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RR-mode bombing - accuracy?


animaal

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How accurate should radar bombing (RR mode) be in the Viggen? I'm having accuracy issues, and I'm not sure whether the issue is my lack of skill or my lofty ambition.

 

I've set up 16 vehicles in a square, on the 'X'-shaped Kobuleti airstrip (see red square in image). The Viggen is fully loaded with low-drag bombs in "series" mode.

 

 

attachment.php?attachmentid=192204&stc=1&d=1534502098

 

Flying head-down, instruments only at night, I can pick up the vehicles as a small return on my radar. I line it up so it looks centred when the radar range is 15km.

 

I quite often get the range about right, but I'm nearly always to the left or right of the targets. Not by a lot, but often there's a runway-width between the vehicles and where the bombs land.

 

Am I pushing the Viggen too far? Or is this something that should be achievable?

Kobuleti.PNG.fd3b54fb0de0589a5418ff5dd83b5274.PNG

Sinclair ZX Spectrum 48K, Kempston joystick Interface, Alba Cassette Recorder, Quickshot II Turbo Joystick

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Radar bombing is as precise as you can lock in your offset point. In the Viggen that's governed by the resolution of the radar display and the size of the radar cursor (and that's not even getting into any systems limitations). So at 5km, whatever the combined error between those two is going to be minimum you can hope for, assuming everything is perfect.

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Azimuth beamwidth of the radar is about 1.8o. At 5 km that leads to a resolution in cross range (perp to your path) of about 160 m. At least this is the rough estimate of the resolution. Being a runway width off, does not sound so bad.

 

In this thread there are more ramblings about RR mode:

https://forums.eagle.ru/showthread.php?t=217707

 

These are mostly about the range error. If you use a waypoint all is fine (technically this is NAV bombing), but if you rely solely on the radar 3 km distance line then, in open beta, you will find that this distance is not placed correctly:

https://forums.eagle.ru/showpost.php?p=3592944&postcount=24

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Thanks. I had thought there was a range issue, and I was altering the release point to compensate.

 

 

 

Reading the two posts above, and the linked thread, it looks like even in real life RR mode is more of a "last resort", and accuracy could be difficult.

Sinclair ZX Spectrum 48K, Kempston joystick Interface, Alba Cassette Recorder, Quickshot II Turbo Joystick

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Radar bombing evolved over the years from WW2. It started out as a backup from when visual bombing wasn't an option, and you were aiming for factory complexes. Precision wasn't great, but it wasn't needed as much either. Then there was the transition to the bombing mission using weapons who's blast radius made a couple hundred meters of error a non-issue. After a period of time, it was realized that conventional bombing was still a thing, and needed to be much more precise than when using nukes.

 

A cold war era bomber, usually used a combination of old school bombardier skills and knowledge combined with some high tech help. The F-4 for a lot of it's cold war career, used the radar for bombing as a real time moving map just like it was in WW2 and Korea. Use your altitude and air speed to figure out your release distance (or fly a planned delivery profile), find the target area based on the radar return, and using a combination of scope markings, calibrated eyeball, and maybe stopwatch, hit the pickle button. For dedicated bombers, radar bombing during that era, was based on using radar fixes to get a pretty good idea of where your own A/C was to be able to accurately figure your bombing solution. The radar was also used to figure out a best guess of where the target was. Dedicated bombers like the B-52 had a lot of automation and sophistication compared to lighter strike AC. With more sophisticated radar options and fixed targets, you'd fly your delivery profile, and use the radar to generate your position fixes to determine that when you're X degrees and NM away from point Y you drop. Even better was using 2 or three simultaneous nav fixes to be REALLY sure you were where you thought you were. We can all imagine what a target that's not where it's supposed to be does to this approach.

 

A little later you could start to punch in where you where, and where you wanted to drop the bombs into the bombing computer and it would spit out a best guess bombing solution, that was then tweaked by the crew. Overall the radar basically served as a navigation instrument, and the bombing part was still on the crew to know when to pickle.

 

The next big change was allowing the radar to talk to the INS to start automating a lot of the work of figuring out where your A/C was, and where the target was. Now we're moving into the A-6 and F-111. You would have specific radar offset points that you'd find and mark with the radar to update where it thought it was (does this start to sound familiar?), and you'd have a target area you're looking for that you'd mark the specific intended point of aim. The computer would do the work for you on calculating the bombing solution, now all you had to do was fly to the right point on the right flight path.

 

Again radar resolution, cursor resolution, etc all contributed to inaccuracy, not even counting things like real bombs don't separate perfectly cleanly, aren't perfectly cylindrical, fins aren't mounted perfectly straight, wind gusts, etc. In the later days of the cold war radar bombing (in no vis conditions) by a dedicate strike AC, was in general about as accurate on a fixed target as visual level bombing was by the same AC. So 50-100m CEP was a good day. Later systems like the Angle Rate Bombing System, shrunk this figure down a lot for visual bombing, and improvements in radar imagery and automation kept pace on the radar bombing side as well.

 

In the Viggen Nav mode bombing with an update to the target waypoint is closer to how most US radar bombing worked. The computer wants to know: where am I and where am I trying to drop bombs. Give it those to pieces and it works reasonably well. The RR mode is more like early Vietnam where the ground radar was used along with a stop watch, calibrated eyeball, and a chart to figure out when to drop. The RR mode automates a lot of the things the F-4 crew would be doing, but it's still going to have some fundamental inaccuracies, you just have to accept when you don't have anything better.

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