The Fire That Started in 2019: Kommandor Susan, MAIB Report 10/2026, and What the Industry Still Gets Wrong About Assumptions

The Incident Didn’t Start on the 25th of January 2025

It didn’t start when smoke began filling the engine room of the Kommandor Susan in the Firth of Forth. It didn’t start when the alarms sounded, when the power went black, or when the crew mustered and scrambled to extinguish a fire that had no business being there.

It started in 2019 — in a shipyard, during a routine overhaul, when someone installed the wrong bearings and nobody noticed.

That’s the uncomfortable truth buried inside MAIB Report 10/2026. The Kommandor Susan didn’t suffer a sudden mechanical failure. She suffered the delayed consequences of a decision made six years earlier, compounded by inadequate oversight, unchallenged assumptions, and extended service intervals applied to components they were never designed for.

No one was hurt. The crew performed well. The fire was extinguished. The vessel made it back to Leith.

But the lesson here is not about what the crew did. It’s about what the organisation failed to do — for six years before anyone struck a match.

What Happened: The Factual Record

At 13:05 on 25 January 2025, the Kommandor Susan — a site investigation vessel operating in the Firth of Forth, Scotland — experienced a catastrophic failure of diesel generator engine number one (DG1) during sea trials.

The failure was violent and immediate. It triggered an engine room fire and a complete power blackout across the vessel.

The crew responded with discipline: the fire was extinguished, all personnel mustered safely, and no injuries were recorded. There was no pollution. But with total electrical power gone, the vessel lost propulsion and began drifting eastward. Attempts to deploy anchors failed — the anchor winches ran on electrical power and were inoperable. Two tugs were called. Limited propulsion was eventually restored. Kommandor Susan was brought back to Leith harbour under tow and her own partial power.

The MAIB investigation, culminating in Report 10/2026, traced the root cause to a 2019 major engine overhaul in which non-genuine components were installed in the Caterpillar 3516B-TA diesel generator engines. Specifically, the big-end and main bearings fitted were not OEM Caterpillar parts. They had a copper backing layer where genuine Caterpillar bearings use aluminium. The bonding between layers was weaker. The durability was inferior. And the extended service intervals that had been approved for these engines — intervals valid only for genuine OEM components — meant the non-genuine parts ran far past the point at which they should have been replaced.

Six years later, one of them gave way.

Root Causes: Five Points of Failure

1. Counterfeit or Substitute Components Installed Without Detection

The most foundational failure was simple: the wrong parts went into the engines. The non-genuine bearings installed during the 2019 overhaul were materially inferior to the OEM specification — different metallurgy, weaker bonding, shorter service life. Post-incident inspection confirmed that pistons, connecting rods, and bearings in DG1 were all non-OEM.

The MAIB notes the parts were installed without the vessel owner’s knowledge — which, on one reading, sounds like an excuse, but on another reading is a damning indictment of the oversight gap that made such a thing possible in the first place.

2. Extended Service Intervals Applied to the Wrong Parts

Extended service intervals for the Caterpillar engines had been approved — and those approvals were legitimate. But they were approved on the assumption that genuine Caterpillar components had been installed. They hadn’t been. The moment non-OEM parts went in, the extended interval regime became a mechanism for running already-inferior components long past their effective service life. No one revisited this assumption. No one asked whether the intervals still applied.

3. No Verification of Component Authenticity

Neither the vessel owner nor the management chain implemented any process to verify that the parts being fitted were genuine OEM components. There was no authentication check, no cross-referencing with Caterpillar approval records, no documentation trail requiring the maintenance contractor to confirm part provenance. The parts went in. The paperwork was filed. The assumption was made.

4. Inadequate Owner Oversight During Critical Maintenance

The MAIB identified what it called “a shortfall in oversight and contractor assurance by the vessel owner during the overhaul.” When a vessel undergoes a major engine overhaul, the owner and superintendent carry a duty to supervise critical work — not just to review completed paperwork after the fact, but to verify that the right parts are being installed in real time. That supervision did not happen here to the required standard.

5. No Accountability Framework for Critical Maintenance Monitoring

The Chief Inspector’s letter to Hays Ships following the investigation highlighted the need for “a structured supervision system that provides clear accountability measures” and systematic monitoring of all critical maintenance work. No such system existed. There was no mechanism to ensure that what was ordered, what was delivered, and what was installed were all the same thing.

The Dangerous Nature of Assumptions

There is a concept in accident investigation called a latent failure — a flaw buried within a system that causes no visible harm until the right (or wrong) set of conditions brings it to the surface. Latent failures are the most dangerous kind, precisely because they are invisible. The system appears to work. The engine runs. The paperwork is clean. The service intervals are extended with confidence. Everything looks fine.

Until it isn’t.

The Kommandor Susan case is a textbook example of how latent failures accumulate. In 2019, a contractor installed non-genuine parts. That was failure one. Nobody checked — failure two. Extended service intervals were applied without verifying the component specification — failure three. Six years passed with no owner audit, no parts traceability review, no challenge to the underlying assumptions — failures four through infinity.

Each of those failures, standing alone, might seem minor. A maintenance contractor cuts a corner. An owner trusts a supplier. A superintendent signs off on extended intervals without cross-checking the OEM specification. None of these, individually, sinks a ship or starts a fire. But they compound. They stack. And then, on a cold January afternoon in the Firth of Forth, the accumulated weight of six years of unchallenged assumptions becomes a catastrophic bearing failure, an engine room fire, and a vessel adrift.

The dangerous thing about assumptions is not that we make them. It’s that, over time, we forget we made them.

What If? — Scenario-Based Escalation

The Kommandor Susan incident resulted in no injuries, no fatalities, no pollution. The crew behaved well. The tugs arrived. The vessel came home. Now remove one or two of those favourable variables.

What if the failure had occurred in heavy weather? In developing North Sea conditions, a vessel adrift with no anchor capability and no propulsion is not merely inconvenienced. She is in immediate danger of foundering, striking offshore infrastructure, or broaching. A fire that was controlled in calm water may not be controllable in three-metre swells.

What if the failure occurred near congested waters or offshore infrastructure? The Firth of Forth is not the open ocean. In the southern North Sea, or near a busy port approach, a vessel adrift with no steerage is a hazard not just to herself but to every structure and vessel in her vicinity.

What if engineers were in the immediate vicinity of DG1 when it failed? A catastrophic bearing failure in a diesel generator is not a gentle event. It can involve ejected components, ruptured oil lines, and immediate fire. The fact that the fire was contained quickly is partly a function of where people were standing when it happened. That is not a variable the crew controls.

What if the other three generators had failed in succession? All four Caterpillar 3516B-TA engines on the Kommandor Susan received non-genuine components in the same 2019 overhaul. They were all running under extended service intervals that did not account for the inferior metallurgy. One failed. A cascading generator failure — DG1, then DG2, then DG3 — offers no second chances.

What if the anchor winch had been hydraulic rather than electric? The anchor deployment failed because the winch was electrically powered and the blackout rendered it inoperable. Emergency redundancy that is not actually independent of the primary failure mode is not redundancy at all. This is one of the corrective actions identified in the investigation: procedures were modified so winch clutches remain disengaged when not in use, allowing manual deployment.

Role-Based Lessons

Deckhands and Ratings

Your job in an emergency is to muster fast, follow instructions, and be where you’re supposed to be. The Kommandor Susan crew did this right. But good seamanship starts before the alarm sounds.

Know your emergency stations cold — not just in theory, but in the dark, with smoke, with noise. Know the manual backup for every powered system. If you notice something unusual about a piece of equipment — a sound, a smell, a vibration — report it immediately. You are often the closest eyes and ears to a developing failure. Don’t assume that because something has always worked, it will work in an emergency.

Engineers

You are the most directly exposed people when machinery fails. During any engine inspection, look beyond the routine checklist: oil condition, bearing clearances, unusual heat signatures, vibration changes — these are early warning signs of premature wear.

When your vessel undergoes a major overhaul, ask to see the parts before they go in. Genuineness of components is not someone else’s problem — it is directly relevant to your safety. Understand which service intervals were approved under which assumptions. If the basis for an extended interval is “OEM parts fitted,” verify that OEM parts are actually fitted. After any overhaul, conduct more frequent initial inspections than the schedule requires — the first 500 hours after a major overhaul are when installation errors manifest.

Chief Engineers

Establish and maintain a parts traceability record: every component fitted during an overhaul should have documented provenance — supplier, part number, OEM certification or equivalent. When taking over a vessel, audit the engineering records including overhaul histories. Do not accept extended service intervals without understanding the approval basis.

Know the OEM specification for every critical component on your main propulsion and generator systems — genuine vs. non-genuine parts often have physically identifiable differences. Create a culture in your engine room where engineers feel safe raising concerns about component quality. The barrier to saying “I’m not sure about these parts” must be low.

Masters

Know your vessel’s emergency capabilities independently of the engineering team — which systems can operate without main electrical power, and which cannot. During sea trials or port departures, always confirm with the Chief Engineer that emergency systems are genuinely independent of the primary power bus.

Conduct regular loss-of-propulsion scenario drills that specifically rehearse the blackout scenario — not just “propulsion fault on bridge,” but total power loss, total anchor loss, communications loss. Ensure you know the tug response time in every port or area you operate. In the Kommandor Susan case, the tugs’ arrival was essential — that relationship should be pre-established, not improvised.

Vessel Owners and Superintendents

The MAIB’s sharpest words in this report are directed here. The Chief Inspector’s letter to Hays Ships specifically called out the absence of a structured supervision system. Implement a mandatory component authenticity verification process for all major overhauls — this means on-site superintendent presence during critical component installation, not just review of completed documentation.

For any extended service interval approval, require written documentation of the parts specification basis. Conduct periodic fleet audits of overhaul records, specifically looking for gaps in parts traceability. Create a direct line for engineers and Chief Engineers to escalate parts quality concerns without fear of commercial pushback. The Kommandor Susan situation was enabled in part by a culture in which that challenge was never made.

Immediate Actions for Vessels in Service Right Now

Based on the lessons of the Kommandor Susan, the following checks should be considered immediate priorities:

• Pull the overhaul records for every diesel generator and main engine on your fleet. Identify any major overhauls conducted by third-party contractors in the last ten years. Ask: can you confirm with documentation that OEM or approved equivalent components were fitted?
• Review every extended service interval approval currently in force. If the approval assumed OEM parts, verify that OEM parts are fitted.
• Test your emergency anchoring procedures under blackout conditions. Can your crew deploy anchors manually if electrical power is gone?
• Audit which emergency systems depend on the same power bus as your primary generators. What happens when that bus fails?
• Inspect bearing condition on all generator engines. If any doubt exists about overhaul history, schedule that inspection now — not at the next planned service interval.

A Final Word

The Kommandor Susan is back in service. Her engines have been rebuilt with genuine Caterpillar parts. The crew, who behaved commendably throughout, are safe. The investigation identified what went wrong and why. The Chief Inspector wrote the necessary letters. In one sense, the system worked.

But consider what had to happen for it to work: a catastrophic bearing failure, an engine room fire, a complete power blackout, a vessel adrift with no anchor capability, two tugs, and six years of accumulated assumptions brought violently to account in the middle of a cold Scottish estuary.

The lesson of the Kommandor Susan is not that non-genuine parts are dangerous, though they are. It’s not that extended service intervals can be misapplied, though they can. The lesson is that accidents are patient. They wait inside systems that look operational, inside paperwork that looks complete, inside assumptions that have never been challenged because nothing has gone wrong yet.

So here is the question this investigation leaves on the table: What are you assuming is safe right now — that nobody has verified since 2019?

Sources: MAIB Report 10/2026 — Kommandor Susan | GOV.UK | Maritime Executive | Baird Maritime | IIMS