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Author Topic: LOP right offset  (Read 5457 times)

Dave Patterson

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LOP right offset
« 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.
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JNev

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Re: LOP right offset
« Reply #1 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.

Interesting and it's good to read your first post, welcome.
- Jeff Neville

Former Member 3074R
 
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Tim Mellon

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Re: LOP right offset
« Reply #2 on: February 19, 2013, 04:27:31 AM »

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.
             

I like your reasoning, too, Mr. Z.

Additionally, it has the benefit of mitigating against extra-strong headwinds from the East, which would have had the effect of pushing the aircraft slightly offcouruse to the left (North).

Tim
Chairman,  CEO
PanAm Systems

TIGHAR #3372R
 
« Last Edit: February 19, 2013, 05:43:11 AM by Tim Mellon »
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Dave Patterson

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Re: LOP right offset
« Reply #3 on: March 28, 2013, 10:41:05 AM »

Getting back to the "right offset", once they arrived at the LOP, Maybe Amelia wanted to look for the "islands" not only straight ahead, but to the direct left rather than looking across the cockpit. Also, maybe they flew beyond the LOP for a few miles before turning left. This would've put the sun on their right and the "islands" to their left like she wanted. After flying 337 for "X" amount of time do a 360 and fly down the 157 corridor "2X" miles offset from where you flew up the 337 leg. Now Fred could take another sun shot out the left window (assuming he's in the rear of the plane and could see it). Now after flying down the 157 leg for "2X" miles, offset the LOP again to a point where you haven't been and repeat. After this process doesn't result in finding land, make the decision to head for the Phoenix, Gilberts or Marshalls. I'm sure somebody will say that the Itasca had a radio bearing NW of Howland. The null that they "might have gotten" could've been to the SW of Howland. There are 2 nulls. Their "guess" was that she was NW because of some cloud cover. They also guessed that the DF on howland had enough battery endurance. One other though; they must've known that they had a headwind all night long, but after the LOP reading at 1K feet, after being awake for 24+ hours, they maybe mistakenly were using the same headwind component from that point to and during the offset maneuver which would've put them beyond the LOP intersect without doing it on purpose.  OK guys and gals......pick it apart.............Dave Patterson


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