investigating Bombing solution seems to use Barometric Altitude only

[ldnz]

In opt mode, a2g, in a dive with a good steady solution bombs appear to always fall short. In active pause, the only thing that appears to affect the indicated slant range is the altimeter setting, laser makes no difference.

It appears that radar altimeter and laser aren't being used for slant range calculation, only baro alt.

Unsure, but in previous mission in mountainous terrain I found a2g cannon with laser (I think, but altimeter would have been no use) to be pinpoint accurate, so possibly just not right with bombs.  

LastMissionTrack.trk

[AeriaGloria]

I have a feeling this has to do with the target altitude in DTC. I couldn’t understand the way Wags explained it exactly what this was changing, and it seemed to be for every waypoint 

[NineLine]

It's quite simple. For accurate ground attack, it helps for the aircraft to know the exact target altitude. If there is a difference in elevation of the aircraft altimeter and the target elevation, that can throw off calculations. The Target Point DTC function simply sets this elevation, just as Wags explained.

[ldnz]

Thanks, but which part of the calculation? Just density? Right now it appears only barometric altitude is used in the slant range calculation, not laser

[Esac_mirmidon]

And we should set barometric altitude to QFE or QNH for the Mig-29 regarding ground attack?

[AvroLanc]

18 minutes ago, Esac_mirmidon said:

And we should set barometric altitude to QFE or QNH for the Mig-29 regarding ground attack?

Set QNH for ground atttck presumably, otherwise there would be no need for setting a target point elevation. This also assumes that, by design, you must ensure the target is co-located as closely as possible with your current Waypoint. 
 

[IvanK]

5 hours ago, NineLine said:

It's quite simple. For accurate ground attack, it helps for the aircraft to know the exact target altitude. If there is a difference in elevation of the aircraft altimeter and the target elevation, that can throw off calculations. The Target Point DTC function simply sets this elevation, just as Wags explained.

But ....based on the limited documentation out there I believe IRL you cannot actually set a target elevation preflight into the INS/WCS. Though the DTC allows it and the DTC capability is being used to neatly simulate data entry by the ground crew on the ground , IRL there just isn't provision for any altitude entry into the system. Happy to be corrected here.

I guess if there is documentation that shows that Baro ranging can be used (and the methodogy) then that would settle the issue ... just haven't seen that in the Docs I can source. So to me the only ranging options are Laser or Radalt.

Though I guess changing the QNH to a dodgy value (aka target area QFE) might work ?? assuming baro ranging is even used 

Edited September 29 by IvanK

[AeriaGloria]

As far as I know, per combat employment manual, all slant ranging is done by either laser or radar altimeter elevation method ( like Mi-24) 

[IvanK]

Found this in the Alan R. Wise version of the manual Page 131:

"The input of ballistic data for the aerial bombs is carried out before flight from the monitor centre by the ground crew setting the wafer switches (coded input) to positions corresponding to the code of aerial bombs used. Depending on the conditions of combat use and the bombing mode, additional information about the target vertical separation relative to the departure airfield and the selected drop angle of aerial bombs in toss bombing is entered from the input monitor panel"

So my take on that is that certainly for toss bombing on a pre planned target the system knows the difference in height between the departure airfield and the pre planned target... a +- DeltaH. Now whether that has any input in the other bombing modes in OPT who knows. More info required as to exactly how this works.

Edited September 29 by IvanK

[ldnz]

Interesting, that makes sense for toss bombing

[IvanK]

11 hours ago, ldnz said:

Interesting

If you are using Baro alt  for your refrence.

[ldnz]

Could we please get some confirmation? In the current public build there is obvious huge barometric altitude input, and no evidence of using the laser when bombing. 

Is this intended (and can more information be given on how to deal with it), or a bug?

[Gierasimov]

Now, color me stupid but how do I get QNH / QFE for the target in DCS?

[razo+r]

23 minutes ago, Gierasimov said:

Now, color me stupid but how do I get QNH / QFE for the target in DCS?

QNH is in the briefing, QFE would either need to be calculated, or use someone who's flying a Viggen to put a waypoint on the target and let him tell you the QFE.

Or fly very low above the target and try to set your altimeter to 0 at the same time.

[Ornithopter]

QFE = QNH - (Target elev/30)

[TeddyThePilot]

In metric: 

1 mm Hg = 11 m,
so QFE = QNH - (T. elev/ 11 )

Or 

Спойлер

 

Edited October 8 by TeddyThePilot

[Gierasimov]

2 hours ago, razo+r said:

QNH is in the briefing, QFE would either need to be calculated, or use someone who's flying a Viggen to put a waypoint on the target and let him tell you the QFE.

Or fly very low above the target and try to set your altimeter to 0 at the same time.

LOL. Thanks 

1 hour ago, TeddyThePilot said:

In metric: 

1 mm Hg = 11 m,
so QFE = QNH - (T. elev/ 11 )

Or 

  Reveal hidden contents

 

 

2 hours ago, Ornithopter said:

QFE = QNH - (Target elev/30)

Thank you 

[UWBuRn]

So it is confirmed that for accurate bombing in OPT mode DTC target altitude and barometric altimeter reference should be set? Is this intended?

I made some testing with yesterday patch (2.9.21.16362) with the following attached missions (one with default pressure, the other with 780 mm-hg). My findings are that, even by using laser rangefinder, you can only aim accurately if:

• Target altitude is set correctly in the DTC
• Baro. alt. reference is set according to target QNH

Proabably you can achive the same by leaving target altitude at 0 and baro. alt. reference at target QFE, but havent tested it atm.

Of course, tihs is relevant if you fly with non-standard weather or if you aim targets on the cliffs. Bombing on standard weather at targets close to sea level you won't notice anything.

In the patch notes there's the entry:

Quote

• Fixed: Corrected self altitude based on the laser range.

Not sure how it should be intended, i was thinking that by using laser rangefinder the target altitude and baro alt reference would not be needed, but doesn't look like the case.

@BIGNEWY or @NineLine, can you clarify a bit about it?

I can post track files, if needed.

Thanks!

MiG-29A Bombing Clear.miz MiG-29A Bombing Pressure.miz

[BIGNEWY]

Hi UWBuRn 

could you include track replays so we can see what is happening, not the miz which is just the mission itself. 

 

thank you 

[ldnz]

Did a quick test and saw exactly the same as previous patch - bombs consistently 100ft short. No response indicating laser was doing anything (ie a2g gun with laser shows range jumping around a bit as you'd expect)

[UWBuRn]

Here's the tracks, no wind in all of them, laser always used:

1. Correct settings: bombs on target
2. Target altitude set in DTC, but no baro reference set (standard 760 instead of target QFE 780), bombs fall short
3. Target altitude not set in DTC, but baro reference set to target QFE 780, bombs fall long
4. Target altitude not set int DTC, no baro reference set (standard 760 instead of target QFE 780), bombs fall long (target altitude effect is greater than pressure diff)

Thanks.

1 - MiG-29A Bombing - Correct settings.trk 2 - MiG-29A Bombing - No alt set.trk 3 - MiG-29A Bombing - No TGT set.trk 4 - MiG-29A Bombing - No TGT-alt set.trk

[CrazyGman]

2 hours ago, ldnz said:

Did a quick test and saw exactly the same as previous patch - bombs consistently 100ft short. No response indicating laser was doing anything (ie a2g gun with laser shows range jumping around a bit as you'd expect)

Odd. I found exactly the opposite with bombs now falling pretty much directly on target. Before the patch I would have to have the piper pass over to get bombs on. Now as long as the laser A shaped symbol comes on on the left of the hud it's bang on. did it with multiple times in testing low drag dumb bombs FAB 250 and FAB 500. Both CCIP and CCRP last night 

Edited Thursday at 03:10 PM by CrazyGman

[Ornithopter]

1 hour ago, CrazyGman said:

Odd. I found exactly the opposite with bombs now falling pretty much directly on target. Before the patch I would have to have the piper pass over to get bombs on. Now as long as the laser A shaped symbol comes on on the left of the hud it's bang on. did it with multiple times in testing low drag dumb bombs FAB 250 and FAB 500. Both CCIP and CCRP last night 

I just did some bombing runs with FABs and was getting bullseyes, on a non-sealevel map.  It looks fixed to me.  I didn't even look at the DTC.

[UWBuRn]

@BIGNEWY, track are in the above post, sorry, i forgot to page quote you.

@CrazyGman, are you using english or russian cockpit? I'm guessing if this can be a factor? Personally i'm using english pit + metric units.

[Esac_mirmidon]

Im using Russian Cockpit + Metric system. Bombs spot on.

 

Worth a try, taking in count issues with VVI and Radar Altimeter for english Cockpit+ imperial metrics

Edited Friday at 08:58 AM by Esac_mirmidon