Cuauhtémoc accident update

In an earlier post, we discussed the bizarre accident involving the Mexican tallship Cuauhtémoc under the Brooklyn Bridge. Below you’ll find the latest information on the facts.

Although there were several reactions to the accident, knowing it to be due to human error, the likelihood of that seems considerably lower than mechanical failure, as we already expected. Meanwhile, the Mexican government was soon at the forefront of exonerating the captain and blaming the pilot. Most likely, however, neither of them had any influence on what happened.

Earlier, we pointed to the particularly instructive video by nautical analyst Sal Mercogliano. He has since collected new information, which shows even more clearly than before what happened. In his latest video, he explains.
Mercogliano holds many reservations. He rightly points out that the US National Transport Safety Board (NTSB) has not yet issued a report on the accident, so no definitive conclusions can be drawn. Nevertheless, it seems very likely that a defect in the pitch propeller, or controllable pitch propeller, caused the ship to reverse at increasing speed, when it should have been moving forward, and in that way end up under the bridge.

Pitch propeller

Immediately on viewing the first images, the question arose as to why the ship seemed to be moving backwards, instead of forwards. Although wind and current were pushing the ship towards the bridge, it had its bow turned forward towards the sea in time; all it had to do was put the propeller in the forward position and accelerate.
Indeed, Mercogliano discovered through images from a tour of the bridge a few years back, that the ship has a controllable pitch propeller, or CPP or pitch propeller for short. This eliminates the need for a reverse gear; instead, the pitch of the propeller blades is adjusted so that they propel the water in either a forward or reverse direction.

The moment the ship was able to yield forward, aided by o.2 knots of current and around 10 knots of wind, it moved at a speed of 2.7 knots towards the bridge. MarineTraffic shows that instead of the aft speed decreasing and being converted to forward, the speed towards the bridge increased. At the moment the ship hits the bridge, it is as much as 6.7 knots, an increase that takes place within a distance of several hundred metres.

Throttle on ‘forward’

An expert by experience reports on Mercogliano’s assumption that it was a pitch propeller failure, saying that he has experienced this twice before:
‘During my career as a marine engineer, I experienced two accidents with CPPs – on two different ships, with two totally different control units, but the failure mechanism was the same. A mechanical failure in the feedback resulted in the CPP going completely backwards. Interestingly, in both cases, the engine controls still gave a “forward” signal (both in the engine room and on the bridge). Both failures were the result of very small parts breaking.’

The NTSB-report will show in detail what caused this probable mechanical failure, and what other circumstances may have contributed to the chain of events that led to the allision with the bridge. When new information comes up, with possible lessons to be learned, we will keep you informed.

Source and image: What’s going on with Shipping.

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