The best ship is a ship at sea – Operational availability
Ships and submarines are complex, powerful, and expensive platforms for surveillance, patrolling, and various operations. However, they are of little use if they remain docked or in shipyards for maintenance.
To ensure high operational availability, i.e., operating hours at sea, many factors must interact seamlessly. The Swedish Navy, by international standards, has a high availability rate and uses its fleet efficiently.
Development and design
A submarine can have a lifespan of up to 50 years, and surface vessels almost as long. Maintenance, upgrades, and modifications must be considered from the design stage to make this a reality. For example, a submarine should be designed for easy modifications and longer-term upgrades, even being cut in half and equipped with new systems, after which the hull is welded back together again.
Smart design can also extend the interval between crucial maintenance periods. For the new Blekinge-class submarines (A26), the annual inspection interval has been extended from 18 to 24 months compared to the Gotland-class. Regarding general overhauls, the interval has increased from 6 to 8 years. These improvements will lead to a significant increase in availability.
Vessels must be designed and built to allow access for inspection and repairs, even in confined spaces. On a submarine, there are ballast tanks to compensate for weight below the surface. It must be possible to access and continuously protect these spaces from corrosion – a task for those without a tendency for claustrophobia. In a crowded submarine, it's also essential to consider how to dismantle and lift out larger components, such as batteries and generators.
On many vessels, there is a shift from hardware-based systems with physical controls, like pumps and valves, to software-based solutions. By integrating sensors into these systems, continuous condition monitoring can be performed. Based on this information, software parameters can be upgraded to improve properties, such as reducing fuel consumption or minimising the signature (noise) of both submarines and surface vessels.
Documentation, planning, and training – ILS
Maintenance is not only performed at the dock and in the shipyard. Continuous maintenance and repairs are carried out by the crew while at sea. Well-documented and planned maintenance procedures enable smaller interventions to be performed immediately. Spare parts, tools, and manuals should be available where needed, even onboard the already crowded submarine.
Integrated Logistic Support (ILS) is a function or department involved from the design stage of the ship. Its aim is to ensure that the vessel can be used and maintained efficiently for high availability and a long service life. This is the foundation for what we call In-Service Support (ISS). ISS can include everything from documentation, maintenance plans, and training to contracts with subcontractors and spare parts planning.
The number of documents required for, for example, a Visby corvette can amount to many metres of shelves. Through a structured, digital documentation system from Saab, called DIS, the crew can always access relevant manuals and save important space onboard.
Maintenance plans cover several levels of complexity, from corrective repairs when something happens to preventive maintenance. All efforts aim to minimise the risk of breakdowns and unexpected events. By measuring and calculating operating hours and calendar time, condition-based maintenance can be performed to replace worn components. Finally, major modifications and capability enhancements are planned during the product’s lifetime.
Planned modifications and capacity increases – MLU and LOTE
Several major modifications of both ships and submarines are planned from the construction phase. These upgrades involve replacing or supplementing larger systems and adding new capabilities, sensors, or weapon systems.
Mid-life upgrades (MLU) are usually carried out 15–20 years after a submarine or ship's launch. This process involves adding new capabilities and adapting the vessels to the changing operational environment.
In 2026, the Swedish Visby-class corvettes will begin their MLU, receiving new air defence systems, among other things. Recently, the Swedish Gotland-class submarines have undergone mid-life upgrades, receiving several systems that will soon be implemented on the new Blekinge-class (A26) submarines.
After another 15 years, it may be time for a Life-of-type-Extension (LOTE). This process also involves adding new capabilities and ensuring that outdated systems are replaced with modern solutions, to extend the lifetime of the boats even more. This could, for example, be something as simple as switching from a "thick TV" to flat screens in the control room.
The disadvantage of these major upgrades is that there can be a long time between them, when there is a need for faster upgrades. This is something that experience of the fighting in Ukraine shows. Code in the morning, fly in the afternoon is a concept that is becoming established. Not only for fighter aircraft but also for ships and submarines.
Operate and sustain – In-Service Support
That is why we focus on ongoing sustainment during operations. This is called In-Service Support (ISS). The art of ensuring that a platform is always relevant, available, and performing at the top of its capability throughout its life cycle.
Through Engineering Support, designers can prepare for upcoming upgrades and ensure they are carried out in the right order and coordinated between different subsystems. Data is also collected from existing systems to see how they have been used.
Parts management and documentation are included in the Logistics Support concept. It also develops training materials for users and support functions.
Spare parts and replacement components are a complex issue. Which spare parts must or can be kept in stock for high readiness? If a supplier that was used when the ship was built 15 years ago no longer exists, how do you arrange new details for an old system?
As the construction of this type of platform takes a long time, five or maybe ten years, there may be systems that were developed early in the process that may need to be replaced or upgraded even before launch. That means that early in a product’s life cycle, you plan for what fits in the concept of End-of-life (EOL), i.e. how to replace components where there are no more spare parts available
Finally, the maintenance work itself must be planned. The term Maintenance, Repairs, and Overhauls (MRO) is often used here. This includes everything from repairs in the event of a breakdown to major upgrades and modifications.
You want to avoid duplicate work; if the engine is lifted out, it might be an opportunity to change parts in the exhaust system at the same time. And of course, the same planning applies to software as well as ship systems, weapon systems, and command and control systems. Everything is connected and interacts to create an optimal platform for the end user, the Swedish Armed Forces.
Close cooperation is required between the developers and engineers who designed the ship and those who plan the implementation of maintenance and modifications. A submarine that comes in to prepare for a simpler mission may be upgraded at the same time if everything is planned and prepared.
When a ship comes to the dock, everything is ready for maintenance work. Components and spare parts are available on site, as well as personnel with relevant expertise. Modifications are made, and documentation is updated onboard.
General agreement for maintenance
In Sweden, Saab, together with the Swedish Armed Forces and the Swedish Defence Materiel Administration (FMV), has developed plans for structured maintenance and upgrades. Sustainment includes principles and routines to ensure that the platforms are up-to-date, relevant, and at the cutting edge of their capabilities.
This has been implemented through several joint framework agreements, divided into different system areas. Each contract area has its own specialists on both the customer side and with the contractors within Saab.
Within the framework agreements, there is room for configuration management, documentation, and actions, much of what we call ILS above. This is to benefit the Swedish Armed Forces’ availability planning and the industry’s occupancy planning with personnel and at shipyards, quays, and docks. There is a lot to consider and take into account when completing the planning.
Keeping waters open and free
Saab has recently signed new contracts with the Swedish Armed Forces and the Defence Materiel Administration (FMV) in several areas of naval systems. The result, bringing together all of the above, is higher operational availability for the Swedish Armed Forces and more efficient operations from Saab, with better predictability, quality, and resource management. All to the benefit of Sweden’s security and readiness.