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Author Topic: The flight plan, magnetic course, headwinds.  (Read 383463 times)

Heath Smith

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Re: The flight plan, magnetic course, headwinds.
« Reply #45 on: January 01, 2012, 12:51:08 PM »

Quote
There was a second airspeed indicator mounted on the copilot's side of the instrument panel which was the reason for the second pitot tube. Noonan' could have been taped into either one. I don't know if there were two separate static ports for the two altimeters, the copilot had one too, they could have been using just one static port and Noonan's would have used the static pressure line for his altimeter.

This would be very useful to know especially if we believe that the belly antenna was indeed ripped off at take off at Lae. Just as a theory, maybe they did extend the co-pilot instrument back to Noonan and when the antenna was ripped off, this tweaked his readings as compared to what Earhart might have seen. Because Noonan might have been sending up commands to Earhart, maybe they did not realize that they were reading two different indicated air speeds? Perhaps Noonan was even sending forward RPM commands to Earhart and she was not able to spot the problem herself? Noonan probably was doing the head wind, true airspeed calculations along with navigation checks and was probably performing the unit conversions as well. Perhaps Earhart was merely executing orders from Noonan. Maybe she was just following indicated air speed or even RPM instructions?

I found a few pictures of the pitot tubes and was able to see a close up of one of them. What I am not sure of is whether the pitot tube in the photo is the one actually used or if this was replaced after the crash in Hawaii. The photo just says 1937, California. Does anyone have an image of the actual stardboard pitot tube taken at Lae or even Australia? If this was the actual pitot tube, is it possible that a piece of the back of the tube was sheared off in the process? Could this cause Noonan to read higher indicated air speeds than was reality?

For whatever reason, I believe that they were achieving a ground speed of 124.5 all the way from Lae to where the Ontario was spotted. The timing is too coincidental to be otherwise (my opinion). If you assume they were achieving 150mph after departing from Nukumanu Island (since they reported a head wind of 23 knots), you are somewhat forced in to assuming that the Myrtl Bank was the ship spotted (or some yet unknown mystery ship) even though very little is known about her true where abouts. This would put the Myrtle Bank about 29 miles off the planned flight path, compared to the Ontario at 8 miles off. I suppose you could think that they flew far North of the Ontario and spotted the Myrtle Bank instead but this would infer a major navigational malfunction. This seems highly unlikely since they had a good fix 3.2 hours earlier and were right on the flight line.

Assuming that they did in fact spot the Ontario, which makes a lot of sense since she was only 8 miles north of the flight path, the distance from that point at 10:30GMT to the "200 miles out" message at 17:42 would be about 1077 miles. This would mean that the ground speed achieved was 149.58 mph on the trip beyond spotting the ship to being near Howland. The 150 mph make sense in that this was the original speed desired in the original flight plan. If you disregard the 10:30GMT ship spotted, and calculate the ground speed achieve from Nukumanu Island to "200 miles out" would be about 141.7 mph that does not seem to fit well from what I can see.

So the basic theory is that a speed discrepancy was discovered when the ship was spotted and the data seems to suggest that this could indeed be the case. How the ground speed achieved could have been mis-read or calculated, I have no idea. A damaged pitot tube seems to be a good culprit. Noonan might have ran some calculations, found a huge error and asked Amelia "Hey, what is your indicated air speed?".
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Gary LaPook

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Re: The flight plan, magnetic course, headwinds.
« Reply #46 on: January 01, 2012, 02:41:34 PM »

Quote
There was a second airspeed indicator mounted on the copilot's side of the instrument panel which was the reason for the second pitot tube. Noonan' could have been taped into either one. I don't know if there were two separate static ports for the two altimeters, the copilot had one too, they could have been using just one static port and Noonan's would have used the static pressure line for his altimeter.

This would be very useful to know especially if we believe that the belly antenna was indeed ripped off at take off at Lae. Just as a theory, maybe they did extend the co-pilot instrument back to Noonan and when the antenna was ripped off, this tweaked his readings as compared to what Earhart might have seen.

