Advanced search  
Pages: 1 ... 3 4 [5] 6 7 ... 10   Go Down

Author Topic: Working the Flight backwards  (Read 122965 times)

Erik

  • T3
  • ***
  • Posts: 185
Re: Working the Flight backwards
« Reply #60 on: September 06, 2011, 08:01:38 PM »

The navigation issue is part of what hurt their chances to find Howland. Another question for our navigators and experts. If a navigator flies long enough with one pilot does the navigator make allowances for that pilots flying habits?  For instance when flying a long distance without distinct land marks would a pilot tend to veer a bit more to the right or left.  At the end of a long leg would they have to fly 50 miles toward the target due to that pilots natural "drift"?  Would a navigator ever factor that in?  Would an aircraft have a tendency to "pull" in one direction more than another?  Without celestial shots and at night can you tell what you're drift is?

What an interesting question.  Puts a whole new twist on wind correction angle i.e. "pilot correction" angle - huh?.  Perhaps a trim-tab setting for individual pilots?  :o

Seriously though, that would be a good question to see if AE had a historical tendancy to be left or right of her target.  Any way to figure that out?

Logged

Gary LaPook

  • T5
  • *****
  • Posts: 1624
Re: Working the Flight backwards
« Reply #61 on: September 06, 2011, 08:17:06 PM »

The navigation issue is part of what hurt their chances to find Howland. Another question for our navigators and experts. If a navigator flies long enough with one pilot does the navigator make allowances for that pilots flying habits?  For instance when flying a long distance without distinct land marks would a pilot tend to veer a bit more to the right or left.  At the end of a long leg would they have to fly 50 miles toward the target due to that pilots natural "drift"?  Would a navigator ever factor that in?  Would an aircraft have a tendency to "pull" in one direction more than another?  Without celestial shots and at night can you tell what you're drift is?

-----------------------------------------------------

If the directional gyro was drifting, and they all do, then the autopilot or the human pilot will follow it and steer off course. An example will help. Earhart sets the DG to agree with the compass and then  sets the autopilot to fly a true heading of 157°. (I am simplifying this by leaving out the complication of variation, deviation and wind correction angle.) The pilot or autopilot controls the plane so that 157° stays under the lubber line (the heading index line). After ten minutes the pilot checks the compass and finds that the plane is now heading 147° even though the DG still shows 157°. The DG has drifted ten degrees. The pilot then resets the DG to 147° and then turns the plane back to 157° on the DG (or the autopilot makes the turn back to 157° on the DG.) However, during that ten minute period the plane was making a gradual turn to the left so the average heading actually flown was 152° so the plane has drifted 5° off course to the left. Most likely the DG will continue to drift at the same rate so if the pilot continues to just reset the DG as described then the plane will actually fly 152° not 157° over time. A 5° deviation will place the plane 29 NM (33 SM) off course on a leg of 350 NM from Howland to Gardner.

gl
« Last Edit: September 06, 2011, 08:28:39 PM by Gary LaPook »
Logged

Gary LaPook

  • T5
  • *****
  • Posts: 1624
Re: Working the Flight backwards
« Reply #62 on: September 06, 2011, 08:26:07 PM »

Still think it would have been easy for them to spot the island from far away?

I guess I should have been more clear in the original intent of my posting.  Perhaps using the word 'easier' as opposed to 'easy' would have been a better choice.

The point was that any vertical obstruction on an otherwise featureless horizon would be a benefit to any observer, regardless of visibility, cloud cover, fatigue, etc.  The greater magnitude of that vertical disturbance, the greater the benefit.

The larger and taller the object is would only increase the ability for naked eye to detect it when scanning the natural, unobstructed horizon.  Gardner certainly fits that category.  Its vertical profile (from the NW) is approximately 100' high by nearly 1/2 mile wide.

That was the intent of the simulation was to demonstrate the 'trigonometry' that would affect the visual cues while scanning the horizon's naturally flat profile.  It would certainly benefit the observer vs. a situation with no vertical obstructions at all.
---------------------------------------------

You could be standing across the street from the Empire State Building and if the fog limited visibility to 20 feet then you would never see the building. It doesn't matter how big an object is or how high the plane is you still will be limited by the prevailing visibility. If the visibility was 20 NM or less, which seems quite likely, then the furthest they could possibly see Gardner was 20 NM or less. And, as you can see from the photo I posted, if flying above them, even scattered clouds will restrict the distance you can see to a lower limit than the prevailing visibility below the clouds. (Oh, and what about cloud shadows?)

gl
« Last Edit: September 06, 2011, 08:33:06 PM by Gary LaPook »
Logged

Ric Gillespie

  • Executive Director
  • Administrator
  • *
  • Posts: 5503
  • "Do not try. Do or do not. There is no try" Yoda
Re: Working the Flight backwards
« Reply #63 on: September 06, 2011, 08:37:50 PM »

If the directional was drifting, and they all do, then the autopilot or the human pilot will follow it and steer off course.

Yes, that's why you periodically reset the DG.  It's as basic to cross-country flying as switching fuel tanks or leaning the mixture at altitude.  AE and FN were both highly experienced long-distance flyers, much of it by DR.  If they couldn't fly competently when they were tired they wouldn't have lived as long as they did.
Logged

Ric Gillespie

  • Executive Director
  • Administrator
  • *
  • Posts: 5503
  • "Do not try. Do or do not. There is no try" Yoda
Re: Working the Flight backwards
« Reply #64 on: September 06, 2011, 08:43:30 PM »

If the visibility was 20 NM or less, which seems quite likely, then the furthest they could possibly see Gardner was 20 NM or less.

Why would you think the visibility was 20 nm or less?  According to Itasca's deck log, visibility that whole morning was "9" - the maximum on the scale, defined as "Prominent objects visible above 20 miles."
Logged

Erik

  • T3
  • ***
  • Posts: 185
Re: Working the Flight backwards
« Reply #65 on: September 06, 2011, 09:02:04 PM »

You could be standing across the street from the Empire State Building and if the fog limited visibility to 20 feet then you would never see the building. It doesn't matter how big an object is or how high the plane is you still will be limited by the prevailing visibility.

Correct.  I should have been more clear (no pun intended) and excluded IFR conditions in the analysis.  I also should've mentioned that AE was not current in her CAT III certification either.  ???  Good grief...

And, as you can see from the photo I posted, if flying above them, even scattered clouds will restrict the distance you can see to a lower limit than the prevailing visibility below the clouds. (Oh, and what about cloud shadows?)

Lost, looking for islands in a sea of nothingness, above the clouds?  Even for AE = Doubtful!
Logged

Martin X. Moleski, SJ

  • Administrator
  • *
  • Posts: 2948
Re: Working the Flight backwards
« Reply #66 on: September 06, 2011, 10:32:50 PM »

Ahh, okay I can see how one can interpret that.  She apparently also used the word 'AND' indicating that both directions had been traveled.  I used the word apparently, because as mentioned in Tighar Tracks, the radio logs are a bit of a mess and the exact wording might not have been recorded properly.


The website is chock-full of information to help you decide what is and is not reliable.

I've got a small page on the last transmission.  On it, you will find a scan of the last transmission from one of the logs:



At the end of the article are ten links to material elsewhere on the site.  The first five links are:
Yes, of course, it is not necessarily the "exact wording."  Maybe she really said "South and North" and the operator wrote "North and South."

I'm satisfied that it is probably sufficiently accurate to tell us what they were doing.  YMMV.

Quote
Exactly.  The thought has also occurred to me that this whole discussion of working backwards from our 3 assumptions, could in itself be food for another Monte Carlo Simulation.  It shouldn't be that difficult for someone to drum up a simulation in Matlab.  Even MS Excel has a Monte Carlo Simulation option I believe. 

Don't just talk about it.  Do it and let us know how it turns out.

Quote
Incidentally, one other thing about Monte Carlo Simulations.  They are very useful in "what-if" scenarios whereby various parameters are changed to gauge their impacts.   From that standpoint it becomes a living mathematical model that can be used for endless "what-if" scenarios.  Perhaps TIGHAR should revisit this tool and perhaps use it on an ongoing basis as new data is found.

TIGHAR is up to its neck in funding the interpretation of the last expedition and designing the next.  The organization is sold on the Niku Hypothesis.  All you get from the simulation is a sense of how the aircraft may have ended up at Niku; knowing the exact path is of no use whatsoever in searching for the wreckage or other telltale material from AE and FN.  The whole question is moot: something about which reasonable people may reasonably disagree; something that can be argued endlessly; something that makes no difference to the next steps that need to be taken.

