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CDU Wind correction done right


Boris
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Since there is no comprehensive, fault free guide on proper wind correction for dumb bombs, I have decided to write one up.

 

Previous guides and videos have shown incorrect wind directions and or speeds. Following these steps should lead to accurate CCIP bombing in complex winds. Where the pipper is pointing on release, that is where the bomb will go. Hopefully this will also dispel the myth that wind correction is not functional.

 

First of all, it is important to understand how the mission editor and the engine handle wind.

Here are the wind settings I’m using for this particular guide:

 

attachment.php?attachmentid=98330&stc=1&d=1400498500

 

As you can see, we have a 20°, 4m/s wind at 10m, a 310°, 6m/s wind at 2000m and a 270°, 8m/s wind at 8000m.

However, this is not all. As the game engine calculates for a natural drop in wind speed at very low altitude, it needs to upscale the wind speed above. We have already entered the wind speed for 10 meters, but the wind speed for most of the bottom layer of wind will be TWICE (2x) that entered in the ME.

So in fact, we will have a maximum wind speed of 8m/s from about 350 to 650m.

 

So layer by layer we actually have:

 

10m 020° 4m/s

500m 020° 8m/s

2000m 310° 6m/s

8000m 270° 8m/s

 

We now have our layers.

 

Next we have to convert these values into something the CDU can use. DO NOT plug these values straight into the CDU, as you will make any wind error even worse.

The mission editor displays in which direction the wind is blowing to. The CDU shows the direction from which the wind is coming, and it shows the magnetic, not the true bearing. So to convert these bearings we need to add 180 to any values below 180, and subtract 180 from any values above 180, to get the bearing on the opposite side of the compass rose. Then we need to subtract 7° to get the magnetic bearing.

 

Eg. 020° + 180° = 200°

200° - 7° = 193°

 

We also need to convert all wind speeds from m/s to knots. This is easy, just multiply each value by 2.

So what we end up with for the CDU is:

 

10m 193° 08 knots

500m 193° 16 knots

2000m 123° 12 knots

8000m 083° 16 knots

 

Now we need to enter this data into the CDU during flight.

 

First enter the CDU System page by pressing SYS on the CDU or FUNC – 1 (SYS) on the UFC.

Then press OSB 7 to enter the LASTE menu.

 

 

attachment.php?attachmentid=98322&stc=1&d=1400498500

 

Press OSB 10 to enter the WIND menu.

 

attachment.php?attachmentid=98323&stc=1&d=1400498500

 

 

Enter the altitudes for the layers you wish to set the wind correction for. In contrast to the three layers in the mission editor, we can enter up to 7 layers in the CDU.

We need to convert the altitude from meters to feet, which is roughly x3.

The layers can be entered in feet in increments of 1000ft in two digits.

ie. Enter 01 for 1000ft, 02 for 2000ft, 03 for 3000ft etc.

Enter the digits on the scratchpad of the CDU or the UFC and press the corresponding OSB.

 

attachment.php?attachmentid=98324&stc=1&d=1400498500

 

The layers will order themselves according to altitude regardless of where they are entered. Press CDU PgUp/PgDn or FUNC - DATA (PG) to cycle between the two pages for more layers.

I’m going to enter layers for 00, 01, 02, 06, and 24 for this example. 00 for the wind at ground level, 01 and 02 to best represent the wind of the bottom layer, 06 for the 2000m layer and 24 for the 8000m layer

Once all layers are entered, press WNDEDIT OSB 8.

 

attachment.php?attachmentid=98325&stc=1&d=1400498500

 

On this page you can now enter the data for each layer: 5 digits for the bearing followed by the windspeed on the left side, 2 digits for the temperature on the right side. Press the corresponding OSBs to enter the data.

Enter 19308 for the first layer 19316 for the first and second, and so on.

For the temperature, I enter the temp from the mission editor for the first layer and the temperatures from there tend to drop by 2° per 1000 feet of altitude. The temperature at the current altitude is shown in the top right corner of the CDU screen if you need to double check.

What you will end up with is the following:

 

attachment.php?attachmentid=98326&stc=1&d=1400498500

 

attachment.php?attachmentid=98327&stc=1&d=1400498500

 

Press OSB 7 (WIND) to confirm and get back to the main wind page.

