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Author Topic: visual counterfeit , navigation and subsequent demise  (Read 84543 times)

Jeff Victor Hayden

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Re: visual counterfeit , navigation and subsequent demise
« Reply #30 on: September 20, 2013, 09:02:57 AM »

What's the rough flying time from the vicinity of Howland to the vicinity of Gardner?

I find it an awfully daunting thought to imagine that once committed to heading southward on the LOP the only prospects were either to hope to spot a small speck of land (after having already missed another small speck of land) or fly until you essentially fall out of the sky.

Tim, the Phoenix Islands offered eight specks of land to aim for plus, these specks of land had green foliage and some azure blue lagoons which stand out a bit more clearly than Howland
Island in the Pacific Ocean. The odds of finding one of them was eight times better than finding the one you haven't found yet.
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« Last Edit: September 20, 2013, 09:04:39 AM by Jeff Victor Hayden »
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Tim Mellon

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Re: visual counterfeit , navigation and subsequent demise
« Reply #31 on: September 20, 2013, 09:11:15 AM »

What's the rough flying time from the vicinity of Howland to the vicinity of Gardner?
I estimate approximately 2.5 hours depending upon winds.
Quote

I find it an awfully daunting thought to imagine that once committed to heading southward on the LOP the only prospects were either to hope to spot a small speck of land (after having already missed another small speck of land) or fly until you essentially fall out of the sky.
Maybe less daunting than you imagine: if they were truly able to determine that they were on the LOP and then chose a course of 157 degrees using the autopilot, they already would have eliminated whatever cross-track error had been accumulated in the first 18 hours of flight. If their turn to the South had occurred anywhere South of the original course, their distance to Gardner would have been decreased correspondingly, making the chances of seeing it greater.

Furthermore, the weather may have improved vastly in the several hundred miles traversed. Not to mention that Gardner Island would have been much easier to see at a given distance because (a) it is larger than Howland by a factor of five, (b) it has a shallow lagoon that presents a very bright optical object, and (c) it had considerable vegetation, unlike Howland, which was flat and practically bare. Also, being several hours later in the day, the sun would have been much higher (reducing glare) and more behind them than ahead of them.

Having flown over such islands in the South Pacific, I would definitely pick the dogleg to the South as Plan B.

EDIT: Jeff Victor Hayden, great minds think alike!
Tim
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« Last Edit: September 20, 2013, 09:23:52 AM by Tim Mellon »
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Jeff Victor Hayden

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Re: visual counterfeit , navigation and subsequent demise
« Reply #32 on: September 20, 2013, 09:33:11 AM »

Let's hope Fred Noonan thought alike as well :-\
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Tim Collins

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Re: visual counterfeit , navigation and subsequent demise
« Reply #33 on: September 20, 2013, 09:34:57 AM »

the Phoenix Islands offered eight specks of land to aim for plus, these specks of land had green foliage and some azure blue lagoons which stand out a bit more clearly than Howland
Island in the Pacific Ocean. The odds of finding one of them was eight times better than finding the one you haven't found yet.

Not to mention that Gardner Island would have been much easier to see at a given distance because (a) it is larger than Howland by a factor of five, (b) it has a shallow lagoon that presents a very bright optical object, and (c) it had considerable vegetation, unlike Howland, which was flat and practically bare.

I'm sure you're right, but somehow I sincerely doubt that AE headed south with such a reassuring scenario in her mind.   
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Ric Gillespie

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Re: visual counterfeit , navigation and subsequent demise
« Reply #34 on: September 20, 2013, 09:40:54 AM »

What's the rough flying time from the vicinity of Howland to the vicinity of Gardner?

Based on the best evidence we have (computer-modeling of the Electra's radio transmission propagation pattern and the reported strength of transmissions heard by Itasca), the airplane was never in "the vicinity of Howland."  The data suggest the following hypothesis:
• They hit the LOP roughly 230 nm southeast of Howland a few minutes before 1912Z ("We must be on you ...").
•They run northwest for about 45 minutes looking for Howland until around 2000Z when AE uses her RDF to try to get a bearing on Itasca ("We heard your signal but unable to get a minimum...").  This was probably their closest approach to Howland.  Speculating that AE remained at 1,000 feet and had backed off her normal at-altitude cruising speed of 130 kts to about 110 kts to conserve fuel, 45 minutes would take her 82.5 nm.  At that point she's still 152 nm miles from Howland and over 110 nm from Baker.  Unable to get a bearing and seeing nothing, they conclude that they must have hit the LOP north of Howland so they turn around and start back-tracking southeast, still trying to find Howland.
• Forty-five minutes later, at around 2013 to 2025Z, they are back where they started from and continuing southeast ("We are on the line 157 337 ... running on line north and south.."). They are 120 nm northwest of Gardner.
• An hour and five minutes later - sometime around 2130Z - they spot Gardner.


