A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Gary LaPook
Date: 2015 Dec 10, 23:05 -0800
I am attaching the pages from the FAA Flight Navigator's Manual (2011 ed.) that have the formulas for computing the new latitude and longitude given distance traveled and course. "Ln" means natural logarithm. These formulas have been published in AFM 51-40 (1983 ed. ); AFPAM 11-216 ( 2001 ed.) and now in the FAA manual. For all that time there has been a typographical error thats prevents finding the rhumb line course. The error is that a set of parentheses was missing from the denominator in the formula, the 180 should multiply all the following terms but without the missing parentheses it only multiplies the first term. I have also attached a page from AFM 51-40 showing where you need to place the parentheses. Also, the FAA manual introduces an additional error, the last formula on page B-6 is for the case when course is NOT zero but the line denoting "not" is missing over the equals sign Compare with the same formula in AFM 51-40.
The entire FAA Fllight Navigator's Manual is available here: