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Author Topic: 17:47 GMT Transmission  (Read 8704 times)

Heath Smith

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17:47 GMT Transmission
« on: February 12, 2012, 12:21:58 PM »

On the Transmission heard from 16020 page:

17:47 GMT : Howland Island states: "Picked up Earhart (using long antenna, S3, hardly any carrier. Seemed overmodulated. Switched over to loop for Bearing, S1 - 0. She stopped Transmission). Bearing Nil. 3105."

This was 5 minutes after her 17:42 GMT transmission where she stated that she was 200 Miles out. The units are presumed to be nautical miles for the report.

Because Howland was fiddling with the radio, switching from voice to the DF, they probably missed what was said. I believe the Itasca log states it was "Working Howland, Passing on the dope" around this time so they probably missed this transmission as well.

What is interesting, if my calculations are correct, the sun would have just peaked over the horizon if the the Electra had not yet descended from 10,000ft. From what I understand, there were recommendations to start the descent at about 150NM out, so it would make sense if they were still at 10,000ft.

Running the numbers for sunrise at a 1,000ft altitude, this event would have not happened until approximately 17:51 GMT.

If she was trying to report seeing the sunrise, this would have validated that they were accurately tracking their speed and distances at least longitudinally as they made their approach to Howland.

It is really unfortunate that they decided to fiddle with the radio on Howland right at that moment as we will never know what she was actually attempting to communicate.

I do however think it is a plausible explanation as to why she popped in on the radio after her 17:42 GMT report.
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richie conroy

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Re: 17:47 GMT Transmission
« Reply #1 on: February 12, 2012, 01:18:16 PM »

according to this radio message they dropped from 10,000ft to 7000ft at 3pm due to cumulus clouds

next message was at 5pm an they were at 7000ft makeing 150 knots
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Heath Smith

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Re: 17:47 GMT Transmission
« Reply #2 on: February 12, 2012, 01:23:21 PM »

Richie,

I am not sure how the reports outside of Lae relate to being at 10,000ft on approach to Howland. I believe that Johnson had recommended 10,000ft for the later portion of the trip.

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Heath Smith

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Re: 17:47 GMT Transmission
« Reply #3 on: February 14, 2012, 07:08:45 AM »


I had another thought about AE witnessing the sunrise on approach and basically flight almost directly toward the sunrise (10 degrees to the port side) for an hour and a half (until 19:12GMT), I am wondering if she suffered from what is called Disability Glare or another form called Scotomatic glare that causes temporary "blind spots" in your vision and also affects your ability to pick up subtle contrast.

Even if she had sunglasses on board, depending on the quality of the lenses, the effect of the sunlight might have impaired her vision especially over a prolonged period of time. While wearing sunglasses, this probably would have impaired her ability to monitor her gauges that we probably only dimly illuminated. This might have reduced the frequency that she was checking on her gauges and especially the compass(es).

I did find some references on the forum (dated back to 2004 and earlier) that she was carrying various types of sunglasses on the Electra at times. Do we have any evidence that she had a pair on her 2nd world attempt? Are there any photos of her wearing a pair before she departed Lae? This would seem to be an important detail.

If she did not have a pair of sunglasses when she departed Lae this probably would have had a major impact on her ability to make the final approach to Howland.

A couple of interesting links:

http://www.ideafinder.com/history/inventions/sunglasses.htm
http://www.visioninaviation.com/sunglasses-aircrew-pg-7
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Harry Howe, Jr.

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Re: 17:47 GMT Transmission
« Reply #4 on: February 14, 2012, 12:11:51 PM »


Another reason to believe that FN planned an offset approach to Howland, either from the NNW on the 337/157 sunline LOP( sun rising off the Port wing) or from the SSE on the 157/337 sunline LOP(sun ising off the Starboard wing)
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Heath Smith

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Re: 17:47 GMT Transmission
« Reply #5 on: February 15, 2012, 05:10:55 AM »


Harry,

If I understood Gary's comments about the rising sun, reliable readings could not be taken at sunrise but rather you had to wait a full hour after sunrise.

Is there any sort of collection of photos taken from Howland that morning? I saw one black and white photo taken from shore toward the Itasca, I am not sure what time, and the sky appeared to be quite overcast.

Despite the fact that they were flying a 157/337 heading an hour after arrival to where they thought Howland should have been perhaps they were unable to take a fix using the sun to determine longitude.
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Tom Swearengen

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Re: 17:47 GMT Transmission
« Reply #6 on: February 15, 2012, 08:21:40 AM »

Heath---my point exactly--
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Jeffrey Neville

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Re: 17:47 GMT Transmission
« Reply #7 on: February 15, 2012, 11:46:15 AM »


Harry,

If I understood Gary's comments about the rising sun, reliable readings could not be taken at sunrise but rather you had to wait a full hour after sunrise.

Is there any sort of collection of photos taken from Howland that morning? I saw one black and white photo taken from shore toward the Itasca, I am not sure what time, and the sky appeared to be quite overcast.

Despite the fact that they were flying a 157/337 heading an hour after arrival to where they thought Howland should have been perhaps they were unable to take a fix using the sun to determine longitude.

I think Gary's point was that you cannot get a reliable 'at sunrise' shot - too much error, but that you can establish a sun line during the first hour of sunrise.

I don't think you can establish a position north or south based on observation of the sun at that time - only by a shot when sun is at the meridian (highest point in day where you are) - that would have been hours too late.  That leaves the flight constrained to DR for north-south placement.

But Gary also did also explain how a second line could have been derived from the moon - thus perhaps a means of establishing within tolerances of some miles what 'point' of the globe you were on (by where the two LOP cross).

