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Author Topic: The flight plan, magnetic course, headwinds.  (Read 528092 times)

Harry Howe, Jr.

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Re: The flight plan, magnetic course, headwinds.
« Reply #390 on: February 22, 2012, 11:00:42 AM »


Heath
Two things
1.  I learned in grade school that the answer cannot be more precise than the number of decimal places in the least known of the numbers being used.  For example, to use PI to 11 decimal places in calculating a circumference when the diameter is only known to 1 decimal place is nonsense and a waste of time (no matter whether you are using a slide rule, a calculator, or a Cray supercomputer).  Use 22/7 ths and you'll be close enough.

2. The point in discussing the rhumb Line versus the Great Circle isn't the ease of navigation on paper, it is the ease of flying a constant heading versus flying a route of 16 segments and changing headings for each one.  Either one will get you there in aout the same time (given the flying speed is the same).  Which  would you rather fly?
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Gary LaPook

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Re: The flight plan, magnetic course, headwinds.
« Reply #391 on: February 22, 2012, 11:45:25 AM »


Heath
Two things
1.  I learned in grade school that the answer cannot be more precise than the number of decimal places in the least known of the numbers being used.  For example, to use PI to 11 decimal places in calculating a circumference when the diameter is only known to 1 decimal place is nonsense and a waste of time (no matter whether you are using a slide rule, a calculator, or a Cray supercomputer).  Use 22/7 ths and you'll be close enough.


Or use 355/113ths which produces Pi accurate to six decimal places, 3.1415929 versus 3.1415926 for Pi. It is easy to remember, 11-33-55, split in half between the two "3"s, and slide the first half under the second half and divide.

gl
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Harry Howe, Jr.

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Re: The flight plan, magnetic course, headwinds.
« Reply #392 on: February 22, 2012, 12:13:45 PM »


Shaking head.
It must be a generational thing, like those born before Da War and those born after Da War. I believe they're called "Baby Boomers"  LOL
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Randy Reid

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Re: The flight plan, magnetic course, headwinds.
« Reply #393 on: February 22, 2012, 12:53:49 PM »

Gary,
I'd wager a considerable part of my fortune ::) that you do not sleep much.
Randy
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Harry Howe, Jr.

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Re: The flight plan, magnetic course, headwinds.
« Reply #394 on: February 22, 2012, 01:10:07 PM »


Randy
Remember that Forum time is Central Standard Time (I thimk) and we out here in California are two hours behind Forum time, i.e Gary's 03:05 AM post is 01:05 AM PST (Pacific Standard Time)
But still, I think that Gary is awake alla time. (that's a compliment Gary)
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Randy Reid

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Re: The flight plan, magnetic course, headwinds.
« Reply #395 on: February 22, 2012, 01:59:53 PM »

HHjr,

I was more noting about the shear quantity of research done by GLP and all of his accomplishments. Is it possible that GLP is more than one person? If not, then super human anyway.

Gary, just in case you think I am critical of you, it is just the opposite. I only wish I were half as intelligent.

Randy
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Heath Smith

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Re: The flight plan, magnetic course, headwinds.
« Reply #396 on: February 22, 2012, 03:12:09 PM »

Quote
The point in discussing the rhumb Line versus the Great Circle isn't the ease of navigation on paper, it is the ease of flying a constant heading versus flying a route of 16 segments and changing headings for each one.  Either one will get you there in aout the same time (given the flying speed is the same).  Which  would you rather fly?

I would fly the rhumb line. Think about taking a fix and observing that you are off the flight line. A few simple trig calculations will get you back to a rhumb line. With a GC flight line, you have to determine exactly where you were time wise, taking in to account the previous heading changes and times per segment, to compute where the flight line is at that moment. By the time you figure that out your data is so old it is about useless. I do not think there is any question of which is easier beside the fact that you only have to follow one heading with a rhumb line.
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richie conroy

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Re: The flight plan, magnetic course, headwinds.
« Reply #397 on: February 22, 2012, 07:21:44 PM »

sorry guys but you's only now have this info thru mishaps like earharts, an advance's in technology

an that seems to be the downfall, to which no one has smokeing gun evidence as too were they ended up

u have to use there way of thinking prior of july 2nd 1937, not what you's know now  :)

   
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Irvine John Donald

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Re: The flight plan, magnetic course, headwinds.
« Reply #398 on: February 22, 2012, 07:30:33 PM »


As for the precision stuff, I am of a completely different mind set. When you write software for a living, you cannot possibly consider and re-consider the practical precision for each calculation that you perform. You would go mad if you attempted to do so. For example, the following constant is used for Pi:

const double PI = 3.14159265359;

