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Author Topic: 17:47 GMT Transmission  (Read 39275 times)

Heath Smith

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Re: 17:47 GMT Transmission
« Reply #15 on: February 16, 2012, 04:25:49 AM »

Quote
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.

The NW intercept does make a lot of sense if that was the original plan. Perhaps the detour after leaving Lae threw a wrench in to those plans. I believe that cost them roughly about an hour and a half to bypass the storm.

Looking at the timeline for approach, when she stated that they were 200NM out at 17:42GMT, and they thought they had arrived at Howland at 19:12GMT, the speed of approach would have been roughly 150MPH. If they were already on the line, headed South taking readings, the should have already been on the line at 200NM out.

If you believe that they saw the Ontario at 10:30GMT and they were already on the line at 17:42GMT ("200 miles out") the ground speed achieved would have been about 153 knots versus 130 knots if they came straight in. Assuming a 23 knot headwind as reported by AE from the ENE, this would put their air speed at roughly 170 knots or 196 MPH. This speed would have required maximum fuel consumption. Of course if you do not believe that the Ontario was seen there is a possibility that the numbers would work out differently.

Perhaps FN had some other motivation for using the 157/337 line as an advanced line of position? He probably spent a considerable amount of time poring over the details of the flight before he left Lae. Other than seen Baker on the way, is there any other advantage to being on that heading regardless of your ETA?

Unless they were already on the line as you suggested, it does not make a lot of sense to stick to the line an hour later. They must have been following a magnetic heading at 20:13GMT. If FN was such a capable guy, why would they have not taken more readings after 19:12GMT that would have put them on a different heading? To me this would almost suggest that further readings were not possible due to the sky conditions.

The one advantage perhaps of stating that you were on the line was that they would know where to start looking for you had you told them that you were North or South of Howland. Because they did not include this information it was a toss up as to whether you looked toward the North or South. They chose North and did not find them.
« Last Edit: February 16, 2012, 04:40:27 AM by Heath Smith »
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Tom Swearengen

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Re: 17:47 GMT Transmission
« Reply #16 on: February 16, 2012, 05:30:15 AM »

I think she saw the Myrtle Bank, which was between Nauru and the Ontario. So her course was a little further north. I say that because, the Captain of the MB sated he heard a plane overhead, and the Ontario didnt report anything. So that tells me she was flying over the MB, south of Nauru Island, and north of the Ontario.
Tom Swearengen TIGHAR # 3297
 
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Heath Smith

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Re: 17:47 GMT Transmission
« Reply #17 on: February 16, 2012, 05:33:07 AM »

I think she saw the Myrtle Bank, which was between Nauru and the Ontario. So her course was a little further north. I say that because, the Captain of the MB sated he heard a plane overhead, and the Ontario didnt report anything. So that tells me she was flying over the MB, south of Nauru Island, and north of the Ontario.

It is also possible that she saw the Ontario at 10:30GMT and the deck hand on the Myrtle Bank did hear the plan sometime later. The position of the Myrtle Bank at the time is very sketchy. The deck hand also reported the time to be around 10:30pm (local time, whatever local time he was using).
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John Ousterhout

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Re: 17:47 GMT Transmission
« Reply #18 on: February 16, 2012, 06:47:08 AM »

Heath's two lines "...They must have been following a magnetic heading at 20:13GMT." and "...The one advantage perhaps of stating that you were on the line..." may imply to some folks that following a line of position is somehow different from flying a compass heading.  You don't/can't follow a fixed line on the map, you can only follow compass headings, allowing for winds.  You still maintain a fixed compass heading while you "fly the line".
Sunrise can give you a known line of position, but not a known point of position.  We believe Fred was likely to have precalculated this line.  Knowing their airspeed, and in real time, he could recalculate the flying time and distance to a parallel line that ran through Howland.  They then "only" needed to fly that calculated distance ("the line"), then turn to the compass heading he figures will take them to Howland, and then fly that compass heading.  It's ded-reckoning, with help from the sun-line to reduce error on one axis.  Somewhere in there their navigational error grew big enough they missed the island.
Cheers,
JohnO
 
