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Author Topic: The flight plan, magnetic course, headwinds.  (Read 412244 times)

Gary LaPook

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Re: The flight plan, magnetic course, headwinds.
« Reply #495 on: April 06, 2012, 10:30:24 PM »

I think that's a very good point, arriving at Howland while it was still dark has a lot going for it. Lights from Itasca, illuminated landing strip? Hindsight is a wonderful but useless thought process knowing what we do now.

It appears that the 10 am takeoff was pretty random and not linked to navigational considerations. Although this time provided a convenient time to be approaching Howland, just shortly after being able to obtain a star fix and with the sun available for final approach (at least as a backup) , prior radiograms from Earhart had announced other, different, departure times. As further proof that having a recent star fix was not a consideration,  we only have to look at the planned Hawaii to Howland flight. They had planned to depart at 11pm Hawaii time (0930 Z) which would have put them at Howland at about 2100 Z, 9:30 am Itasca time. They actually attempted the takeoff at 5:40 am Hawaii time ( 1610 Z) so would have arrived at Howland at about 0340 Z, 4:10 pm Itasca time with no opportunity for star or moon fixes. Of course the landfall sun line approach was still doable at those arrival times and they did have a radio operator on board so the RDF approach would have been  more reliable.
gl

Gary LaPook
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Gary LaPook

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Re: The flight plan, magnetic course, headwinds.
« Reply #496 on: April 07, 2012, 01:18:16 AM »



But if the weather was permitting up to daylight, shouldn't FN have had star shots from which he could have DR'd for only a couple of hours?  Would have given him a good idea of what winds he'd been fighting through the night, and how to correct for the remaining passage.  Does that make you wonder if the weather was not cooperating so well where he was in the last hours before Howland area?

LTM -
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 using the stars and
the moon 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 accuracy 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  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.

After about 1830 Z the sun was high enough to observe where they were located and the moon was also available, it was high in the sky, about 76°, so it would be difficult to shoot but we know that Noonan was able to observe the sun on the way to Dakar at an altitude of 75° and also on the flight to Hawaii he observed a star at 75°. If he couldn't quite get to the 76° necessary to observe the moon (constrained by the angle of the windows) then Earhart could have slipped the plane by several degrees or slowed the plane down to pitch the nose up a few degrees for the three minutes necessary to take the shot, thus allowing a higher altitude sight to be taken. So even after sunrise he could have gotten sun-moon fixes.

gl
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Heath Smith

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Re: The flight plan, magnetic course, headwinds.
« Reply #497 on: April 07, 2012, 08:22:38 AM »


If Noonan had a fix at 17:40GMT, their heading would have to be off by almost 9 degrees and almost certainly to the North side of Howland in order to miss it.

The red circles represent 25NM (approximate visibility), the green circle around Howland is 30NM in diameter.

The little green circle at 17:40GMT (about 200NM out) is 10NM in diameter.
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Irvine John Donald

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Re: The flight plan, magnetic course, headwinds.
« Reply #498 on: April 07, 2012, 10:15:43 AM »

I like your idea Gary. I am going to Fiji next year on vacation. I should make sure you work with the airline to get me there safely.  :D

Arriving during night conditions with Itasca casting a beacon may in fact have been the best solution. Nice thinking out of the box.

Respectfully Submitted;

Irv
 
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Irvine John Donald

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Re: The flight plan, magnetic course, headwinds.
« Reply #499 on: April 07, 2012, 08:21:28 PM »

Sad to think about how much preparation "could" have gone into this trip. Then we could be celebrating the 75 anniversary of her "successful" world trip flight.
Respectfully Submitted;

Irv
 
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Martin X. Moleski, SJ

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Re: The flight plan, magnetic course, headwinds.
« Reply #500 on: April 07, 2012, 10:08:44 PM »

Who can recall the dates or details of Post's round-the-world flights - the second truly an astonishing solo effort?

It's in the wiki.

Quote
Hughes?  He did it in three days and some hours in a later, more modern variant of the Electra.