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Tim Mellon

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Re: visual counterfeit , navigation and subsequent demise
« Reply #35 on: September 20, 2013, 12:25:38 PM »

• Forty-five minutes later, at around 2013 to 2025Z, they are back where they started from and continuing southeast ("We are on the line 157 337 ... running on line north and south.."). They are 120 nm northwest of Gardner.
• An hour and five minutes later - sometime around 2130Z - they spot Gardner.

Ric, the scenario you paint implies that they were way further off-course towards Howland than I ever imagined. How have you determined that their original course intersected the LOP only 120 NM Northwest of Gardner, and that all along they were much closer to Gardner than to Howland?

Tim
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Chris Owens

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Re: visual counterfeit , navigation and subsequent demise
« Reply #36 on: September 20, 2013, 01:50:56 PM »


Maybe less daunting than you imagine: if they were truly able to determine that they were on the LOP and then chose a course of 157 degrees using the autopilot, they already would have eliminated whatever cross-track error had been accumulated in the first 18 hours of flight.

Nearly, but not completely:   Two things:
  • A simple autopilot (or a human pilot, for that matter) steers to a heading (the direction in which the aircraft's nose is pointing) and not to a course (the direction the aircraft is moving over the ground).  The pilot's instruments tell her what the airplane is doing relative to the air, but in order to understand what's happening relative to the ground, you need to take wind into account, which leads directly to:
  • Turning South at a given instant might remove cross track error, but it would not remove any error resulting from the aircraft being  not as far or further along the track than expected (due to the headwind component of the wind being greater or less than expected)
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Tim Mellon

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Re: visual counterfeit , navigation and subsequent demise
« Reply #37 on: September 20, 2013, 02:59:42 PM »


Maybe less daunting than you imagine: if they were truly able to determine that they were on the LOP and then chose a course of 157 degrees using the autopilot, they already would have eliminated whatever cross-track error had been accumulated in the first 18 hours of flight.

Nearly, but not completely:   Two things:
  • A simple autopilot (or a human pilot, for that matter) steers to a heading (the direction in which the aircraft's nose is pointing) and not to a course (the direction the aircraft is moving over the ground).  The pilot's instruments tell her what the airplane is doing relative to the air, but in order to understand what's happening relative to the ground, you need to take wind into account, which leads directly to:
Yes, Chris, my autopilot has both heading and course modes. Hers had no course mode because there was no navigation radio signal with azimuth available. Having only heading mode she would have had to compute the offset to compensate for crosswinds and factored that into the heading.
Quote

    [li$i]Turning South at a given instant might remove cross track error, but it would not remove any error resulting from the aircraft being  not as far or further along the track than expected (due to the headwind component of the wind being greater or less than expected)[/li]
    [/list]

    This would not be significant, and would only change (slightly) the time of arrival at Gardner. The assumption here is that she did not turn north/south until reaching the LOP derived from the rising sun.
    Tim
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    Tim Mellon

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    Re: visual counterfeit , navigation and subsequent demise
    « Reply #38 on: September 20, 2013, 03:03:45 PM »

    Here's another - the first that really caught my eye on the thing (and I do like donuts...).

    I have learned something today. Thank you, Jeff.

    (But I'm afraid I've eaten my last donut....)
    Tim
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    John Ousterhout

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    Re: visual counterfeit , navigation and subsequent demise
    « Reply #39 on: September 20, 2013, 06:05:46 PM »

    Tim - the donut isn't the dangerous part - it's the hole!
    (sorry, couldn't resist)
    Cheers,
    JohnO
     
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    Tim Mellon

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    Re: visual counterfeit , navigation and subsequent demise
    « Reply #40 on: September 20, 2013, 06:21:48 PM »

    Tim - the donut isn't the dangerous part - it's the hole!
    (sorry, couldn't resist)

    I'm sure they'll think of some pathetic excuse for why I can't eat the hole either.

    Tim
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    John Balderston

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    Re: visual counterfeit , navigation and subsequent demise
    « Reply #41 on: September 20, 2013, 07:22:30 PM »

    Tim - the donut isn't the dangerous part - it's the hole!
    (sorry, couldn't resist)

    I'm sure they'll think of some pathetic excuse for why I can't eat the hole either.

