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Author Topic: LaPook Hypothesis: Box Search around 157-337  (Read 111137 times)

Jeff Victor Hayden

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Re: LaPook Hypothesis: Box Search around 157-337
« Reply #30 on: June 07, 2012, 05:59:00 PM »

But if you had some drift and other problems then you in theory could 'miss' the object you were looking for?

I'm no navigator, just throwing straw in the wind  ;D

Nor me Chris that's why I always read Garys input as he seems to be the man. Page 237 deals with the drift part of a search pattern in Garys link. You don't need a LOP, just headings and distances relative to each other for a search pattern (I think  ???)
This must be the place
 
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richie conroy

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Re: LaPook Hypothesis: Box Search around 157-337
« Reply #31 on: June 08, 2012, 07:40:46 PM »

for me, this page from the last flight notes, sums up why it went wrong ?

even with 4 people they were all kept busy

because there was only 2 people an the work doubled, if Fred knew there location, i think Amelia would ov been too busy looking for land and checking instruments to even take in Fred's  notes about location speed etc
We are an echo of the past


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Gary LaPook

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Re: LaPook Hypothesis: Box Search around 157-337
« Reply #32 on: June 09, 2012, 01:04:22 PM »

for me, this page from the last flight notes, sums up why it went wrong ?

even with 4 people they were all kept busy

because there was only 2 people an the work doubled, if Fred knew there location, i think Amelia would ov been too busy looking for land and checking instruments to even take in Fred's  notes about location speed etc
Let me tell you, it's just long boring hours where your main job is just staying awake. As the pilot you check your compass every ten minutes, or so, and reset the directional gyro as necessary, then go back to boredom. For the navigator (I did both jobs both myself at the same time) shooting a three star fix and doing the computations takes about 25 to 30 minutes every two hours or so. Flying a "wind star" to find the wind with the drift meter takes about 10 minutes every one or two hours. Not much of the navigator to do in between, read comic books?

Amelia talks about all the radio chatter but that was Manning on morse code, he was loquacious, Earhart was not.

gl

« Last Edit: June 22, 2012, 11:07:48 AM by Gary LaPook »
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Irvine John Donald

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Re: LaPook Hypothesis: Box Search around 157-337
« Reply #33 on: June 09, 2012, 08:57:28 PM »

Gary, was autopilot reliable in those days?  If AE relied on it like her voice comm gear and DF hardware then could a drift take them off course or would the compass checks catch it?
Respectfully Submitted;

Irv
 
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Gary LaPook

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Re: LaPook Hypothesis: Box Search around 157-337
« Reply #34 on: June 10, 2012, 02:39:31 AM »

Gary, was autopilot reliable in those days?  If AE relied on it like her voice comm gear and DF hardware then could a drift take them off course or would the compass checks catch it?
That's the reason that you check you compass every 10 minutes or so, to correct any drift in the directional gyro from whence the autopilot gets its information. There were three compasses in the plane, the standard pilot's compass mounted above the instrument panel, an aperiodic compass mounted on the floor in front of the co-pilot's seat, and another aperiodic compass mounted at Noonan's nav station. An aperiodic compass is much more accurate than the standard pilot's compass. But something to keep in mind, gyros drift very little near the equator. The explanation is somewhat complicated. We are talking about precession of a gyroscope. There are two types of gyro precession, real and apparent. Real precession is caused by friction in the bearings which then causes a torque which causes the gyro to precess. In new gyros this tends to be very little. What most pilots see as gyro precession is not real precession but apparent precession. The gyroscope in the directional gyro keeps its alignment with a spot out in space while the earth turns under it. This means that the gyro appears to drift while, in fact, it is not drifting, or precessing, but merely maintaining its alignment in inertial space. A directional gyro in a plane over the north pole will appear to precess at a rate of 15.04 degrees per hour since this is the rate that the earth turns in relation to inertial space. (In relationship to the sun it turns at a rate of 15.00 degrees per hour.) In the latitude of the U.S., pilots are taught that a DG will precess at about 10 degrees per hour, which is simply the 15.04 rate multiplied by the sine of the latitude as this is what determines the rate of the apparent precession.
The latitude being flown was near the equator, zero degrees of latitude. The sine of zero degrees is zero so the apparent precession near the equator is also zero (15.04 times 0 = 0 ) so Earhart's gyros should not have appeared to drift at all or very little due to real precession due to friction in the bearings.

gl
« Last Edit: June 12, 2012, 02:47:26 PM by Gary LaPook »
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Adam Marsland

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Re: LaPook Hypothesis: Box Search around 157-337
« Reply #35 on: June 22, 2012, 03:45:08 AM »

Hey Gary...Adam here...want to tell you I appreciate your putting forth your ideas to critique, and I always respect when people with expertise bring their ideas to bear.