I've added him to the article.
LTM,

           Marty
           TIGHAR #2359A
 
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Gary LaPook

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Re: The flight plan, magnetic course, headwinds.
« Reply #501 on: April 08, 2012, 03:53:51 AM »

I like your idea Gary. I am going to Fiji next year on vacation. I should make sure you work with the airline to get me there safely.  :D

Arriving during night conditions with Itasca casting a beacon may in fact have been the best solution. Nice thinking out of the box.
Are you  bare boating in Fiji?

gl
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Irvine John Donald

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Re: The flight plan, magnetic course, headwinds.
« Reply #502 on: April 08, 2012, 04:49:09 AM »

I like your idea Gary. I am going to Fiji next year on vacation. I should make sure you work with the airline to get me there safely.  :D

Arriving during night conditions with Itasca casting a beacon may in fact have been the best solution. Nice thinking out of the box.
Are you  bare boating in Fiji?

gl

The itinerary hasn't been set yet. Lots of time yet.
Respectfully Submitted;

Irv
 
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Re: The flight plan, magnetic course, headwinds.
« Reply #503 on: May 14, 2012, 09:34:05 AM »

                                             Nauru – Ice Cream Cone on the Pacific
   The “Chatter Report” contained in your extensive archive contains the evidence which my friend and I believe miss led Mr. Fred.  The light at Nauru was telegrammed to be at an altitude of 5600 feet.  We believe this not to be correct.  At that day and time we speculate it should have read 560 feet but verification is ongoing as today the island height is just over 200 feet. 
   We believe Mr. Noonan would have used his “Pelorus Drift Site” and estimate his distance from the island especially at night below the cloud layer and he had probably used this technique all during the day as the flight progressed.   He knew his altitude, he could have obtained a negative angle sighting and checked current flight altitude for elevation, apply his trig tables and derive a distance from Nauru.  This drift site was their third means of navigation provided, celestial and radio navigation would not have been available or useable.
   If he had taken two sightings and plotted them, they would have a good ground speed and wind data to apply a corrective heading for Nuribenua Island, his next landfall.
   This works out why they missed and ended up south of Howland for us.  Does it work for you? 
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Gary LaPook

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Re: The flight plan, magnetic course, headwinds.
« Reply #504 on: May 14, 2012, 05:24:47 PM »

                                             Nauru – Ice Cream Cone on the Pacific
   The “Chatter Report” contained in your extensive archive contains the evidence which my friend and I believe miss led Mr. Fred.  The light at Nauru was telegrammed to be at an altitude of 5600 feet.  We believe this not to be correct.  At that day and time we speculate it should have read 560 feet but verification is ongoing as today the island height is just over 200 feet. 
   We believe Mr. Noonan would have used his “Pelorus Drift Site” and estimate his distance from the island especially at night below the cloud layer and he had probably used this technique all during the day as the flight progressed.   He knew his altitude, he could have obtained a negative angle sighting and checked current flight altitude for elevation, apply his trig tables and derive a distance from Nauru.  This drift site was their third means of navigation provided, celestial and radio navigation would not have been available or useable.
   If he had taken two sightings and plotted them, they would have a good ground speed and wind data to apply a corrective heading for Nuribenua Island, his next landfall.
   This works out why they missed and ended up south of Howland for us.  Does it work for you?
First, it's drift sight, not site. See Navy manual, H.O. 216.

Here is the radiogram from Nauru:



Apparently you did not detect that I had my tongue firmly in my cheek when I made this series of posts, I was just attempting to poke a little fun at some others' interpretation of Noonan's navigation.  Please review my posts here:

