Workhorse of Swedish naval aviation


While the Type 4 helicopters of the Swedish Air Force were assigned to a fairly specific task, the Swedish Navy Type 4s had a wider range of jobs which required them to be adapted in accordance with the main work they were required to carry out. On the whole the Type 4 was well suited for this role as its transportation and passenger space could be described as a long steel tube which allowed in relatively short order (depending on the assignment) the helicopter to be prepared for a completely different job. On one day for instance it could be airlifting a platoon of coastal soldiers and then the next acting as a medevac helicopter. One task that the Navy Type 4s were especially renowned for was submarine hunting.

The Swedish Navy helicopters were from the outset based at the Berga naval facility outside Stockholm and another at Säve outside Gothenburg. Later on a third group was established in Karlskrona.

Whisky on the rocks

In the evening of October 27, 1981 there began the most flagrant intrusion into Swedish territory of modern time. A Soviet submarine, called by the Swedish Defence Force U137, but with Soviet identification S-363, went aground at Gåsefjärden, 6 miles from Karlskrona in Blekinge County. This incident is even today still hotly discussed in Sweden as over the years there have been several attempts to dismiss the often repeated official Soviet explanation dating from 1981, namely that the submarine simply made a navigational mistake and accidentally entered Swedish waters.

Karlskrona is the Swedish Navy’s absolutely most important base where its military activity is of a most sensitive character. This not least applies to Swedish submarines that currently form a very important part of Sweden’s military defences. To have a foreign submarine appearing near to Sweden’s most sensitive military defence area should be enough to raise most eyebrows.

U137 was a submarine of the Project 613 type, called the Whisky class by NATO. These submarines dated from the 1950s, which is why many believed that it could well have suffered a navigational error, for otherwise why should the Soviets assign an old submarine to a secret mission. Afterwards several retired officers from the Soviet Navy have confirmed that the submarine was on a secret mission to enter Swedish waters. It was not meant to run aground, but there would have been another submarine in the area acting as a mother ship, for divers and mini-submarines. A number of Whisky submarines were also armed with nuclear-tipped torpedoes to be fired at important targets in case of war. One of the predetermined targets would be Karlskrona with its naval facilities. And U137 was carrying nuclear weapons.

The Swedish Navy’s secret torpedo tests.

That same evening the Swedish Navy performed top secret testing of a new torpedo, Torpedo Type 42 that had been developed specifically for submarine hunting. The tests were carried out just off Karlskrona, and among the vessels involved was the Swedish submarine Neptun along with two Type 4 helicopters from the 13th Helicopter Squadron. There were therefore strong reasons for Soviet submarines and/or spies to be present in the area trying to obtain information and if possible secretly observe the tests.

Because these tests were top secret, they were not mentioned at the time of the grounding or even later after the incident became public, so that this part of the U137 story remained unknown to most people.

During the subsequent days a tense drama was played out not only between the Swedish and Soviet military, but also at the highest political level. After negotiations had been completed, U137 was permitted to leave Swedish territorial waters after being towed off. An escape had been planned, but this was cancelled at the last moment, because the Soviets didn’t know how strong the Swedish forces were that guarded the area.

Submarine hunting

It used to be that the Swedish military fired at suspected submarines. A particular incident that remained classified for a long time happened as long ago as 1955 at Fårösund on the island of Gotland, whereby Swedish coastal artillery fired on a submarine and forced it to depart. This was succeeded by several more similar incidents, but none of them hit the headlines. It was only after U137 that intruding submarines became front page news.

Throughout this time the Swedish Navy came to the gradual realisation that Sweden’s ability to detect, attack and sink foreign submarines was not good enough. Swedish submarines were well equipped to find other submarines but they could not be everywhere. In other respects the available equipment was often ageing.

Depth charges mounted on a Type 4 Helicopter. Photo AEF.

Helicopters had early on demonstrated that they were extremely useful and comprise one of the most dangerous opponents that a submarine could face, but even the best helicopter can only do so much if it doesn’t have a good search system and efficient weapons. In terms of a weapon there is the depth charge, and the type of depth charge a helicopter is capable of carrying is relatively weak. It must explode very close to a submarine in order to damage it. But at the time of U137’s grounding the Helicopter Type 4 was equivalent to a submarine in being one of the few Swedish units with efficient enough equipment to be a serious threat to intruding submarines.

The Torpedo Type 42 was considered to equip Sweden with an efficient weapon against submarines that could even be fired from helicopters and guided towards targeted submarines. It is therefore not so strange that the Soviet Navy wanted to know more about this new weapon being tested by Sweden. A helicopter-borne torpedo would powerfully reinforce Sweden’s ability to hunt and deal with submarines.