Here's the thing:  you have a navigator who's been up for 24 hours straight, there's limited fuel and...here's the kicker:  the noise of the engine makes complex direct two-way communication well-nigh impossible.  So, yes, in THEORY, one could execute a search pattern.  But success or failure would depend on making -- and correct me if I'm wrong -- a series of course corrections that would require careful keeping track of where one thought one was, and how one progressed in relation to it.

I would submit that, under the circumstances, this just would not have been practical in a real world way.  Yes, of course FN was a competent navigator, and he'd been passing AE written course corrections.  But now everyone's tired, stressed, time is running out, and if FN wanted to embark on this course of action, first he would have to explain/persuade it to AE, and then execute the course corrections calmly and carefully.  To me, in that kind of a situation, there's just too much margin of error.  What if AE doesn't understand what she's doing?  What if out of stress or fatigue, someone screws up a course heading, or just fails to keep proper track of the last turn?  Without real time two way communication, there's no way to really work these details out in a crunch situation.  And my understand is this did not exist.  They wrote each other on a blackboard.  So any communications have to be simple and direct.

 To me, whatever they did, given the limits in time, extreme likelihood of error owing to fatigue, stress and fear, and the inability to really communicate, it would have had to be kept simple.
You make it sound so complicated, it's not and all the planning can be done at the beginning so no work needs to be done during the search itself. An expanding square search pattern consists of legs that are at right angles to each other so each leg is followed by a ninety degree turn, all in the same direction. The first two legs are flown for twice the visibility, the next two for four times the visibility, then six times visibility then eight times visibility, etc. A simple example will  make this clear. They have been flying on a course of 157 degrees at a ground speed of 120 knots and the visibility is 20 NM. (We will ignore the wind correction angle for this illustration but that is easily allowed for in computing the headings to use to maintain the desired courses.)

At 1912 Z they have a four hour reserve of fuel and they know that they must have missed Howland. Noonan passes a note to Earhart.

"Turn left now to 067 degrees and maintain that heading until 1932 Z.
Then turn left to 337 degrees and maintain that heading until 1952 Z.
Then turn left to 247 degrees and maintain that heading until 2032 Z.
Then turn left to 157 degrees and maintain that heading until 2112 Z.
Then turn left to 067 degrees and maintain that heading until 2212 Z.
Then turn left to 337 degrees and maintain that heading until 2312 Z."

The first two legs take 20 minutes and cover 40 NM, twice the visibility. The next two legs take 40 minutes and cover 80 NM, four times visibility, the next two legs take 60 minutes and cover 120 NM, six times visibility. At the end of the four hours of fuel they have searched a box 160 NM on a side covering 25,600 square nautical miles, basically 80 NM in each direction from the starting position.

Rather than me drawing a diagram, see flight navigation reference materials available here.

gl

Actually, you yourself make it sound pretty complicated.  Again, I don't see this going down between two people half deaf from a 20 hour plane ride who are limiting to screaming at each other or writing words down on a chalk board (were they even passing paper notes, and as big as the one Gary described?  I don't know, myself).  Once again, you've reiterated something that's certainly theoretically possible and probably quite doable in a controlled environment but does not give any consideration to the actual situation on the plane, and the limits to real-time communication, as far as I can see.

So to me, you've basically restated the premise more or less as I thought it was going in, and not really addressed my point at all other than to reassert that it's simple and could be done, assuming Fred makes this plan correctly on the fly and in a stressful situation that is both changing constantly and where time is ticking away, is sure of his calculations, is comfortable taking control of the situation when he isn't the pilot, Amelia doesn't ask him wtf he is doing in a situation where they can't really discuss it...etc.  Yes, it's possible.  But in the real world, would it happen?  Really, really doubt it. 

