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CDU Wind correction done right


Boris

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Do you have a link?

 

I mean, there were several lengthy threads about this topic. What I took from them was, a) the topic es really complex and "I entered the wind and it still missed!!1" does not mean much. There are many more variables that come into play when it comes to dumb bomb delivery. And b) maybe just because of a) there were no real errors with CDU wind correction as such reported. It always came down to either wrong delivery technique or just wrong expectations.

 

Hi Flagrum,

 

i think it was this Thread https://forums.eagle.ru/showthread.php?t=146465

I have tested it today, MK82' from different Alt, angle and direction, calculated with that tool https://www.digitalcombatsimulator.com/de/files/683972/

Active pause on every pickle,

the solution with Wind and Temp (BOTH), was every time way of the Impact Point. But the calculated solution without windcorrection (NONE) was every time correct.

20170120213752_1.thumb.jpg.7635b2fe4971b1ac1b78c5a3c248d95d.jpg

20170120213807_1.thumb.jpg.de92b1c4c8a66caf4614e4fb8e08d80e.jpg


Edited by Jafferson
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Awesome! Tested it in Nevada with light winds in the column and result was a near-perfect hit with GP LD MK82's from 10.000 ft (ISA) close to Tonopah AB. I used my own spreadsheet with RL conversion parameters, but round-off errors will give about the same values as with simple math aids... +1 for first post!

 

Tip: better not expect GP bombs to be accurate from high alt... that is why we have low level popup deliveries :) or any low level delivery for that matter!

 

Cheers, Scub


Edited by Scuby

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LASTE understands wind even if you don't enter anything manually. The true test if manual atmo entry is to set values and notice a difference compared to no numbers.

 

I'll believe manual atmo info has an effect if they show that really bad numbers make the solution noticeably different/worse than hands off.

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LASTE understands wind even if you don't enter anything manually. The true test if manual atmo entry is to set values and notice a difference compared to no numbers.

 

I'll believe manual atmo info has an effect if they show that really bad numbers make the solution noticeably different/worse than hands off.

 

 

It did. On several occasions the atmo info entered was for weather at HP and not for TGT. Result was bomb impact was way way way off intended impact point.

I think it is not realistic updating the atmo when above the TGT, I mean there is risk involved in trying to do that. Also, I think I found that setting LASTE WIND mode set to NONE does not work either! If so, perhaps best not to enter anything in LASTE WIND page ever, like you mentioned...


Edited by Scuby

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"NONE" should use no manual data entry which is the same as doing no action. The WIND, TEMP, BOTH, NONE is asking what manually-entered data should be used. Other data comes from other sources.

 

OK, test and wind/none definitely changes solution. Temperature doesn't seem to.

 

I set up situation

500 42m/s 276

2km 42m/s 276

8km 0 m/s 276

 

Discovered by INU flight

00 089/66 +19

04 089/82 +12

08 089/82 +04

12 089/80 -04

16 089/53 -12

20 089/10 -20

24 089/00 -28

 

Test with 00 entered as wind or no entry: slight downwind impact which makes perfect sense.

 

Test with winds entered as above, huuuuuuuuge upwind impact like wind effect on aiming is very exaggerated compared to effect on actual trajectory.

 

Try again with winds set at 1/4 value (80 knots = 20 knots): still upwind but much more accurate, perhaps an error in delivery. Try again: OK still too much.

 

Try again but divide wind speeds entered to 1/10th. 80 knots becomes 8 knots, etc. Calculation is very good and bombs land neither left or right of target.

 

Conclusion: In this particular case LASTE wind manual entry does change delivery solution. With wind present and no assumed wind delivery is downwind. With wind present and wind accurately entered delivery is excessively upwind. With wind present and wind entered 1/10th of actual strength delivery is accurate.

 

Yet to test: Climb through all wind layers so LASTE can memorize the wind at all levels and see how accurate automatic memory mode is. Quantize test running along X or Z axis direction. Try different weapons other than BDU-33.

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Test2.

 

Target Z+00568815

Automatic flyover impacts 151, 170, 70m downwind avg. 130m.

 

Accurate LASTE manual entry, impacts 850m average upwind (2 bombs, ~50m between). Suggests reduce LASTE wind entry to 13% of real value.

 

With 13% wind value set bomb pair landed ~50m a part (44s TOF, 26kft) and target was between impacts.

 

ME

50m/s at .5 and 2km, 0m/s at 8km

 

Measured values

00 089/50

04 /98

08 /97

12 /96

15 /79

18 /35

22 083/03

26 180/00

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That 10/13% is a really nice find! So I understand it to be for all speeds... in that case, how would you enter the lower layers windspeed? (if original winds were low like 2 or 8 kts) Reduce those to 0 or 1?

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I am confused... Doesn't the CDU gather data automatically ? If you are at a AO how would you know what the specific weather values are ? Except maybe at a target range ?

 

If you get a CAS call, how would you know what are the specific wind values over that particular area ?

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'Shadow'

 

Everybody gotta be offended and take it personally now-a-days

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...how would you know what are the specific wind values over that particular area ?

 

Making a show of force pass help the airplane to understand what needs.

However, the plane is not stupid and uses the standard vertical wind model, which means that the wind drops in intensity and turns in x degrees every 1000ft or something similar.

So, let the plane do the work.

 

If you set a standard fixed weather (not the dynamic) you can disregard the problem because your airplane know well (data acquired during takeoff) every single location of your map.


Edited by Gruw
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That 10/13% is a really nice find! So I understand it to be for all speeds... in that case, how would you enter the lower layers windspeed? (if original winds were low like 2 or 8 kts) Reduce those to 0 or 1?

Yes, I divided and rounded in this particular case. It was what I found for that particular wind profile, weapon, speed, height etc. In no way should it be relied upon as universal.

 

What I'm not sure of is how this will compare to more reasonable situations. I wanted the most exaggerated and simpleminded scenario.

 

I am confused... Doesn't the CDU gather data automatically ? If you are at a AO how would you know what the specific weather values are ? Except maybe at a target range ?

 

If you get a CAS call, how would you know what are the specific wind values over that particular area ?

The airplane already solves for wind at altitude by comparing the local data with the motion of the INU platform through space. Then it models that downward. This usually produces a good prediction.

 

I've heard but haven't tested that the airplane also remembers the atmospheric details as it passes those layers in the climb. I don't know if I believe that because how is it choosing between climb memory and downward modeling? Stranger things have made their way into combat airplanes though.

 

If that's true in DCS it's simple enough to test: a start-at-height and a climb-to-height bombing run with no manual LASTE info (in my crazy wind gallery) would produce different bombing results. Start at height would have the bomb drift downwind because it was totally ignorant of the wind below itself and the climb to height would remember that there's some wind in the mid level to deal with.

 

Who would tell you manual wind data? Someone who knows. The weather planning cell or some controller on site or one of the many resources of the USAF. I guess you could find it out by the own resources of your flight (convoy protection type mission?). What I've heard is that it's rarely used. How often is the improved solution from manual info even noticeable?

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