# TIGHAR

## Amelia Earhart Search Forum => Celestial choir => Topic started by: Dave Patterson on February 18, 2013, 12:34:53 PM

Title: LOP right offset
Post by: Dave Patterson on February 18, 2013, 12:34:53 PM
I'm new here. Commercial pilot licensed since '71. Every time I look up Noonans navigation theory, it seems possibly wrong to me. I would've used the right offset even though left offset was closer. I would rather try to find 2 dots in the Pacific than one, and by using the right offset method, it would bring you closer to Baker than the left; in other words, set your course for 1/2 way betweeen the 2 islands and some time after after getting the sunrise LOP, offset to the right until you intersect 157/337. Then turn left hoping to see one. Sorry if this is posted in the wrong place and if somebody else suggested it. Also, after x amount of time, I would've headed for the Gilberts whether they were friendly or not. With enough feul you're bound to run into an island somewhere in that direction.
Title: Re: LOP right offset
Post by: JNev on February 18, 2013, 03:51:25 PM
I'm new here. Commercial pilot licensed since '71. Every time I look up Noonans navigation theory, it seems possibly wrong to me. I would've used the right offset even though left offset was closer. I would rather try to find 2 dots in the Pacific than one, and by using the right offset method, it would bring you closer to Baker than the left; in other words, set your course for 1/2 way betweeen the 2 islands and some time after after getting the sunrise LOP, offset to the right until you intersect 157/337. Then turn left hoping to see one. Sorry if this is posted in the wrong place and if somebody else suggested it. Also, after x amount of time, I would've headed for the Gilberts whether they were friendly or not. With enough feul you're bound to run into an island somewhere in that direction.

My thinking on the LOP / possible intercept (offset) is close to yours with regard to the idea of a right offset.  I don't know that we know that FN actually intended an offset approach (maybe I missed something) but it has been put-up as an idea and certainly was a well-known and applied technique.

I recall having seen something put up on left offset, but the trouble I see with that (and I am not a qualified celestial navigator, mind you) is that if you fly SSE along the LOP once reaching it and don't see Howland, then what?  I'd want my 'last heading' to be SSE because that is where other lands did happen to lie: Gardner and others of the Phoenix group.

Recall that I said my thinking was 'close to yours', not quite the same - notably having to do with two concerns for the Gilberts:

- If you can't be sure how far NNW or SSE you were on the LOP when you turned back toward the Gilberts, could you have reasonable assurance of finding them (not knowing where you were north or south)?  I'm not sure you would but may be wrong - it's been postulated that 'you can't get to Gardner if you don't know where you are' either, but the difference as I see it is that progressing along a reasonably attained LOP established earlier and now maintained by dead reckoning, you have a reasonable shot of proceeding down that line to the Phoenix group.  Going back to the Gilberts is different - I don't think you could have the same confidence as to how far north or south you might be of track, but maybe that is a big enough group to eventually bang into something anyway, don't know for sure.
- Fuel - not sure what would have been left after 20 or so hours aloft would get you back to the Gilberts, would it?  Best estimates seem to indicate about 24 hours of endurance for the Electra that day - would 4 hours do it?  That too makes the Phoenix group more attractive as 'doable' to me, today, which is a long way from being inside of Noonan's or Earhart's head that day in 1937.