    LOL  :D
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    Jeff Palshook

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    Re: visual counterfeit , navigation and subsequent demise
    « Reply #42 on: September 21, 2013, 04:39:49 AM »

    Ric,

    In your hypothetical timeline above (Reply #38), you seem to be mixing and matching Zulu time (aka GCT in 1937) and time zone used on ITASCA (zone time +11-1/2).  This is very surprising, since I know you know the primary source data much, much better than your post suggests.  Specifically:

    0742 on ITASCA (1912Z):  "We must be on you but cannot see you ..."

    0758 - 0800 on ITASCA (1928 - 1930Z):  "We are circling [or 'listening', as you speculate] but cannot hear you... We received your signals but unable to get a minimum ..."

    0843 on ITASCA (2013Z):  "We are running on the line 157-337 ..."

    The first time interval, 0742 to 0758 ITASCA time (1912 to 1928Z), is 16 minutes, not 45 minutes as you stated.

    The second time interval, 0800 to 0843 on ITASCA (1930 to 2013Z), is about 45 minutes as you correctly stated.

    So your scenario of about 45 minutes flying to the northwest, then 45 minutes flying back to the southeast, at 2013Z back where they started from, doesn't fit the primary source data.  Did you just goof on the times?  Care to revise your scenario?

    Also, what is your evidence that AE and FN initially chose to fly northwest (vice southeast) along the LOP?

    Thanks,

    Jeff P.
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    Greg Daspit

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    Re: visual counterfeit , navigation and subsequent demise
    « Reply #43 on: September 21, 2013, 10:10:22 AM »

    Consider two pieces of the evidence together:
    1. The 2 hour safe landing window (close to Gardner)
    2. The radio Donut(In between Gardner and Howland when combined with the 2 hour window)

    Then there is the LOP she said they were runing North South on.

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    Ric Gillespie

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    Re: visual counterfeit , navigation and subsequent demise
    « Reply #44 on: September 23, 2013, 07:41:09 AM »

    So your scenario of about 45 minutes flying to the northwest, then 45 minutes flying back to the southeast, at 2013Z back where they started from, doesn't fit the primary source data.  Did you just goof on the times?  Care to revise your scenario?

    Yeah, I just goofed on the times.  Gotta slow down.  Let's try again.

    Hypothetical:  After sunrise Fred took a sun shot and established an LOP. Additional sun shots (speed lines) gave him their ground speed. He then gave AE an ETA for when they would reach the LOP that passes through Howland. He probably wrote it on a piece of paper - maybe just "ETA 19:10."

    0742 on ITASCA (1912Z):  "We must be on you but cannot see you ..."

    Fred would never say something like that. Amelia doesn't understand that the ETA is for arrival at the LOP.  It will only be the ETA for arrival at Howland if they were dead on course after a whole night of no celestial sightings due to overcast conditions. Fred knows that's not likely.
    Fred knows they'll need to search up and down the LOP to find Howland.  There are alternative islands to the southeast of Howland but not to the northwest so the sensible thing to do is search northwest hoping that you've hit the LOP southeast of the island - but you can't afford to search northwest very far because if you're going to search to the southeast you'll have to back-track to your starting point. 

    Fred tells her to head northwest. After about 15 minutes she still hasn't heard any reply from Itasca so she gives up on asking them to take a bearing on her and decides to try to use her loop antenna

    0758 on ITASCA (1928Z):  "We are listening but cannot hear you. Go ahead on 7500 with a long count either now or on the scheduled time on half hour." (For AE the "scheduled time on half hour" is in two minutes.  She has forgotten, or never realized, that ITASCA has no voice capability on 7500 Kcs.  They can't send a "long count."  They can only send code.)
     
    0800 on ITASCA (1930Z): "We received your signals but unable to get a minimum ..."
    How far do you dare go before you turn around?  Fifteen minutes?  Half an hour?  Forty-five minutes?  We'll never know and it doesn't really matter. The fact that Itasca heard a strong signal during the entire period from 1912Z to 2025Z suggests that the plane was within the highest probability of reception range during that time. 

    0843 on ITASCA (2013Z):  "We are on the line 157-337 ..."
    0855 0n ITASCA (2025Z):  "Running on line north and south"

    Also, what is your evidence that AE and FN initially chose to fly northwest (vice southeast) along the LOP?

    Logic.  All of the alternative islands are to the southeast.  Use your remaining fuel heading in the direction that could bring you to an island.  Also, she said, "Running on line north and south" not "south and north."

    Ric
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