Lights To Port - Lights to Starboard
An Objective Analysis of the 1956 Collision Between Stockholm and Andrea Doria
At 23:11, local time, on  a foggy night on 25 July 1956, the eastbound Swedish passenger liner Stockholm collided with the westbound Italian luxury
Andrea Doria in what was described as the world's first radar assisted collision at sea. At 10:09 the following morning, Andrea Doria capsized
and sank about 18 nautical miles west by south of the Nantucket Shoals lightship.

Until now, a truly detailed and objective analysis of the collision between those two ships was never presented. Even though some works on this
subject have started out that way, when all was said and done, they tend to take one side or the other and claim one ship was more to blame than
the other. In my work on this subject, I was able to prove that the stories given by both sides in pretrial hearings that took place after the event
simply do not hold up. It is not a question of one side being right and the other side being wrong. They both were inaccurate in what they claimed
took place that night, including the details about distance and direction to the other vessel when visual contact was first established.
There certainly was plenty of fog that night. The Andrea Doria was well into it, and the Stockholm was almost into it when both ships saw
each other for the first time. It was then that they tried to take desperate evasive actions. The
Andrea Doria was indeed seen to port of
Stockholm, and Stockholm was indeed seen to starboard of Andrea Doria when visual contact was made. At the time they came into view of
each other, a collision was all but unavoidable. It's just a question of which ship would have struck the other if actions taken would have been
slightly different.

An interesting theory have been offered that the radar on the
Stockholm was set on the wrong range scale. This was first put forth by John
Carrothers in a paper he wrote back in 1971. It was picked up by Capt. Robert Meurn of the US Merchant Marine Academy as well as by the
late David Bright. This theory, despite strong denials by the Stockholm's third officer, who was officer on watch at the time when the accident
happened, also shows up in Pierette Domenica Simpson's relatively recent book,
Alive on the Andrea Doria, and on the
website of the late Anthony Grillo. I tend to believe that such a misreading error was very unlikely. If the range was set to the 5 mile scale
instead of the 15 mile scale, as the theory claims, the officer would not have failed to notice a closure speed that corresponded to something like
120 knots between ships. Something moving toward you at that high a relative speed is very hard to miss. Thus, in my opinion, there was no
scale error. One look at the course recorder graph shows clearly why the bearings reported by the
Stockholm’s helmsman at the time could
not be reliable. Bad input data gives bad output data leading to wrong conclusions and bad decisions. Likewise, on the
Andria Doria, those
responsible never bothered to plot what was unfolding right  in front of them,. They never had a clear picture of what was happening.

We do know what each party had claimed happened. From this I was able to create radar plots that not only show what was claimed to have
been seen on their respective radars, but also such things as direction and distance to the closest point of approach predicted by the reported
radar data, as well as the other ship's course heading calculated from radar vector triangles to compare against what was claimed. I was also
able to analyze what was shown in the course recorder data of each ship, and work out the actual paths of both vessels relative to the collision
point in a spreadsheet in 1/2 minute increments. In addition, the relative bearings and ranges of one vessel as seen from the other up until the
collision itself was also worked out from the recorder data. I also was able to calculate the energies before and after impact, and the immediate
movements of each ship from just moments before to moments just after impact which I was able to put into an animated sequence to recreate
the collision itself. This is shown below.
The following link provides the complete report (in pdf format) of this work along with a foreword written by Capt. Les
Eadie , Assistant Professor of Marine Transportation Operations , Maine Maritime Academy, Castine, Maine.
Detailed Analysis Report
Andrea Doria Post-Collision
Stockholm Post-Collision
Andrea Doria Pre-Collision
Stockholm Pre-Collision
The results of this analysis were presented before a class on casualty analysis at Maine Maritime Academy (MMA) in
November 2008. The complete presentation can be viewed by clicking on the following link: