A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Gary LaPook
Date: 2013 Feb 25, 22:05 -0800
|I also believe the two hundred mile estimate was DR.|
The plane had to start a descent from the cruising altitude down to 1,000 feet quite a distance prior to the estimated point of LOP interception to ensure that they did not miss the island by overshooting the LOP. A normal descent is 300 feet per nautical mile so the descent would take at least 30 NM plus an allowance to avoid an overshoot would mean they had to start a descent about 50 NM prior to the estimated interception point resulting in 5 NM DR uncertainty. If the sun sight was taken at 1822 Z they still had about 90 NM to the interception which would cause 9 NM in DR uncertainty
In addition to these DR uncertainties you have to add the possible error in the sun line of about 7 NM and additional possible errors due to the difference in the wind as determined at altitude and the most likely reduced wind speed at the lower altitudes.
--- On Sun, 2/24/13, Don Seltzer <timoneer@GMAIL.COM> wrote: