Question: GBU-24/B Paveway III

[twistking]

Hello,
can someone enlighten me on the logic behind the new GBU and it's FCS integration?! First of all, has the bomb data-connection to the aircraft, or is it just a "dumb" connection like on the other LGBs? I assume it has no data, since it can be carried on the inner stations. If it has no data connection, how does the bomb determine if it should do the loft-maneuvre, since it cannot get the distance to target from the laser track.
Also i do not really understand the logic behind the settings for range cue and dive angle. Why would you need to change these if the weapon would not receice these information anyway?
Can someone explain why these settings exist? Also would you lase the target directly after seperation? (As we know on the simpelr LGBs this is not recommended because it can lead to the bomb overcorrecting and loosing energy in the earlier stage of flight...)
Thanks.

[llOPPOTATOll]

1 hour ago, twistking said:

First of all, has the bomb data-connection to the aircraft, or is it just a "dumb" connection like on the other LGBs

Correct, no data connection

1 hour ago, twistking said:

Also i do not really understand the logic behind the settings for range cue and dive angle. 

Range cue is simply a marker to use, doesnt really specifically mean something, it can mean whatever you set it as. The setting you enter are just used for DLZ and calculations jet side, doesnt affect the bomb at all.

1 hour ago, twistking said:

Also would you lase the target directly after seperation?

you can, yes

Edited May 29, 2022 by llOPPOTATOll

[AvroLanc]

10 hours ago, twistking said:

Hello,
can someone enlighten me on the logic behind the new GBU and it's FCS integration?! First of all, has the bomb data-connection to the aircraft, or is it just a "dumb" connection like on the other LGBs? I assume it has no data, since it can be carried on the inner stations. If it has no data connection, how does the bomb determine if it should do the loft-maneuvre, since it cannot get the distance to target from the laser track.
Also i do not really understand the logic behind the settings for range cue and dive angle. Why would you need to change these if the weapon would not receice these information anyway?
Can someone explain why these settings exist? Also would you lase the target directly after seperation? (As we know on the simpelr LGBs this is not recommended because it can lead to the bomb overcorrecting and loosing energy in the earlier stage of flight...)
Thanks.

 

There are clearly lots of Paveway III details that ED simply doesn't have access to, which is a massive shame since they did once indicate that a new autopilot would be coming for PIII. Even Wag's video wasn't clear...is there a new flightpath model/autopilot implemented for PIII or is it just the same as Paveway II?? It's clear as mud at this point.

The Range Cue and Release angle settings do have some logic. The way I understand it, Paveway III is a very 'canned' weapon i.e. it's limited to fly in a very specific 'pre-planned' flightpath. It's very pre-planning intensive and the delivery has to be spot on in terms of Airspeed/Dive/Altitude to hit those pre-planned parameters. This is because the weapon has fixed non-flexible fuzing and when you use PIII you want the impact angle and fuzing etc to be planned spot on for the type (hardened!) of target you're going after. This is not a TOO CAS weapon. Therefore the Range Cue and Release angle setting's are there to pre-set a condition to release, they don't influence the actual bomb at all, they just make sure you're flying the pre-planned delivery.

Having said that, the gliding flightpath can be 'shaped' to achieve what you want by making a setting on the 'MODE' switch. On Paveway III, this is a physical switch on the bomb itself. Just like a PII's laser code. The 'MODE' setting knob has positions 1-8. I imagine these are the 8 gliding profiles or trajectory shaping modes. This detail is what ED lacks. But I say, let's make em' up.....

MODE 1. Standard medium/high alt level delivery that priorities range over terminal shape.

MODE 2. Medium alt drop that produces glide path the flattens in terminal stage for vertical targets (you want to hit side of a tower)

MODE 3. Medium alt drop that produces glide path that steepens terminal stage for horizontal targets (hit top of the target)

MODE 4 and 5. Low altitude drops that optimised for <5000ft deliveries for same vert or horiaontal as MODE 2 and 3.

MODE 6. Low altitude LOFT flight path to acheive max range in LOFT delivery for vertical impact angle 

MODE 7. Same as 6, but for different terminal stage 

etc etc Paveway III needs constant lasing in order to continually know it's relative position to the target. It also has a barometric altimeter, for rate of change of height.

 

Now, I've made the mode details up, but the 8 position MODE knob is real and I'm willing to bet I'm not too wrong...... I don't see why ED can't bow to a gameplay perspective here. Inactive and non-functinonal MFD buttons and labels should have no place in DCS in 2022. We're not in 1998 anymore and I expect more.

 

Edited May 29, 2022 by AvroLanc

[Lima29]

I was wondering about these things too, and while AvroLanc makes some logical sense I can’t see ED going with the “let’s do something that seems logical” approach when at every other step they’ve done they refuse to go with the logical approach & refuse to do things or adjust things because they haven’t seen some evidence of it.

 

On a slightly different (maybe, some would say, minor) point Wags / ED have called this “new” bomb the GBU-24/B, but the “ /B ” version is the version that uses the normal Mk-84 low drag GP warhead while in the video the bomb on the aircraft is clearly using the BLU-109 penetrator warhead which would make the bomb we have the GBU-24A/B. It might not make much difference to some but others are sticklers for the details!

[Fromthedeep]

3 hours ago, AvroLanc said:

This detail is what ED lacks. But I say, let's make em' up.....

The issue is that the real GBU-24 has 2 different behaviour depending on a specific altitude for each mode. And the guidance scheme it follows also depends on not just the altitude but the attitude at which the bomb was released. Mode 1 is detailed in a 1988 publication that's completely open source and it should be the first thing anyone finds who's researching the weapon, however, all the guidance scheme is incredibly complex and resource intensive to simulate.

 

3 hours ago, Lima29 said:

are sticklers for the details

It's a different weapon, I mean it's not the same bomb body, not the same parameters and performance and not even the same modes can be used, because certain modes can only be associated with the 109 bomb body, not a Mk 84.

[Dragon1-1]

3 hours ago, Lima29 said:

I was wondering about these things too, and while AvroLanc makes some logical sense I can’t see ED going with the “let’s do something that seems logical” approach when at every other step they’ve done they refuse to go with the logical approach & refuse to do things or adjust things because they haven’t seen some evidence of it.

That's because the military does not always do things in a particular way just because it's logical. Just because it's a 100k$ weapon, or a multimillion $ jet doesn't mean it has to make sense or be sensibly designed. Assuming the logical way is dangerous, because it might just be one of those systems at which real pilots and chiefs look and think "who designed this crock?" I hope ED will be able to find out enough information to model it properly.

[Frederf]

I thought PWIII had 4 modes in the switch. Maybe a newer version has more? PWIII has a barometric sample port and autopilot of sorts. After launch there is a mandatory "bump up" maneuver (most if not all modes) then a decision window after launch where it determines if it's loft/level/dive category. Then it does some shaping stuff depending with possibly some break level alt flight then on laser acquire it G-biases and attempts a certain terminal angle (mode-dependent).

PWIII is a lot like PWII in the sense it's a hand grenade. You pull the pin and throw it with a laser spot to get. But PWIII is significantly smarter, about as smart as a Maverick in that it flies and shapes its trajectory. A big limitation of PWII was low-level delivery (from 500-1000') since the guidance is simplistic and the fins binary in motion. PWIII was known as the LLLGB or low-level LGB. It's normal for the bomb to climb above the launching height when released low.

[AvroLanc]

3 hours ago, Dragon1-1 said:

Assuming the logical way is dangerous, because it might just be one of those systems at which real pilots and chiefs look and think "who designed this crock?" I hope ED will be able to find out enough information to model it properly.

Well, if those real pilots and crew chiefs want to offer their opinion then they’re free to help out any time. The problem is they don’t/can’t. It doesn’t really matter if it’s ‘dangerous’ or embarrassing later on, if they weren’t willing or unable to contribute towards a more realistic 100% correct solution right now then……who cares. The real info may never come in these specific cases. 

Getting a few sensible and knowledgeable heads together to construct a reasonable solution is that best we can hope for in these cases. It either this or make do with a equally incorrect Paveway II copy that adds absolutely nothing to current gameplay or simulation. I say again……I’m 100% done with static menus and non functional inactive menu options. I want depth and functionality above and beyond the same old combat sims I’ve been playing for 25 years. 

Futhermore, if that depth and true consequential gameplay can’t be provided through lack of documentation for the chosen module, then by heck choose to model a more appropriate airplane in the first place. 

Edited May 29, 2022 by AvroLanc

[Fromthedeep]

16 hours ago, AvroLanc said:

Getting a few sensible and knowledgeable heads together to construct a reasonable solution is that best we can hope for in these cases

USAF bombs at least use mode 1-4.. Mode 1 is described in publically available literature on DTIC, it's a fully public release document so much so that I could be linked even on the forum. The other modes need the BLU-109 bomb body and depending on the release altitude trajectory shape against certain type of targets. The big problem however is that the actual modes incorporate entirely different kind of guidance schemes depending on certain scenarios and the  trajectory shaping is designed to achieve specific impact parameters depending on the target and the capability is designed mainly for penetration. DCS doesn't model penetration so I find it really unlikely that it will ever be modelled. 

[Dragon1-1]

18 hours ago, AvroLanc said:

Futhermore, if that depth and true consequential gameplay can’t be provided through lack of documentation for the chosen module, then by heck choose to model a more appropriate airplane in the first place. 

Myself, I'd love a Block 10, with analog SMS, F-8 style HUD, 6xMERs and Sidewinder-only AA loadout. I'm also getting tired of this "classified this, classified that" thing, or of lack of exportable documentation, even if it's pretty much known how the feature actually works. I want the Viper to have parity with the one from other sim (core features notwithstanding), and the Hornet to be done to the same standard. If that's not possible, why not just give us an older model without all this classified crap? Yeah, what we have is nice, but if I want a truly realistic experience, I'll fly the damn Phantom.

Chances are, someday someone will release the documents, under a FOIA request or just the regular timeout thing. Stuff occasionally comes out like this, I remember the time when even the functionality of the CMS switch on the stick was classified. So things might be changed if that happens. However, it's a slow process.

[NineLine]

4 hours ago, Fromthedeep said:

USAF bombs at least use mode 1-4.. Mode 1 is described in publically available literature on DTIC, it's a fully public release document so much so that I could be linked even on the forum. The other modes need the BLU-109 bomb body and depending on the release altitude trajectory shape against certain type of targets. The big problem however is that the actual modes incorporate entirely different kind of guidance schemes depending on certain scenarios and the  trajectory shaping is designed to achieve specific impact parameters depending on the target and the capability is designed mainly for penetration. DCS doesn't model penetration so I find it really unlikely that it will ever be modelled. 

As stated, we do need more evidence, but we are open to it if anyone finds it.

Also, penetration is modelled, it might be more simplified in some cases, but this is more of an issue on damage modelling than issues with penetration. Thanks.

[Fromthedeep]

1 hour ago, NineLine said:

As stated, we do need more evidence, but we are open to it if anyone finds it.

 

I will link it as soon as I can, but currently DTIC is undergoing some kind of maintanence or it has technical issues. I don't think it will be fixed until Wednesday or so.

[TEOMOOSE]

12 hours ago, NineLine said:

As stated, we do need more evidence, but we are open to it if anyone finds it.

Here is a pdf that goes in to some details, very informative. From page 9.
https://www.globalsecurity.org/military/library/policy/navy/ntsp/gbu-24-a_2001.pdf

 

[NineLine]

46 minutes ago, TEOMOOSE said:

Here is a pdf that goes in to some details, very informative. From page 9.
https://www.globalsecurity.org/military/library/policy/navy/ntsp/gbu-24-a_2001.pdf

 

Thanks, I will take a look.

[KlarSnow]

@NineLine

This is the DTIC article that clearly lays out how Mode 1 for the GBU-24/B (And A/B) works. from 1988, completely open and lays out all of the guidance modes and release modes. There isnt any easy to find data on modes 2-4 that is open source so good luck with that. But Mode 1 would offer a ton of functionality and it is laid out in entirety in this document.

Precision Guided Weapons Training and Employment

Starts on Page 7

Figure 1 on page 38 has a graphical flowchart depiction of its decision making process, also the different scan modes the seeker uses to acquire the laser spot, based on flight profile.

Edited May 31, 2022 by KlarSnow

[BIGNEWY]

1 hour ago, KlarSnow said:

@NineLine

This is the DTIC article that clearly lays out how Mode 1 for the GBU-24/B (And A/B) works. from 1988, completely open and lays out all of the guidance modes and release modes. There isnt any easy to find data on modes 2-4 that is open source so good luck with that. But Mode 1 would offer a ton of functionality and it is laid out in entirety in this document.

Precision Guided Weapons Training and Employment

Starts on Page 7

Figure 1 on page 38 has a graphical flowchart depiction of its decision making process, also the different scan modes the seeker uses to acquire the laser spot, based on flight profile.

 

Thanks for the reply and the information, but it is not enough to show detailed information such as DDI, HUD indications, options ect, that is required for modelling correctly. 

 

[KlarSnow]

You have already modelled that stuff correctly..... .This is what happens AFTER the bomb releases, and how it gets to the target. this is what everyone cares about. The HUD and symbology will not change other than the LAR if you change the mode. The HUD and jet does not take any of this into account.

 

This document is what "Mode 1" means on the MFD. There are other things that would happen if you could set Mode 2,3, or 4 but those are not openly available that I'm aware of. All happens in the bombs autopilot based on release angle and altitude. 

All setting Mode 1 on the jet means is that the Jet is calculating a generic LAR bucket for a GBU-24 that is going to fly based on how this document lays it out. It does not change and there are no other indications or setting in the HUD or on the MFD's. The bomb automatically decides what it is doing based on your release attitude and altitude as described here. Nothing will change in the cockpit. How the bomb behaves will change drastically as you can see if you read this document.

Edited May 31, 2022 by KlarSnow

[BIGNEWY]

7 minutes ago, KlarSnow said:

You have already modelled that stuff correctly..... .This is what happens AFTER the bomb releases, and how it gets to the target. this is what everyone cares about. The HUD and symbology will not change other than the LAR if you change the mode. The HUD and jet does not take any of this into account.

 

This document is what "Mode 1" means on the MFD. There are other things that would happen if you could set Mode 2,3, or 4 but those are not openly available that I'm aware of. All happens in the bombs autopilot based on release angle and altitude. 

All setting Mode 1 on the jet means is that the Jet is calculating a LAR for a GBU-24 that is going to fly based on how this document lays it out. It does not change and there are no other indications or setting in the HUD or on the MFD's. The bomb automatically decides what it is doing based on your release atittude and altitude as described here. Nothing will change in the cockpit.

 

There are to many assumptions being made, we have to be very methodical when implementing features. As mentioned we have passed the information on to the team. 

thanks

[KlarSnow]

I am not making assumptions. If you want to take this to PM I'm happy to.

[BIGNEWY]

Yes please do, but do not compromise yourself, only use public information. 

Thank you. 

[Bananabrai]

I was always wondering why it is so different from RL. Cockpit indications should be correct as they are now.

Besides, with the info there is now, why is the approach in ED/DCS still this hardliner style old fashioned:
"Let's do it not at all"
instead of
"Let's do it with the best assumptions we can make, because we have some people and some docs here, that help us make it close to the real deal."

Because 'it could be not real enough'? 

[Fromthedeep]

3 hours ago, Bananabrai said:

Besides, with the info there is now, why is the approach in ED/DCS still this hardliner style old fashioned:

When it comes to the GBU-24 I completely understand their sentiment. Even the publically document features are incredibly complex, require an indescribeable amount of work (in complexity it would be on par with the modern air to air missiles) and generally they rely on a level of weaponeering and preplanning that doesn't exist in DCS and not even the tools exist for it. 

As a developer, they constantly have to ensure that the level of resources required for a feature are not to excessive for the benefit. In case of a realistic GBU-24 this limitation is very likely a strong consideration. 

[TEOMOOSE]

On 5/31/2022 at 1:30 AM, NineLine said:

Thanks, I will take a look.

I hope this helps.

What i have learned from that document: 

• Guidance is provided by laser energy reflected from the target
• The weapon can be delivered in high/low altitude, level/dive/loft
• Four delivery options modes can be selected by setting the mode switch (on the side of the Guidance Control Unit (GCU)) prior to aircraft takeoff
  
  The bomb has three phases: Initialization, Midcourse, and Terminal Guidance.
  
  Initialization:
   During Initialization phase, there is an approximate two-second wait period to permit safe separation distance of the weapon from the aircraft. The control system is then activated. The GCU determines the mode selection and examines altitude data from the barometer within the GCU. From this available information, an optimum midcourse flight trajectory is determined.
  
  Midcourse:
   The midcourse flight selection is based upon the conditions measured during the Initialization phase. The midcourse flight profile and seeker scan functions are optimized to provide the best possible probability for acquiring the target, while maintaining the maximum energy for penetration. The midcourse phase is maintained until the target is acquired.
  
  Terminal Guidance:
   After the weapon acquires the target, it enters the Terminal Guidance phase of flight. During this phase the weapon trajectory is optimized to provide the best possible penetration of the target, based upon the target conditions determined by the GCU during the Initialization phase of flight.

[TEOMOOSE]

you can sort of see it from here how the bomb guide itself by going up and down in its midcourse flight
 

 

[QuiGon]

On 6/1/2022 at 9:43 AM, Bananabrai said:

Because 'it could be not real enough'? 

Yes and I praise ED for this. I would rather not have functions than having made-up fantasy functions.