Helge Ingstad Accident Report

[Kennebec_Captain]

@Klaveness

One pertinent question which may bear some attention due to its universal relevance, is why the people running visual nav on the HI (the OOWT and OOWAT) failed to identify the Sola as a moving object. Seeing as the helmsman figured it out without really trying,

This is not at all a surprising result, expected in fact. The OOWT and OOWA are busy with the task of collecting then plotting data. This is a step-by-step process that takes time and attention and only the final result, the fix is usefull. The numbers (the bearings) by themselves tell you very little. Similar to copying the lat and long off a GPS, of no use till plotted.

By contrast the helmsman is staying in one spot on the bridge watching the changes in the relative bearings.

This can be observed in the wheelhouse. Experienced navigators will plant themselves next to the centerline compass with an occasional trip to the radar while the inexperienced will make a constant loop from radar to chart.

I laid this out in detail on this post Ditch the Map. It's Ruining Your Brain - A General Overview of Human Factors and Navigation

@Kennebec_Captain

When there is a pilot aboard the pilot navigates by looking out the window and converting what he sees into a mental model which he then uses to navigate. This requires familiarity with the area and experience in making the mental conversion.

The third mate on the other hand can not do this. Instead he uses a much simpler method. Using the paper chart the mate takes measurements (bearing and ranges) and enters that data into the model (the paper chart is a simple model of a small part of real world) and gets an output - the ship’s position.

This is why the third made cannot “start turning back towards the lanes when abeam…”. The captain is using the language of the pilot’s method but the third mate is not a pilot. Instead, when abeam the third mate plots a fix on the chart. That’s the only way he can make sense of the situation.