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Heath Smith

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Re: 17:47 GMT Transmission
« Reply #19 on: February 16, 2012, 06:49:55 AM »


John,

The reason I mentioned the 20:13GMT and the heading is because as Gary pointed out, they would not have been on a 157/337 if they had obtained a new celestial observation using the sun. This sort of implies a new fix was not possible.
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John Ousterhout

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Re: 17:47 GMT Transmission
« Reply #20 on: February 16, 2012, 07:09:19 AM »

Heath,
thanks for the clarification.  You also made a good point that " perhaps ...stating that you were on the line was that they would know where to start looking for you...".  This makes sense to me, but the point seems to have been missed by the Captain of the Itasca.  He did not steam up and down "the line" looking for the aircraft.  That makes me think that even he didn't appreciate the significance of the "157/337" line.
Cheers,
JohnO
 
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Harry Howe, Jr.

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Re: 17:47 GMT Transmission
« Reply #21 on: February 16, 2012, 10:19:39 AM »


Commander Thompson prolly didn't have anymore info then than we have now,  200 miles out, 100 miles out, miust be on you,  running on line,circling, running NesS and maybe only half hour of fuell left.  Was she flying NNW 337 or SSE157?  He guessed NW.  50/50.

Did anyone even think about alternate Plan B? and look at a chart and ask themselves which way theymight fly to hit land after they missed Howland?  Closest land wasn't NW it was 40 nm away to the SE   Baker Island.  But... Just a dimple in the ocean.

That's what happens when ya put all your eggs in the "success" basket and don't ask "What If" we (They) miss Howland?
No Worries Mates
LTM   Harry (TIGHAR #3244R)
 
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Harry Howe, Jr.

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Re: 17:47 GMT Transmission
« Reply #22 on: February 16, 2012, 11:23:57 PM »


Heath
When she reported "200 miles out" was she reporting statute miles or nautical miles?
Half an hour later she reported "100 miles out" If we are to believe thhis then she was flying 200 statute miles per hour in the first instance or 200 knots (230 mph) in the second instance.  The never exceed speed for the Electra was 202 mph.  In the first case she was burning fuel like crazy at a time when she could ill afford to.  Likewise in the second  case and also prolly burning up the engines.

Do we know anything aboit her reporting habits, statute miles and mph or nautical miles and knots or did she even have any consistent reporting habits?
No Worries Mates
LTM   Harry (TIGHAR #3244R)
 
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Heath Smith

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Re: 17:47 GMT Transmission
« Reply #23 on: February 17, 2012, 03:13:41 AM »

Harry,

Initially I was under the assumption that the units were statute miles. After asking around on the forum and checking several books on the subject, all agree that it must have been in nautical miles. I am not sure if she had made similar statements on the radio during other approaches but that would be interesting to attempt to verify.

If you read the transcripts or carefully Earhart stated that she "will" transmit at 100 miles out. She never said "we are" 100 miles out. It appears that most witnesses on the Itasca assumed she meant that she "was" 100 miles out. For example at 18:12 GMT we find "Itasca bridge log states: "Miss Earhart reported position 100 miles from island reception fair.". See Transmissions heard from NR16020.

For myself, I believe they were approaching at about 150 MPH (130 knots). With that assumption at the time of the 18:12 GMT transmission they would have been about 132 NM out (150 SM). Again using the 150 MPH assumption, the actual "100 miles" out message should have been received around 18:28 GMT however this was never received. What is interesting is that they also did not hear from Earhart at 18:45 GMT which would have been on her normal schedule. From 18:12 GMT to 19:10 - 19:12 GMT, nothing was heard from the Electra. Perhaps Earhart slipped up as they were approaching after such a long flight. It is also possible that Itasca or Howland was transmitting at the time walking over her transmission as was the case at 17:47 GMT. If the Itasca and Howland were listening, they should have picked up a signal even if very weak but there was nothing in the logs that I can find.
« Last Edit: February 17, 2012, 03:22:50 AM by Heath Smith »
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Tom Swearengen

