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Author Topic: The flight plan, magnetic course, headwinds.  (Read 439585 times)

Harry Howe, Jr.

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Re: The flight plan, magnetic course, headwinds.
« Reply #465 on: March 15, 2012, 10:07:13 PM »


John
There is a 50/50 chance, or maybe better, that FN's chart on which he drew his rhumb line course from Lae to Howland had the Island mis-located by 5 nm to the west of its true position.  Add that to the 10 nm uncertainty in the "fix", the 14nm band width, and the 40 nm DR potential error and I'm not surprised that they missed Howland.  Emphasizes again how critical their RDF was and the trailing wire antenna which, as far as I understand its frequency capabilities is concerned, would have enabled them to send a signal that the Itasca RDF could get a bearing on.

It's always said in these type cases that "they" took a "Calculated" risk.  Except  that the risk is never calculated and the potential unanticipated consequences are never analyzed.
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Gary LaPook

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Re: The flight plan, magnetic course, headwinds.
« Reply #466 on: March 16, 2012, 02:01:34 AM »

Quote from: Gary LaPook
The only way that they could identify being on the 157/337 line is that they got at least one, and probably several, observations of the sun in the vicinity of Howland.

If that were true, given the error of 14NM, Howland would have been impossible to miss. Are you suggesting that passed within 14NM and failed to see Howland?
The band of uncertainty is 14 NM thick centered on the LOP so the maximum error should not exceed 7 NM and should be less most of the time. If they had the correct coordinates for Howland then they should have passed within 7 NM of the island. If they were aiming for the Williams coordinates, about 5 NM west of Howland, then they should have passed within 7 NM of that point meaning that it was limited to 12 NM west of Howland to 2 NM east of Howland. I am suggesting that something went wrong possibly a malfunction of the octant.
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I would suggest that they were simply following a magnetic heading.

The 157° - 337° was a true course not a magnetic heading.
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The line was pre-plotted and was good as another other heading to search along.
Why did they choose such an odd number to pre-plot for the approach to the island, in your theory? The LOP defined by the sunline running 157° - 337° true is better than any other course line since he could take additional observations to ensure staying on this line.
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The way the established the line was to fly straight in at Howland. When they did not find it,

How would they know that they had reached the location of Howland and so  know that it was time to start searching?
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they circled then followed the 157/337 line North and South. I would suggest that they then performed a creeping line search where the 157/337 lines comprised the long parallel lines in the search.

As I stated before, I do not believe they were any where near the 157/337 line (North or South of Howland) at the moment of sunrise at Howland.


Of course not! Sunrise at Howland was at 1745 Z which is the same time that Earhart radioed "200 miles out."

gl
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Heath Smith

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Re: The flight plan, magnetic course, headwinds.
« Reply #467 on: March 16, 2012, 03:58:01 AM »

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The 157° - 337° was a true course not a magnetic heading.

I meant to say, they were not on the actual 157/337 sun line that passed through Howland, they were just flying the heading 157/337 back and forth. Without some reference it was just a heading.

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Why did they choose such an odd number to pre-plot for the approach to the island, in your theory? The LOP defined by the sunline running 157° - 337° true is better than any other course line since he could take additional observations to ensure staying on this line.

My opinion is that the intent was to arrive in the area earlier than they had, possibly with a Northern intercept as was suggested however that appears not to have happened. As you have pointed out on your page, the 157/337 line is only perpendicular to the Sun's azimuth at sunrise. FN had probably pre-established this line of position on his map and that was the intent but it did not work out that way probably due to the delay of bypassing the storm outside of Lae that cost them over an hour of time.

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How would they know that they had reached the location of Howland and so  know that it was time to start searching?

They tracked their speed since the last known fix and when the ETA was zero that is when they were on the mic stating "we must be on you". I believe the intent was to fly straight in and use the DF to guide them in. When they realized that was not going to happen they circled until they came up with the search strategy.

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Of course not! Sunrise at Howland was at 1745 Z which is the same time that Earhart radioed "200 miles out."

