Wind Drift Calculations

[dlps73]

Good grief Mike - that URL make it looks way too easy!

 

And sadly the major reason I keep working (on the problem) is that I read somewhere this week that you can actually create new brain cells in old farts like me by doing work of this nature. What you'd call a win-win situation....

 

Cheers........Doug

 

 

[Guest pelorus32]

Well Doug,

 

do you reckon it works or not;)

 

If it does then it's just up to you to put a pretty wrapper around it:cool:

 

Regards

 

Mike

 

 

[dlps73]

Fair go Mike!

 

I only started the process this week and you can't rush genius (or zimmer frames).

 

Cheers.......Doug

 

 

[Bruce Robbins]

You blokes are making my head hurt!

 

If you can't sleep go to here

 

http://williams.best.vwh.net/avform.htm

 

..........and when you finally get to sleep, go to here in the morning and download the fruits of some-one else's labour.

 

http://www.airborne-aviation.com.au/resources/flightplan/flight_planner.zip

 

It's a brilliant piece of excel programming and works a treat. I used a password cracker a few years ago to peek at the formulas when I first started to use it. Took one look and quickly closed the bonnet again!

 

 

[dlps73]

Bruce - do you still have the password for the macros?

 

That flight planner is brilliant - far surpasses anything I had in mind!

 

Why re-invent the wheel..........?

 

Cheers.........Doug

 

 

[Yenn]

The little spreadsheet is good but I am trying to have a spreadsheet which you input:- Wind speed, wind direction, TAS and desired track. The output is Heading and G.S.

 

I think I am nearly there with only a little problem of having to convert negative co-ordinates to positive to get G.S.

 

Should have it going later today hopefully.

 

I also like to solve a problem if I can and had to teach myself trigonometry years ago for work after idling my time away at school. It is easy to do it using trig tables and paper, but talking to the computer is the problem and I have only been using a computer for just over 20 years and every time the computers crashed at work I got the blame. That is what you get for being the granddady of the office.

 

 

[Guest pelorus32]

Hi Ian,

 

I'm with you. The spreadsheet was only intended as a demo for Doug of the two triangles that needed solving to arrive at the xwind and head/tailwind components. Those items are needed if you are going to achieve your intent of solving the next triangle(s) which are about heading.

 

As far as negative and positive are concerned I think that the calcs in that spreadsheet bring the signs out right for crosswind but wrong sign for head/tailwind. If you change the calc in B7 to read: =-(COS(B10)*B3)

 

Then I think that will give you a head or tailwind that you can arithmetically use - simply add it to your TAS to arrive at GS.

 

If you have a big drift angle you will need to allow for the reduction in GS as a result of the difference between heading and track. I posted a quick rule of thumb in an earlier post and you can do it trigonometrically as well.

 

Regards

 

Mike

 

 

[Jex207]

G'day All,

 

Here is a little flight planning spreadsheet I cooked up a couple of weeks ago. It should be fairly self explanatory...!

 

Feel free to have a stuff around with it and modify it for your own purposes, or drop me a line if you've got any questions about it.

 

cheers

 

Jeremy

 

 

[dlps73]

Jeremy kindly sent me a copy of this yesterday and here's the instructions he noted which gives you some idea of its versatility.

 

The ground speed calculation is done using trig, so it is accurate for large drift angles.

 

 

 

The EET column also adds a factor for time to altitude. It looks at the cruise altitude column and also the aircraft climb data down below to calculate this. In that aircraft data box you can fill in the aircraft's cruise and holding fuel flows, it's climb speed and the rate of climb you usually get for an en route climb.

 

 

 

The fuel planner just adds up all the EETs and does all the other basic arithmetic for you.

 

 

The whole thing is sized so when you hit print it fits neatly into the top half of an A4 page, so you can fold it in half and stick it on your kneeboard!

 

 

I had a quick look at the wind drift formulas but they did my head in!

 

Ian and Mike - I think we have a winner!

 

Cheers.......Doug

 

 

 

[Jex207]

G'day again,

 

I've just uploaded an updated version. I've re-worked the equations for calculating groundspeed and also figured out a slightly simpler way of calculating the drift.

 

I'm in the process of putting together a word document that explains all the formula used, which I'll post here once complete.

 

cheers

 

Jeremy

 

 

[Yenn]

I downloaded jex207'S spreadsheet and at first glance it appears very complex, but I used a separate column for each step of my formula and it still is not finished. Mine seems redundant now but I may post it later if it has any saving graces.

 

Jex not only are you a wizard with the spreadsheet but your photos are quite good on flickr. I posted some there ages ago and have not been back for a while, used yen I think as my name. Maybe I should put in some later stuff.

 

 

[dlps73]

Ian

 

at first glance it appears very complex

Uumh - it doesn't get any easier at the second glance either. It appears the ArcTangent function has gone and the ArcSine fuction added and a reduction in the brackets (I counted 9 in the first edition!)

I'll wait for Jeremy to finish the book that explains it all...........got a horrible feeling I won't understand that either :confused:

 

Talk about "Be careful what you wish for"........

