# Wind Drift Calculations

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Hi all,

I've drawn up a basic Flight Plan using Excel and want to increase its functionality by inserting the wind speed and direction (obtained from the current AFORS, etc) and then, using embedded formulas within the spreadsheet, derive the actual heading and ETI.

Unfortunately "googling" hasn't been forth coming with the mathematics required to enable me to accomplish this.

Does anyone know (the formulae) or can point me in the direction of a site that has it?

Cheers.........Doug

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Hi Doug,

Sounds like a good idea but I'm not pc savvy so can't help. Just want to say G'day

Cheers.......Doug;););)

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Can anyone tell me how to reduce the wasted space below my posts?

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Can anyone tell me how to reduce the wasted space below my posts?

The space is taken up by the information on the left of the post - this causes the empty space

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G'Day Doug - maybe we should have a forum just for Doug's - we obviously dominate!

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Well we've been around since Roman times, and they certainly dominated. For what it's worth, the name originally meant Dark Waters or River. The nearest link I have is a Roman nose, it's roaming all over my face:clown:

Thanks Ian, guess I'll have to try and fill it.

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Hi Doug,

a mate of mine who trained as a pilot and air navigator back in the dark ages gave me this:

#########

direction of the wind relative to track:

0Ã‚Â° = 100%/0%

15Ã‚Â° = 97%/25%

30Ã‚Â° = 87%/50%

45Ã‚Â° = 70%/70%

60Ã‚Â° = 50%/87%

75Ã‚Â° = 25%/97%

90Ã‚Â° = 0%/100%

Headings are then calculated according to the following formula:

X/W ÃƒÂ· (TASÃƒÂ·60) = drift

TAS (ISA +15 @ 5,000ft) = 110% CAS (good enough for government work - of

course % increases with altitude to about 120% @10,000ft and reduces by

####

I also think I know where there's a specific formula for this. I'll come back to you.

Regards

Mike

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Doug,

go here for an explanation of the triangles and the formulas. Head/Tail wind component is a cosine relationship and crosswind is a sine relationship.

Also remember to reduce groundspeed to allow for the impact of your dirft correction. The page has a simplified table for that.

Let us see a copy when it's finished!!

Regards

Mike

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Thanks Mike - I was just browsing there and saw the table and my initial thought was "eek! Look-up tables" which was one area where I didn't want to go........:confused:

Why is it that something that sounds so simple evolves into a huge time consuming problem? Not to worry - at least I know there is a solution somewhere. When I find it I'll let you know!

Doug - If "Still waters run deep" what do Dark waters run - dirty maybe :big_grin:

Cheers..........Doug

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dips73. I wrote a program for use on a programmable hand held calculator and it should be convertible to XL. I will see if I can get it into a usable format and post it.

May take a day or two to find the time as I am a retiree.

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Thanks Mike - I was just browsing there and saw the table and my initial thought was "eek! Look-up tables" which was one area where I didn't want to go........:confused: Why is it that something that sounds so simple evolves into a huge time consuming problem? Not to worry - at least I know there is a solution somewhere. When I find it I'll let you know!

Doug - If "Still waters run deep" what do Dark waters run - dirty maybe :big_grin:

Cheers..........Doug

Hi Doug,

I think it's simpler than that: The solution of both the xwind component and the headwind component is trigonometrical and can therefore be programmed. The allowance for reduction in groundspeed can be programmed as an IF statement. No lookup tables needed.

Regards

Mike

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Ian - thank you - I'm sure your program will be a lot neater that mine...

Mike - my trig's very rusty - I didn't realise you could use sine/cosine in scalar triangles - thought it was only right angled ones - duh!

Hopefully this should make it easier.

Cheers........Doug

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Hi Doug,

yeah the right angle ones you deal with using the SOHCAHTOA mnemonic. But non-right triangles you use the sine or cosine rules. And for spherical trig you use Napier's rules. See here for examples of sine and cosine rules:

It's an Irish site but for all that it seems OK ;-)

Regards

Mike

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On this note:

Can anyone tell me how to reduce the wasted space below my posts?

You can go to tools then edit signature then add something in there.For example, mine is fly safe with a link to my web page.That way it does not look so blank below.It is filled with some text.

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Thanks Darren, How's this for a start? Got to make the photo clearer without making it bigger or I'll go over the limit.

To think, I've been in every one of them, plus hell of a lot more.

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Yes mate. That is a start.About the image, not sure how to get it clearer.You can always post a link (as I have for my web page) so when we click, we get the image.I'm not sure that's what you want to do though.Any signature looks better though without that big 'blank' you were talking of down the bottom don't you think?You can basically add anything you want down there.

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dips73.

I have made a start on a spreadsheet program and it will have to be modified quite a bit from the calculator program, but a good exercise for the mind.

I use trig to get Easting and Northing co-ordinates so the program wont work over very long distances, but we don't usually fly legs of thousands of miles.

It may be easier on the spreadsheet as I can use negative sin and cosine results and not have to ensure everything is positive.

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Hi Ian - I was working on a formula that probably paralleled yours and was having a few problems with the the square root of a cosine function when it was negative - it's certainly stirring up the grey matter!

I'm at work tomorrow so I'll have more time to focus on it.....

Cheers........Doug

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dips73.

I am also having problems. If wind and track align I get an incorrect answer and I am still checking all 4 quadrants. My big problem is working in radians, which I detest, but I'me getting there slowly.

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Ian - you appear to be further ahead than I am!

I've got a pdf copy of the Dummies Book of Trignometry which I'm browsing through.

Is the formula your using based on the "Law of Sines" and the "Law of Cosines"?

Cheers......Doug

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Hi Doug,

I think that you have to use both the sine and the cosine formula - you are solving two triangles - once for the xwind component and 1 for the head/tailwind component.

If you go here again you will see them drawn out halfway or more down the page in Fig 5:

Regards

Mike

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You blokes are a worry working all that stuff out. I don't even allow for planned wind when I go places, take off and see how goes it then allow for drift.

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Have a look at this sheet, it shows you how it is calculated.

Only change the numbers outlined in orange. the answers are in bold.

Regards

Mike

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You blokes are a worry working all that stuff out. I don't even allow for planned wind when I go places, take off and see how goes it then allow for drift.

My problem is SP that if you give me a problem I've got to solve it. Never mind that your answer is probably the right one:;)3:. I need to get a life:cool:

Regards

Mike

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My problem is SP that if you give me a problem I've got to solve it. Never mind that your answer is probably the right one:;)3:. I need to get a life:cool:Regards

Mike

No problem, glad somebody does it. Me I just look out the window and think..........ooooohhhhhh, with my IQ of 75 life just drifts passed. :big_grin: