Laydown CBU-87 falling long

[BJ55]

Today I was testing the CBU-87 in L mode, all fell long after the target, I've also tried with 0 release advance and was the same. Release speed (450) and height (2000) was not precise, but in DL mode bombs hit the target. Am I doin' something wrong? Is it a bug?

F-4E_laydown_sinai.trk

[MagicSlave]

If I understand correctly, you need to be on planned ground speed, altitude above target and 0 pitch, since the WRCS doesn't provide any corrections based on your actual speed, altitude or pitch angle

Sent from my FP4 using Tapatalk

[Zabuzard]

Right. I would be careful with CBUs currently though, as our Bombing Tool does not consider the fact that the container opens at a certain height yet. Instead, it is treated as if it would fall like a ballistic bomb all the way down from release to impact on the ground.

Although that should usually result rather in everything falling too short, as the container opens mid-flight, leading to the bomblets all falling down before the target.

(This is of course something we will address eventually. In the meantime you probably would have to add the release altitude of the bomb fuze to the target altitude to get usable values. I haven't tested this a lot yet.)

Ive seen a detailed report regarding CBU and Laydown with similar results before already though. Its possible that there is a bug here, probably in the Bombing Tool, given that it works just fine with some of the other standard bombs.

[BJ55]

Did some more tests...

01 L CBU-87: 450TAS (indicated +-5), run in 2000 (+-100 AGL), IP 4nm, TA 0, 91 mil - bombs released when target was aligned the center of the radar display, hit after target.

02 L CBU-87: 450TAS (indicated +-5), run in 1500 (+-100 AGL), IP 3nm, TA 0, 89 mil - bombs released when target was aligned the center of the radar display, hit after target.

03 L CBU-87: 450TAS (indicated +-5), run in 1500 (+-100 AGL), IP 1nm, TA 900 (fuze), 39 mil - dropped at button press, hit before target.

04 L CBU-87: 450TAS (indicated 453), run in 2000 (+50 AGL), IP 3nm, TA 0, 119 mil - hit after target.

05 Direct CBU-87: 450TAS (indicated +-5), RA 2000 (+-100 AGL), TA 0, DA 20°, 118 mil - on target.

06 L MK-20: 450TAS (indicated +-5), run in 1000 (+-50 AGL), IP 2nm, TA 0, 91 mil - on target.

 

Then I thought, what if Jesta is missing something? Aaand yes, drag coefficient remains unchanged (1.02) for every bomb type.

Edited September 3, 2024 by BJ55

[Zabuzard]

1 hour ago, BJ55 said:

Then I thought, what if Jesta is missing something? Aaand yes, drag coefficient remains unchanged (1.02) for every bomb type.

The drag coefficient is only used in DT and TGT FIND modes. All other modes release based on the range or counters that you have to enter. For Laydown, release happens after you travelled the entered RELEASE RANGE value (measured using the INS ground speed).

How are you designating the target/the IP?

Are you pressing bomb button when you are visually over your desired IP? Or when the depressed sight lines up with the target? If latter, perhaps the issue is in the sight depression computation.

Edited September 3, 2024 by Zabuzard

[HB_Painter]

Hey so first of all thanks for the track. The Drag Coefficient is not used in conjunction with Laydown. Thus can be ignored here. What I noticed was that in the track the bombs opened directly and did not fall any distance. Could you maybe provide some other track for double checking? Thanks in advance

 

[BJ55]

@HB_PainterEdit: added track and mission.

@Zabuzard I depress the button when aim dot is on TGT and speed/alt/att/dist are within parameters, also I check both altimeters:

What I've noticed is that with the bombing calculator in L mode speed and bomb type don't affect mils, so if I fly at 400TAS I hit the target, any other speed is a miss.

Edit2: I also change fuze settings, usually with the CBU-87 I set 1200 for >2000AGL and 900 for <1500AGL, that could also be part of the problem, since bombing calculator don't have an airburst altitude field.

(btw: lower hbui refresh rate had a huge impact on performance, now I can run at 8x simulation rate without big stutters, thanks a lot!)

F-4E_laydown_sinai2.miz F-4E_laydown_sinai2.trk

Edited September 3, 2024 by BJ55
added files

[MagicSlave]

@HB_PainterEdit: added track and mission.
@Zabuzard I depress the button when aim dot is on TGT and speed/alt/att/dist are within parameters, also I check both altimeters:

What I've noticed is that with the bombing calculator in L mode speed and bomb type don't affect mils, so if I fly at 400TAS I hit the target, any other speed is a miss.

Edit2: I also change fuze settings, usually with the CBU-87 I set 1200 for >2000AGL and 900 for <1500AGL, that could also be part of the problem, since bombing calculator don't have an airburst altitude field.
(btw: lower hbui refresh rate had a huge impact on performance, now I can run at 8x simulation rate without big stutters, thanks a lot!)
F-4E_laydown_sinai2.miz F-4E_laydown_sinai2.trk

That is because the mils setting depends only on run in height and IP to TGT distance. The release range changes depending on the run in speed, as is shown on your screenshots.