If this was the actual pitot tube, is it possible that a piece of the back of the tube was sheared off in the process? Could this cause Noonan to read higher indicated air speeds than was reality?

For whatever reason, I believe that they were achieving a ground speed of 124.5 all the way from Lae to where the Ontario was spotted. The timing is too coincidental to be otherwise (my opinion). If you assume they were achieving 150mph after departing from Nukumanu Island (since they reported a head wind of 23 knots), you are somewhat forced in to assuming that the Myrtl Bank was the ship spotted (or some yet unknown mystery ship) even though very little is known about her true where abouts. This would put the Myrtle Bank about 29 miles off the planned flight path, compared to the Ontario at 8 miles off. I suppose you could think that they flew far North of the Ontario and spotted the Myrtle Bank instead but this would infer a major navigational malfunction. This seems highly unlikely since they had a good fix 3.2 hours earlier and were right on the flight line.

Assuming that they did in fact spot the Ontario, which makes a lot of sense since she was only 8 miles north of the flight path, the distance from that point at 10:30GMT to the "200 miles out" message at 17:42 would be about 1077 miles. This would mean that the ground speed achieved was 149.58 mph on the trip beyond spotting the ship to being near Howland. The 150 mph make sense in that this was the original speed desired in the original flight plan. If you disregard the 10:30GMT ship spotted, and calculate the ground speed achieve from Nukumanu Island to "200 miles out" would be about 141.7 mph that does not seem to fit well from what I can see.

So the basic theory is that a speed discrepancy was discovered when the ship was spotted and the data seems to suggest that this could indeed be the case. How the ground speed achieved could have been mis-read or calculated, I have no idea. A damaged pitot tube seems to be a good culprit. Noonan might have ran some calculations, found a huge error and asked Amelia "Hey, what is your indicated air speed?".
The idea that the belly antenna was torn off is based on the rear support mast being close to the ground while in the three point attitude, tail on the ground. In this same attitude the pitot tubes are well above the ground (head high, see attached photo) and this continues after the tail comes up.

If the rear of the pitot had been ripped off, opening it to the air, then the airspeed indicator attached to that pitot tube would read zero. There is no particular reason for  Noonan's airspeed indicator to be plumbed into the pitot tube for the copilot's ASI, it could just as easily have been connected to Earhart's. if it was connected to the copilot's then Noonan's would read the same as the copilot's and Earhart could have noticed the discrepancy between the speed displayed on her ASI compared to that displayed on the copilot's ASI.

A general comment. Many on this forum attempt to do navigation computations to an impossibly high level of precision that was never achievable in flight, carrying out calculations to such a level accomplishes nothing. Just because your calculator has ten decimal places doesn't mean you should use all of them. Mr. van Asten was the poster child for this, calculating the time to fly from Lae to Howland to be exactly 18 hours, 50 minutes and 8 seconds! The same for Google Earth, just because it gives data to the 1/100th of a degree and to the 1/100th of a mile doesn't mean that those extra decimal places have any meaning in the real world. A hundredth of a nautical mile is only 60 feet, this level of precision only became available with GPS. A hundredth of a degree change in heading would result in being off course only four-tenths of a statute mile after flying the 2556 SM from Lae to Howland.

People also get hung up on the idea of staying exactly on the course line but in flying long distances over the ocean there is no reason to do this since there is only an extremely small penalty even for wandering far off course. For example, flying 2556 SM from Lae to Howland, if you wandered off course 100 SM at the midpoint of the flight it would add only 8 SM to the total route, only three minutes and twelve seconds to the flight. If you find yourself off course you don't make a large change in your heading to get back on the course line that you had drawn on your chart but change heading to head directly towards the destination, never regaining the course line until you arrive at the destination. You do it this way because that is the shortest distance from your off course position to the destination. Trying to regain the course line creates a dog leg, adding distance. For example, the mid-point of the Lae to Howland leg is 1278 SM from Howland. If at that point you discover that you are actually one hundred miles off course and you then make a sharp turn of ninety degrees to intercept the course line at the midpoint you would have to fly a total of 1378 SM to get to Howland, the 100 SM to get to the course line plus the remaining 1278 SM along the course line. Instead you adjust your heading to head directly to Howland from the off course fix and the distance you have to fly is only 1282 SM, 4 SM longer than if you had stayed on course and 96 SM shorter than regaining the course line.

Studying Noonann's chart work on the flight from Oakland to Hawaii shows that they did not try to stay on the course line. Noonan plotted six fixes on that flight, 0317 Z, 60 NM left of the great circle; 0446 Z, 60 NM left of the great circle; 0738 Z, 25 NM left of the great circle; 1007 Z, 65 NM right of the great circle; 1328 Z, 130 NM right of the great circle; and 1520 Z, 20 NM right of the great circle. They got off the pre-planned course line early and just made gradual changes in heading to keep the destination ahead of them and they never regained the pre-planned course line until they arrived in Hawaii.

Looking at Noonan's chart for the Natal to Dakar leg the 1341 Z running fix showed them to be 130 NM left of the pre-planned course line. They made no attempt to regain the course line but changed heading to intercept the course line and the coast of Africa south of Dakar, both at the same time. See discussion of the navigation on this flight here.

Another thing that people get hung up on is about the need to fly the great circle course instead of the rhumb line course. A rhumb line maintains the same true direction for the entire flight while to follow the great circle you must calculate and then make periodic changes in your heading. The great circle is shorter than the rhumb line so that is why people think you must follow the great circle. However this really only makes a difference at higher latitudes but makes virtually no difference when flying near the equator. The great circle distance between the exact coordinates used by Williams for this leg, 06° 47.000' south, 147° 00.000' east for Lae and 00° 49.000' north, 176° 43.000' west for Howland is 2556.1 SM and the rhumb line is 2556.2 SM, exactly one-tenth of a statute mile longer. I can see poor Mr. Williams computing each segment (14 in all) of the great circle between Lae and Howland by hand using logarithmic trig tables only to save 1/10th of a statute mile. Leaving Lae, the initial great circle course is 079.4° true and it changes in steps so that the GC course approaching Howland is 077.6° true. The rhumb line for the entire flight is 078.1° true, only 1.3° difference. And the two course lines lie close to one another, never more than 9 SM apart which is so close that Noonan would not have been able to tell the difference, he would not know if he was on the great circle course line or on the rhumb line course line. Here is a link to Mr. Williams chart. and his data form is attached.

The reason that I specified those coordinates so exactly was so that I could compute the distances to the nearest one-tenth of a statute mile. Williams and all flight navigators would only use coordinates to the nearest one minute of latitude and longitude, one nautical mile of precision. When the input data is only accurate to one nautical mile it is improper to calculate a distance to a greater precision than that of the original data but many people do this and it is not valid. Using the coordinates as Williams did, only good to one minute, would make the distance for the GC course 2556 SM and for the rhumb line also 2556 SM, there is no difference based on the level of precision of the data used by flight navigators.

So when you do your calculations give some thought as to what the numbers actually signify.

gl
« Last Edit: January 03, 2012, 01:51:45 AM by Gary LaPook »
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Erik

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Re: The flight plan, magnetic course, headwinds.
« Reply #47 on: January 02, 2012, 08:28:28 AM »


Take this scenario for example:
They are in flight, then lose celestial observations due to overcast.  No big deal.  They revert to dead reckoning using the magnetic compass and directional gyro.  The DG suffers a bit more than its usual gyroscopic pression (maybe from a vacum leak).  AE corrects for it, but turns the DG needle to one hash-mark (or two) shy of it's actual correct heading.  Now they are are off by 10 degrees and don't know it.  They fly this heading for an unknown period of time.  Not knowing how long they have been flying the wrong heading, they dont know how much to compenstate to get back on course.  Fred notices the discrepency.  They are now closer to their destination and decide not to make matters worse by trying to counter-correct the problem.  But, rather to fly a 'parallel' heading an intercept an offset LOP.  Problem now they dont know exactly how far off course they are when reaching the LOP.  To compound the problem, say for example, the magnetic compass wasn't swung correctly or a 'typo' was on the correction card.  Combine that with unknown wind conditions.  Now things are starting to add up in a more complex way - creating a compounding effect.  They hit the LOP with as good of timing they have but even it is off slightly by several seconds.  Unbeknownst to them, the strip chart has Howland charted erroneously 6 miles too far east. 

