The UK Marine Accident Investigation Branch (MAIB) has identified the cause of the engine-room fire and complete blackout aboard the 3,388-gt UK-flagged site investigation vessel Kommandor Susan during sea trials in the Firth of Forth on 25 January 2025: non-OEM Caterpillar spare parts. After the 1999-built vessel left Leith, diesel generator 1 failed at 13:05, triggering a fire and a complete loss of propulsion that allowed the ship to drift eastward before limited propulsion was restored and the vessel returned to Leith with tug assistance. All 14 people on board were accounted for and no injuries were reported, but the generator suffered substantial damage.
According to the MAIB, the root cause traces to the "premature wear" of Costex Tractor Parts components fitted to the Caterpillar 3516B-TA engines during a 2019 major overhaul carried out under the previous owner, Hays Ships Limited. The MAIB found that the bearings supplied with those parts had weaker material bonding than genuine Caterpillar components. Caterpillar had previously extended the service interval for the 3516B-TA engines on the vessel to 24,000 hours conditional on the use of genuine components; at the time of the casualty, DG1 had run only 13,466 hours since the 2019 overhaul.
The investigation also concluded that Hays Ships had limited oversight of the 2019 overhaul and did not verify the authenticity of parts used by contractors. The MAIB additionally noted that the vessel's anchoring procedure did not account for a total power loss, leaving the anchors unavailable when the ship began drifting. The MAIB issued no formal recommendations, citing actions already taken, but the Chief Inspector of Marine Accidents wrote separately to Hays Ships on the oversight of critical maintenance.
The vessel's registered owner and manager, Gardline Shipping Limited — part of Great Yarmouth-based marine survey specialist Gardline and, by extension, a wholly owned subsidiary of the Dutch Boskalis group — has rebuilt DG1 with genuine spares, overhauled DG2, DG3 and DG4 with genuine Caterpillar parts, and revised onboard anchoring procedures. From a supply-chain perspective, the incident becomes a concrete reference case on how the use of non-OEM spare parts creates a life-safety and commercial-loss exposure in shipping: contractor oversight, parts-authenticity verification and service-interval compatibility on the owner side can decide whether a single generator fault stays an isolated event or migrates into a fleet-wide governance issue.
Key Takeaways:
1. MAIB has determined that the 25 January 2025 engine-room fire and blackout aboard the 3,388-gt Kommandor Susan was caused by premature wear of non-OEM Costex Tractor Parts components.
2. DG1 had run only 13,466 hours since the 2019 overhaul — well below the 24,000-hour service interval Caterpillar had granted on the condition of genuine parts.
3. The MAIB found that Hays Ships did not verify parts authenticity during the 2019 overhaul and that the anchoring procedure failed to address total power loss.
4. Owner-operator Gardline Shipping (Boskalis group) has since rebuilt all four generators with genuine Caterpillar parts and revised onboard anchoring procedures.
5. The case becomes a concrete reference on how non-OEM spare-parts use can create life-safety and commercial-loss exposure in shipping, foregrounding contractor oversight and parts-authenticity verification.
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