This is pretty unisveral in software development. You run your calculations using this value and you do not consider the precision of the particular task in the real world that is being performed, you use the theoretical value.
We all do that when dealing with programming a computer. When I wrote programs to do navigational calculations I often ran into a "division by zero" type of error message caused by a trig function for that angle being zero. .....

gl

Gary, when did you do this programming?  Hobby?  Serious commercial programming or just personal?  I own a company where we write software for self serve kiosks and am interested in your background in programming.
Respectfully Submitted;

Irv
 
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Heath Smith

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Re: The flight plan, magnetic course, headwinds.
« Reply #399 on: February 23, 2012, 04:15:37 AM »

I am not sure whether this page was already posted but it has source code for calculating the great circle and rhumb lines.

See:

Calculate distance, bearing and more between Latitude/Longitude points

Using the rhumb line calculator for Lae to Howland produces (using accurate latitude and longitude values):

Distance:   4124 km
Bearing:   078°16'04"

If FN did use a rhumb line for the Lae to Howland flight would he have created a flight plan where the only segments in the plan would be where the magnetic variations exceeded some acceptable amount of error along the rhumb line? I am guessing this flight plan would really just be instructions for AE to follow compass headings. If this is the case, and FN wanted to make a course correction based on celestial observations would he essentially ignore the error created by the magnetic variations and use only the rhumb line itself for calculations?

As to the source of the magnetic variation data, were Williams and FN drawing from some published Air Almanac for this data? I have not looked at any of FN's previous flight plans, do they include any magnetic variation data that can be tied to a single source?
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Harry Howe, Jr.

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Re: The flight plan, magnetic course, headwinds.
« Reply #400 on: February 23, 2012, 10:17:38 AM »


Well, I am glad that we, Heath, JeffN, me , and of course our flight instructor Gary agree that we would opt to plan a Rhumb Line route for the Lae to Howland leg.  Given his training, experience,qualifications as a pilot, expert navigator, certified ship's Captain, etc so woul Fred Noonan.
 Now, can we all reach agreement that FN planned to have AE fly an offset landfall approach, prolly after his last celestial fix at approximately 600 nm out (DR error about 60 nm)?  Prolly to approach on a course of 067 degrees (90 degrees to the LOP157/337) about 60 nm NNW of Howland?
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Heath Smith

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Re: The flight plan, magnetic course, headwinds.
« Reply #401 on: February 24, 2012, 02:20:04 PM »


Harry,

I am not sure we are ready to create the offset quite yet. First we need to do a flight plan reconstruction then we can add it afterward. Hopefully I can spend some time on it this weekend unless Gary has already created one.

Are you suggesting that they flew directly in to the sun with that approach?

Thanks.
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richie conroy

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Re: The flight plan, magnetic course, headwinds.
« Reply #402 on: February 24, 2012, 03:32:31 PM »

 :)

sorry guys my comment was typed wrong, it sounded ok as i spoke it.

but reviewing it now it's a bit disrespectful to you's that spend the time doing all this research so sorry

what i meant was maybe researching navigation methods pre 1937 we may!! or i may understand better how it works

being from a non pilot, flying, sea faring, background   i tend to just look at obvious stuff

for instance

 the 157/337 L.O.P runs diagonally thru howland and gardner

337 L.O.P to the NNW

157 L.O.P to the SSE

now givin there flight path, an Itasca visibility 

what would be the time difference from the 200 miles out log

to joining L.O.P NNW

to joining L.O.P SSE 

?



 
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Gary LaPook

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Re: The flight plan, magnetic course, headwinds.
« Reply #403 on: February 24, 2012, 04:04:41 PM »

:)

sorry guys my comment was typed wrong, it sounded ok as i spoke it.

but reviewing it now it's a bit disrespectful to you's that spend the time doing all this research so sorry

what i meant was maybe researching navigation methods pre 1937 we may!! or i may understand better how it works

being from a non pilot, flying, sea faring, background   i tend to just look at obvious stuff


 
Here is a source for you to learn about flight navigation as practiced in 1937.

gl
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richie conroy

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Re: The flight plan, magnetic course, headwinds.
« Reply #404 on: February 24, 2012, 04:52:09 PM »

:)

sorry guys my comment was typed wrong, it sounded ok as i spoke it.

but reviewing it now it's a bit disrespectful to you's that spend the time doing all this research so sorry

what i meant was maybe researching navigation methods pre 1937 we may!! or i may understand better how it works

being from a non pilot, flying, sea faring, background   i tend to just look at obvious stuff


 
Here is a source for you to learn about flight navigation as practiced in 1937.

gl

thanks gary will check it out
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