Things have gotten real ugly real quick!
Pilots are trained to check their DG about every 10 minutes so Earhart would have caught the errors you are concerned about after only a short period of time.  There were actually three compasses in the plane and Noonan had one of his own back in the nav station so his job was to check up on Earhart flying the correct heading that he had given her so another reason that any such error was promptly corrected. In addition to the standard "pilot's" compass mounted above the instrument panel, Earhart had a much more accurate and stable compass mounted on the floor in front of the co-pilot's seat, see attached photos. Mounted directly above this second, aperiodic compass, is the correction card to this compass. Aperiodic compasses were generally called "the navigator's compass" because they were mounted at the nav station of our bombers and transport planes during WW2. Noonan had one of these mounted on the floor under the chart table with a window in the chart table to allow him to see this compass. Aperiodic compasses must be read from above, not from the side as is done with the normal "pilot's" compass. Since each of them had one of these very accurate and stable compasses available it makes you scenario very unlikely. Noonan also had an altimeter, airspeed indicator and an outside air temperature gauge at his station so he could compute the true airspeed of the plane and didn't have to rely on Earhart passing this information back to him. This was a very well thought out navigation arrangement, it had worked for 3/4ths of the way around the world.

Regarding "precession" of the directional gyro, pilots are not taught all the details of what they see in the cockpit. There is "real precession" and "apparent precession" but pilots don't know this, only flight navigators are taught to deal with these distinctions. Real precession is cause by friction in the bearings of he gyroscope that causes the DG to change from if setting and this is all that pilots are taught. Real precession is normally very small (unless the DG has been damaged or the bearings are very worn.) What pilots are actually seeing is "apparent precession" which is caused by the rotation of the Earth on its axis. The Earth rotates 15.04° per hour (in inertial space) and even though the gyro is maintaining it's direction in space, since the earth is turning under it, the DG appears to precess in the opposite direction. A plane flying over the North Pole would see the DG precess at this rate of 15.04° per hour. However the rate of apparent precession varies with the sine of the latitude so pilots in the U.S. see their gyros precess about 10° per hour (the sine of 45° latitude is 0.7 times 15.04° per hour equals 10.5° per hour.) The reason I have gone through this exposition is because the sine of zero degrees is zero which multiplied by 15.04 equals zero thus making the apparent precession at the equator, latitude zero, also zero. Since almost all of the precession seen in the DG is actually apparent precession, Earhart's DG would not have precessed much, if at all, since she was flying along the equator.

The first three attached photos show Earhart's cockpit, the aperiodic compass and its correction card. The fourth photo is of an exemplar aperiodic compass, not Earhart's, which has finer graduations on the azimuth scale than Earhart's. We don't have a photo of Noonan's aperiodic compass but it may also have had the finer graduations.

gl

Quote
Pilots are trained to check their DG about every 10 minutes so Earhart would have caught the errors you are concerned about after only a short period of time.
We dont know for sure.  What if she forgot to check for 2-3 times in a row?  Or what if she had checked and made a simple interpretation mistake?  This is where experimenting with possible scenarios, helps us come up with ideas that generate other ideas to help solve this riddle.

Quote
There were actually three compasses in the plane and Noonan had one of his own back in the nav station so his job was to check up on Earhart flying the correct heading that he had given her so another reason that any such error was promptly corrected.
I didn't realilze that - thanks for the info.  That would have meant three different correction cards too?  Hmm... Do we know any more about Noonan's compass?  I dont remember seeing referenced in the diagrams, but would like to learn more about it.  Of course he didn't have a DG back there - just a magnetic compass - correct?