If FN managed to get all those things done, something else must have happened because it obviously didn't work out so well...

If it was overcast where NR16020 happened to be, then those shots would have been pretty tough to make, to say the least.

If it was undercast where NR16020 happened to be, then spotting an island might have been pretty tough, too. 

So much we don't know - and it's been illustrated here by the 17:47 prospect that we (from Itasca and Howland records) may not know all the calls that AE actually made, and will never know if there were more.  If calls were made but not heard, they could have included much other crucial information - clues we'll never have.  We can proceed only on what we do know.

LTM -
- Jeff

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Heath Smith

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Re: 17:47 GMT Transmission
« Reply #8 on: February 15, 2012, 03:48:38 PM »


Quote
I think Gary's point was that you cannot get a reliable 'at sunrise' shot - too much error, but that you can establish a sun line during the first hour of sunrise.

I believe he was saying that FN could not take an accurate reading until the sun was 6 degrees above the horizon.

He also stated that FN would need to wait at least one half hour to take a reading and that an optimal reading would require waiting a full hour before attempting to do so.

If it was overcast an hour after they arrived and they were maintaining the 1,000ft altitude as they had upon arrival, it is possible that they could not take either a reading using the sun or the moon. Perhaps the intent was to fly the 157/337 heading until they could take a reading but that appears to have not worked out.

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richie conroy

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Re: 17:47 GMT Transmission
« Reply #9 on: February 15, 2012, 06:37:20 PM »

simple mistake's seem to be main concern by radio man of itasca

i am gunna quote what i think it shud say

KHAQQ TO ITASCA WE ARE ON THE LINE 157 337 WE WILL REPT MSG, WE WILL REPT THIS ON 6210 KCS WAIT 3105 /A3 S5

KHAQQ XMISION WE ARE RUNNING ON N ES S, LSNIN 6210 KCS

THE RADIO MAN THEN GOES ON TO SAY PLZ STAY ON 3105 KCS DO NOT HR U ON 6210

OBVIOUSLY HE DONT BECAUSE SHE IS LSNIN ON 6210 KCS NOT TALKIN

or av i got that wrong  ???



 on attached image

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richie conroy

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Re: 17:47 GMT Transmission
« Reply #10 on: February 15, 2012, 06:54:05 PM »

an if am right they are trying to communicate with her on 3105 when she is listerning on 6210 kcs

so is amelia at fault because she was speaking on 3105 then changeing to 6210 to listern for reply ?

even thou she wouldnt hear them anyway
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Ted G Campbell

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Re: 17:47 GMT Transmission
« Reply #11 on: February 15, 2012, 07:43:44 PM »

Wasn't the observation window for FN on the right side of the aircraft?  If so, wouldn't it make sense for AE/FN to turn to the North in order to get that last sun shot?  If these ideas are correct wouldn't a South offset be the logical assumption?

Ted Campbell
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Gary LaPook

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Re: 17:47 GMT Transmission
« Reply #12 on: February 15, 2012, 09:56:05 PM »

Wasn't the observation window for FN on the right side of the aircraft?  If so, wouldn't it make sense for AE/FN to turn to the North in order to get that last sun shot?  If these ideas are correct wouldn't a South offset be the logical assumption?

Ted Campbell
There were windows on both sides so observations could be made on either side as was done on the flight to Hawaii. I read on TIGHAR that a special window has been installed on the left side made out of special flat glass so that observations to the left side could be a little more accurate than in other directions but I don't know where this information comes from, Ric? If this is true, then this is one more reason to intercept to the north-northwest which would place the sun out on the left wingtip. Either way, sights were taken on all bearings.

gl
« Last Edit: February 15, 2012, 10:21:27 PM by Gary LaPook »
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Gary LaPook

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Re: 17:47 GMT Transmission
« Reply #13 on: February 15, 2012, 11:04:09 PM »


Quote
I think Gary's point was that you cannot get a reliable 'at sunrise' shot - too much error, but that you can establish a sun line during the first hour of sunrise.

I believe he was saying that FN could not take an accurate reading until the sun was 6 degrees above the horizon.

He also stated that FN would need to wait at least one half hour to take a reading and that an optimal reading would require waiting a full hour before attempting to do so.

If it was overcast an hour after they arrived and they were maintaining the 1,000ft altitude as they had upon arrival, it is possible that they could not take either a reading using the sun or the moon. Perhaps the intent was to fly the 157/337 heading until they could take a reading but that appears to have not worked out.
He had to wait 25 minutes for the sun to climb above six degrees because his computation tables were limited to higher altitudes, see attached refraction table from Noonan's navigation tables. Also see further discussion available here.

The sun rose at 1745 Z in the vicinity of Howland island. The sun climbed to six degrees at 1810 Z. The sun's azimuth changed to 066° at 1847 Z which would change the LOP to 156° - 336° so we know that Noonan did his calculations for the period prior to 1847 Z leaving about a half hour for the observations.

gl
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Heath Smith

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Re: 17:47 GMT Transmission
« Reply #14 on: February 16, 2012, 04:41:45 AM »

Quote
if am right they are trying to communicate with her on 3105 when she is listerning on 6210 kcs

Richie,

I believe the radio guy was quickly trying to talk to her hoping that she was still listening when he asked her not to go to 6210 Khz. The reason he did this was because the Itasca did not have voice capability on that frequency, they could only send her Morse code on that frequency that neither AE or FN were proficient at. This would have limited any information that Itasca could send to her since it had to be transmitted very slowly for them to understand it. Even then, they might not have been able to properly decode.
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