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Old 08-10-2018, 11:41 AM   #21
corvinus
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Thanks for your reply, excellent suggestions!


Quote:
Originally Posted by Jenrick View Post
So radar bombing in the Viggen is a bit of black art.

A couple things that can be issues:

1) The radar refresh/raster sweep rate leads to having to guess when the target is "exactly" under the radar bombing cross. The higher or faster you're moving the more this will effect your final bomb strike location.
This is a good point, I'm flying about 280 m/s, and the update time is a bit less than a second. So if your radar image is 1.0 s old you are 280 m too late. The error I'm getting is in the order of 800 m, which cannot fully be explained by latency issues like this.


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Originally Posted by Jenrick View Post
2) Radar resolution, it's not super high like you might find in say the F-15E or the F-18, you are trying to put the terrain feature or the target blob under the center of the radar bombing cross. Radar bombing is only as accurate as the radar can generate a location or offset.
In the 15 km setting the pulse length is 0.5 microseconds. If the radar does not use pulse compression that would set the range resolution to about 75 m. If the radar does use pulse compression (I'm not sure if that was common in that era) then the radar resolution would be even better. So one can safely say that the range resolution is better than 75 m.

Now if you add the two errors the maximum error is about 350 m, which is significant if you want to hit a ship.



Quote:
Originally Posted by Jenrick View Post
3) Wind this may or may not be an issue in your mission, but it certainly is one real world.

So I found through trial and error, you are having to basically guess when to release due to the sweep rate; the higher and faster, the bigger the chance of error. I've gotten to where I can hit most terrain features with a stick of bombs, or a building complex. I can USUALLY managed to get a hit on a stationary ship, but that's in good weather.

Did you also try this with the latest openbeta update? I'm asking because if I use the B-scope, the 3 km line in the B-scope seems way off. Therefore I am also a bit suspicious of the placement of the 3 km in the PPI. I think it was correct before the update, but I'm not sure.
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Old 08-10-2018, 11:43 AM   #22
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Quote:
Originally Posted by Sharkh View Post
Anyway it seems it works for me every time I press release at 3km with a speed 0.80+mach at 400m from the ground.

Sorry to get back at this point, but it is not clear if you use the PPI or the distance indicator gauge (top-right front panel) to determine if you are at 3 km distance.
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Old 08-10-2018, 12:59 PM   #23
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The way I interpreted the RL manual is that the 3km cross is used to mark the target for bombing and then you follow the directions on the HUD as you would with a normal NAV-bombing. This is how it is implemented in DCS. No automatic measurements or something as implied above, it’s just up to the pilot to figure out if the cross is on the target and the computer more or less just handles the count-down to release. Real-life Viggen pilots mentioned that you could see individual buildings in the size-range of the Globen in Stockholm and ships contrasted to the sea but not much else hence I don’t think this mode was very useful.

Please note that the next release of Viggen (likely OpenBeta on Wednesday) will include improvements to the accuracy of the bombing. Most important change I think is that I implemented a “catching-up”
logic in the release interval where if the computer detects it is releasing long it will release more bombs at once so at least the final bombs will have correct ground interval (so 8 bombs before the target and 8 bombs after even if the first bombs start releasing long). It will not be able to compensate perfectly depending on how quickly the pilot changes attitude etc but tries to do its best to predict fast changes in altitude etc.
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Old 08-10-2018, 01:11 PM   #24
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Quote:
Originally Posted by RagnarDa View Post
The way I interpreted the RL manual is that the 3km cross is used to mark the target for bombing and then you follow the directions on the HUD as you would with a normal NAV-bombing. This is how it is implemented in DCS. No automatic measurements or something as implied above, it’s just up to the pilot to figure out if the cross is on the target and the computer more or less just handles the count-down to release.

This is how I understood it from the manual. Imho the 3 km cross does not correspond to 3 km, I checked this by placing a waypoint. The distance indicator gauge indicates 3 km before the 3 km distance line in the PPI is over the waypoint.



What do you make of the screenshot below? The plane is at 3 km distance from the waypoint, but the PPI 3 km distance line is not at the waypoint. Doesn't that mean that the PPI distance line is not placed correctly? Note that this is after a few minutes of flying, so I don't think INS drift is an issue here.



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Old 08-10-2018, 02:24 PM   #25
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Yes it does look like the cross is misplaced. Thanks for the report!
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Old 08-10-2018, 02:42 PM   #26
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I have tested the mission and RR further and now I think I was right that this release mode is semiauto.

I have played the mission 3 times same speed same altitude, same time pressing release etc. so everything the same. Except I set different QFEs

1st test run - I set the accurate QFE of the target waypoint I set my speed to 8.4 mach and pressed release at right after the waypoint distance instrument went below 3km. It was a perfect hit.

2nd test run- I have done everything the same except QFE set to higher(wrong QFE) so the settings was higher and the computer expected we are on a higher altitude from the ground and guess what happened the bombs fall short and it felt the release happened sooner.

3rd test run - I have set the QFE lower(wrong QFE) so the computer expected we are on lower altitudes than in reality than the bombs fall long and it felt the release happened later.

So if the release button press was done at the same time with same speed same alt and the release happened the same time (so manual release) than this could only happen if the bombs would have some computer guided surface to make them fly differently (as far as I know these are simple bombs so they don't have anything like that) or it happened because the release time was controlled by the computer.


Than I have tried all of this(3 test above) on lower speed (0.7mach) also and the result was the same why I felt also that the computer also try to calculate the lower speed so every release happened a bit later. So I am pretty sure the release is semiauto .


After I practiced this a lot by now I think that its the most accurate while going above 0.8 mach with a very precise QFE set and release pressed at about 2.8km from the target waypoint(waypoint distance instrument )


Ahh and I also realized you don't have to enter any code (I guess the 251 is set as default in DCS so it doesn't have be entered)
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Last edited by Sharkh; 08-10-2018 at 02:44 PM.
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Old 08-10-2018, 02:42 PM   #27
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Quote:
Originally Posted by RagnarDa View Post
Yes it does look like the cross is misplaced. Thanks for the report!

You're welcome!
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Old 08-10-2018, 02:46 PM   #28
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Quote:
Originally Posted by Sharkh View Post
I have tested the mission and RR further and now I think I was right that this release mode is semiauto.

I have played the mission 3 times same speed same altitude, same time pressing release etc. so everything the same. Except I set different QFEs

1st test run - I set the accurate QFE of the target waypoint I set my speed to 8.4 mach and pressed release at right after the waypoint distance instrument went below 3km. It was a perfect hit.
I see, remember the RR modes has two submodes: radar release and nav release. If you time your trigger moment on the distance indicator gauge you are essentially doing a nav release kind of thing. This also works for me. Try to remove the waypoint and see if you can hit the target ;-)

Without a waypoint you have to use the PPI only (no distance indicator guage to help you). As the 3 km indicator on the PPI is a bit misplaced, the bombs fall long.
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Old 08-10-2018, 02:48 PM   #29
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Quote:
Originally Posted by RagnarDa View Post
Yes it does look like the cross is misplaced. Thanks for the report!
Thanks for the replies . Its a bit more clear now how it should work.
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Old 08-10-2018, 02:54 PM   #30
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Quote:
Originally Posted by corvinus View Post
I see, remember the RR modes has two submodes: radar release and nav release. If you time your trigger moment on the distance indicator gauge you are essentially doing a nav release kind of thing. This also works for me. Try to remove the waypoint and see if you can hit the target ;-)

Without a waypoint you have to use the PPI only (no distance indicator guage to help you). As the 3 km indicator on the PPI is a bit misplaced, the bombs fall long.
But now we know why thanks to the official reply. Sorry I haven't tried navigation bombing before nor this so I had no idea that its the same. I just found away to hit the targets in your track. but even if its misplaced we could be able to adapt and find out which position is the 3km using the PPI. I guess this mode is there to correct small navigation errors than.

Edit: so I have tested and talked about Nav bombing the entire time everybody here seems familiar with . Now I feel dumb.
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Last edited by Sharkh; 08-10-2018 at 03:23 PM.
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