Combat Boats and Landing Craft

One of the earliest aspects of the current wave of close Finnish-Swedish military cooperation has been that between the marine infantry in the two countries. This was formalised as the Swedish Finnish Amphibious Task Unit (SFATU), which originally was envisaged as a crisis management tool for the littorals. In later years the scope has been increased, as can be seen during the upcoming weeks when the unit will be training in Finnish waters. Parallel to the Navy’s main exercise Silja, the unit will perform a short pre-exercise which started 27 May, and on 3 June SFATU will switch over to the main exercise and take part in Silja together with the better part of the Finnish Navy (including the marines and coastal units). The Swedish marines are joining in the fun with a total force numbering around 400 personnel and around 40 boats.

jehu and cb90 Silja Merivoimat piste fi
Finnish Jehu-class in the foreground with a Swedish CB 90H in the background. Note the differences in profile. Source: Merivoimat.fi

As usually when the two forces operate next to each other the differences in equipment has raised some questions, especially in this case where both units are tailored to operate in the same niche environment that make up the Northern and Western coastline of the Baltic Sea. The most striking difference is the combat boats used, which don’t show much of a resemblance to each other. It should be noted here that in my line of work at Kongsberg Maritime Finland Oy, formerly Rolls-Royce Oy Ab, I have come into contact with both vessels. However, all information in this post is based purely on open sources (as is all my writing). In addition, I won’t discuss concepts of operations or similar details covered by OPSEC in this post, even in cases where such information is available in open sources.

The CB 90H is a truly iconic vessel. The development work took place in the late 80’s, and the first vessels entered operational service in late 1990 under the designation Stridsbåt 90. The Swedish designation literally means Combat Boat 90, and in the same way as Strf 90 thanks to it’s export success is universally known as CV 90 the boat quickly went from StrB 90 to CB 90 internationally. From the outset the vessel was known as CB 90H (‘H’ coming from its ability to transport half a platoon) to distinguish it from the somewhat similarly looking but smaller and simpler 90E (‘E’ standing for Enkel, the Swedish word for simple).

20160604_joethu01_BALTOPS_52
A CB 90H showing the twin mounted 12.7 mm FN M2 heavy machine guns next to the bow doors. Source: Joel Thungren/Försvarsmakten

CB 90 was an almost instant success both domestically and on the export market. At a time when many navies still used open landing crafts powered by traditional propeller/rudder-arrangements or outboards it employed twin waterjets to give superior maneuverability and a very good acceleration and top speed. The vessel also came armed with heavy machine guns which could support the landing, and the possibility to lay mines or drop depth charges over the stern. But perhaps the most visually striking detail is the extremely low profile. This is made possible by moving the control station to the very front of the vessel, allowing the crew a good view over the bow despite being placed low inside the hull. The vessel scored a number of export deals, including to Norway, Mexico, Malaysia, and the US Navy (known locally as Riverine Command Boat, RCB). Both for the export market and for domestic use a number of different versions have been developed, including versions sporting ballistic protection. The latest version is the Stridsbåt 90HSM for the Swedish marines, which feature better protection, a new driveline, and provisions for a remote weapon station. The latest order means that Dockstavarvet, nowadays owned by Saab, will be able to celebrate 20 years of CB 90 production (though not continuously).

Swedish CB 90s of the 2. battalion of Amf 1 forming up during exercise Aurora 17. Source: Mats Nyström/Försvarsmakten

The general layout has been successful enough that it has been adopted by a number of foreign projects, none of which have enjoyed the same success of the original design. It isn’t completely without drawbacks though. The most important drawback is that the placement of the crew stations in front of the passenger compartment leads to a chokepoint when the marines exit between the navigator and the helmsman. Sitting close to the bow also means that the crew will experience heavier loads on their bodies when encountering waves (especially at speed in rougher conditions). Rearward vision also suffers, and in general keeping a low profile means that there are certain limitations once it comes to situational awareness and the ability to mount sensors and weapons high. Still, these are of secondary importance to a vessel whose main purpose is to get marines ashore, and fast.

Jurmo Merivoimat FB
A Jurmo under way in the Finnish archipelago. From the picture it is easy to see that the pivot point around which the hull moves when encountering a wave is rather far aft, meaning that the pitch when encountering waves in a planning vessel will be worse in the bow compared to further aft. Source: Merivoimat FB

At the same time as the Swedish Navy was busy driving around in combat boats, the Finnish marines had to make do with open and semi-open landing crafts. These weren’t necessarily bad landing crafts, but they offered little combat potential (no, a pintle-mounted 12.7 mm NSV doesn’t make a combat boat) and worse protection for both the crew and the embarked marines. On the positive side, their conventional layout meant that loading larger cargo was possible, and swiftly getting marines out of the passenger compartment was relatively easy. Having the crew at the rear also meant that slamming the bow in heavy weather doesn’t affect the crew in the same way, instead letting the unfortunate few marines closest to the bow take the beating. Especially the Jurmo-class was a very good ‘truck’ for the marines. But it was still a truck, and the Swedish marines were driving around in (light) APCs.

The answer to the demands of the Finnish marines came to be the Jehu-class, where much of the focus is placed on combat ability. The Jehu, or Watercat M18 AMC as it is known to its builder Marine Alutech, comes with both ballistic- and CBRN-protection, a roof-mounted RWS (Saab’s Trackfire RWS in Finnish service), and a serious communications suite. Following on the Finnish traditions, the passenger compartment is close to the bow, meaning that the control stations are in a raised deckhouse found midships. This means that the vessel in general will be higher (adding weight), but also offers more space for the crew working area. To compensate for being larger, the vessel has some serious power, with the twin engines being rated at 1,150 hp (compared to two times 625 hp on the original CB 90H and two times 900 hp in ‘operational‘ setting on the 90HSM).

Bigger isn’t always better, but the increased size of the Jehu compared to both CB 90H as well as earlier Finnish designs opens up new possibilities, such as the fitting of a 120 mm NEMO mortar turret (with a direct fire ability). This is a capability the Finnish Navy urgently needs, and something which almost gave the Swedish marines their SB 2010 a decade ago. In the end, SB 2010 remained a paper product, cancelled by overzealous politicians, but the concept had called for a larger combat boat, with a general layout not completely unlike that of the Jehu.

Jehu landstigning merivoimat fb
Finnish marines disembarking from a Jehu-class landing craft. Note the Trackfire RWS which is mounted high with an excellent field of fire. Source: Merivoimat FB

In the end, the CB 90H and Jehu are examples of the principle that the same operational environment can lead to rather different solutions, all depending on how you prioritise between the inevitable trade-offs.

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One thought on “Combat Boats and Landing Craft

  1. Perman

    Interesting comparison. Maybe it should be mentioned that CB 90H first had a 30 mm ADEN gun (AKAN m/55) from J35 Draken in the bow, but this was later removed. The KSP 88 in the ring mount can be exchanged for a 40 mm automatic grenade launcher. SAAB’s Trackfire RWS has been ordered in two batches so far for the new CB90 HSM, and first batch will be delivered from Q3 2018 to Q3 2019.

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