 

attachment.php?attachmentid=98328&stc=1&d=1400498500

 

Finally, you can press OSB 7 to cycle between BOTH, WIND, TEMP and NONE. Make sure you’re using either BOTH or WIND (ideally BOTH) to make sure the layers entered are taken into account. I find NONE useful if I want to see the wind currently measured by the aircraft to input any extra layers.

 

attachment.php?attachmentid=98329&stc=1&d=1400498500

 

If you don’t have any wind data from the ME, in multiplayer for example, you can just take the wind measurements as you climb out. No conversions necessary of course, as the data comes straight from the CDU and is in the correct format.

At this stage you should be ready to put bombs on target.

 

I have recorded two tracks to demonstrate the effectiveness of this, one where I try to CCIP bomb 6 T-80s without wind correction and another in which I kill 6 T-80s with wind correction. The tracks are attached at the bottom of this post.

Wind_01.jpg.0f53c076330dcba9fdc372daa7f902d4.jpg

Wind_02.jpg.525622a15e7a5b2ec82ccdbaa492ab69.jpg

Wind_03.jpg.7a6a40acda0d2ed7db5cbddec7af0f18.jpg

Wind_04.jpg.16736d0521a288ff82661cb1b41a41b1.jpg

Wind_05.jpg.75bdc5eac44a33c6aeabe161db38629a.jpg

Wind_05_2.jpg.b2ccf5b9f99cbd1f327c2a765fe03aa7.jpg

Wind_06.jpg.2d7c53e05ffd468cbb458415b7749153.jpg

Wind_07.jpg.4dec093391be0d8330e6a4e1ed0ec585.jpg

Wind_ME.jpg.9baaf0c53a604d5320d87b13ab6c7530.jpg

Mk-82 CCIP no Wind Correction.trk

Mk-82 CCIP with Wind Correction.trk


Edited by Boris
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Very nice!

 

In the past and for quite a long time, the wind correction with multiple layers in the CDU was broken. If it was the calculation itself that the CDU performed or if it was just that entering the data was errorneous - it lead to that people claimed that wind correction does not work. Even after all issues were solved by ED (with version ... dunno ... 1.2.5? 1.2.6?), people - some of them up to this day - still believe this.

 

Maybe you want to add some sort of "foreword" to your tutorial, like

 

Yes, it WAS broken, but it is FIXED now and in fact it WORKS as DESIGNED (*1)

 

___________

*1 it is STILL no magic bullet and especially dropping dumb bombs from high altitudes in strong winds will still be difficult and may not be as precise as a JDAM/LGB

... or something similar. :o)
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When wind layers are listed in the mission briefing, like on campaigns, are they in the correct format, or do they also need to be adjusted 180 and for magnetic north?

 

I had a campaign mission once that listed three wind layers, all at 000°. When I tried to enter e.g. 00004 into one of the slots, it would throw an input error. I found I had to use e.g. 00104 to get values entered...I didn't think of trying 36004. Anyway, I wonder if it should have been 17304 anyway...

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When wind layers are listed in the mission briefing, like on campaigns, are they in the correct format, or do they also need to be adjusted 180 and for magnetic north?

 

I had a campaign mission once that listed three wind layers, all at 000°. When I tried to enter e.g. 00004 into one of the slots, it would throw an input error. I found I had to use e.g. 00104 to get values entered...I didn't think of trying 36004. Anyway, I wonder if it should have been 17304 anyway...

 

I'm pretty sure the wind data generated by the mission briefing comes from the mission editor and also needs to be converted. If in doubt, look at the current wind reading on the CDU. It doesn't lie.

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I'm pretty sure the wind data generated by the mission briefing comes from the mission editor and also needs to be converted. If in doubt, look at the current wind reading on the CDU. It doesn't lie.

You are correct, sadly. Just double checked it (never payed too much attention to this, lol), the weather data of the briefing screen is taken 1:1 as set up in the mission editor, i.e. with wind "blowing to".

 

People always are confused about the way the ME handles this, as in real life, wind is always (and everywhere) stated as "blowing from". So while the ME uses "blows to", it should really convert the data automatically to RL conforming "blows from" for the briefing screen.

 

I would consider this as an actual bug.

 

edit:

fwiw: reported this as a bug, including a fix: http://forums.eagle.ru/showthread.php?p=2070245


Edited by Flagrum
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I guess I just see the world differently as a programmer...all my array indices start at 0.

 

Maybe that explains why you wouldn't want to use 000 on a radio call, but it seems weird that the CICU would throw an input error still... What help is it to throw the err?