It just doesn't seem to me that you've thought through the eye-level realities of the situation at all, just looked at it from a technical standpoint of what would be the most logical thing to do in abstract.  Communication of a even a marginally complicated plan (for that matter, conceiving it) is just not that simple, ever...particularly there's issues of life and death, who is in charge, lack of sleep, etc., and most of all people not being able to have a real two-way conversation.  I think that's assigning a perfect world scenario to a chaotic, noisy environment where such communication was extremely limited and two people were tired, deaf and under extreme stress.  This is rather the same problem I have with your take on the Lambrecht overflight, btw.  So, again, with all due respect, I am unpersuaded, and I've stated clearly and logically why.  Which, I think, is respectful and fair.
« Last Edit: June 22, 2012, 03:58:31 AM by Adam Marsland »
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Gary LaPook

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Re: LaPook Hypothesis: Box Search around 157-337
« Reply #36 on: June 22, 2012, 11:06:32 AM »



Actually, you yourself make it sound pretty complicated.  Again, I don't see this going down between two people half deaf from a 20 hour plane ride who are limiting to screaming at each other or writing words down on a chalk board (were they even passing paper notes, and as big as the one Gary described?  I don't know, myself). 

  I think that's assigning a perfect world scenario to a chaotic, noisy environment where such communication was extremely limited and two people were tired, deaf and under extreme stress.  This is rather the same problem I have with your take on the Lambrecht overflight, btw.  So, again, with all due respect, I am unpersuaded, and I've stated clearly and logically why.  Which, I think, is respectful and fair.


Well all the problems you state are pure speculation. You think that the computations are complicated, they are not and are child's play for any trained navigator. This method is the STANDARD and was used by navigators many, many times. My post showed that after Noonan worked out the headings and lengths of the legs (which, BTW, took me less than five minutes and Noonan was at least as good a navigator as I am) he had nothing to do except look out the windows for Howland since all the information was in that ONE note passed to Earhart, either on the fishing pole or by Noonan crawling over the fuel tanks, which we know he did on prior legs.

All Earhart had to do was to set the first heading into the autopilot then look out the window for twenty minutes, glancing at the clock periodically, and then repeat this after twenty minutes more and then forty minutes, etc. This is a piece of cake for the pilot. You think that this is hard? Try flying a Standard Instrument Departure (SID) or a Standard Terminal Arrival Route (STAR) into or out of JFK or ORD or LAX. I have attached one example of each at Los Angles International Airport. There are 14 different STARs and 18 different SIDs at LAX, and it is similar at most large airports. These are flown thousands and thousands of times every day nationwide.

As to your concern about fatigue, I know that I have landed after ferrying a plane across the ocean after being awake for more than thirty six hours, flying solo without autopilots and doing celestial navigation at the same time. But stronger evidence on this point than my experience is the experience of the many other ferry pilots.  I posted here information showing that there have been at least 6,000 planes ferried across the Pacific to Australia by solo pilots in single engined airplanes that are slower than the Electra with the legs being longer than the Lae to Howland flight and many or most of those planes did not have autopilots. It is 2600 SM from Honolulu to Pago Pago and in a Cessna 172 that only cruises at 100 mph that is 26 hours, or longer if you have a headwind, so the 20 hour flight from Lae to Howland was nothing out of the ordinary for thousands of ferry pilots. In case you are missing the point I am trying to make, "solo" means that your are the only person in plane and if you don't have an autopilot and you fall asleep then you are rudely awakened by the ocean coming through the windshield. With two pilots on board, Noonan was also a pilot, they could take turns napping if necessary and Noonan's navigation duties did not require his full time attentions. On the flight to Hawaii he got star fixes approximately every two hours each of which take less than 20 minutes to accomplish, plenty of time in between to nap or to spell Earhart on the controls.

Deaf, put some cotton in your ears. It is always loud in twin engined planes because the props must be located only inches from the side cockpit windows due to center of gravity considerations. Yet many thousand of the planes are flown safely and the pilots manage to communicate. Prior to intercoms and headsets you turned to your copilot and leaned his way and spoke into his ear, if necessary, you raised your voice. The same when flight instructing in twins. If they needed to discuss something there is nothing to keep Noonan from slithering over the fuel tanks, probably only took 30 seconds, and we know that he did it and Manning did it too. The fishing pole with note attached was merely a convenience for short messages not requiring discussion. You SPECULATE that they would be deaf but ask any multi engine pilot if they ended up deaf after flying in their plane and they will look at you like you are nuts. So, have you got any proof to back up your speculation? Earhart was met at every stop by news reporters, do you have any newspaper stories saying "Right after she landed we met her climbing out of her plane and we attempted to ask her some questions but she couldn't respond to our questions because she was deaf."  Got any stories like that?