https://tighar.org/smf/index.php/topic,555.msg8186.html#msg8186

https://tighar.org/smf/index.php/topic,555.msg8204.html#msg8204

https://tighar.org/smf/index.php/topic,555.msg8207.html#msg8207

https://tighar.org/smf/index.php/topic,555.msg8212.html#msg8212

The 5600 foot height for the light was an obvious error just like the longitude of 16.55 east was an obvious error since that longitude is in Africa and the correct longitude for Nauru is 166° 55' east. The correct height, as confirmed from other sources, places the light 560 feet above sea level. Doing my tongue in cheek computation, using the erroneous 5600 foot height, shows the geographical range for the light, as seen from sea level, was between 93.1 to 102.0 SM while from 560 feet the range, as seen from sea level, was only 31.2 SM. (The radiogram states that the light can be viewed from 34 SM away, not 31.2, this is based on the observer being a little over five feet tall.) Then, using the normal procedure, I added the distance to the horizon from the 10,000 altitude of the plane, which is 117.8 SM, making the total range of the light, as seen from 10,000 feet, between 210.9 and 219.8 SM. Using the correct height of the light reduces the range to only 149.0 SM as seen from 10,000 feet. (BTW, any object viewed on the horizon from 10,000 feet is always at a negative 1° 37' so measuring it's altitude is not useful and, in addition, you can't take altitude measurements with a MK 2 drift sight nor can you take negative altitude measurements with the Pioneer octant that Noonan had.)

But, let's go with your idea. Just by coincidence, the direct course from Lae to Howland passes 149 SM abeam of Nauru. If Noonan had actually used the obviously incorrect height, as I did, then he would have calculated his distance from Nauru, as he passed abeam of that island, as being approximately 70 SM too far to the south, 70 SM off course to the right. In response to this erroneous conclusion he would have altered course to the left to correct for this and the plane then whould have ended up 70 SM north of Howland (assuming that he got no star sights), NOT south, which would have placed the plane further away from Gardner, not nearer, so less likely to have ended up there.

Also keep in mind that these are theoretical maximum geographical ranges based only on the curvature of the earth while the actual range is further restricted by the prevailing visibility. For example, if the prevailing visibility in the vicinity of Nauru was 20 SM, then the light could not be seen even at the maximum sea level range of 31.2 SM and the light has to make it out to the local horizon to be able to be seen from an airplane beyond the local horizon at high altitude. In fact, to be visible from the plane, the prevailing would have to have been more than twice the distance to the local horizon from the position of the light so the minimum visibility had to exceed 62 SM which is highly unlikely over the sea. This is because the ray of light would be traveling for 62 SM in the dense air below 560 feet. And this assumes that the haze layer in only 560 feet thick when it is usually two or three thousand feet so the visibility would have to be a lot more. Assuming the haze extended up to 2,000 feet, the minimum prevailing visibility would have to have been 119.8 SM for the plane to see the light from 10,000 feet, a highly unlikely possibility.

But, to answer your question, even though it would add support for my position, I do not believe that Noonan would have made that type of erroneous computation, so, no, it does not work for me.

gl







https://tighar.org/smf/index.php?action=dlattach;topic=555.0;attach=660
« Last Edit: May 14, 2012, 06:30:30 PM by Gary LaPook »
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Gary LaPook

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Re: The flight plan, magnetic course, headwinds.
« Reply #505 on: July 26, 2012, 03:04:03 AM »


Since starting the idea of timing how long I could hear a plane as a way to estimate how far away a plane can be heard, every time I hear a plane I immediately look at my watch. This afternoon I was walking around my neighborhood and I heard that wonderful sound of round engines and I looked at my watch. I then looked up and saw the B-25 coming towards me, it was flying at about 1,500 feet and about 150 knots. It went directly over me and I again looked at my watch and timed it until I could no longer hear it, one minute and 25 seconds. The plane flew away from me about 3.75 NM during that period. The B-25 has two R-2600 engines which are twice as large (and loud) as Earhart's R-1340s. So I doubt that Earhart's plane could be heard as far away as the B-25.

I live about 15 miles from Camarillo airport and there are two B-25s based there.

gl
A month ago a group of four T-6s made several circles over my house as they set up a formation and when it was put together the four passed directly over my house going straight away. I could hear them for 55 seconds and they were flying at about 150 knots so I could no longer hear them at a distance of 2.3 NM. The T-6s have the same engines as the Electra and there were four of them, not just two.

You can do the same experiment yourself.

gl
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Mart Stegle

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Re: The flight plan, magnetic course, headwinds.
« Reply #506 on: July 27, 2012, 03:48:13 AM »

Earlier in this thread Chris Johnson asked: given that, at 1030Z, AE probably saw the Myrtlebank, what if she misidentified it as the ship she expected to be there, the Ontario?  Well, I wonder if that could give them a really nasty problem.  The mistake would introduce a pernicious error into FN's navigation, and I hope someone with a better grasp of geography, time, and navigation will be able to correct the back-of-an-envelope calculations that follow.  (I'm also aware that this account short-cuts a lot of possibilities like possible lights on Nauru and possible stellar fixes in the middle of the night).

