A Radar-Assisted Collision Page 2

Electronics — December 2004
By Ben Ellison

A Radar-Assisted Collision
Part 2: A mere 15 minutes after the incident began, Wahkuna’s crew saw a wall of steel emerge from the fog.

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When the guys eyeballing the radar screen on Wahkuna decided that there was a risk of collision and slowed way down, the Vespucci’s ARPA quickly picked up the change. The captain sent a lookout to the port bridge wing and had manual steering engaged but did not change course, as it seemed that Wahkuna would pass two tenths of a mile to port. On Wahkuna—now sort of circling or, in retrospect, behaving like a squirrel in front of a truck—they thought the ship would pass more than a mile ahead of their intended track.

A mere 15 minutes after the incident began, Wahkuna’s crew saw a wall of steel emerge from the fog, and according to the MAIB report, “The container vessel’s bulbous bow struck the forward part of Wahkuna’s port hull, demolishing the first twelve feet of her bow [and dismasting her]. As a result of the impact, Wahkuna rose up six feet on the container vessel’s bow wave and slalomed at an angle of 20 degrees to 30 degrees down her starboard side, stern first, for a distance of approximately 250 feet before being dropped back into sea.”

Amazingly, though their yacht soon sank and their EPIRB failed to work, the Brits were picked up from their liferaft five hours later, uninjured. Even more amazingly, and confirming a phenomenon I’d always considered mostly mythical, the crew of the Vespucci neither felt nor saw the collision. The captain also said he never lost sight of the radar target.

So here we have an accident between two boats that could see each other on radar and whose skippers were both, at least on paper, expert seaman. Conclusions? MAIB faulted Wahkuna’s skipper, who directly caused the collision by changing speed, for “inability to use radar effectively.” The investigators also faulted the ship captain for “over-confidence in the accuracy of ARPA,” which led to too small of a passing distance (CPA). There you have two opposite ways—too little skill and too much confidence—that can get you in gizmo trouble. It’s really about good judgment, isn’t it?

Was is it easier before electronics? No way; Wahkuna joined wrecks that have been collecting on the Channel’s bottom for centuries. I will grant, however, that in the old days no one was driving 900-foot ships stacked with containers at 25 knots in near-zero visibility. This incident caused the British Coast Guard to issue an advisory about “safe speed”—not its first. But defining that speed exactly is quite complicated, as detailed in MAIB’s report. Suffice it to say that a French shore station that was monitoring channel traffic that morning reported that only one of several dozen ships seemed to slow down in the poor visibility.

That’s reality in the 21st century. At the risk of provoking more letters from our verbose PMY readers, my guess is that safer passagemaking will come from even better electronics, like AIS, and better electronics training, like simulators accessible to yachtsmen and programmed with scenarios like this one. The good news is that such collisions are quite rare, even in the very busy and often foggy English Channel.

There’s much more in MAIB’s thorough analysis, like why that EPIRB failed and what causes ARPA inaccuracies. You can find it and many more instructive casualty reports in the MAIB publications section at www.dft.gov.uk. For details on some U.S. incidents, visit the National Transportation Safety Board at www.ntsb.gov. Check out the publication describing a U.S. Coast Guard 24-foot patrol boat ramming the tour boat Bayside Blaster one night in Biscayne Bay. Fortunately no one was seriously hurt, making it easier to enjoy this incident’s full comic value.

The report states that the patrol crew tried to turn hard left to avoid the collision but failed, leading to their “unexpected ejection,” which—along with kill-switch failure—left their twin 250-hp Boston Whaler doing unmanned high-speed pirouettes (fully diagrammed), again striking the tour boat, then modifying the bow of a docked sportfisherman, before finally getting corralled against a pier by a marine police boat, whose operator ultimately subdued the outboards by beating the mangled console controls with his baton. And, whew, in this case the investigators don’t even mention the electronics—just, as usual, the human errors.

Next page > Electronics Q&A > Page 1, 2, 3, 4, 5, 6, 7

This article originally appeared in the November 2004 issue of Power & Motoryacht magazine.

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