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Yep... Its for phonetic reasons.. Same reason number nine its pronounced nainer.

And same reason they change the "position and hold" to enter a runway and hold there to "line up and wait"

 

They could get confused with other instructions.

 

Funny thing, in spanish the word "wait" sounds almost the same as "take off"

Imagine all airplanes recieving order to line up and take off hahaha... We change it back to position and hold

A.K.A. Timon -117th- in game

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  • 3 months later...

Has anything changed with regard to this in the current version, are the wind directions still off by 180 in the ME?

I tried this today and my bombs didn't even hit the right time zone...:cry:

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Has anything changed with regard to this in the current version, are the wind directions still off by 180 in the ME?

I tried this today and my bombs didn't even hit the right time zone...:cry:

No. As the ME uses that small "compass"-thingy for inputting headings(!) for everything that has anything to do with an angle, it is still "where the wind blows to" in the ME. Unless ED reworks the ME completely, that will likely not change. So I would not expect it to happen before version 2.x, imho. (but no big deal in my eyes, tbh ...)

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  • 1 month later...

Recommend sticky

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AWAITING ED NEW DAMAGE MODEL IMPLEMENTATION FOR WW2 BIRDS

 

Fat T is above, thin T is below. Long T is faster, Short T is slower. Open triangle is AWACS, closed triangle is your own sensors. Double dash is friendly, Single dash is enemy. Circle is friendly. Strobe is jammer. Strobe to dash is under 35 km. HDD is 7 times range key. Radar to 160 km, IRST to 10 km. Stay low, but never slow.

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Wind in m/s are knots in sim ??

 

When i start a mission at the beginning of the rwy, with the wind exactly on the nose and the wind in mission editor set at 50 m/s .

 

I get an Airspeed indication of just below 50 KTS ??

50 m/s should give an Airpeed of 97 KTS.:huh:

 

If this is a bug, I hope it will be fixed.

I can imagine that this fault can induce all kind of errors in flight dynamics and weapon trajectory calculations.

 

Anyone with the same opinion ??

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When i start a mission at the beginning of the rwy, with the wind exactly on the nose and the wind in mission editor set at 50 m/s .

 

I get an Airspeed indication of just below 50 KTS ??

50 m/s should give an Airpeed of 97 KTS.:huh:

 

If this is a bug, I hope it will be fixed.

I can imagine that this fault can induce all kind of errors in flight dynamics and weapon trajectory calculations.

 

Anyone with the same opinion ??

 

First of all, 50 m/s is a huge wind speed. That's a category three hurricane! This is beyond anything you should set your wind to.

 

By airspeed indication, do you mean your aircraft's indicated airspeed? If so, this isn't used to measure the direction and speed of the wind outside, but the speed at which the aircraft is traveling through the air. The IAS doesn't go below 50 anyway, so no wonder you're getting an indication of around 50.

 

If you look at the screens in my first post, you can see the atmospheric wind direction and speed in the top right corncer of the CDU screens.

 

123/012 for example. A 12 knot wind coming from a magnetic bearing of 123 degrees.

 

EDIT: I've thought about this and I've come to see your point. If you're sitting on the ground and have a head wind faster than 50 knots, why doesn't it show as indicated airspeed??? Anyone? Also, how does the CDU know the current atmospheric winds, given that the plane is moving through the air?


Edited by Boris

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The way the wind is modelled in DCS might be the reason here. I can't recall the exact details atm, but I do recall that - I think it was Yo-Yo - said that the wind near the ground (up to 10 meters) is slowed down (due to obstacles like buildings and vegetation).

 

So if you set the wind in the ME to 50 m/s at alt=10 m (you can't even go lower!), you will experience much less wind when sitting on the runway.

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I believe current wind is calculated by the mission computer by comparing air speed measured from the analog instruments to aircraft velocity as derived from INS and GPS. That calculated wind velocity is valid only for the current altitude, of course.

 

Thanks, I suspected this would be some sort of complex calculation rather than a single sensor.

 

The way the wind is modelled in DCS might be the reason here. I can't recall the exact details atm, but I do recall that - I think it was Yo-Yo - said that the wind near the ground (up to 10 meters) is slowed down (due to obstacles like buildings and vegetation).

 

So if you set the wind in the ME to 50 m/s at alt=10 m (you can't even go lower!), you will experience much less wind when sitting on the runway.

 

I did some extensive testing on this. Yes, it is true that the wind is slower at ground level. I tried to explain this in the first post of this thread.