So, they've been flying for hours into the Pacific night, with no landmarks since 0718Z at best; they're looking out for the lights of their waypoint, the Ontario; and they reach it, as they think, at 1030Z, which is on the late side but still not wrong enough to sound alarm bells.  Thank heavens.  They've got halfway, something important enough to merit her breaking her radio schedule to transmit the message "Ship in sight", that was picked up in Nauru.  They now have, as they think, the thing they most want: an unambiguous fix on their position, since they know in advance the intended position of the Ontario. They can restart dead reckoning from a "last known good" position. Regrettably, if it's actually the Myrtlebank, the position is wrong, by about 112nm basically westwards.

They fly on for 5 ½ more hours, through the possibly overcast night, getting no help from celestial navigation as they go.  At dawn (about 1800Z), Fred does the sunrise shot, and calculates the distance to the advanced LOP.  All well and good.  But his estimate of their current ground speed will be significantly too fast, by approximately 112 nm over 5 ½ hours, or 20 knots.  As a result, they'll turn off onto the advanced LOP about an hour later and (say) 20 nm too early.  They'll be short of their destination.

A couple of other points about this possible mistake:

•   Wouldn't AE have been worried by the lack of radio contact with the ship in the night?  No. She already knew the originally agreed radio protocol was made useless by the fact that the ship had no HF reception equipment.  She had sent a telegram trying to change that protocol, but she knew it probably hadn't reached the ship yet.  She wasn't expecting radio contact.
•   Could she have mistaken the 400-foot Myrtlebank for the 150-foot Ontario?  That begs further questions: how good was her ship identification at night?   How much did she even know about what the Ontario was supposed to look like?  Bear in mind she presumably didn't know that the Myrtlebank was in the area.
•   How had they missed the Ontario earlier?  Well, the Ontario's log mentions cloud cover from 20 to 40%; what's more, it wasn't precisely at the latitude she seems to have been expecting.  All too easy to miss.
•   What happens after they come up short? They end up flying the LOP south, and if they're starting short - from west of Howland - that brings them, as it happens, very nicely to Gardner.
•   Finally, this makes sense of the conjecture that some of the numbers in Betty's notes represent the Ontario's intended position.  If Fred is out of action, and AE can't take or doesn't trust her own measurements of where they are, the Ontario is still AE's "last known good" navigational position.  Not so good, in reality.

Any thoughts?
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Gary LaPook

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Re: The flight plan, magnetic course, headwinds.
« Reply #507 on: August 04, 2012, 04:27:19 AM »

Earlier in this thread Chris Johnson asked: given that, at 1030Z, AE probably saw the Myrtlebank, what if she misidentified it as the ship she expected to be there, the Ontario?  Well, I wonder if that could give them a really nasty problem.  The mistake would introduce a pernicious error into FN's navigation, and I hope someone with a better grasp of geography, time, and navigation will be able to correct the back-of-an-envelope calculations that follow.  (I'm also aware that this account short-cuts a lot of possibilities like possible lights on Nauru and possible stellar fixes in the middle of the night).

So, they've been flying for hours into the Pacific night, with no landmarks since 0718Z at best; they're looking out for the lights of their waypoint, the Ontario; and they reach it, as they think, at 1030Z, which is on the late side but still not wrong enough to sound alarm bells.  Thank heavens.  They've got halfway, something important enough to merit her breaking her radio schedule to transmit the message "Ship in sight", that was picked up in Nauru.  They now have, as they think, the thing they most want: an unambiguous fix on their position, since they know in advance the intended position of the Ontario. They can restart dead reckoning from a "last known good" position. Regrettably, if it's actually the Myrtlebank, the position is wrong, by about 112nm basically westwards.

They fly on for 5 ½ more hours, through the possibly overcast night, getting no help from celestial navigation as they go.  At dawn (about 1800Z), Fred does the sunrise shot, and calculates the distance to the advanced LOP.  All well and good.  But his estimate of their current ground speed will be significantly too fast, by approximately 112 nm over 5 ½ hours, or 20 knots.  As a result, they'll turn off onto the advanced LOP about an hour later and (say) 20 nm too early.  They'll be short of their destination.