Quote
Nice graphic.  This is the crux of the error isn't it?  Speaking as a novice, it's easy for me to believe that Fred's navigation was well off in a north-south direction because of the overcast that likely prohibited the course corrections needed for the overnight flight.  Simultaneously, it's more difficult to believe that Fred would have blown the dawnline measurement.  So both of those together seem to strengthen the notion that the flight was on the LOP probably well south (probably 150 miles south per the Strength 5 radio reception and 3105 donut discussions).   But most of the TIGHAR assumptions seem to be that the flight was actually much further west, which is what has me puzzled.

The assumption that counts is that the flight ended at Niku with sufficient fuel to account for the post-loss radio messages that seem to be credible.  Any number of flight paths from Lae to Niku can lead to that result.
LTM,

           Marty
           TIGHAR #2359A
 
Logged

Gary LaPook

  • T5
  • *****
  • Posts: 1624
Re: Working the Flight backwards
« Reply #67 on: September 06, 2011, 10:36:18 PM »

If the visibility was 20 NM or less, which seems quite likely, then the furthest they could possibly see Gardner was 20 NM or less.

Why would you think the visibility was 20 nm or less?  According to Itasca's deck log, visibility that whole morning was "9" - the maximum on the scale, defined as "Prominent objects visible above 20 miles."
---------------------------------

O.K., 21 miles based on Itasca's deck log. ;)

You don't think it was a 100 NM, do you? Visibilities over the ocean are never that great which is why the scales max out at 25 NM in the Climatic Atlas and at 20 NM in the Navy reporting scheme. They may exceed 25 NM but never by much.

60% probability = "quite likely" in my dictionary.

But Itasca was 350 NM from Gardner and there was no reported weather observation taken at Gardner that day so my basis, as I stated, is the U.S. Navy's Climatic Atlas for the Gardner area for any day in the month of July of any year. Do you have any other information that is more authoritative as to the conditions at Gardner on that date?

We can also compare the visibility as observed at Howland with the expected conditions at Gardner. Based on the Navy Climatic Atlas, in the vicinity of Howland in July, you can expect visibility less than 25 NM 70% of the time; less than 20 NM 60%; less than 15 NM 50% and less than 10 NM 39% of the time. So 40% of the time the visibility will equal or exceed 20 NM. Itasca logged at least 20 NM so there is a 10 % chance that it was more than 20 NM but less than 25 NM and only a 30% chance that it exceeded 25 NM and probably not by a lot more than 25 NM. Comparing this with the data for the vicinity of Gardner shows a three times higher likelihood that the visibility was more than 25 NM at Howland than at Gardner (30% compared to only 10%.) Based on this comparison, the visibility I stated for the Gardner area is quite reasonable and has more support than any other speculation about it.

gl
« Last Edit: September 06, 2011, 11:12:38 PM by Gary LaPook »
Logged

Gary LaPook

  • T5
  • *****
  • Posts: 1624
Re: Working the Flight backwards
« Reply #68 on: September 06, 2011, 10:39:29 PM »

You could be standing across the street from the Empire State Building and if the fog limited visibility to 20 feet then you would never see the building. It doesn't matter how big an object is or how high the plane is you still will be limited by the prevailing visibility.

Correct.  I should have been more clear (no pun intended) and excluded IFR conditions in the analysis.  I also should've mentioned that AE was not current in her CAT III certification either.  ???  Good grief...

And, as you can see from the photo I posted, if flying above them, even scattered clouds will restrict the distance you can see to a lower limit than the prevailing visibility below the clouds. (Oh, and what about cloud shadows?)

Lost, looking for islands in a sea of nothingness, above the clouds?  Even for AE = Doubtful!
--------------------------------------------------

O.K., below the clouds, visibility limited only by the prevailing visibility, 90% probability it was less than 25 NM and 60% probability that it was less than 20 NM.

gl
« Last Edit: September 06, 2011, 10:42:41 PM by Gary LaPook »
Logged

Gary LaPook

  • T5
  • *****
  • Posts: 1624
Re: Working the Flight backwards
« Reply #69 on: September 06, 2011, 11:17:25 PM »

You could be standing across the street from the Empire State Building and if the fog limited visibility to 20 feet then you would never see the building. It doesn't matter how big an object is or how high the plane is you still will be limited by the prevailing visibility.