Quote
Real precession is normally very small (unless the DG has been damaged or the bearings are very worn.) 
This is exactly what I was suggesting.  I wasn't very clear in my original post, but I meant that the 'real' precession was being affected by this phenomenon of mechanical failure.  What if the DG was experiencing a slight wear, or if a vacum leak was gradually getting worse?  Imagine they didn't catch this fact for 30-45min, and found themeselves gradually flying 5-10 degrees off course.  When they caught the error (assuming no celestial observations), how would they have been able to get back on the original course line?
Quote
Earhart's DG would not have precessed much, if at all, since she was flying along the equator.
Under normal circumstances, barring mechanical problems.

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Erik

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Re: The flight plan, magnetic course, headwinds.
« Reply #48 on: January 02, 2012, 08:44:20 AM »

So the basic theory is that a speed discrepancy was discovered when the ship was spotted and the data seems to suggest that this could indeed be the case. How the ground speed achieved could have been mis-read or calculated, I have no idea. A damaged pitot tube seems to be a good culprit. Noonan might have ran some calculations, found a huge error and asked Amelia "Hey, what is your indicated air speed?".

Heath, I think you are onto something here.

I like the way you are tying this into the Ontario's position.  If we can establish the ship's position with better accuracy, we can start to correleate other events to each other.  Including airspeed and other factors.  If ground speed airspeed turns out to be in error, then wouldn't that have caused Noonan to possibly calclate the wrong wind corrections too?  Causing a cascading effect of errors and possibly even leading to them to dial in the wrong heading as a result of these incorrect readings.

Dont forget a 'clogged' pitot tube either.  Or even a 'clogged' static port.  There was a DC-4 crash on the east coast in the late 30's 40's where the plane's altimeter had suffered moisture water in the static system.  It wasn't clogged per se, but nonetheless, the plane hit terrain about 1600 feet - just 50 feet or so shy of missing the mountain ridge.  Another example of how something so simple (without complexities) can cause such catastrophic results.

« Last Edit: January 02, 2012, 09:29:18 AM by Erik »
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Erik

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Re: The flight plan, magnetic course, headwinds.
« Reply #49 on: January 02, 2012, 08:57:12 AM »

I don't know if there were two separate static ports for the two altimeters, the copilot had one too, they could have been using just one static port and Noonan's would have used the static pressure line for his altimeter.

Gary, do we know anything about the plane's static system?  Where the port(s) were located, etc?
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JNev

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Re: The flight plan, magnetic course, headwinds.
« Reply #50 on: January 02, 2012, 09:36:58 AM »

Very interesting discussion of some of the many variables that can figure into getting lost over the ocean - or finding one's way.

One thing that may help keep things clear is the independence of many airborne indication systems from mother earth and the universe itself: with the exception of magnetic compasses and RDF equipment (and today's GPS, etc.) other indications are based on what the airplane can sense from its environment.  An airplane is not a car on a pavement - without outside observations of earth, stars, etc. airspeed and headings provide for no more than dead reckoning.  Dead reckoning is subject to drift, headwinds and tailwinds, etc.

Gary's done a great job of describing how both the airborne sensing and external observation elements fit, IMHO, and as a flight instructor he knows them quite well.  He's also done a great job of giving clarity to great circle and how its application varies with the latitudes - and why it was negligible in the Lae - Howland case.

He has also ably demonstrated why being off-course mid-route is not such a danger or penalizing thing:

GL -
"For example, flying 2556 SM from Lae to Howland, if you wandered off course 100 SM at the midpoint of the flight it would add only 8 SM to the total route, only three minutes and twelve seconds to the flight. If you find yourself off course you don't make a large change in your heading to get back on the course line that you had drawn on your chart but change heading to head directly towards the destination..."

What needs to be considered also is awareness of that error at an early enough time to correct for it - Gary's statement "...If you find yourself off course you don't make a large change in your heading to get back on the course line..." is a reminder that timely awareness of the error is crucial if one would avoid the need of major correction at the end of the course line.  "IF" becomes a large word.

