Amelia Earhart Search Forum > Celestial choir
LOP-Possible stupid question
Gary LaPook:
--- Quote from: Chris Johnson on August 22, 2011, 06:37:08 AM ---Thanks Gary! Think I may still flunk this class but at least i'm trying.
I see how a LOP works and understand that without reference points then yes you would more than likely struggle to stay on the line. It wouldn't stop you from getting there with some good fortune and luck though.
In simple terms why do the lines change from 157 to 153, 148 and finaly 126? re read again and had a light bulb moment.
Can you not navigate a LOP and take into account the counter clockwise rotate centred on Howland? Thus keeping along the LOP. Otherwise by the looks of it TIGHAR should be looking on Kanton not Niku ;)
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The LOP is plotted at right angles to the azimuth of the Sun. From 1745 Z to 1845 Z the azimuth of the Sun was 067° plus 90° makes 157°. As the earth turns the sun moves across the sky and the azimuth changes during the day. But the LOP didn't stop at 126° since the sun kept moving. At noon the azimuth of the sun at Howland was straight north so an LOP taken at that time would have run 090/270°. The azimuth was changing in a counter-clockwise direction which may be confusing you since you are probably used to seeing the direction of the sun changing in a clockwise direction. But from a position south of the sun, the sun moves in the opposite direction and noon occurs with the sun to the north while for the U.S. and Europe the sun is south at noon.
gl
Harry Howe, Jr.:
AE/FN probably knew exactly where Gardner was relative to Howland before they took off and had it in mind as a possible alternative forced landing place.
That is my belief.
They also probably had places to the NW in the Marshalls for the same purpose but also knew that they were close to twice as far away as Gardner. . They also would have known that the Japanese were in control of the Marshalls. Their choice would have been to the SSE to Baker, McKean, and Gardner, Common Sense.
John Kada:
Gary,
Thanks for answering my question.
I assume that Williams is the standard navigational reference that FN would have used, and apparently the value for the magnetic variation at Gardner given in Williams matches the NOAA value for all practical purposes, so we have no reason to think that a magnetic variation correction error was a factor in the loss of the flight.
Harry Howe, Jr.:
John Kada
The magnetic declination and variation of the compass probably did not play a part in the failure of the flight from Lae to Howland, however we really don't know what went on in that cockpit. Only AE and FN knew and they aren't with us.
Whether they adjusted their compass for magnetic declination and variation at takeoff and periodically during the long west to east flight, I do not know. Their failure to find Howland and/or to be rescued at Gardner was a result of many errors, the moist egregious of which was to take off without knowing that their RDF (Radio Direction Finder) was working properly and that they knew and understood the limitations of the RDFs at Howland and on the Itasca.
Gary LaPook:
--- Quote from: John Kada on August 23, 2011, 09:33:26 PM ---Gary,
Thanks for answering my question.
I assume that Williams is the standard navigational reference that FN would have used, and apparently the value for the magnetic variation at Gardner given in Williams matches the NOAA value for all practical purposes, so we have no reason to think that a magnetic variation correction error was a factor in the loss of the flight.
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Williams had the variation for Lae, Howland and some places in between but not Gardner.
gl