Correct.  I should have been more clear (no pun intended) and excluded IFR conditions in the analysis.  I also should've mentioned that AE was not current in her CAT III certification either.  ???  Good grief...

And, as you can see from the photo I posted, if flying above them, even scattered clouds will restrict the distance you can see to a lower limit than the prevailing visibility below the clouds. (Oh, and what about cloud shadows?)

Lost, looking for islands in a sea of nothingness, above the clouds?  Even for AE = Doubtful!
-------------------------

She didn't complete her instrument rating so she could not have qualified for CAT 3 authorization. And the Electra didn't have a radar altimeter so it couldn't even qualify for CAT 2 approaches.

But you are trying to avoid my point, that the distance that they could have seen Gardner was limited by the prevailing visibility and that the size of the island doesn't change that one bit.

gl
Logged

Mark Petersen

  • T3
  • ***
  • Posts: 125
Re: Working the Flight backwards
« Reply #70 on: September 07, 2011, 12:10:41 AM »

Don't just talk about it.  Do it and let us know how it turns out.

To be honest this is something that I've mulled over for awhile now.  I have a modest background in numeric methods and have worked on mathematical modeling before (finite differencing models used to predict the behavior of solid-state devices).   It used to be the case that custom software was needed in order to do this sort of work, but this is the era of Matlab and heavy duty MS Excel scripts and plug-ins.  The only problem is getting the free time necessary.  After attending the Tighar Field School, I've started to put a lot of my free time into wreck chasing, for example I will be hiking to the summit of Mt. Whitney this weekend to check out the pair of F6F Hellcat's that crashed back in '46.  If others in Tighar were to feel that a new MC Simulation has value though, I would be more inclined to put the time into it.

Quote
TIGHAR is up to its neck in funding the interpretation of the last expedition and designing the next.  The organization is sold on the Niku Hypothesis.  All you get from the simulation is a sense of how the aircraft may have ended up at Niku; knowing the exact path is of no use whatsoever in searching for the wreckage or other telltale material from AE and FN.  The whole question is moot: something about which reasonable people may reasonably disagree; something that can be argued endlessly; something that makes no difference to the next steps that need to be taken.

That may be true, but isn't that the whole point of this thread?   

Quote
The assumption that counts is that the flight ended at Niku with sufficient fuel to account for the post-loss radio messages that seem to be credible.  Any number of flight paths from Lae to Niku can lead to that result.

Yes, but the point is that if we accept the Niku hypothesis and work backwards, we might be able to rule out some of those flight paths and perhaps have a better understanding of what happened and perhaps even what went wrong.  This seems to be a reasonable goal and something that could also benefit from a MC simulation. 

LTM,  Mark  #2850
Logged

Gary LaPook

  • T5
  • *****
  • Posts: 1624
Re: Working the Flight backwards
« Reply #71 on: September 07, 2011, 12:35:41 AM »

Still think it would have been easy for them to spot the island from far away?

I guess I should have been more clear in the original intent of my posting.  Perhaps using the word 'easier' as opposed to 'easy' would have been a better choice.

The point was that any vertical obstruction on an otherwise featureless horizon would be a benefit to any observer, regardless of visibility, cloud cover, fatigue, etc.  The greater magnitude of that vertical disturbance, the greater the benefit.

The larger and taller the object is would only increase the ability for naked eye to detect it when scanning the natural, unobstructed horizon.  Gardner certainly fits that category.  Its vertical profile (from the NW) is approximately 100' high by nearly 1/2 mile wide.

That was the intent of the simulation was to demonstrate the 'trigonometry' that would affect the visual cues while scanning the horizon's naturally flat profile.  It would certainly benefit the observer vs. a situation with no vertical obstructions at all.

-------------------------------
Unfortunately for your simulation, the trees on Gardner would not be silhouetted above the horizon. From 3,000 feet the horizon is 72.1 SM away (I assume that you are using statute miles.) This is from Table 9 of Bowditch or by formula: distance to the horizon (SM) = 1.317 times the square root of the height in feet. The 100 foot high trees are only 1.3  minutes of arc (1/60 of a degree) tall at that distance.  Because your diagram is for 50 SM, the island and its trees would appear about a quarter of a degree (16 minutes of arc) below the horizon,  so the 100 foot tall trees would not pierce the horizon. To be tall enough to break the horizon the trees would have to have been more than 1200 feet tall!

Looking at your second example, 25 SM, the same situation applies. From 1500 feet the horizon is 51.0 SM away and your island is only 25 SM away so is also well short of the horizon At this distance the trees are 2.6 minutes of arc tall. The island, only 25 SM away, is also more than a quarter of a degree below the horizon (19 minutes of arc) so, again, the trees would not pierce the horizon. To be tall enough to break the horizon the trees would have to have been more than 700 feet tall!

Your last example, 10 SM at 1,000 feet, puts the horizon is 41.6 SM away. The island, only 10 SM away, is 23 minutes of arc below the horizon and the 100 foot high trees are only 6 minutes tall so the tops of the trees will be 17 minutes below the horizon so also will not be silhouetted against the sky. To be tall enough to break the horizon the trees would have to have been more than 350 feet tall!

Don't rely on Google earth, do the trig yourself.

gl
« Last Edit: September 11, 2011, 12:51:51 PM by Gary LaPook »
Logged

Gary LaPook

  • T5
  • *****
  • Posts: 1624
Re: Working the Flight backwards
« Reply #72 on: September 07, 2011, 12:58:11 AM »

Erik,  if you "flew" the route from SW of Howland on Google Earth at 1,000 feet and did a 360 degree search, as you fly, is it possible to see any other land?

Not really.  The only other 'land' is McKean, which is more of a reef/atoll environment more so than it is real land.  Even McKean would have been approximately ~50 miles away from a SW Howland-Gardner route, and difficult, if not impossible to see.  Without any vertical elevation McKean would have been way over the horizon.  It would have been doubtful it was visible unless flying at higher altitudes such as 6,000 thousand feet or greater. 

The other possible visible features (at 1,000 feet) may have been the chain of reefs enroute.  They look like islands in the map below, but they are not.  Although not land per se, these reefs may have provided visible whitecaps if the tide was just right.



I don't think so but it would be nice to have more info. As pointed out in previous posts we should not rely on the accuracy of Google Earth as it is only a software program that has some issues.  Perhaps the new X Flight simulator will give a more accurate representation.

Google Earth's accuracy is horrible for some things and nearly perfect for others.  As with anything, it's a tool that needs to be used correctly within reason.  For example, it's accuracy in terms of precise topography, up-to-date imagery, and street networks may be in question.  On the other hand, measurements such as the entire length of Gardner island are very precise to the extent that you could measure it with an accuracy within a a few yards if you really wanted to

Using Google Earth as a model to generate simulations and provide graphics to back up verbal and written concepts is where it is very powerful tool!  It's mathematical coordinate precision for inputing your own data is accurate to 6 decimal places of a degree, which is roughly about 4 inches.  So, in other words, it is not Google Earth itself that is in question, but rather the originating source that is being used.

To derive the height of the island, I mainly used maps on TIGHAR's own website and recounts of the of the buka trees height to generate the dimensions of the models used here.  After researching, I found these figures were fairly accurate with Google Earth coincidently.  If I didn't have both sources, you are correct, I would have abandoned Google Earth's accuracy and sought additional information.  But in this case, they all matched.
--------------------------------------------


I decided to do some checking on the accuracy of Google Earth coordinates to make sure they were accurate in the Pacific. I found the published coordinates of Mili airport, 6º 05' N, 171º 44'E;  Mujuro airport, 7º  03' 44'' N, 171º 16' 19" E; and Kosrae airport, 5º 21' 25" N, 162º 53' 30"E since these were the closest to Howland. Then going to them with Google Earth I found that the Google Earth coordinates were exactly right, correct to the accuracy of the positions given in the airport database. Mili was only given to the nearest minute but the others were to the second. ( A second is only 100 feet!) You can check for yourself, just go to Google Earth with those coordinates which you will see fall on the runways.

gl
Logged

Gary LaPook

  • T5
  • *****
  • Posts: 1624
Re: Working the Flight backwards
« Reply #73 on: September 07, 2011, 03:56:41 AM »

Ok---I'll ask the question of our navigator friends. IF the weather was cloudy during the nighttime part of the flight, Fred would NOT have been able to shoot a celestrial plot. So, when he was able to shoot the 157/337 sunline, how would he have known where along the sunline he was? He wouldnt have been able to guage their drift, so they actually "could" have been south of Gardner. AT 1000 feet, they may not have been able to see Howland, which "could" have been a few miles over the horizon from their position.