Any number of things can lead to such a large mid-course error - and any number of things can prevent its detection.  Most simply perhaps is finding one's self unable to get reliable information from outside the airplane - fixed points on mother earth or in the heavens, for example.  Then one is reliant on the airborne sensing as mentioned - proceeding by mag heading and nothing but airspeed and assumptions from forecasts as to winds, and therefore assumptions about speed over the ground.  The later that detection is made, the greater the penalty that must be overcome; if not detected with certainty by the end of the course line, one is "lost".

All very interesting.  There are so many variables that could have played into AE's and FN's predicament - including the possiblity of unrealized error mid-course and finding themselve with a fairly large penalty - perhaps even of unknown direction - at the end of the course line. 

Like most accidents, some combination of things likely conspired to deliver the pair into a loss situation at the end of that line - it could have been instrument error, it could have been a lack of sufficient readings from outside fixed objects for any number of reasons, or a combination of such things.

LTM -
- Jeff Neville

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« Last Edit: January 02, 2012, 09:41:27 AM by Jeff Neville »
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Gary LaPook

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Re: The flight plan, magnetic course, headwinds.
« Reply #51 on: January 02, 2012, 11:47:19 AM »


Pilots are trained to check their DG about every 10 minutes so Earhart would have caught the errors you are concerned about after only a short period of time.
We dont know for sure.  What if she forgot to check for 2-3 times in a row?  Or what if she had checked and made a simple interpretation mistake?  This is where experimenting with possible scenarios, helps us come up with ideas that generate other ideas to help solve this riddle.
First off, it's hard to misinterpret. Secondly, a precessing DG doesn't affect Noonan's compass. (They did find a note floating on the sea not far from Howland (the Coast Guard covered this up) that said "Amela, get back on course, my compass shows you way off!" ;)


Quote
Real precession is normally very small (unless the DG has been damaged or the bearings are very worn.) 
This is exactly what I was suggesting.  I wasn't very clear in my original post, but I meant that the 'real' precession was being affected by this phenomenon of mechanical failure.  What if the DG was experiencing a slight wear, or if a vacum leak was gradually getting worse?  Imagine they didn't catch this fact for 30-45min, and found themeselves gradually flying 5-10 degrees off course.  When they caught the error (assuming no celestial observations), how would they have been able to get back on the original course line?

The DG was a new instrument that had very few hours on it so the bearings should not have been worn. Also, the autopilot had it's own gyro that was independent of the pilot's DG so it is unlikely that they would both precess exactly the same amount, any discrepancy between the two would have been quickly noticed by Earhart.

gl
« Last Edit: January 03, 2012, 01:22:14 AM by Gary LaPook »
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Irvine John Donald

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Re: The flight plan, magnetic course, headwinds.
« Reply #52 on: January 02, 2012, 01:54:22 PM »

in looking at the recent posts in this thread one thing leaps to the forefront.  There "was" an error.  When was the "error" detected?  When the error was detected would dictate your corrective action, would it not?  A gradual return to course if discovered early on, or a dramatic change in course if discovered later on.  There were no indications from radio signals of "any" navigation issues being detected.  In fact the radio message"We must be on you..." suggests that at least AE thought she knew where she was.  Other radio messages give positions like "200 miles out".  A sign that they know where they are. 

What evidence do we have that AE and FN knew there was an error?  None that I know of.  I think the key is what is said in the radio messages.  No one who heard the radio messages reported that they thought they were off course or had made a change from the original flight plan.  No one in their official reports to their superiors reports possible course corrections reported or errors. 

This is the core of the "How did they miss Howland?" mystery.  If FN was following his carefully laid out navigation plan and used all his experience to get from Lae to Howland then how did they miss Howland?  I don't believe they thought they were off course but the numbers FN would get from his sightings would have said otherwise.  One of two scenarios come to light for me.  First is that they knew where they were at all times and they were on course for Howland as planned.  For some reason FN got them to within a few miles of Howland but they did not visually pick it up.  Absence of sound of the aircraft over Howland is NOT evidence that they weren't close.  The second scenario is that FN wasn't getting any info to show they were off course.  Overcast the whole way, FN was incapacitated, AE was in a mood and wouldn't listen to him, I don't know. but its almost as though he wasn't in the plane with her and she DR'd all the way.   Controversial ideas?  Sure but food for thought. 
Respectfully Submitted;

