrod’s crew were focussing on his part of the sea, the DCO lowered the periscope. He briefed the Control Room "Okay team, I believe that the Nimrod may have got a faint indication from her radar of our presence and is now attempting to verify that using active sonobuoys. We will remain at low speed in this shallow water to avoid classification."

For the next hour the DCO continued with intermittent looks through the periscope as the single sonobuoy transmitted and the Nimrod patrolled at low level to the north of the submarine. ORCA continued to creep above the seabed at less than walking pace to reduce any wake from the periscope during its periods of exposure. "New contact on sonar, bearing 080, diesel audible, in/out, classified fishing vessel" reported the senior sonar watch keeper. The DCO thought about this new piece of information. Could he use this contact to mask his exit from his current haven and skulk out to the northeast to close the expected track of the SSBN? What if it started trawling? Where was it likely to fish? Will it mask the presence of ORCA’s target? The all round look, essential to maintain safety from other quiet contacts, was due again. This time the fishing vessel could be seen, it was in transit and heading to the deep waters to the east of the Gap. But that wasn’t all that there was – the Nimrod had disappeared only to be replaced by two Sea King helicopters heading towards ORCA. The DCO was about to announce the sighting to the control room when the underwater telephone speaker again seized everyone’s attention.

Sea King Mk6 type helicopter with dipping sonar (Photo: © DCC Navy).¹

"Berrrrwuuuuppp!!!" The first transmission from the Sea King dipping sonar reverberated from the speaker. The dipping Sea King was 3000 yards to the north of ORCA. It was now apparent to the DCO that the Nimrod had gained some sort of contact on ORCA and the Sea Kings were being employed to prosecute the datum. The DCO was now forced to remain at slow speed to defeat the active transmissions from the helicopters. The shallow water and proximity to shore would also mean that there would be lots of reverberations that would confuse the sonar returns.

It was time for the next all-round look. The DCO stepped up onto the viewing platform having checked the displays and plots. After a quick glance at ship control the attack periscope was raised and his assistant started his stopwatch. "5 ……, 10 seconds……". The DCO slowly turned the periscope keeping the horizon just in view as he searched for new contacts. Suddenly the eyepiece seemed filled with the bow-like structure and bulbous nose of the Sea King. It was just 600 yards away and stationary lowering the sonar body into the water. The DCO felt the hairs down the back of his neck rise as he looked momentarily at the helicopter. He could almost look into the eyes of the pilot. "15 …….., 20 seconds". "Down!" the DCO barked as he completed the all round look. The underwater telephone speaker seemed to burst into life as it reported another sonar transmission. "That was from one of the Sea Kings, currently at red 130 at a range of 600 yards" announced the DCO, "we will proceed deep, continue at low speed and hug the bottom to avoid visual counter-detection from the helos". "Five down, keep 35 metres".

Gradually ORCA descended from periscope depth. An operator was closed up on the echo sounder to report the changes in sounding as the boat inched its way above the seabed. After 12 minutes the closest Sea King ceased transmitting and opened away from ORCA to the north. Soon a new contact started pinging out to the west. The transmissions were quickly classified as belonging to a Type 23 frigate. The increasing strength and bearings of the sonar indicated that the frigate was conducting a search along the coast from the west. It appeared ORCA had slipped away just in time. The DCO now increased speed to open out away from the shallow water and as he did so he took the submarine deeper to get below the layer of warmer water to make it even harder for the different sonar's to gain contact on the ORCA. He was also conscious that he had to make ground to where he anticipated the SSBN to be. It was probable that the SSBN would be routed to the north side of the channel if his opposition had believed that it was ORCA they had detected just off the island.

After a two hour ‘stroll’ at a speed of eight knots ORCA was ready to return to periscope depth. The sonar traces were analysed revealing a cluster of contacts out to the east and faint transmissions from the Type 23 to the southwest. There hadn’t been any sign of aircraft activity for the last hour. "Ten up, keep eighteen metres" ordered the DCO. ORCA slowly came shallow, the DCO gradually ordering less and less speed as the submarine approached its ordered depth. He allowed the submarine to settle at eighteen metres before raising the attack periscope and conducting the all round look. With a racing heart he ordered the attack periscope lowered. "Ship Control, pipe the submarine to Action Stations". "All positions two contacts in sight, the SSBN at six thousand yards and just behind her a Type 22 frigate. Standby set-ups!" ORCA was poised to attack.

Members of the Perisher 2002 course in the wardroom of a Walrus submarine

 

The Trade, November 2002.

¹: Type-23 frigate, P3 Orion and Sea King photo added by the webmasters.

 

 

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