A couple of other points about this possible mistake:

•   Wouldn't AE have been worried by the lack of radio contact with the ship in the night?  No. She already knew the originally agreed radio protocol was made useless by the fact that the ship had no HF reception equipment.  She had sent a telegram trying to change that protocol, but she knew it probably hadn't reached the ship yet.  She wasn't expecting radio contact.
•   Could she have mistaken the 400-foot Myrtlebank for the 150-foot Ontario?  That begs further questions: how good was her ship identification at night?   How much did she even know about what the Ontario was supposed to look like?  Bear in mind she presumably didn't know that the Myrtlebank was in the area.
•   How had they missed the Ontario earlier?  Well, the Ontario's log mentions cloud cover from 20 to 40%; what's more, it wasn't precisely at the latitude she seems to have been expecting.  All too easy to miss.
•   What happens after they come up short? They end up flying the LOP south, and if they're starting short - from west of Howland - that brings them, as it happens, very nicely to Gardner.
•   Finally, this makes sense of the conjecture that some of the numbers in Betty's notes represent the Ontario's intended position.  If Fred is out of action, and AE can't take or doesn't trust her own measurements of where they are, the Ontario is still AE's "last known good" navigational position.  Not so good, in reality.

Any thoughts?
Your post brings up a number of points to discuss. You correctly point out that IF they mistook the Myrtlebank for the Ontario, and IF they started a new dead reckoning from the coordinates they had been given for the Ontario, and IF they used this position as the starting point for calculating their ground speed with the sunrise line of position as the ending point for the ground speed calculation, and IF they got no celestial observations between those points, and IF they got no additional sun observations after the sunrise observation then they would have advanced the sunrise LOP an incorrect distance so that when they intercepted that advanced LOP and followed it they would not have flown over Howland. I have attached a file with several illustrations to help you follow along.

The first illustration shows the locations of interest, the position reported at 0718 Z and the positions of the Ontario and Myrtlebank. Illustration 2 shows the position reported at 0718 Z a few nautical miles west of the western end of Nukumanu. The radioed coordinates recorded by Chater are 4° 33' south, 159° 07' east. Noonan determined this position by visually observing the island because it was not possible to have determined it by celestial navigation due to being in daylight with only the sun available and the sun had not been positioned at azimuths that allowed for a running fix. Our modern chart shows these coordinates as being slightly west of the island but it is also possible that the chart Noonan was using depicted the island further west that it actually is. Some have mistakenly claimed that this position was too far west of Nukumanu to have allowed them to see the island but this mistake is due to referring to the published position of Nukumanu, 4° 35' S, 159° 30' E, which is 23 NM east of the Electra's reported position. However, the published coordinates are for the far south-east corner of Nukumanu and the island is 11 NM long, east to west so the Electra was, at most, 12 NM west of the western end of the island, and possibly less if the chart had it improperly placed.

Illustration 3 shows the course to the position of the Ontario at 1030 Z at 2° 59' S, 165̊ 23' E, a distance of 387 NM. Illustration 4 shows the course to the position of the Myrtlebank at 1030 Z at 2° 20' S, 167° 20'E, a distance of 501 NM. Jacobson provides incorrect distances of 350 NM and 462 NM respectively in his paper. He does this because he incorrectly interpreted the coordinates from Chater for the 0718 Z position report as though they were decimal degrees, 4.33° S, 159.7° E (claiming that the latitude was "four and a third degrees south," something no navigator would ever say) which is the same as 4° 20' S, 159° 42' E, about 38 NM closer to the ships. This is shown in illustrations 5 and 6. How do we know that Chater's notation of “POSITION 4.33 SOUTH 159.7 EAST". used the "." to separate degrees and minutes and not decimals of a degree? That is easily determined because the Chater Report contains its own "Rosetta Stone" to decipher his notation with. His report also contains the text of the radiogram received from Nauru giving the coordinates of the light on that island. Chater writes it as "THE FOLLOWING FROM NARAU STOP NEW NARAU FIXED LIGHT LAT 0.32 S LONG 16 .55 EAST." We know the location of Nauru is 0°32'S., 166°55'E, see attached page from Sailing Directions Pacific Islands. It is clear that  Chater's ".32" is minutes of latitude and the ".55" is minutes of longitude. They are not decimals of degrees. Balfour used the same notation, using "." to separate degrees from minutes, see attached radiogram from Nauru.

