In attempting to reconstruct the trackline of a vessel after a collision, often the reconstruction expert is given the vessel's chart, course recorder, the bell log and the deck log. These are the essential documents from which an expert works. In addition, the maneuvering information required to be posted on the bridge of all vessels entering U. S. waters by 33 CFR 164.35(g) will give the corresponding speeds for the vessel at various RPM and will permit the RPM to be translated into speed.
Often, time has passed since the collision before the expert is called in, and the depositions of the vessel's crew have been taken and the crew have dispersed to the four corners of the globe only to be recalled at great expense and over the strong objections of the opposing counsel.
It is thus essential that the attorneys assure that several things are done as soon as possible after the collision.
Times are critical to all reconstructions. It is rare that the true time, the time of the clocks on the bridge from which log entries are made, the clock mechanism of the course recorder and that of the bell recorder are synchronized. Often, crew members will swear that they corrected and synchronized all clocks - but the expert in attempting to reconstruct the events will find inconsistencies such as the engines were running ahead at sea speed for 9 minutes after the collision occurred even though the statements of the crew are that they were backing three minutes before the collision. Clearly a vessel would not continue at sea speed after colliding. The only answer is that the clock mechanism of the bell recorder was in error - and thus could not have been corrected five hours before they sailed.
A Coast Guard investigator, often one of the first on the scene, should check the times immediately. If he doesn't, a suggestion to him or her will usually be sufficient. The easiest way to do this is to take an accurate clock (a modern electronic wristwatch will serve the purpose) and check and record the time differences between the bridge clock, the engineroom clock, the course recorder, and the bell recorder. Then check them against a time standard. This information is extremely valuable during the reconstruction. Where an expert is not retained until later and a Coast Guard investigator doesn't record the times, someone else must do it and preserve the information.
Two other items to check while aboard a vessel immediately following an accident is the radar and the gyro. Check the true bearing of the radar against the master gyro to see if there is any error. Using a bearing circle, take a relative bearing on some object which would be distinguishable on the radar, and compare it with the relative bearing from the operative radar. If two radars were in operation, check both. The purpose is to see if there is an error which could have caused a plotting error of the vessels own position or the position of the vessel with which they collided.
To reconstruct the track line of a vessel, have the original of the course recorder photographically enlarged. Usually a printing firm can do this very inexpensively. This will reduce the error in interpreting the heading. Be careful in your interpretation of the recorder. An author of a famous book on the collision between the Stockholm and the Andria Doria based his theory of the collision on what appeared to be a jump in the trace on the course recorder. He assumed it was caused by the stylus being jarred by the force of the collision. However, he used a copy of the course recorder, and had not seen the original. The apparent jump in the stylus was actually a fault in the reproduction process when the course recorder was copied. A small number immediately adjacent to the heading trace had blended in with the trace during reproduction giving the appearance of a jump in the trace.
Using a computer spread sheet, enter the true times in the first column. Times taken from the course recorder or the bell log can be entered in the second and third columns if desired. Other columns should have the engine order, the speed through the water, the current, the calculated speed over the bottom, the heading, the calculated rate of turn (used to check the headings - markedly different rates in a single turn may indicate an error in transposing the date from the course recorder) and a remarks column. The remarks column can be used to record data from the log, or a comment that speed was changed.
Depositions taken of the vessels crew must also include extensive questions relating to past clock error rates and when and how it was last set. Questions to see whether the deponent is telling the truth are appropriate. How did he physically reset the mechanism? Who saw him do it? Did he make a record of it? How accurate was the clock mechanism? How often did it have to be checked and how often was it reset when checked?
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