You tell the WRCS your run in altitude and distance from IP to target. WRCS tells you the mils setting so that the pipper reaches the target when you are at the IP. You tell the WRCS when you are above IP by pressing and holding the pickle button and it then waits x amount of time before releasing, when it calculates that you have reached the release range, based on time and speed.

Hope that this makes sense. The WRCS is not measuring your actual height, speed or distance, it assumes that you fly the numbers you pre planned

(I hope I have this right, correct me if I'm wrong)

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[BJ55]

Yep, right! Today I'm a little confused...  So only remains the fuze settings, I will try with the default 1500.

[BJ55]

Tested all possible combinations, this time with max fuze delay so only HoF is used, always the same result.  The CBU's ripple is problematic with other aircrafts too, only the A-10 seem unafected.

[BJ55]

Found: automatic entries in AC weight with the reload button don't affect mils depression value, only manual input of AC weight is effective.

But still can't explain why at low altitude (TGT 200ft) with default fuze settings it's always a miss, while in Nevada (TGT 4500ft)...

Wrong AoA value in the calculator because of unpredicted CG shift and air density?

[BJ55]

@Zabuzard: did you had some spare time to check if the weight reload button has the correct behaviour?
Another question: why the bombing calculator in DL mode has the sight depression value? It must have the same layout of DT mode, since  the target is designated by using the radar. (release in DL seems really bugged)
Thanks.

[Aero4000]

Based on my practice, CBU and Hi Drag bombs do not have good accuracy now. The most accurate are conventional MK82 in DT mode. I note that the Lay down modes are designed for low-altitude bombing. At low altitude precision L and DL are really better. When use L mode I recommend to pick up such a distance of IP, where the depression of the sight turns 120 and more mil in order to reduce trigonometric errors.

[Stickler]

On 9/17/2024 at 10:43 AM, BJ55 said:

Found: automatic entries in AC weight with the reload button don't affect mils depression value, only manual input of AC weight is effective.

For Laydown, the aircraft's weight should not affect the sight setting at all since the reticle image is pitch stabilized with reference to the horizontal plane of the inertial platform. AoA, which is dependent on the aircraft's weight, therefore has no effect on the correct sight setting. This is correctly implemented in the game but incorrectly implemented in the bombing calculator.

Edited December 1, 2024 by Stickler

[BJ55]

Could you try the attached missions? I keep on having the same .....y results in L/DL modes.

To hit the column I have to set 80-81 mils instead of 91, forgot to take note of the difference at 450kts 500ft 1nm.

Don't know if ED changed something lately, but also the F1 bombing tables must be redone.

F-4_ag_train_cauc_82.miz F-4_ag_train_cauc_82SE.miz

[Aero4000]

1 час назад, BJ55 сказал:

Could you try the attached missions? I keep on having the same .....y results in L/DL modes.

To hit the column I have to set 80-81 mils instead of 91, forgot to take note of the difference at 450kts 500ft 1nm.

Don't know if ED changed something lately, but also the F1 bombing tables must be redone.

F-4_ag_train_cauc_82.miz 14.15 \u043a\u0411 · 3 загрузки F-4_ag_train_cauc_82SE.miz 14.3 \u043a\u0411 · 0 загрузок

Just use short IP to Target distances to get large sight depression. For example, 1 NM and 173-174 calculated mil. Lift up the chair and go! This way there is less aiming error and WRCS are less likely to make incorrect bomb release delay calculation )). I have completed 2 successful attempts with 13/14 destroyed targets.

Спойлер

 

Edited December 5, 2024 by Aero4000

[BJ55]

Doing that way it works, but with that ammount of mils the delay is near to zero, like in direct mode (2° dive -> 160 mil), and at the moment DL is useless. At least now I know that it's not a "pilot error".

[Aero4000]

1 час назад, BJ55 сказал:

Doing that way it works, but with that ammount of mils the delay is near to zero, like in direct mode (2° dive -> 160 mil), and at the moment DL is useless. At least now I know that it's not a "pilot error".

Exactly.

But DL works for me with the same Bomb Calc inputs. Bombs falling a little short.

In general, the calculator or the WRCS is not working correctly yet. We can only play with what we have.

The latest patch has changed some calculator data entry fields, but bombs are falling as before.

[BJ55]

This is realism: pilots have to deal with gremlins of all kinds.

[Mike_CK]

On 9/2/2024 at 4:01 PM, Zabuzard said:

Right. I would be careful with CBUs currently though, as our Bombing Tool does not consider the fact that the container opens at a certain height yet. Instead, it is treated as if it would fall like a ballistic bomb all the way down from release to impact on the ground.

Although that should usually result rather in everything falling too short, as the container opens mid-flight, leading to the bomblets all falling down before the target.

(This is of course something we will address eventually. In the meantime you probably would have to add the release altitude of the bomb fuze to the target altitude to get usable values. I haven't tested this a lot yet.)

Ive seen a detailed report regarding CBU and Laydown with similar results before already though. Its possible that there is a bug here, probably in the Bombing Tool, given that it works just fine with some of the other standard bombs.




 

Ahhhh. That’s why my CBUs fall short; unless I drop on a steeper decline and low level