We don't know the exact time that Noonan determined the position reported at 0718 Z but it seems unlikely that they just happened to arrive at the island at the exact time that Earhart was scheduled to call Lae on the radio at eighteen minutes after each hour. This is an unknown for us but not for Noonan. In his computations, Jacobson makes the assumption that they were there at 0700 Z, which is reasonable, and I will use the same time so they we can compare my calculations directly with his.
From 0700 Z to 1030 Z is three and a half hours so if the plane spotted the Ontario after flying 387 NM then the ground speed was 111 knots, Jacobson computed just 100 knots for his 350 NM distance. This is very close to the ground speed from Lae to Nukumanu, 105 knots for that 737 NM leg. If they were actually looking at the Myrtlebank then their ground speed would have to have been 143 knots (Jacobson, 132 knots) well above the already experienced ground speed and necessitating a tailwind since their normal cruising airspeed was 130 knots (150 mph), a highly unlikely situation since all the forecasts and weather reports showed consistent headwinds in the 20 to 25 knot range. Based on the highly unlikely high ground speed, we can eliminate the Myrtlebank. Also, the only reason to even consider the Myrtlebank is the report of hearing a plane pass over the ship made by the third mate in 1990, 53 years later. No one else reported it and there was no contemporaneous writing so all we have is an unsupported anecdote and a "long in the tooth" one at that.

Noonan, however, didn't know the location of Ontario or of Myrtlebank at 1030 Z, all he had were the coordinates for the station that the Ontario was supposed to maintain, 3° 05' S, 165° 00 E as shown in illustration 7. The distance from the 0718 Z position and the assigned station for Ontario is 364 NM so the ground speed determined by Noonan was 104 knots, 7 knots slower than the actual ground speed to the actual position of Ontario since the Ontario was actually 23 NM farther east than the coordinates that Noonan had. Ontario did not maintain its exact station, as the attached log of its positions for  July 1 and 2 shows. During this period, when Ontario could expect Earhart to arrive, the ship moved through an area 17 NM from north to south and 41 NM from east to west as depicted as a box in illustrations 8 and 9. Illustration 10 shows that Ontario was at the northeast corner of this box when the Electra flew over. Ontario could not anchor in that deep water and had to maintain steerage way and had no pressing  need to maintain an exact position since Ontario believed that they could send their correct position by radio to the Electra when the time came, they did not know that Earhart could not use the international calling frequency of 500 kcs. There used to be ocean station vessels positioned in the Atlantic and Pacific to take weather observations and to provide radio beacons for aircraft. These vessels also did not maintain exact positions but radioed their actual positions to aircraft passing over so that the aircraft navigators had the correct information for their computations. Because Noonan could not be certain of the position of the Ontario, it is unlikely that he would have used it as  fix to restart his dead reckoning. It would make more sense for him to take a celestial fix in that area (Ontario reported good conditions for celestial sights) so he could be certain of his position and would know of the size of its uncertainty.

Illustration 11 shows the relationship of these ships and the points of no return based on several assumptions as previously discussed on the Point of no return thread. Illustration 12 shows the rest of the flight to Howland and shows the position of a sunrise LOP at approximately 1749 Z which is about 180 NM short of Howland. The distance from the given position of Ontario to the LOP is 1128 NM covered in the 7:19 period making Noonan's computed ground speed 130 knots. But, from the actual position of Ontario, the distance is actually only 1104 NM so the actual ground speed is 126 knots. Using the 130 knot speed that Noonan would have had, he would compute that it would take 1:23 to fly the 180 NM to reach the advanced LOP through Howland so the plane would have turned onto the LOP at 1926 Z. But, flying 1:23 at the actual ground speed of 126 knots would make the plane travel only 174 NM so would turn 6 NM too soon and fly on an LOP 6 NM west of Howland. Looking at the scenario that you were interested in, that they actually saw the Myrtlebank, then the same computation shows that the plane's actual ground speed was 111 knots for the 811 NM from Myrtlebank to the LOP. They then would fly 1:23 at the actual ground speed of 111 knots, covering only 154 NM and so turn short by 46 NM onto a line parallel to the correct advanced LOP but 46 NM to the west.

gl
« Last Edit: August 04, 2012, 07:12:12 PM by Gary LaPook »
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Mart Stegle

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Re: The flight plan, magnetic course, headwinds.
« Reply #508 on: August 07, 2012, 06:27:03 AM »

Those pictures and numbers are very helpful.  Thank you.

I'll come back on some points of detail:

- a contemporary document does state that they saw the Myrtlebank.  It's the State Department telegram quoted by Jacobson: "Message from plane when at least 60 miles south of Nauru received 8.30 P.M. Sydney time, July 2 saying ‘A ship in sight ahead.’ Since identified as steamer Myrtle Bank sic which arrived Nauru daybreak today."  I don't know on what basis the Nauru guys concluded that it was the Myrtlebank, but they had some reason to think so.  We're not dependent solely upon the 53-year-old anecdote.

- The main problem, though, is, the 0718Z position, once correctly understood, seems too far west for them to reach the Myrtlebank by 1030Z, barring an unexpected tailwind, and even if you backdate that position to 0700Z. One could start to conjecturally move it earlier still… but then the tail would be wagging the dog.  Yes.

- The "Rosetta Stone" reference - has anyone noticed that it comes with a problem attached?  The relevant bit runs (as quoted in the TIGHAR transcription):
THE FOLLOWING FROM NARAU STOP NEW NARAU FIXED LIGHT LAT 0.32 S LONG 16 .55 EAST FIVE THOUSAND CANDLEPOWER 5600 FEET ABOVE SEA LEVEL
For sure, it suggests that the Chater report records lat/longs in minutes not decimal fractions.  But it also suggests that the Chater report might be a poor document when it comes to numbers.  Of the three testable numbers in here - the latitude, the longitude, and the height - two are completely corrupted in transmission.  It's not Eric Chater's fault, he's faithfully reproducing the cablegram, but the Rosetta Stone offers a sample that suggests that there are  going to be frequent undetectable errors elsewhere in the numerals in the Chater report.

- I was interested by that calculation that even if they got the right ship, and then didn't get any more observations (etc), they'd end up 6nm short.  In that scenario, it would only take a couple of other accumulated small errors to leave them short enough to be in trouble.  And that initial IF about "IF they got no additional sun observations after the sunrise observation…" - could a malicious god grant Fred a proper celestial fix close to sunrise, so that he knew his exact position on the ground, but too close in time to the sunrise observation to do much to refine his speed?

But, anyway, the main thing is that point about the 0718Z position.  Thanks for making that material available to make it clearer.




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Gary LaPook

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Re: The flight plan, magnetic course, headwinds.
« Reply #509 on: August 08, 2012, 10:36:53 AM »

Those pictures and numbers are very helpful.  Thank you.

I'll come back on some points of detail:

- a contemporary document does state that they saw the Myrtlebank.  It's the State Department telegram quoted by Jacobson: "Message from plane when at least 60 miles south of Nauru received 8.30 P.M. Sydney time, July 2 saying ‘A ship in sight ahead.’ Since identified as steamer Myrtle Bank sic which arrived Nauru daybreak today."  I don't know on what basis the Nauru guys concluded that it was the Myrtlebank, but they had some reason to think so.  We're not dependent solely upon the 53-year-old anecdote.
The Nauruans did not know that the Ontario was there but they knew of the arrival of the Myrtlebank from that direction so, reaonably, jumped to the conclusion that Earhart must have seen that ship.
Quote


- The main problem, though, is, the 0718Z position, once correctly understood, seems too far west for them to reach the Myrtlebank by 1030Z, barring an unexpected tailwind, and even if you backdate that position to 0700Z. One could start to conjecturally move it earlier still… but then the tail would be wagging the dog.  Yes.

- The "Rosetta Stone" reference - has anyone noticed that it comes with a problem attached?  The relevant bit runs (as quoted in the TIGHAR transcription):
THE FOLLOWING FROM NARAU STOP NEW NARAU FIXED LIGHT LAT 0.32 S LONG 16 .55 EAST FIVE THOUSAND CANDLEPOWER 5600 FEET ABOVE SEA LEVEL
For sure, it suggests that the Chater report records lat/longs in minutes not decimal fractions.  But it also suggests that the Chater report might be a poor document when it comes to numbers.  Of the three testable numbers in here - the latitude, the longitude, and the height - two are completely corrupted in transmission.  It's not Eric Chater's fault, he's faithfully reproducing the cablegram, but the Rosetta Stone offers a sample that suggests that there are  going to be frequent undetectable errors elsewhere in the numerals in the Chater report.

Don't be too hard on poor Mr. Balfour, after all, he was just the person who heard what he heard of the Morse code "dahs" and "dits" coming through the aether from Nauru. Remember, "it takes two to tango" and there is no reason to place the blame on Balfour since it is more likely that it was a poorly sent transmission by the Nauru operator. Telegrapher's errors were fairly common in that era, poor sending (the sending operator's "fist"), simply extending the the timing slightly of the dots, dashes, and spaces (the length of each dot and the spaces between them is only 0.03 seconds, THREE-ONE HUNDRETHS OF A SECOND, for code sent at the fairly standard thirty words per minute of skilled operators) can change one letter into two different letters or characters plus static and noise on the frequency. The omitted "6" in the longitude of Nauru and the repeated extra "0" in the altitude of the light were almost certainly made by the sender as adding a character or dropping a character are fairly common errors in sending Morse. But this does not affect the fact that the standard notation used by Balfour and others of that era (there are many other examples of this) to use dots to separate degrees from minutes and that is obvious in this case since ".32" and ".55" accurately states the minutes in the position of Nauru and so proves that the 0718 Z position report was in degrees and minutes. We have discussed this before here. I remember a case we studied in law school on this point. A principal had sent a telegram to his agent, "buy 10,000 tons of ....(some comodity)" and the message delivered to the agent said "buy 100,000 tons of ....". The market dropped for that commodity and the man lost a great deal of money on the extra 90,000 tons of stuff so he sued the telegraph company. He lost because the court held that this was a common type of transmission error and, that  because of this, that if the sender needed to be sure that his message had been sent accurately, the tariffs of the telegraph company provided that, for an extra charge, the telegram would be transmitted back from the destination to the sender so that the sender could check the accuracy of the telegram as delivered. The principal had not paid this extra fee and the tariffs disclaimed liability for this type of transmission error without that extra fee. This was one of the reasons that telegraphic codes were developed because the code word for "10,000" might be "thasius" and the code word for "100,000" might be  "tibullis", no way to make that type of error when using a code. See attached excerpt of the ABC Code.

There is a very good reason that telegraphers used the "." to separate degrees from minutes, it is because there is no Morse code character for the degree symbol so "degrees" would have to be spelled out, D-E-G-R-E-E-S (- . .   .   - - .   . - .   .   .   . . . ) , instead of using just the period (. - . - . -) in Morse code.
Quote

- I was interested by that calculation that even if they got the right ship, and then didn't get any more observations (etc), they'd end up 6nm short.  In that scenario, it would only take a couple of other accumulated small errors to leave them short enough to be in trouble.  And that initial IF about "IF they got no additional sun observations after the sunrise observation…" - could a malicious god grant Fred a proper celestial fix close to sunrise, so that he knew his exact position on the ground, but too close in time to the sunrise observation to do much to refine his speed?

But, anyway, the main thing is that point about the 0718Z position.  Thanks for making that material available to make it clearer.

The 0718 Z report was not in Morse code, Earhart was speaking on the radio and Balfour took down what she said and placed the standard "." to separate the degrees from the minutes. Earhart did not say, "four point three three degrees south" she said either "four degrees thirty three south" or, more likely, she said "four (slight pause) thirty three south." This is also corroborated by the 0519 Z position report in which the longitude was recorded as "150.7 east" which everybody knows is impossible. But "157° east" is very reasonable given her ground speed. Earhart simply said "longitude one five seven east" and Balfour thought he heard a slight pause between the "5" and the "7" and so placed his dot there. See prior discussion of this point here.

gl
« Last Edit: August 09, 2012, 03:31:01 AM by Gary LaPook »
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