Irv
 
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richie conroy

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Re: The flight plan, magnetic course, headwinds.
« Reply #53 on: January 02, 2012, 01:59:43 PM »

the thing is tho if the navigators door at back of plane was closed an the pilot hatch was closed an the surf lifted the electra off the reef what are the chance's ov the current carrying it round past the ship wreck an out into ocean ?
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richie conroy

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Re: The flight plan, magnetic course, headwinds.
« Reply #54 on: January 02, 2012, 02:20:54 PM »

right need sum help about earharts electra, the roof hatch above cockpit was that universal opening ?
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Heath Smith

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Re: The flight plan, magnetic course, headwinds.
« Reply #55 on: January 02, 2012, 02:53:35 PM »

Quote
If ground speed airspeed turns out to be in error, then wouldn't that have caused Noonan to possibly calclate the wrong wind corrections too?

Erik, at this point I think it is difficult to know for sure whether or not achieving the 124.5 mph ground speed was intentional or not. As they made their way around the storms East of Lae, it probably did not matter what ground speed was achieved during the diversion. They flew far enough South and high enough (10,000ft) to make sure they avoided the storms. We know that two legs of this journey was 909 miles and the ground speed was 124.5 mph. I recall reading that Fred had estimate the head winds at 23 knots before he left Lae and this did not change after they had a visual on Nukumanu Island.

From my perspective, once they flew over Nukumanu Island and intercepted the flight path, approaching the end of a segment in the flight plan and they were right on the line, this was probably not by accident. I would have expected them to them resume their original flight plan that did include achieving a 150 mph ground speed going forward regardless of the 23 mph head wind. AE announced her altitude, and headwinds, so it is a bit of a mystery why they would continue at a reduced speed unless there was some other concern or perhaps an equipment malfunction that was undetected. I cannot believe he just poked through the Lockheed documents and thought that this 124.5 mph ground speed was an ideal speed. There was no time to re-compute the entire flight plan on a whim and I have not heard any evidence that he would make such an attempt.

Another factor that I have been thinking about is that once they departed Nukumanu Island, this was about 0718GMT and I do not believe the sun had set at that point in time. They proceeded 3.2 hours after leaving Nukumanu Island before spotting the Ontario, how much time did that provide for Noonan to perform his celestial navigation? That would be interesting to know.

What is interesting is that if we assume that reduced speed, the timing works out to have spotted the Ontario where she was drifting and not where she was supposed to be (she was 29 miles away from her commanded position). Again, this seems more than coincidence. If we determine the ground speed achieved, assuming they did see the Ontario at 10:30GMT, it is also coincidental that they achieved a ground speed of 150mph from that point all the way to 200 miles out (where they thought 200 miles out was). When you have several coincidences that happen to line up, perhaps there is a bit more to the story. Personally I believe they discovered something and were able to accurately overcome the problem. It could have been a mis-calculation, math conversion, or even a faulty instrument. It is quite possible that they real reason cannot be known.

I suppose it is possible, albeit a stretch that the could have assumed they were achieving 150 mph but were never did detect a problem and that would explain the timing of the radio transmissions. This would have landed them 183 miles short of the "200 miles out" in reality. When they declared that they should be at Howland at 19:12GMT, they would have been 194 miles out. I did not triple check these numbers but I believe they would be correct.

Now why the navigation itself might have failed, that is a different story. I am inclined to believe that they were entering cloudy conditions after spotting the Ontario that worsened as time went on. If we assume that to be true, they might have used DR all the remainder of the trip (1277 miles). As daybreak came, even if the conditions improved from overcast, the stars might have been impossible to spot. So I think it is quite possible that they did not find another reference after spotting the Ontario. What is the magic number again? 10% of 1277 miles? Does this suggest that they were off by a maximum of 127 miles? That is quite a large hole if you ask me. Forced to guess, I would say they were at a minimum of 40 miles off target since they did not spot the Itasca mast or the smoke she was laying out for them that stretch out 10 miles (although I would still like to hear an estimate of how high that smoke rose in the 8mph cross wind).