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Re: 17:47 GMT Transmission
« Reply #24 on: February 17, 2012, 11:11:41 AM »

I can remember reading somewhat that AE stated that if she had trouble finding Howland, that she would fly back to the Gilberts. That certainly would have put her at fuel exhaustion. Noonan had the pacific charts, and knew that the Phoenix gro was SSE of Howland. If they missed Howland, fly SSE to see Baker, then possibly Jarvis. Gardner and McKean are further south, but one of the reefs (Winslow?) is between the 2.
Am I correct  :o tht at 1000 feet altitude you have visibility of about 40 miles in clear weather? That would be 80 total miles in either east to west visibility, and 40 in the direction of flight. (No point in looking backwards). Now spotting an island at 40 miles and 1000 feet would be tough.
Perhaps if it were possible for her to gain some altitude it would help. Gradual climb wouldnt effect the fuel burn too much, but at, say 3500 feet, there would be a better chance of seeing an island in the blue water, AND if necessary more glide time if needed.
Just a thought-
Tom Swearengen TIGHAR # 3297
 
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Harry Howe, Jr.

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Re: 17:47 GMT Transmission
« Reply #25 on: February 17, 2012, 11:57:15 AM »


Tom
Remember that in a climb you are trading forward speed for altitude , and using more fuel to lift the plane up to a higher altitude and extending the time to get  there because of the reduced speed.  Obviously a trade off to extend your visibility by the square root of the increased altitude.
Decisions, decesions, decisions.
No Worries Mates
LTM   Harry (TIGHAR #3244R)
 
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Tom Swearengen

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Re: 17:47 GMT Transmission
« Reply #26 on: February 17, 2012, 02:01:44 PM »

harry ---I menat to say a gradual climb--maybe 200-300 feet /minute. Slightly aft wheel, but not changing the engine profile alot. Yes it would take a awile to go to the extra 2000 feet----10 min-15 mins---but the extra visiblilty would be worth it as long as the winds aloft, and clod cover didnt ruin the plan. I would thik that the electra might glide farther from 3000 ft than at 1000 feet.
Unless of course, it glides like boulder---
Tom Swearengen TIGHAR # 3297
 
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Harry Howe, Jr.

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Re: 17:47 GMT Transmission
« Reply #27 on: February 17, 2012, 05:11:14 PM »


Tom
Yes it would glide farther and longer time-wise from 3000 than 1000.
The plane would have an optimum rate of descent for maximum glide distance.  I don't know what was for the Electra

Since there is no free lunch, even at 200 ft/min you would have to increase power to climb. It's still a trade off but maybe the increased visibility would be worth it.
No Worries Mates
LTM   Harry (TIGHAR #3244R)
 
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John Ousterhout

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Re: 17:47 GMT Transmission
« Reply #28 on: February 17, 2012, 07:10:18 PM »

The Electra's props didn't feather.  Planes with props that don't feather tend to glide like really efficient bricks.  It helps if the props can be stopped, but that also loses airspeed and altitude, both of which are precious.  A pilot thinking ahead would land with engines idling, given the option.  That would tend to guarantee at least a little fuel left in the tanks.
Cheers,
JohnO
 
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Gary LaPook

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Re: 17:47 GMT Transmission
« Reply #29 on: February 17, 2012, 08:46:01 PM »

The Electra's props didn't feather.  Planes with props that don't feather tend to glide like really efficient bricks.  It helps if the props can be stopped, but that also loses airspeed and altitude, both of which are precious.  A pilot thinking ahead would land with engines idling, given the option.  That would tend to guarantee at least a little fuel left in the tanks.
Even though the props don't feather you still pull them back all the way which reduces drag and improves the glide performance.

gl
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