Fleet Availability – Ensuring the ‘ultimate guarantee of our security’

Nuclear submarines play a crucial role in protecting and defending the high seas. Navigating often difficult waters across thousands of miles each year, this silent force deters aggression and helps ensure global security and prosperity.

The Royal Navy notes that the submarine arm is the ‘ultimate guarantee of our security.’[1] Yet these vessels are only effective as a deterrent when out at sea.

At IMI, we pay close attention to this area, working closely with the defence industry to maximise fleet availability. But why is this so critical? And how are we responding?

It’s all about readiness

Vessels must be active to work as intended by the UK’s continuous at-sea deterrent programme. This is especially true for nuclear submarines equipped with ballistic missiles.

They must be operational, within range, and capable of launching a strike should the need arise. Global events develop quickly, and the threat of reprisal strongly modifies the actions of possible belligerents. Even the presence of a vessel acts as a powerful signal. In August 2024, for instance, the US Navy officially announced its movement of a submarine to the Middle East in response to escalating regional tensions.[2]

These interventions, however, are only possible when a fleet is ready to respond. This issue has been highlighted recently, not least for the Royal Navy.

In August 2024, a report stated that no SSN nuclear-powered attack submarine had been deployed for 47 days. What was perhaps even more concerning was the fact that the report suggested no UK attack class submarine had been at sea for over four months [3] with delays attributed to long-standing maintenance backlogs.

That said, this problem isn’t unique to the UK. It’s well known that the split between active submarines and those needing repairs rarely occurs where it needs to be. Or, at least, where a naval leadership would consider as ideal.

Recognising our role

This situation has implications not only for national security but also for a critical socio-economic dimension. Submarines are crucial in protecting undersea cable networks that underpin global trade, communications, and the digital economy. Additionally, many remote islands rely heavily on the protection of shipping lanes for food, fuel, and medical supplies, all safeguarded by naval assets.

Submarines cost large sums to build and significant additional expenditures to sustain, all of which come from the public purse. Debates continue about the relative value of these programmes, further emphasising the need for vessels to be out at sea for as long as possible. This is the evidence navies need to demonstrate a return on investment.

Having worked closely with the defence industry for decades, we have recognised the role IMI can play in improving fleet availability. In recent months, and in collaboration with our naval partners, our team has begun pinpointing bottlenecks in the supply chain and introducing measures to free up the flow of parts. This recognises our role throughout the process, from supplying valves during submarine construction to sustaining them once they leave the builder’s yard.

We have, for instance, moved the most frequently used spares closer to where they are needed so parts can be replaced quickly without requiring new manufacturing. We maintain a defined stock level that helps minimise delays based on an analysis of our sales data and recognised trends throughout our time in defence.

Moreover, we are now seeking to place engineers at customer sites so they can act as on-site expert partners, which allows us to see issues first-hand. In practice, preventative maintenance programmes like this mean we can avoid unnecessary delays if components do not function properly at the point of commissioning. In the marine defence world, this could prove to be of critical importance.

Perhaps the biggest change, however, will take place at our factory in Aston, UK. Here, we will soon have a dedicated cell for emergent spare parts with the longest lead times – with the capacity to reduce lead times from up to 52 weeks for some to under 26 weeks.

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Proactive, not reactive

The above interventions detail some of the ways in which we address the challenge. However, historical barriers must also be negotiated before navies can reach an optimal position where maintenance is unimpeded.

Procurement is a good example. There’s certainly room for workflow improvements at both ends of the spectrum. We currently rely on the input of a navy’s procurement department to determine what is needed and why. This way of working has developed naturally and is partly due to how industry has interacted with defence over time. However, it is by no means the most efficient.

Instead, it would be preferable for an OEM’s field engineers to assume control of the asset and outage management programme. First, the company retains the best operational knowledge of a specific technology. Second, it has been proven effective in other industries, with our work in power generation providing a strong example. Yet this seldom happens due to the sensitive nature of work in defence.

But herein lies the point. We are now striving hard to ensure that fewer submarines are docked for maintenance and more are available to protect us at sea. Companies like ours are making a difference through a more proactive approach, ensuring greater fleet availability. This is truly breakthrough engineering for a better world.

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1. https://www.royalnavy.mod.uk/news/2017/december/21/171221-defence-secretary-pays-tribute

2. https://www.bbc.co.uk/news/articles/c1l5v4dg04qo

3. https://ukdefencejournal.org.uk/no-british-attack-submarines-at-sea-for-over-47-days/

All submarine images featured on page, courtesy of crown copyright.