I do think that make a better guess as to the actual speeds they were flying along the route. I think that we can guess that they were at an 8,000 foot altitude as was the recommendation, so the fuel consumption up to the point that they thought they were at Howland should be fairly accurate. I started such a project in Excel but ran in to limitations with the accuracy of the gross weight of the Electra over large periods of time (1 hour). I will need to write an application to have much better granularity so far as the fuel consumption is concerned.
« Last Edit: January 02, 2012, 02:57:15 PM by Heath Smith »
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Richard C Cooke

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Re: The flight plan, magnetic course, headwinds.
« Reply #56 on: January 02, 2012, 03:02:03 PM »

in looking at the recent posts in this thread one thing leaps to the forefront.  There "was" an error.  When was the "error" detected?  When the error was detected would dictate your corrective action, would it not?  A gradual return to course if discovered early on, or a dramatic change in course if discovered later on.  There were no indications from radio signals of "any" navigation issues being detected.  In fact the radio message"We must be on you..." suggests that at least AE thought she knew where she was.  Other radio messages give positions like "200 miles out".  A sign that they know where they are. 
That throughout the flight AE was making radio calls reporting "everything is OK" indicates that they thought they knew where they were.  Its also my main objection to the Long theory that they opened up the throttles and arrived at Howland with minimal reserves of fuel.  Planing a flight with a 35% fuel reserve and then changing it en route to arrive with minimal fuel to spare would have me worried and I definitely would not be reporting "everything is OK".

rc
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richie conroy

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Re: The flight plan, magnetic course, headwinds.
« Reply #57 on: January 02, 2012, 07:06:42 PM »

We are an echo of the past


Member# 416
 
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Irvine John Donald

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Re: The flight plan, magnetic course, headwinds.
« Reply #58 on: January 02, 2012, 07:08:35 PM »

So Richard, if they thought they knew where they were then what happened???  Was FN working with AE?  Did they just miss Howland?
Respectfully Submitted;

Irv
 
« Last Edit: January 02, 2012, 07:40:30 PM by Irvine John Donald »
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Erik

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Re: The flight plan, magnetic course, headwinds.
« Reply #59 on: January 02, 2012, 07:19:35 PM »

Another factor that I have been thinking about is that once they departed Nukumanu Island, this was about 0718GMT and I do not believe the sun had set at that point in time. They proceeded 3.2 hours after leaving Nukumanu Island before spotting the Ontario, how much time did that provide for Noonan to perform his celestial navigation? That would be interesting to know.
Good point.  Couldn't agree more!  Curious too.  BTW (bit straying from topic),  I thought read somewhere that Noonan was doubtful about calibrating his chronometers at Lae because they didn't have a connection to the National Bureau of Standard's timing-signals.  Any truth to this does anyone know?

Now why the navigation itself might have failed, that is a different story. I am inclined to believe that they were entering cloudy conditions after spotting the Ontario that worsened as time went on. If we assume that to be true, they might have used DR all the remainder of the trip (1277 miles). As daybreak came, even if the conditions improved from overcast, the stars might have been impossible to spot. So I think it is quite possible that they did not find another reference after spotting the Ontario. What is the magic number again? 10% of 1277 miles? Does this suggest that they were off by a maximum of 127 miles? That is quite a large hole if you ask me. Forced to guess, I would say they were at a minimum of 40 miles off target since they did not spot the Itasca mast or the smoke she was laying out for them that stretch out 10 miles (although I would still like to hear an estimate of how high that smoke rose in the 8mph cross wind).

Yep.  That's the ticket if you ask me.  My gut tells me this is where things started to go south (no pun intended)!  Minimum 40 miles is reasonable.  Now consider complicating the heading induced errors with timing induced errors, mis-calculated wind correction, charted postion inaccuracies, etc.  Things get real messy real quick.  Confusion would be sure to set in.
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