Precisely why I believe it was a pre-planned line of position and nothing more. Why travel that line to take further observations? It would depend on the time that you arrived if you wanted to be perpendicular to the solar azimuth at the time of your new fix and that is not what they did. Again, I think it is evident that they never established a new fix while in the vicinity of Howland. The only thing that the sunrise could tell them was that they were on track longitudinally when they were 200NM out at 10,000ft at 17:47GMT.

If they ended up North of Howland, it was cloudy there. They were probably at 1,000ft and would not be above the cloud layer to take further observations. If the sun were obscured by clouds or a higher cloud layer toward the East there may have been no opportunity to shoot the sun or anything else.

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Dan Swift

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Re: The flight plan, magnetic course, headwinds.
« Reply #468 on: March 21, 2012, 08:55:50 PM »

This may not be the thread to pose this question....if not...my apologies.  AND if this has been discussed.....my apologies again.  Every flight has an alternate destination.  Should be no exceptions to that basic rule.  "If we can't find Howland...or weather doesn't permit approach....what is our alternate?"  Not too many choices in that area to say the least, but given a few hours extra fuel on board, wouldn't it be south toward islands where you could land?  Maybe even with a landing strip or an airport.  I am sure this was dealt on with years ago on this forum, but why would your alternate be north...toward open water?   That is where they first searched?????
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Heath Smith

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Re: The flight plan, magnetic course, headwinds.
« Reply #469 on: March 22, 2012, 04:15:46 AM »


Because they might have initially searched to the North, that does not imply that they were expecting to find a destination other than Howland. When they arrived where they thought Howland  was there was nothing is sight. The winds were out of the ENE so there is a good chance that upon their last celestial fix, maybe at 16:23GMT they discovered that they were South of their intended flight path. When they arrived they might have considered that they had drifted South again so initially searching to the North would make some sense.

As far as an intention of reaching a secondary target goes, I do not believe there was any such intention. If there was such an intention it would be reasonable to assume that they would have mentioned such a plan to someone on the ground before they departed Lae. They had a high confidence in FN's ability as well as the direction finding equipment on board. The also assumed that they would have radio contact with the Itasca and it appears that she never confirmed that the radio was functioning after departing Lae. It would appear that the belly antenna was ripped off during take-off from Lae.
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Gary LaPook

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Re: The flight plan, magnetic course, headwinds.
« Reply #470 on: March 22, 2012, 04:38:35 AM »


My opinion is that the intent was to arrive in the area earlier than they had, possibly with a Northern intercept as was suggested however that appears not to have happened. As you have pointed out on your page, the 157/337 line is only perpendicular to the Sun's azimuth at sunrise. FN had probably pre-established this line of position on his map and that was the intent but it did not work out that way probably due to the delay of bypassing the storm outside of Lae that cost them over an hour of time.

What I actually said is the exact opposite,

"The myth of the "sunrise observation" was created by people who know "a little bit" about celestial navigation. The 157°-337° sunline line of position (LOP) was derived by an observation of the sun when the sun's azimuth was 67° true since the LOP is at right angles to the azimuth to the celestial body. When the sun rose in the vicinity of Howland on July 2, 1937 its azimuth was 67° true. Those with "a little bit" of knowledge fastened on this fact to claim that Noonan took a sunrise observation and used only it in planning the approach to Howland. (They apparently believe that Noonan then opened the door and dropped his sextant into the sea.) But what these people didn't understand is that the sun's azimuth stayed at 67° until 1847 Z, an hour after sunrise at Howland! This means that Noonan would have computed the same 157°-337° LOP from any sight taken during this one hour period. He would have taken several additional sights as he approached the LOP then more after the interception to ensure staying on it...

As the day goes on and the azimuth of the sun changes the LOP plotted through the destination will rotate as though on a pivot stuck on the destination. So a one degree change in the azimuth of the sun to 066°  at 1847 Z (which lasted until 1923 Z including the time of the "must be on you" message) results in a 156°-336° LOP and would result in only a one nautical mile (NM) error in you position only if you were at least 60 NM out from the destination on the LOP. ( The sine of one degree is approximately 1/60th. so a one degree change results in a one mile change for each 60 miles flown. It is actually one part in 57.3 but navigators use the approximation of one part in 60.) A one mile error falls well within the margin of error of the sextant shot.

