Sight depression calculation with Bombing table for Laydown is incorrect?

[Aernov]

If I recall correctly, in Laydown mode you can use properly depressed sight to determine the moment to start holding Pickle since the sight mark would be on target at the moment of IP overflight. But in my attempts to utilize this method, I encountered a seemingly consistent issue - sight depression, as calculated by in-game Bombing table, is too big, resulting in sight mark being off-target (marking position significantly closer to the plane), so if the mark-on-target method is used to initiate release (instead of normal IP overflight), bombs will fall long (as far behind the target as the mark was before it at the IP). I tried Mk82 LD, Snakeeyes in HD mode, M117 and Mk84 LD, altitudes from 500 ft to 10000 ft, all at 450 KTAS, and the results were the same: depressed sight mark was lower than it should have been to be over the target at the moment of IP overflight. Attached are two tracks with Mk82 slick (3000 ft, 4nm IP-TGT) and Snakeeyes (500 ft, 1 nm IP-TGT). Also, some screenshots with sight mark position relative to the target at the moment of IP overflight.

1) F-4E L Mk82.trk Bombing table setup for this track:

Sight mark at IP:

Result after aiming with sight:

2) F-4E L Mk82 Snakeeye.trk Setup for the track:

Sight at IP:

Impact:

If IP overflight is used to initiate release, bombs fall on target, so the error here is in the sight depression.

[Zabuzard]

Thanks for the details. Try with the aircraft weight set to 0.

Afaik in Laydown the sight is horizon stabilized (by the INS) and hence the AoA correction isnt needed.

This is an already reported oversight, cheers.

[Aernov]

Sight seems to be stabilized judging by the reticle behavior. I'll try zero weight, thanks.

[Aernov]

Just tried setting zero aircraft weight in bombing table, resulting sight depression makes it so the bombs fall way short of target.  Screenshot shows reticle position while overflying IP.

So, with zero weight depression is too low. I tried setting the correct depression manually while sitting in an active pause over the IP (by adjusting sight depression until the reticle is over the target), for this case (Mk 82, 450 KTAS, 3000 Ft, 4 nm IP-TGT) the setting was 119-120 mils. Then I tried to enter total aircraft weight that will result in 119 mils calculated depression, it was around 27000-27900 lbs.

Edit: 118 mils results in this:

Slightly short (no release advance was set), but pretty close for this release mode.

Edited August 10 by Aernov

[Zabuzard]

(Careful with active pause. In many cases people use it in a way that gives totally incorrect results because the aircraft isnt unloaded first. The pipper needs to be stabilized naturally on the target, no G load or heavy stick movement, else the AoA is all over during active pause.)

[Aernov]

Yeah, I've heard that active pause messes some things up for different modules. I used it once to manually place the pipper over the target and write down the mils. All actual test bombing runs were done without active pause, and the "normal" pause was used only to take screenshots of sight and F10 map at the same moment of IP overflight. So, the results above are unaffected by active pause.

[Sandman1330]

Can someone tell me what I'm doing wrong here? I'm consistently hitting long. I'm flying the numbers (TAS of course). I'm probably just missing something small but I consistently end up hitting long. Track attached.

 

laydown.trk

[BJ55]

Probably nothing, I was never able to hit a target with L / DL mode, now I only use direct mode with my own bombing tables.

Edit: the track doesn't display the bombing calculator parameters, so it's difficult to see if you're following the profile, also in your track the 82SE are hitting short, had the same issue while trying to report my findings...

P.S.: for the first time I've had perfect results with 3 releases of Mk-20, 450TAS, tgt at 200ft, release alt. 750ft, distance 1 or 2 nm (don't remember), depression 100. Will try with 82's later...

Edited Sunday at 04:22 PM by BJ55

[BJ55]

Did some tests in Nevada with Mk-82, Mk-82SE HD and Mk-20, 50% fuel, 29.92, no wind, accuracy seems good:

Since I've had the same results at 100ft MSL it's not a target high elevation issue... Have you tried with different speed/altitude parameters?

Edit- be aware that "target range" must be bigger than "release range", look at the pic below:

1- TR > RR (ex. 120 mil), you hold the bombs release button when the pipper is above the targer, it takes the time to travel from TR to RR for the bombs to be released.

2- TR = RR (ex. 130 mil), you hold the release button, in this case the time to travel from TR to RR is zero, so bombs are released at button press.

3 TR < RR (ex. 150 mil), you hold the release button, in this case the time to travel from TR to RR is "negative" (impossible without flux capacitor mod), bombs are released at button press, but the impact has an offset = RR - TR.

With Laydown I set the TR distance in order to obtain a 80-110 mil sight depression, otherwise I use Direct mode.

Edited Monday at 10:01 PM by BJ55

[Sandman1330]

Doing more testing, I tried manually choosing my IP using a distinctive ground feature, then depressing the pickle button over that feature rather than when the sight was over the target. It was a shack - perfect hit. But the sight was still well short of the target when I was over the IP, consistent with my bombs always landing long. When I use the sight to identify the IP the bombs always seem to release when over the target rather than ahead of it, so they’re always long. Manual IP worked perfectly.

This was of course after calculating the distance from IP to target, inputting the info into the bombing table, and setting the sight depression to the correct mils setting. I flew it a bit higher (500agl) in order to get a more defined sight picture. Coming in low it can be tough to know exactly when the sight is over the target.

I have done all my testing so far with snakes, which I note @BJ55 you didn’t test with. Maybe there’s an error in the bombing table sight depression calculation for snakes? The data input by jester was all correct as indicated by my successful attack from a defined IP. It seems to be an issue with the sight - either I’m doing something wrong or there’s a calculation error.

 

[BJ55]

5 hours ago, Sandman1330 said:

...snakes...you didn’t test with...

"Did some tests in Nevada with Mk-82, Mk-82SE HD and Mk-20"

I've recreated your bombing profile, test at 6000ft / 0.98nm, 130mil:

test at 1.3nm, 99mil:

Reticle depression is accurate, screenshot took when pipper over target:

When I had the RTX 3070 laydown never worked, now with the RX laydown is almost perfect... It's a mistery.

f-4_nevada_laydown.miz

Edited 12 hours ago by BJ55

[Sandman1330]

3 hours ago, BJ55 said:

"Did some tests in Nevada with Mk-82, Mk-82SE HD and Mk-20"

I've recreated your bombing profile, test at 6000ft / 0.98nm, 130mil:

test at 1.3nm, 99mil:

Reticle depression is accurate, screenshot took when pipper over target:

When I had the RTX 3070 laydown never worked, now with the RX laydown is almost perfect... It's a mistery.

f-4_nevada_laydown.miz 14.32 kB · 0 downloads

Sorry,  I took that for 82air - skimming on a tiny phone screen is always dangerous!

Strange that a video card would make the difference… I’m assuming you watched my track and didn’t identify anything I might be doing incorrectly? I also tried in caucuses and had the same results.