Hårsfjärden and Operation Notvarp (Roundup)

A year after the U137 incident a comprehensive submarine hunt was launched in Hårsfjärden fjord between 1st and 13th October. The Swedish Navy suspected that foreign submarines had at regular intervals operated in Swedish waters not far from another of Sweden’s most important naval bases, Berga outside Stockholm. Operation Notvarp was the name of an attempt to capture a foreign submarine in Hårsfjärden, in which the intention was to lay a hydrophone system to listen under water and to prepare lines of mines to make it possible to shut in and force any intruding submarines to the surface.

It seems that at least one submarine was caught in the trap, but then the deficiencies in the Swedish equipment were revealed. The fixed hydrophone lines were not as effective as was hoped. The level of operators’ experience was uneven. Swedish patrol boats rushed to the scene but their passive (listening only) hydrophones were obsolete and not very efficient. However the Helicopter Type 4 had an efficient active (ping and listen) hydrophone that like a sonar could search below the surface and along the seabed for possible submarines, even if they were stationary and silent. So the helicopters and patrol boats worked together, whereby the helicopters led in the patrol boats with their powerful depth charges against suspected targets.

However Sweden’s most flexible antisubmarine system did not have a really effective weapon. The exercise ended with the foreign submarine (or submarines) succeeding in escaping from the trap. Ever after, the image of a hovering Helicopter Type 4 with a hydrophone dangling in the water would be a symbol of the Swedish hunt for submarines.

Torpedoes arrive and tactics improve

In the mid-1980s the Torpedo Type 42 at long last was added to the Helicopter Type 4’s armament. From the outset it was thought that each helicopter would carry four torpedoes, but this was found to be impractical. Depth charges were not abandoned, as after all they were cheaper than torpedoes and could be used as warning devices, which, even if they exploded some distance away would give a clear signal to the foreign submarine that it had been detected and get out if the area.

A Helicopter Type 4 equipped with an anti-submarine torpedo. Photo AEF

The Swedish Navy helicopter crews refined their tactics and became increasingly effective. The Type 4s operated in co-operating pairs. By using two hydrophones detecting a submarine from two different angles its position could be defined with much more certainty. It was found that the active hydrophones were more reliable in the shallow Swedish coastal waters than the passive listening system. The equally shallow waters of the Swedish archipelago form on the other hand an excellent area in which a submarine could hide, but the Swedish Navy’s submarine hunting helicopter crews were also getting better at searching in Swedish waters.

A Swedish Naval Aviation submarine group consisted of two Type 4 and one Type 6 Helicopters. The Type 6 did not have a hydrophone but was equipped with a surface surveillance radar that was used to search for periscopes, snorkels and radar masts belonging to submerged submarines. The Type 4s searched under water. As the submarine hunts progressed, these groups became all the more proficient. The Torpedo Type 42 entered service in 1985 and was found to have limitations in shallow waters, which meant that depth charges continued to be the most important weapon despite its own limitations. Most often one Type 4 helicopter would be armed with two torpedoes and the other with 6 depth charges.

On the basis of the Torpedo Type 42 experience an improved version appeared, the Type 43 entered service by 1987. This had better performance in shallow water and was just what was needed. In parallel with their equipment’s improvements, so the Swedish crews upped their game and already by the end of the 1980s submarine intrusions began to diminish. The torpedoes were wire-guided and could be steered towards their targets from the helicopter whilst the active sonar tracked the submarine’s movements.

Retired Swedish Naval Aviation Commander Roger Eliasson, formerly commanding officer of the 2nd Helicopter Squadron at Säve, near Gothenburg, found that the torpedoes became a turning point in the fight against submarines.

“It was so obvious that when the torpedoes came along the intrusions were reduced and to all practical purposes ceased altogether. It had become simply too dangerous for them to continue.”

The intrusions cease

The combination of an efficient active hydrophone and a torpedo that could be steered towards its target was something the Helicopter Type 4 could share with other advanced anti-submarine helicopters worldwide. For a submarine the presence of a helicopter is terrifying as it can come from nowhere without warning, whereas an approaching ship can be tracked with both passive and active sonar. However to watch out for helicopters the submarine must raise its radar mast above the surface which in turn makes it easier to detect the submarine using both radar and visual means.

In 1992 an unknown submarine was detected in Swedish territorial waters off Oxelösund and the situation developed to the point that a submarine-hunting torpedo was fired. The suspected submarine managed to avoid being hit. Nothing more happened after this. The Cold War had ended and so had any interest in using Swedish waters in case of a conflict. The Soviet Union, which had been the suspect of most of the intrusions, had fallen apart and the Russian Commonwealth did not have the resources to continue this expensive spying habit. Also, the Swedish capability of being able to hunt submarines was at its peak and the Swedish Navy had shown that it was ready and willing to use its new weapons if necessary.