 

While wind speed is in fact about half as slow at ground level, it doesn't work as one would expect.

 

For example, in the mission editor we have set the following:

 

10m - 10 m/s

 

2000m - 10 m/s

 

8000m - 10 m/s

 

Here we would expect a constant wind speed of 10 m/s at all altitudes, with somewhat slower wind of around 5 m/s below 100m from the ground.

 

But what we see in game is a little different.

 

What we actually end up seeing is something like this:

 

10m - 10 m/s

 

100m - 12 m/s

 

500m - 20 m/s

 

1000m - 15 m/s

 

2000m - 10 m/s

 

8000m - 10 m/s

 

The reason for this strange behaviour, is that the wind speed for the bottom layer is set at only 10m.

We have already set this at 10 m/s. However, the engine wants to simulate slower wind speeds at very low altitude. So it needs to upscale the wind for the rest of the layer to compensate in order to give the effect that the wind is slower below 100m.

This upscale happens to be TWICE the wind speed actually entered.

From about 350m to 650m the wind speed is 20m/s and then drops in order to blend with the layer above.

 

So if we want to achieve a constant airspeed of 10m/s for all layers, we would need to enter the following:

 

10m - 5 m/s

 

2000m - 10 m/s

 

8000m - 10 m/s

 

As a rule, the bottom layer always needs to be half the speed you actually want it to be.


Edited by Boris
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^^^ That is a nice bit of research but it begs the question, why the devs could not have documented this fact in the ME from day one.

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^^^ That is a nice bit of research but it begs the question, why the devs could not have documented this fact in the ME from day one.

 

Or why they don't jut simplify things and change the altitude for the bottom layer setting to something like 500m.

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First of all, 50 m/s is a huge wind speed. That's a category three hurricane! This is beyond anything you should set your wind to.

 

By airspeed indication, do you mean your aircraft's indicated airspeed? If so, this isn't used to measure the direction and speed of the wind outside, but the speed at which the aircraft is traveling through the air. The IAS doesn't go below 50 anyway, so no wonder you're getting an indication of around 50.

 

If you look at the screens in my first post, you can see the atmospheric wind direction and speed in the top right corncer of the CDU screens.

 

123/012 for example. A 12 knot wind coming from a magnetic bearing of 123 degrees.

 

EDIT: I've thought about this and I've come to see your point. If you're sitting on the ground and have a head wind faster than 50 knots, why doesn't it show as indicated airspeed??? Anyone? Also, how does the CDU know the current atmospheric winds, given that the plane is moving through the air?

 

Okay,

 

As for the Extreme High wind setting...i was just trying stuff out :book:.

 

Thanks for the answer Boris, and I stand corrected for my mistake that the airspeed indicator starts at 0 Kts, You are right It starts at 50 Kts !!

So the m/s to Kts calculation in DCS is right, (how could i ever doubted that :smilewink:).

 

And as a reply on youre edit i can say that it does shows as indicated airspeed in the aircraft on the airspeed indicator (needle about halfway between 50 and 100 Kts ).

 

CDU knows current wind (only during flight) by comparing groundspeed and Track with Aircraft heading and True Airspeed.

When the aircraft is on the ground the CDU can not calculate wind.

 

Greetz.

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update: I tried your method but CDU always puts a degree less to bearings. Is this normal?

 

I used weaps training mission and you can try punching 333 degrees with 10 kts at surface layer it is turned to 332 @ 10 kts on CDU. Please advise.

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update: I tried your method but CDU always puts a degree less to bearings. Is this normal?

 

I used weaps training mission and you can try punching 333 degrees with 10 kts at surface layer it is turned to 332 @ 10 kts on CDU. Please advise.

 

Unless you have your own layers entered, the CDU is constantly using the currently measured wind at your altitude to correct the weapons.

 

If you only have one layer entered, the CDU will blend this entry with the actual measurements at your current altitude.

This is probably why you're seeing a slightly different value.

 

Often it is enough to enter only the bottom layers that the bombs will fall through, relying on the aircraft's measurements for the drop altitude.

 

If I don't have any wind info on the mission, I usually read the wind values off the CDU as I climb out. If you're entering these as you go, make sure the wind correction is set to NONE, to make sure you're getting the aircraft's readings, not the one's you've manually corrected for. And then of course, once you have all your layers punched in, remember to set it back to WIND or BOTH, to make sure your changes are taken into account.


Edited by Boris
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