The azimuth of the sun stays at 066° until 1923 Z; 065° until 1945 Z; 064° until 2003 Z and was 063°at 2012 Z when they reported being on the LOP. So even at 2012 Z it would only produce a 4 NM error at 60 NM from Howland on the LOP and only 2 NM if 30 NM from the island. You would expect that this period would have allowed enough time for them to find Howland."

The few degrees of change in the azimuth results in such a small movement of the LOP that these changes can be ignored in practical navigation.

Quote from: Gary LaPook
How would they know that they had reached the location of Howland and so  know that it was time to start searching?
Quote from: Heath Smith

They tracked their speed since the last known fix and when the ETA was zero that is when they were on the mic stating "we must be on you". I believe the intent was to fly straight in and use the DF to guide them in. When they realized that was not going to happen they circled until they came up with the search strategy.
So they determined when they should be at Howland solely by dead reckoning. The problem with this is the uncertainty in the DR position after flying the leg since the last fix. We have been using as an example that they had a fix at 1623 Z and flew about 400 miles after that so the DR uncertainty, including the 10 NM uncertainty in the original fix, is 50 miles, not nearly accurate enough to find the island which is why getting a sun observation was so critical.

Quote from: Gary LaPook
Of course not! Sunrise at Howland was at 1745 Z which is the same time that Earhart radioed "200 miles out."
Quote from: Heath Smith

Precisely why I believe it was a pre-planned line of position and nothing more. Why travel that line to take further observations? It would depend on the time that you arrived if you wanted to be perpendicular to the solar azimuth at the time of your new fix and that is not what they did. Again, I think it is evident that they never established a new fix while in the vicinity of Howland. The only thing that the sunrise could tell them was that they were on track longitudinally when they were 200NM out at 10,000ft at 17:47GMT.

You take additional sights of the sun to ensure staying on the LOP that should pass within 7 NM of the destination. This would require flying a course of 157 or 337 true to stay on the LOP that they were depending upon to take them to Howland. And no, they could not take a sight at 1747 Z, 200 miles west of Howland because the sun had not yet risen there, it had just risen at Howland, and they would also have to wait approximately a half hour after they saw the sun for it to be high enough to take a measurement, see https://sites.google.com/site/fredienoonan/discussions/the-myth-of-the-sunrise-lop
Quote from: Heath Smith


If they ended up North of Howland, it was cloudy there. They were probably at 1,000ft and would not be above the cloud layer to take further observations. If the sun were obscured by clouds or a higher cloud layer toward the East there may have been no opportunity to shoot the sun or anything else.
That is possible that they ended up north of Howland but I they were flying south east towards Gardner then they would have flown into the clear area around and south of Howland which would have allowd them the opportunity to shoot the sun and to shoot the moon, establish a fix, and go back to look for Howland, their planned destination where there was  runway to land on.

gl
« Last Edit: March 22, 2012, 06:42:59 PM by Gary LaPook »
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Heath Smith

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Re: The flight plan, magnetic course, headwinds.
« Reply #471 on: March 22, 2012, 06:17:12 AM »

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That is possible that they ended up north of Howland but I they were flying south east towards Gardner then they would have flown into the clear area around and south of Howland...

That is assuming that they could see that it was clear to the South. Had they gone North and found themselves in cloudy conditions they might not have known it was clear as the Itasca had observed. Exactly how far North they could have been, well, as you pointed out before, that could have been up to 55NM where the estimate was that the visibility was no more than 20NM North of Howland.
« Last Edit: March 22, 2012, 02:18:14 PM by Heath Smith »
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Gary LaPook

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Re: The flight plan, magnetic course, headwinds.
« Reply #472 on: March 22, 2012, 11:38:59 AM »

Quote from: Gary LaPook
That is possible that they ended up north of Howland but I they were flying south east towards Gardner then they would have flown into the clear area around and south of Howland...