Along with many other things that happened during the Cold War, there is much today that remains classified and it will probably be a long time if ever before certain facts see the light of day. Who else possibly infringed Swedish waters in that dramatic 1980 decade we will probably never know.

Everybody did it (Everybody’s still doing it)

During the 1990s and 2000s several former Soviet officers confirmed that the Soviet Navy and their specialist units did operate in Swedish waters. They didn’t see this as particularly strange. Everybody did it. Everyone was spying on everyone else. Both then and now. Someone who met and interviewed many such officers was Per Andersson, who was asked by one of them why we in Sweden cared about such ancient history. It was of course really not so remarkable, except that U137 happened to run aground. All naturally spied on each other, and even Swedish submarines were involved, spying on Kaliningrad. That was really just the way the world worked. Everybody did it and it was part of the game to pretend that you weren’t doing it.

Perhaps the comments made by those officers provide an explanation as to why it has been so difficult for some Swedes to understand why anyone should spy on and prepare for war against Sweden. If everyone abided by international agreements there would be no conflicts and no-one would want to wage war. Against this idealistic way of thinking there stands a more pragmatic stance that is reflected in the counter question Per Andersson received. A view that is based on the idea that one must always be ready to deal with the worst that can happen, and that those who are prepared will hold the advantage if something goes wrong. That one should not trust that others will do as they say, but by means of intelligence gained by every possible means to find out exactly what is going on. Although wants war, sometimes it is inevitable.

These witness statements confirm what many people in Sweden don’t want to know; that Soviet submarines have come stealthily into Swedish waters. Also that spies have been put ashore and taken off again. Areas have been reconnoitred where Special Forces could be inserted, and so on. Underlying this is the principle that you can never trust anyone, that no-one tells the whole truth and sometimes war cannot be avoided.

Where are our helicopters?!

In October 2014 the Swedish Defence Forces carried out what was called an intelligence operation in the Stockholm archipelago. This was after indications had arisen that foreign underwater actions were going on. The results now revealed that defence forces cuts over the years meant that they had lost the ability to effectively take action against underwater intruders.

It was with surprise and dismay that the Swedish public now discovered that the hovering Type 4 helicopters no longer existed! To be sure there were many who thought that those lurking submarines must have been figments of the imagination, but the helicopters had nevertheless proved to be very useful machines in many different ways. At the same time that insight sank in that Sweden’s once internationally recognised efficient submarine hunters belonged in the past, it was clear that the “green angels” that came to the rescue at sea and during forest fires were gone.

Out of all the reductions that took place within Swedish Defence it was just the phasing out of the Type 4 helicopter, or rather the realisation of the consequences, which made even people who otherwise were forceful opponents to military defence question this action. In the eyes of many the Helicopter Type 4 was a system that was of real benefit to the whole of Sweden. For many the Type 4 was primarily a means of rescue than a weapon system.

However by the time opinion had changed, it was too late. The helicopters had been sold to Columbia Helicopters in Canada, who had taken over from Boeing Vertol, and said that they had never seen so well preserved “second-hand” machines. A few examples were handed over to become museum examples in 2011.

Yngve70. The only airworthy Helicopter Type 4/Vertol 107 outside North America. Photo Peter Langsdale

September 29th 2018 – Yngve 70 takes to the air again

Three Type 4s ended up at the Aeroseum, which initiated a project. A society was set up consisting mainly of people who had previously worked on the Helicopter Type 4. With the blessing of the Swedish Defence Forces the society was christened 2nd Helicopter Squadron since a squadron of that name no longer existed. The aim was to ensure that Helicopter Type 4 Yngve 70, which still had many flying hours left, would once again fly over Gothenburg. It would however take seven years of battling bureaucracy until those people who had serviced and flown the helicopter in its military role would acquire the right to fly it as a civilian machine. The authorities who needed to approve such use were themselves forced to learn all about the system.

Rather simplified, one can say that those who flew the helicopter in its military guise had to train those who would give approval for it to be flown as a civilian aircraft! It therefore took time for the bureaucratic mill wheels to turn, but that time was profitably used to prepare both the society members and the helicopter itself.

So finally came the day, September 29th 2018, when a Helicopter Type 4 once again graced the skies above Gothenburg. Today Y70 is the only flying Helicopter Type 4/Vertol 107 on this side of the Atlantic, and Gothenburg’s national bird can once again be seen in flight on special occasions.