 

Cheers........Doug (Not waving - drowning)

 

 

[Jex207]

Light Reading

 

Here is some light reading for those interested in the calculations behind the spreadsheet!

 

cheers

 

Jeremy

 

 

[Yenn]

At second glance I was completely baffled at the start and it didn't get better. I still have not got my formula sorted. I am using open Office Org and I can't find If then, but it must be there so I keep looking. My answers are OK but headings are not in 360 deg format but plus and minus, and ground speeds come out incorrectly sometimes if wind and track are the same or 180 deg different.

 

Keep trying.

 

 

[Guest wish2bflying]

I've created a spreadsheet that is sort of a combination of both of these other ones, I'll try to get it uploaded somewhere if I can remember my password to my ISP ftp account. Mine takes all the winds and data from the ARFOR, calculates your climb and cruise TAS values and works out your fuel burn and time to TOC as well as cruise fuel burn values. It also transposes all these to a kneeboard with all the critical data. I've also done up a page with the ASA Domestic Flight Notification Form with editable fields so you can save your form for later use.

 

As far as the HDG and GS calculations, it's pretty straightforward, you just have to remember that Excel works in Radians by default, you have to convert the numbers to degress by using SIN(RADIANS(NUMBER)) or COS.

 

Cheers ...

 

 

[Admin]

Wish2bflying - if you like to you could email it to me and I will post it up on the downloads page of the website

 

 

[poteroo]

The Jeppeson CR-3 whizwheel that I've used since 1963 saves lots of error with the decreased TAS due to laying off big mobs of drift. It calls for you to read off the effective TAS from the TAS setting on the windside of the CR-3. It's a log function, but because I've long since lost the handbook, I'm unable to advise just how it works.

 

happy days,

 

 

[Guest wish2bflying]

You can download my spreadsheet from http://www.geosim.com.au/users/michael/NAVToolkit.xlt - any comments are welcome.

 

I've password protected the sheets to prevent accidental stupidity ;) , but I haven't hidden the formulas, so feel free to have a look and pass on any comments. If you want to unprotect the sheets to personalise it, the password is "mpe". I've provided some fairly reasonable instructions, hopefully they make life easier for you.

 

Like I said before, it's a very localised solution, and certainly doesn't boast some of the fantastic features of the other spreadsheets shared here, but it meets my current needs, and some of you might like it.

 

Poteroo - with the Jeppeson whiz wheel, if your drift is more than ten degrees, you just read left of the original TAS on the wheel directly below (in black) to where the drift angle is and read the ETAS directly above the drift angle amount. Unfortunately I haven't worked out how to implement this into my spreadsheet, but my (limited) experience is that at lower speeds, close enough is good enough.

 

At 120 TAS, a 10° drift will only cost you 1.5 knots, 15° = 4 knots and 20° = 7 knots. Most of my flying so far hasn't needed more than 10° drift, so I'm willing to accept a 1.5 knot error in my calculations. Laying off 20° of drift at 120 knots would make for a fairly sporting day - landing at the wrong airfield would exceed my crosswind limits. :ah_oh: I don't think I'd like to be out navving on a day like that.

 

If you're interested, I could probably get a copy of the CR-2 manual for you.

 

Michael.

 

 

[Guest floatHigh]

I like that simple table Mike posted in #7.

 

Just right for me, seeing as wind drift is not an exact science due the variability of wind. :)

 

 

[Guest wish2bflying]

We call that the "Clock code" - imagine a clock, 60 minutes = 60°. 15° = 1/4, 30° = 1/2, 60° = 1

 

If the wind is more than 60°, we just assume the crosswind component is the full value of the wind strength. Then the drift angle is as described -

 

XW component = Drift angle

 

GS (nm per minute)

 

Which is really easy if you can approximate the cruise GS to 120 knots, ie. 2 nm/min.

 

The HW/TW component is just the reciprocal angle of the crosswind component.

 

Using this method, you never have to even use a whiz wheel - every time I've estimated heading and GS using the clock code it's never been more than a couple of degrees off.

 

Cheers,

 

Michael.

 

 

[Guest floatHigh]

Yes, simple ideas are cool because at all times you can carry them around in your head.

 

Some years ago as the sole passenger with a charter pilot (Paul Brogan), I remember that when he flew me to the remote NW corner of SA,

 

and without useful landmarks or Nav-Aids, he kept mumbling something about wind strength and direction changing and making continuous adjustments to arrive spot-on target!

 

Either that or a forced landing LOST in the desert!

 

I thought then that it was pretty cool, and more so now that I fly! :)

 

 

[Guest wish2bflying]

I noticed a few errors in my fuel calculations for trips that don't include a climb component, so I've amended the spreadsheet and uploaded the new version.

 

Cheers,

 

Michael.

 

 

[Guest wish2bflying]

Anyone looking for the CR-2 manual can download it here from the Jeppesen website:

 

http://www.jeppesen.com/download/misc/crinstructions.pdf

 

Cheers,

 

Michael.