Some have claimed that the Williams' strip chart and list of courses for the Howland to Lae flight as the flight plan that Noonan and Earhart used for that flight but that is very unlikely. First, keep in mind that there is no proof that Noonan used Williams' plans and, since Noonan was a more experienced flight navigator than Williams, Noonan most likely did his own computations, not trusting the work of others. I know I would have if I were in Noonan's position, I have always done my own computations in the past, I don't rely on anybody else for this type of work.
But, in fact, there is strong evidence that Noonan did not use Williams' flight plans. All you have to do is compare Williams' strip chart for the Atlantic crossing from Natal to Dakar with Noonan's chart for the crossing and the differences jump out at you. I have attached both of these charts. Williams' strip chart for this route is just like the one for the Lae to Howland leg, with a line plotted connecting calculated points along the great circle, also spaced every 2° 30' of longitude, just like on the Howland to Lae strip chart. He calculated the distances in statute miles between these points, consisting of seven legs and each of these legs is a different length. He also marked the expected flying time for each of these legs and these times are all different since the legs were all of different lengths. He calculated the true great circle course from Dakar to Natal at various points along the great circle starting at 221.6° near Africa, 220° in the middle of the Atlantic and 220.4° near Brazil. Because the variation also changed along the line, the magnetic course is listed by Williams as 240° all the way and 060° for the eastbound direction.
Now look at Noonan's chart. He did not plot any great circle points, he just drew in a straight line, which is the rhumb line, from Natal to Dakar. He did this simply by using a straight edge laid on the chart from Natal to Dakar. How do we know he did it this way? Look at the bottom of the chart and you will see that the course line and the other line, ten degrees to the left of the course line, extend past the neat line (that is the line making the border of a chart) and converge on the position of Natal. Since Natal is not on this chart, Noonan used the standard method used by navigators for this situation, you simply attach an extension piece of paper to the chart on which you plot the departure and then lay your straight edge from that point to the destination. Ask any of your pilot friends how they plot a course on their Sectional Charts and they will tell you that this is the standard method that they use when both the destination and the departure are not on the same side of the chart.
Noonan then marked the magnetic course as 061° for the first part of the route and 060° for the end near Africa, not the constant 060° that Williams used for the whole route.
Noonan then marked check points spaced evenly at 150 SM intervals representing one hour of flying time for each leg at the planned speed of 150 mph.
We can also see that Noonan actually used nautical miles for his navigation. Next to the left most line, ten degrees to the left of the course line, just at the bottom of the chart, we find Noonan's notation "410" which is the distance in nautical miles from Natal to that point crossing the equator at the bottom of the chart. Follow further up that line and you will also find Noonan's notation of "1017 mi from Natal" and those are also nautical miles.
So, it is very clear that Noonan had a very different method of planning his routes than Williams did so it is most unlikely that he used Williams' chart for the last leg but it is highly likely that he used used own, his preferred methods when planning the Lae to Howland leg. Unless someone can come up with evidence showing that Noonan used Williams planning documents we can conclude that he did not but that he did his own planning and plotting using his methods that he showed us on the Natal to Dakar chart.
I would bet money that Noonan chuckled, as did I, at all the unnecessary work that Williams did, planning all those unnecessary great circle points and courses, when Noonan knew, based on his superior flight navigation experience, that a simple rhumb line was the better way to go.
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