In 1935 Earhart flew solo from Hawaii to California, it took 18 hours. Was she deaf on arrival? Was she so fatigued that she just fell out of the plane to go immediately to sleep on the tarmac? The flight to Hawaii in 1937 took almost 16 hours. Were Earhart and Mantz, who sat next to her in between the engines, both deaf when they arrived? Did they fall immediately to sleep due to fatigue?
In 1935 two guys set an endurance record of 653 hours aloft, more than 27 days, without landing. The really exciting part of that record was the necessity of greasing the rocker arms on the engine every 50 hours. They had a bar mounted along each side of the plane, and every 50 hour one guy would climb out on the left side, move to the nose and use a grease gun on the nipples on his side. He then climbed back into the plane, handed the grease gun to the other guy who then did the same on his side of the engine. They had to do this 13 times. They didn't die from fatigue or go deaf. Then, in 1986, Dick Rutan and Jeanna Yeager flew around the world in 216 hours, more than nine days, and didn't go deaf or die from fatigue either.

You come up with speculative problems that do not really exist in practice.

(I just turned my TV on and the movie Spirit of Saint Louis is on, and Lindbergh flew for 33 and half hours solo. And he didn't sleep in the plane the night before so he had to spend some hours prior to the takeoff so he had probably been up 36 to 40 hour by the time he landed at Le Bourget in Paris.)

gl
« Last Edit: June 23, 2012, 11:47:02 AM by Gary LaPook »
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Jeff Carter

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Re: LaPook Hypothesis: Box Search around 157-337
« Reply #37 on: June 22, 2012, 01:29:49 PM »


.....  You think that the computations are complicated, they are not and are child's play for any trained navigator. This method is the STANDARD and was use by navigators many, many times. .....


Your post reminded me of this video.  $245 a month, and didn't graduate from college...  :)

Where would they be without the Navigator?
http://www.youtube.com/watch?v=gu-TZfml9ck

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Gary LaPook

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Re: LaPook Hypothesis: Box Search around 157-337
« Reply #38 on: June 22, 2012, 04:53:59 PM »



Your post reminded me of this video.  $245 a month, and didn't graduate from college...  :)

Where would they be without the Navigator?
http://www.youtube.com/watch?v=gu-TZfml9ck
Cool, and narrated by General Jimmy Stewart, the same guy portraying Lindbergh.

gl
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John Ousterhout

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Re: LaPook Hypothesis: Box Search around 157-337
« Reply #39 on: June 22, 2012, 09:23:42 PM »

For those who aren't pilots, "flying a heading" already accounts for the effects of winds.  If FN sends a note to E to "fly 067 until 1932", any trained pilot of her day would have understood that to mean "turn to a magnetic heading of 067 until 7:32pm".  Fred already took the cross-wind effect into account before he told Amelia what heading to fly.   At the same time, she would understand that he was already compensating for wind effects.
Keep in mind that they had a LOT of time working together.  The Around the World Flight up to that point would have required something like 161 hours flying time.  That's a LOT of time to spend together, so I'm willing to assume they had developed an efficient communication system by then.
Cheers,
JohnO
 
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Gary LaPook

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Re: LaPook Hypothesis: Box Search around 157-337
« Reply #40 on: June 24, 2012, 06:44:12 AM »

Since Adam, and probably others, think that doing the computations for a square search would be too difficult for Noonan after being in the air for many hours, I decided to provide the readers of this forum some flight instruction and I won't even send anybody a bill for my services.

Noonan had a Dalton Mark VII Aircraft Navigational Computer which was an early model of the ubiquitous E-6B which was further developed into the MB-4A. We know he had this tool because it said so in a letter which is attached. I have also attached two PDFs, one showing how this computation is done on a navigational computer and the second has the table of computed data for the search.

The first two photos show the computer which consists of a circular base and a rectangular slide that can be moved up and down. The first shows the front side which is used for time, speed and distance computations and the back side is used for vector diagrams that solve the wind correction and ground speed problems.