That is assuming that they could see that it was clear to the South. Had they gone North and found themselves in cloudy conditions they might not have known it was clear as the Itasca had observed. Exactly how far North they could have been, well, as you pointed out before, that could have been up to 55NM where the estimate was that the visibility was no more than 20NM North of Howland.
It doesn't matter if they knew or didn't know that it was clear around Howland because they can't get to Gardner without passing through this clear area where they would be able to take sights and find Howland. According to Itasca it was clear for a considerable distance to the north so sights were available even to the north of Howland. As to the cloudy area to the north, clouds that appear quite solid from the side and from a distance may be well spread out and allowing celestial observations even in the cloudy area seen by Itasca.

gl
« Last Edit: March 22, 2012, 06:41:47 PM by Gary LaPook »
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Heath Smith

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Re: The flight plan, magnetic course, headwinds.
« Reply #473 on: March 22, 2012, 02:37:19 PM »

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But they can't get to Gardner without passing through the clear area where they would be able to take sights and find Howland. According to Itasca it was clear for a considerable distance to the north so sights were available even to the north of Howland. As to the cloudy area to the north, clouds that appear quite solid from the side and from a distance may be well spread out and allowing celestial observations even in the cloudy area seen by Itasca.

Considerable distance sounds rather subjective, I will need to re-read the reports of the clouds that day. I do recall that to the North-West and to the North it was cloudy. I would also assume to the North-East it was cloudy as well since the winds were out of the East. They reported partly cloudy at 16:23GMT at about 400NM out. It is quite possible they flew in to denser clouds as they approach from the North and we never able to obtain a new fix nor able to see a clearing to the South.

If they did obtain the fix, creating a how could they have missed Howland, again? Given your earlier estimations the area of uncertainty would have to be tiny and impossible to miss. Are you suggesting that they ran out of gas as they approached this tiny area of uncertainty?

If the octant was that far out of whack, how did they make it so close to Howland in the first place?
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Gary LaPook

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Re: The flight plan, magnetic course, headwinds.
« Reply #474 on: March 22, 2012, 03:48:42 PM »

Quote from: Gary LaPook
But they can't get to Gardner without passing through the clear area where they would be able to take sights and find Howland. According to Itasca it was clear for a considerable distance to the north so sights were available even to the north of Howland. As to the cloudy area to the north, clouds that appear quite solid from the side and from a distance may be well spread out and allowing celestial observations even in the cloudy area seen by Itasca.

Considerable distance sounds rather subjective, I will need to re-read the reports of the clouds that day. I do recall that to the North-West and to the North it was cloudy.

Itasca reported clear until the clouds 40 miles to the north and northwest.
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I would also assume to the North-East it was cloudy as well since the winds were out of the East.

You can assume anything you want to assume but the fact is that Itasca did not report clouds in that direction.
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They reported partly cloudy at 16:23GMT at about 400NM out. It is quite possible they flew in to denser clouds as they approach from the North and we never able to obtain a new fix nor able to see a clearing to the South.

It is just as likely that they flew into clear areas after the 1623 Z report and stayed in the clear until possibly encountering some cloudiness about 40 NM northwest of Itasca. And even there, it is also likely that observations could still be taken as the clouds usually look more dense as seen from the side and from a distance and planes fly, usually above the clouds, so the view is different from the plane than from the ship.
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If they did obtain the fix, creating a how could they have missed Howland, again? Given your earlier estimations the area of uncertainty would have to be tiny and impossible to miss. Are you suggesting that they ran out of gas as they approached this tiny area of uncertainty?

If the octant was that far out of whack, how did they make it so close to Howland in the first place?
How far out of whack would the octant have to be for them to miss Howland, only about one-quarter of a degree which would make all the observations produce LOPs that are in error by 15 NM. Add the 7 NM uncertainty in normal observation and the plane could pass 22 NM by Howland and not be close enough to see the island. If the octant had a real big error then Noonan should have discovered it because his prior fixes would have been well away from the DR position, significantly more than the expected 10% difference. Flying a standard search pattern would have solved this problem. Remember, Dolittle's plane was lost due to a dropped octant which, on examination by the navigator prior to takeoff, didn't show any apparent damage. It's too bad Noonan didn't take my advice and fly over Nauru to confirm the accuracy of his octant on the way to Howland.

gl
« Last Edit: March 22, 2012, 06:38:21 PM by Gary LaPook »
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Heath Smith

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Re: The flight plan, magnetic course, headwinds.
« Reply #475 on: March 22, 2012, 05:33:14 PM »

The 1937 Search The Lexington Search

The Itasca responded that the most probable area was between 2°N 179.3°E to 5oN, 178.15°E to 5°N, 175.45°E and 2°N, 177.5°E,54 all well to the north and now far to the west of Howland. These estimates were based upon the heavy cloud bank 50 miles visible north and west of Howland and a drift rate of 1 knot due west. This is the first time that Thompson reveals why he thought Earhart went down northwest of Howland (i.e. the cloud bank there), and why he searched that quadrant first.

USCG Itasca History:

The flying conditions within a radius of 40 miles of Howland Island were excellent with an east wind of 8 to 13 miles per hour, the sea smooth and ceiling unlimited as far as could be observed.  The sun was rising clear and bright, with the island, the ship and the smoke screen in its glare.  Visibility to the north and west was excellent to the horizon, but beyond that continuous banks of heavy cumulus clouds were visible.  The plane's transmissions had indicated a flight through cloudy and overcast skies throughout the night and morning, and that dead reckoning distance had been accomplished.  The plane's signal strength had been high and unchanged during the last hour of transmission, and its line of position had indicated that the dead reckoning had run correct.  Throughout the proceeding night stellar navigating possibilities south and east of Howland and close to Howland had been excellent

Due to the conditions which existed north and west of Howland and due to the fact that the plane obtained no fix during the latter part of its flight due to cloudy weather, it was assumed that the plane may have missed the smoke screen, ship or island visually due to their lying in the glare of the rising sun, and passed north of Howland some two hundred miles.  It was further assumed that the line of position obtained was a sun" line, obtained when the plane emerged from the cloudy area north and west of Howland, and that it may have carried the line of position found along its line of flight for the  period necessary for the navigator to work and plot his line of position not in excess of one hundred miles.  From these assumptions it was deduced that the plane did not come down within a radius of forty miles of Howland Island.  The most logical area of search, therefore, lay in a sector of a circle between forty and two hundred miles off the island and between bearings 337° and 45° true from it. Five of the personnel and a radio operator were left on the island in charge of high frequency radio  direction apparatus to obtain bearings, if possible, on the plane.  Itasca searched throughout the day to the northward of Howland Island and during the night of 2-3 July with searchlights, extra lookouts posted and all hands on the alert. Information received from San Francisco indicated that there was a possibility that the plane might use radio while on the water. It might also keep afloat a considerable time. It had an emergency rubber boat and plenty of emergency rations. Itasca had suggested to the Commander of the Hawaiian Section the desirability of a Navy seaplane assisting in the search from Pearl Harbor.

---

Since the Itasca suggested that the most likely location was 337 to 45 true out to 230NM, this would suggest that is where the cloud bank was located. This would be a line to the North-West and the North-East, so it was likely that it was cloudy to the North-East although this was not mentioned specifically.
« Last Edit: March 22, 2012, 05:39:07 PM by Heath Smith »
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Gary LaPook

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Re: The flight plan, magnetic course, headwinds.
« Reply #476 on: March 22, 2012, 06:28:32 PM »

The 1937 Search The Lexington Search


Since the Itasca suggested that the most likely location was 337 to 45 true out to 230NM, this would suggest that is where the cloud bank was located. This would be a line to the North-West and the North-East, so it was likely that it was cloudy to the North-East although this was not mentioned specifically.
And by the same logic, you must also be claiming that the Itasca had some way to determine that the clouds extended all the way out to 230 NM from the Itasca. How do you think they determined that?

But back to the point that I was making, Noonan had clear enough skies to take observations of the sun and moon from at least 40 NM north of Itasca continuing well south of Itasca so would have been able to obtain such sights if they were preceding in the direction of Gardner. These observations, would have shown them that they were closer to Howland than to any other island so that the logical thing for them to do was to fly a search pattern to locate Howland.

gl
« Last Edit: March 22, 2012, 06:40:01 PM by Gary LaPook »
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Gary LaPook

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Re: The flight plan, magnetic course, headwinds.
« Reply #477 on: March 22, 2012, 06:57:27 PM »

This may not be the thread to pose this question....if not...my apologies.  AND if this has been discussed.....my apologies again.  Every flight has an alternate destination.
Not every flight has an alternate. Even in airline flying, the most conservative type of flying, you can make a flight to an island destination that does not have a geographically available alternate as long as you have a three hour reserve of fuel if the plane has propellers and only a two hour reserve if it is a jet.