So--as they flew south along the sunline, they came across Gardner.
Does this make any sense to anyone??
----------------------------------------------
There is no reason to think that Noonan had not been able to get celestial fixes. Earhart wrote
that “Noonan must have star sights” so they would not have just changed their minds about this
requirement.
The “Point of No Return” is a standard calculation done by flight navigators, taking into account
air speed, wind speed and endurance, to determine the point along the planned course at which
the plane could reverse its course and return safely to the departure airport.


If Noonan thought he had a 24 hour endurance, using the 23 knot wind component that he measured in flight then he would have calculated the PNR as 1407 Z at 1511 NM from Lae, just five hours and 710 NM short of Howland.
Using a 15 knot wind component then he would have gotten 1323 Z at 1539 NM and with a 25
knot wind he would have gotten 1418 Z and 1502 NM.

It also turns out that there was an airport at Rabaul, 344 NM along the course line to Howland.
Noonan could have calculated a PNR for a departure from Lae with a return to Rabaul. Since
Rabaul was closer to Howland then this PNR would also be closer to Howland. Doing this
calculation we find the PNR occurs at 1526 Z, 1653 NM from Lae, only four hours and 570 NM
short of Howland. So if Noonan had not been able to get fixes they could have turned around and
returned safely to Lae or Rabaul and try again another day.

Air Force Manual 51-40 states the uncertainty of dead reckoning as 10% of the distance flown
from the prior fix.

So contrary to what many people believe, “that they had no idea where they were north and
south" when they intercepted the sunline LOP, we can expect that any error or uncertainty would
be limited to 10 miles for every 100 miles that they had flown since their last fix.

Sunrise at Howland was 1745 Z and civil twilight occurred 22 minutes
earlier at 1724 Z at which point the sky would have been too bright to
see the stars and to obtain a fix. Sunrise and civil twilight would have
occurred even later at their position west of Howland by an additional
one minute for each 15 miles that they were west of Howland. We can
assume that they had arrived close to Howland at 1912 Z when they
reported "must be on you." This is 1 hour and 48 minutes after civil
twilight at Howland and the Electra would have flown 235 nautical miles
in this time at 130 knots. Civil twilight occurred 16 minutes later 235
NM west of Howland so they could have obtained a fix slightly later than
1724 Z at 1740 Z. We can assume that Noonan was busy right up to the
time of civil twilight so that they would have the latest and most
accurate fix to use in locating Howland.

From 1740 Z to 1912 Z NR16020 would have flown 199 nautical miles at 130
knots so the accuracy of their position would only have deteriorated 20
nautical miles based on 10% of the distance flown in that period, If you add this 20 nautical miles
to the uncertainty of the original fix, 10 nautical  miles according to
navigation textbooks, Federal Aviation Regulations, and also based on what
Noonan himself reported to Weems in a letter published at Weem, page 423 page 424 & 425, (see:
https://sites.google.com/site/fredienoonan/resources/weems/weems-422-423.JPG?attredirects=0 and https://sites.google.com/site/fredienoonan/resources/weems/weems-424-425.JPG?attredirects=0  ) they should have known their position within 30 nautical miles.  Although we do not know the time
of his last fix, Noonan did know and would have used that knowledge
in planning his approach and in figuring the possible uncertainty and
how far to aim off.

Looking at this uncertainty in the north-south direction you end up with a 30 nautical mile north-south uncertainty. Noonan would have made the same calculations based on his previous experience, maybe he even rounded this value up for extra safety.

There has been concern expressed that clouds could have prevented Noonan from taking star
sights that late (1940 Z). They had reported flying at 12,000 feet, which normally is above most
clouds. Even if some clouds where higher than 12,000 feet it is unlikely that they blocked the
entire sky for hundreds of miles along the flight path. It has been claimed that Earhart reported at
1415 Z and again at 1515 Z "cloudy and overcast" but these words are not found in either radio
log so there is no support for the claim that Noonan had been prevented from shooting stars. But
what is actually recorded in the radio log, more than an hour after this 1515 Z possible report of
"overcast" conditions, is at 1623 Z Earhart reported "partly cloudy." There are no reports after
this "partly cloudy" report so it is the most current report, in both time and location, so there is no
actual evidence that the weather deteriorated later so as to prevent celestial observations. Earhart
did not report descending to 1,000 feet until almost two hours later at 1818 Z.

Based on this last report of in-flight weather conditions, we can be almost certain that Noonan was able
to take sights at 1623 Z, only two hours and forty-nine minutes before the "must be on you"
transmission at 1912 Z. So looking at this as the worst case scenario, we can do the same
computations as before about the uncertainty of the D.R. position at 1912 Z. In two hours and
forty-nine minutes the plane would have covered 366 NM at 130 knots so the uncertainty caused
by dead reckoning for 366 NM is 37 NM for the 10% estimate of DR accuracy. We have to add
to these estimates the original 10 NM uncertainty in a fix obtained at 1623 Z so the totals is 47
NM of uncertainty at 1912 Z. Noonan knew the time that he obtained his last celestial fix and
would have used the right amount of offset to allow for the possible uncertainty.

So these two cases mark the bounds of the possible uncertainty in the north and south direction, 47 NM if the last fix was obtained at 1623 Z and 30 NM if the last fix was obtained as late as possible (clouds permitting) at 1740 Z. Either way they would not have flown for hours southward still expecting to find Howland.


Also see:
https://sites.google.com/site/fredienoonan/topics/landfall-procedure
https://sites.google.com/site/fredienoonan/topics/accuracy-of-dead-reckoning
https://sites.google.com/site/fredienoonan/topics/accuracy-of-celestial-fixes
https://sites.google.com/site/fredienoonan/discussions/navigation-to-howland-island
gl



« Last Edit: September 07, 2011, 04:01:16 AM by Gary LaPook »
Logged

Martin X. Moleski, SJ

  • Administrator
  • *
  • Posts: 2948
Re: Working the Flight backwards
« Reply #74 on: September 07, 2011, 05:43:35 AM »

... If others in TIGHAR were to feel that a new MC Simulation has value though, I would be more inclined to put the time into it.

Perform to self-set standards.  If it interests you, working on it would be worthwhile.

If not, not.

Quote
Quote
The whole question is moot: something about which reasonable people may reasonably disagree; something that can be argued endlessly; something that makes no difference to the next steps that need to be taken.

That may be true, but isn't that the whole point of this thread?   

Understanding the 157-337 message is part of the backstory for TIGHAR's searches on Niku.

Getting a general sense of the challenges faced by AE and FN in using celestial navigation is helpful in assessing the odds of their ending up at Niku with enough fuel to transmit the post-loss radio messages that seem credible.

Calculating with the greatest precision what route or set of routes have the highest probability under some untestable assumptions goes beyond those modest goals.  I predict that if you do the exercise, you will find (as Randy did) many routes that work and some that leave them in the ocean. 

Quote
Quote
The assumption that counts is that the flight ended at Niku with sufficient fuel to account for the post-loss radio messages that seem to be credible.  Any number of flight paths from Lae to Niku can lead to that result.

Yes, but the point is that if we accept the Niku hypothesis and work backwards, we might be able to rule out some of those flight paths and perhaps have a better understanding of what happened and perhaps even what went wrong.  This seems to be a reasonable goal and something that could also benefit from a MC simulation. 

OK.  Go for it.  I'm sure you will find lots of people here willing to offer you peer review after you've built your model.   :)
LTM,

           Marty
           TIGHAR #2359A
 
Logged
Pages: 1 ... 3 4 [5] 6 7 ... 10   Go Up
 

Copyright 2019 by TIGHAR, a non-profit foundation. No portion of the TIGHAR Website may be reproduced by xerographic, photographic, digital or any other means for any purpose. No portion of the TIGHAR Website may be stored in a retrieval system, copied, transmitted or transferred in any form or by any means, whether electronic, mechanical, digital, photographic, magnetic or otherwise, for any purpose without the express, written permission of TIGHAR. All rights reserved.

Contact us at: info@tighar.org • Phone: 610-467-1937 • Membership formwebmaster@tighar.org

Powered by MySQL SMF 2.0.15 | SMF © 2017, Simple Machines Powered by PHP