Look at the second PDF "Square search plan" and the first image shows the form for the plan. The first image shows the information we are starting with. The true airspeed (TAS) is 120 knots to be consistent with my prior "no wind" example, the wind is coming from 090° at 25 knots, and the visibility is 20 nautical miles. Based on the visibility we know that for a standard search pattern that the first two legs will be twice the visibility, 40 NM, the next two legs will be four times the visibility and the last two legs will be six times the visibility (assuming four hours of fuel for the search.) We also know the true courses we will be flying, 067 - 337 - 247 - and 157 degrees. We put this information on the form. We need to compute the Wind Correction Angle (WCA) which we combine with the TC to determine the True Heading (TH) that we will point the nose of the plane at, and actually fly, which will correct for the wind so that we will make good the desired true courses. The Ground Speed (GS) we need to compute the time to spend on each leg. Combining the GS with the distance gives the Estimated Time Enroute (ETE) on each leg and by adding up these times with the original starting time we can figure when to make the turns onto subsequent legs.

We start on the back side. The circular clear surface is used for drawing the vector that represents the wind and it can be rotated through 360°. This is used in conjunction with the slide which has diverging lines starting at the bottom and arcs representing speeds. We start by turning the disk so that the direction that the wind is coming from, "E" or 90° in this example, is under the index at the top. (pic 3)
We then move the slide until the "100" arc is under the center small circle on the disk (called the "grommet".) Next we go up the center line from the grommet 25 units, the speed of the wind. and place a dot on the disk lined up with the 125 arc. (pic 4) This is the only mark that is normally placed on the disk but I have added an arrow from the dot to the grommet to make it clearer. (pic 5) This arrow represents how far the wind would move the airplane in one hour so if you were starting at the position of the dot, after one hour you would be at the grommet.

Next we turn the disk to the first TC, 067°, and move the slide until the TAS, 120 K, is under the dot. (pic 6) We see which diverging line the dot is on top of, in this case 5° right (the lines are every two degrees in this section of the slide) and this is the WCA, R 5° and we put this on the form for each of the 067° TCs. We add the "right" WCA to the TC to arrive at at the TH of 072° which we enter at two places on the form. We then look at the grommet and the arc under the grommet is the GS, 97 knots, which we also enter on the form in two places. (second image) We always check our work by asking the question, "does this make sense?" On the first leg the wind will be from the right so we know the correction must be towards the right and the wind will be a bit of a headwind so the slower ground speed of only 97 knots also makes sense. We then repeat this process for the following three TCs (pics 7, 8 & 9) and (images 3 & 4)

Now we flip the computer over and use the front side to compute the time on each leg. We turn the center disk until the big arrow on the center disk, that represents 60 minutes, is lined up with the ground speed of 97 knots on the outside scale. (pic 10) We then look for the distance on the first leg, 40 NM, (pic 11) on the outside scale and read out the time on the first leg of 25 minutes and put that on the form. (image 5) Then, without moving the disk, we look at the distance on the second 067° leg, 120 NM, and read out the time on that leg of 74 minutes. (pic 12) We then repeat the process for the remaining legs. (pics 13 & 14 and image 6) We enter the time that we will start the first leg, 1912 Z and then add the subsequent times of each leg to determine the times to turn to each succeeding leg. (image 7 & 8 ) One thing to notice, it takes 13 minutes longer with the wind compared to the no wind example, and it always takes more time if there is a wind when flying a search pattern.

That is all there is to it. It took me three minutes to actually do the computations and a lot longer to type up the explanation. Think this would be too hard for a navigator of Noonan's experience? Well, every student pilot, prior to starting his cross country training, knows how to use this computer for this exact computation and they only have about 15 to 20 hours in their logbooks at the time! This is really very basic pilot stuff and even beginner pilots have no trouble doing these computations. Also note that you don't have to do any plotting on the chart to do this search pattern, all the information you need comes off the computer.

(To keep the explanation simple, I left out the additional corrections for variation of magnetic north and deviation of the installed compasses but these corrections were known to Noonan, 9° easterly variation in the vicinity of Howland from he charts he had, including the Williams planning charts, and the compass deviation from the compass correction card on the instrument panel which shows in some of the Purdue photos. Noonan would have applied these also, about 30 seconds more work.)
 gl
« Last Edit: October 25, 2012, 10:05:17 PM by Gary LaPook »
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Gary LaPook

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Re: LaPook Hypothesis: Box Search around 157-337
« Reply #41 on: June 24, 2012, 06:49:31 AM »

For those who aren't pilots, "flying a heading" already accounts for the effects of winds.  If FN sends a note to E to "fly 067 until 1932", any trained pilot of her day would have understood that to mean "turn to a magnetic heading of 067 until 7:32pm".  Fred already took the cross-wind effect into account before he told Amelia what heading to fly.   At the same time, she would understand that he was already compensating for wind effects.
Keep in mind that they had a LOT of time working together.  The Around the World Flight up to that point would have required something like 161 hours flying time.  That's a LOT of time to spend together, so I'm willing to assume they had developed an efficient communication system by then.
I left out the complications of wind and variation and deviation in my first, "no wind," example to keep it simple.

gl
« Last Edit: June 24, 2012, 11:38:06 AM by Gary LaPook »
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Jeff Victor Hayden

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Re: LaPook Hypothesis: Box Search around 157-337
« Reply #42 on: June 24, 2012, 07:10:36 AM »

Thanks for posting that Gary, even I can understand how it works now.
It seems a pretty thorough search pattern and makes you wonder why, if it was implemented, didn't they locate Howland.
Not as close as they thought they were by a huge margin?
Ran out of gas midway through search pattern?
Headed straight for phoenix islands?
Headed back where they came from on reciprocal course?
Gary, they knew they were on the 157º-337º LOP, but not where on the line? would the search pattern be implemented from an unknown position on the LOP? If so what would have been the consequences?
This must be the place
 
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John Ousterhout

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Re: LaPook Hypothesis: Box Search around 157-337
« Reply #43 on: June 24, 2012, 07:54:13 AM »

"...would the search pattern be implemented from an unknown position on the LOP? If so what would have been the consequences?"
I think the answer depends on their ability to get a navigation fix, and the accuracy of the location of Howland Island.  As I understand it, you start your search pattern when you have concluded that you're "lost" ('We must be on you but cannot see you').  Whatever navigation methods got you to that point are assumed to have gotten you close to your destination, plus or minus some reasonable error margin.  The search pattern should start small, centered on your initial position, and gradually expand.  That way, you cover the most likely location (the center of the expanding box) first.

To put it a different way, you NEVER know precisely where you are while in flight.  There is always some margin of error.  When they said they were "on the line", they likely knew they were within a short distance of the island, but had no way to determine which direction to fly to get closer (radio DF would have solved that problem).  That's when a search pattern would most likely begin.

While we don't actually know what happened to prevent them from finding Howland Island, by hypothesizing what sort of search they most likely performed helps us identify what might have gone wrong. 
Cheers,
JohnO
 
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Andrew M McKenna

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Re: LaPook Hypothesis: Box Search around 157-337
« Reply #44 on: June 24, 2012, 01:24:21 PM »

Gary,

I've tried to plot out your search pattern on Google Earth (maybe you've already done this?) with the start of the search at Howland  Island.

Looking at the legs, they end up between 40nm and about 50nm (on the diagonal when they reach the corners) miles away from Howland, on the first 4 legs, then out to 90 miles at the end of the 5th leg, 110 nm at the end of leg 6.  I presume that you do not think they would abandon their search at this point, so I've added the 7th leg of 160 nm.  Since you only give them about an hour before the "END" I presume that you think they ran out of fuel some 3/4 of the way down leg 7. 

Abeam Howland on the LOP during leg 7, they are some 80nm away from Howland.  With visibility at 20 nm, that means that they can see all the way out to the 100 nm point along the LOP.

Since we know that they didn't find Howland, and that also presumably means that they didn't find Baker Isl, it follows that they must have started their search at least 100 nm up the LOP from Howland, or down the LOP from Baker Island, and perhaps as far away as 120 nm from Baker on a diagonal if they misjudged where the LOP was, which seems unlikely since most everyone seems to think that Fred was good enough to get to the Advanced LOP through Howland.

so, I'm curious how, with all your descriptions of how easy it is to use celestial navigation, Fred can be 100 to 120 nm off of his intended target?

I find it interesting that the Monte Carlo analysis puts them to the south, and a few point are well to the south where if they were to then navigate to the advance LOP, they might be 80 - 100 nm south of Howland / Baker.

My only other comment is that 20 nm visibility might be optimistic given that Howland has no lagoon, cloud shadows etc.  If you look at the Waite institute video, it was very hard to see from even 12 nm (if memory serves), so using a 20nm visibility as the basis for their expanding square search may have been logical, but may not have served them well.

In any event, since they said they were running on the line 157 337, north and south, it doesn't sound to me like they were engaged in an expanding square search.  They were looking for Howland on the LOP.

Andrew

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