§ 121.621   Alternate airport for destination: Flag operations.

(a) No person may dispatch an airplane under IFR or over-the-top unless he lists at least one alternate airport for each destination airport in the dispatch release, unless—
...

(2) The flight is over a route approved without an available alternate airport for a particular destination airport and the airplane has enough fuel to meet the requirements of §121.641(b) or §121.645(c).

...
§ 121.641   Fuel supply: Nonturbine and turbo-propeller-powered airplanes: Flag operations.
...

(b) No person may dispatch a nonturbine or turbo-propeller-powered airplane to an airport for which an alternate is not specified under §121.621(a)(2), unless it has enough fuel, considering wind and forecast weather conditions, to fly to that airport and thereafter to fly for three hours at normal cruising fuel consumption.

§ 121.645   Fuel supply: Turbine-engine powered airplanes, other than turbo propeller: Flag and supplemental operations...
(c) No person may release a turbine-engine powered airplane (other than a turbo-propeller airplane) to an airport for which an alternate is not specified under §121.621(a)(2) or §121.623(b) unless it has enough fuel, considering wind and other weather conditions expected, to fly to that airport and thereafter to fly for at least two hours at normal cruising fuel consumption.
gl
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Gary LaPook

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Re: The flight plan, magnetic course, headwinds.
« Reply #478 on: March 23, 2012, 12:47:36 AM »

Timing audibility of a twin Beech - The B18 began its takeoff roll at a distance of a little more than 2 miles from where I was standing to the North of runway 22.  From first visible motion until I could no longer hear the engines at all was 2 minutes, 51 seconds.  At 120 mph, that's a distance travelled of only 5.7 miles, made even shorter by virtue of taking off somewhat towards me, then turning and departing the vicinity nearly straight away from my position.  My previous eyeball estimate method would have assumed it was about 10 miles away when I could no longer hear it or see it, but now I believe it was less than 5 miles.  It was very hard to make out against the scattered cloud layer with the naked eye.

Ambient noise level was relatively low at the time - no other traffic, very light wind, some light industrial noises in the distance.  Weather cold (below freezing), scattered clouds at a couple thousand feet AGL, early morning light (<0800).  Under the conditions I experienced this morning, a Lockheed Electra flying 5+ miles from my location at 1000 feet would have been impossible for me to spot by unaided eye, or hear be ear.
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
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Heath Smith

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Re: The flight plan, magnetic course, headwinds.
« Reply #479 on: March 23, 2012, 04:33:53 AM »

Quote
But back to the point that I was making, Noonan had clear enough skies to take observations of the sun and moon from at least 40 NM north of Itasca continuing well south of Itasca so would have been able to obtain such sights if they were preceding in the direction of Gardner. These observations, would have shown them that they were closer to Howland than to any other island so that the logical thing for them to do was to fly a search pattern to locate Howland.

Ok, lets run through a scenario. If they ended up North of Howland, say in the clouds just 60NM North of Howland at 19:28GMT ("We are circling"). Since they could not obtain a fix while circling they had to pick a direction to fly so that Fred could take a fix. Since as you say Fred knew that a degree change in the solar azimuth was insignificant, lets run with that idea. So for Fred to take a reading he would have wanted AE to fly the heading 157/337 so he could take an observation correct?

I believe your theory would require that they would have flown South in order to obtain a fix. I also believe that would require that they knew it was clear to the South. But for the sake of argument lets say that this was the case. Say they flew South at 130MPH, they would have been in clear skies in only 5 minutes. How long did you say it requires to take a fix? Lets say 3 readings at 5 minutes per? So say at 19:50GMT they had a fix.

By this time, the would have flown about 38NM to the South of where they started. Assuming that they were 60NM North originally, this would be roughly 22NM North of Howland. The would have perhaps made a longitudinal adjustment, and would have been on the line by 20:13GMT.  In any case, they should have flown within a very close distance to Howland, well within the visual range as they continued South.

So why did this scenario not pan out?
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