AIM-7 Performance

[nighthawk2174]

Good posts IASTAG & Shagrat!

 

IMHO, the radar issue has become a bit of a red herring for some people. Yes, the radar in the F18 is very much so EA/WIP and is borked. BUT, for IASTAG, a few others in this forum, and myself the bigger issue is the missile kinematics and guidance.

 

This issue has been ongoing for much longer than several years now where most if not all missiles (SAM included it seems like) suffer from:

 

A) abnormally high drag. A number I saw floating around was 50%... This isn't just normal drag either but induced, aka when the missile is turning, it loses a lot of energy it shouldn't

B) Terminal guidance from the second the missile leaves the rail. This in combination with point A causes the missile to commit ritualistic suicide via high drag and extreme high G maneuvers. Where lofting and other navigation tricks (in more modern missiles pattern recognition is a thing) would prevent the missile from losing as much energy.

 

Overall I'm not saying that the radar isn't contributing to the bad performance of the aim7, in fact, if you roll to quickly you will lose lock. But at least we know ED is looking into the radar performance the missile performance not as much so (although I hope I'm 100% wrong on this last point)

Edited June 22, 2018 by nighthawk2174

[IASGATG]

Well the definition of relative max range is clearer than aerodynamic max range. Relative max says that the missile will impact at the same speed as launch speed. This gives a very clear picture of how much the missile should be decelerating by.

[blkspade]

Good posts IASTAG & Shagrat!

 

IMHO, the radar issue has become a bit of a red herring for some people. Yes, the radar in the F18 is very much so EA/WIP and is borked. BUT, for IASTAG, a few others in this forum, and myself the bigger issue is the missile kinematics and guidance.

 

This issue has been ongoing for much longer than several years now where most if not all missiles (SAM included it seems like) suffer from:

 

A) abnormally high drag. A number I saw floating around was 50%... This isn't just normal drag either but induced, aka when the missile is turning, it loses a lot of energy it shouldn't

B) Terminal guidance from the second the missile leaves the rail. This in combination with point A causes the missile to commit ritualistic suicide via high drag and extreme high G maneuvers. Where lofting and other navigation tricks (in more modern missiles pattern recognition is a thing) would prevent the missile from losing as much energy.

 

Overall I'm not saying that the radar isn't contributing to the bad performance of the aim7, in fact, if you roll to quickly you will lose lock. But at least we know ED is looking into the radar performance the missile performance not as much so (although I hope I'm 100% wrong on this last point)

 

In reference to the F-18, it does seem as though you can alter the operating parameters after locking a contact. Like the bar scan, azimuth (in 20 deg increments) and contact aging, which seems to sometimes delay the loss of lock for a slightly harder bank to one side.

[Pikey]

It's the "instant-chase-my-lead-interception-guidance" that's the problem. Not so much the weight, drag, air thickness rubbish that keeps getting rolled out in defence by the "oh what altitude and speed was that launched at" crew ...

 

Its the same code that makes the ai wingman stick so close, the same logic that you watch that ai on his intercept course magically alter his aspect INSTANTANEOUSLY with you, the same that affects all missiles equally like SAM's, hey, wait, THE guidance logic, because after ten years watching missiles do their "twitch lead pursuit" you know what, the story is old because it IS old, it's more than a decade old and it needs revisited, because missiles grow old before their time since the guidance is not realistic, it's burning up the drag and energy by constantly moving a lead intercept path and it's the reason these silly barrel rolls have slaughtered the missile behaviour and folks in pvp sit and do such silly things. It needs to have just a little bit more thought in the code level before it's going to satisfy newcomers arriving at Hornet time.

 

Missiles in general need a revisit Eagle, and people know. It makes a great sim model feel poor and brings it down when the end delivery of a weapon has such a basic behaviour compared to the superb modelling of the latest release (and most of the others too)

[blkspade]

It's the "instant-chase-my-lead-interception-guidance" that's the problem. Not so much the weight, drag, air thickness rubbish that keeps getting rolled out in defence by the "oh what altitude and speed was that launched at" crew ...

 

Its the same code that makes the ai wingman stick so close, the same logic that you watch that ai on his intercept course magically alter his aspect INSTANTANEOUSLY with you, the same that affects all missiles equally like SAM's, hey, wait, THE guidance logic, because after ten years watching missiles do their "twitch lead pursuit" you know what, the story is old because it IS old, it's more than a decade old and it needs revisited, because missiles grow old before their time since the guidance is not realistic, it's burning up the drag and energy by constantly moving a lead intercept path and it's the reason these silly barrel rolls have slaughtered the missile behaviour and folks in pvp sit and do such silly things. It needs to have just a little bit more thought in the code level before it's going to satisfy newcomers arriving at Hornet time.

 

Missiles in general need a revisit Eagle, and people know. It makes a great sim model feel poor and brings it down when the end delivery of a weapon has such a basic behaviour compared to the superb modelling of the latest release (and most of the others too)

 

They are both issues that feed into each other. Fixing one would greatly alleviate the issues generated by the other. The problem is there is actual data (official docs and independent CFD modeling) to point at aerodynamic failings of the flight model that has continued to be ignored for years. We have nothing to compare the guidance logic against other just saying "its stupid". We think the logic is wrong, but know the drag wrong. Altering a couple parameters to match known data to me seems simpler to me than guessing at how guidance is handled in the real world.

[IASGATG]

Sorry for the wall of images below, if someone knows how I can do some sort of "spoiler" hide button or something please let me know.

 

The first series shows the vanilla AIM-7M fired at sea level, 30kft and 50kft, showing the base relative maximum range as defined previously. It shows that at sea level the missile is has a range of 10nmi instead of 14nmi. At 30kft it's about 24nmi instead of 25nmi. Lastly at 50kft it is 50nmi instead of 38nmi. The missile is too slow, even at 30kft, and especially at lower altitudes, whilst is too fast at extreme altitudes.

 

The second series is my modified version, which is not perfect by any means, but attempts to provide better low level performance without over performing at higher altitudes. It shows that at sea level the missile is has a range of 13nmi instead of 14nmi. At 30kft it's about 25nmi. Lastly at 50kft it is 50nmi instead of 38nmi.

 

Edit: It's 14 huge pictures, nevermind, please take my word for it. It's a big mess if I try and upload it. :(

 

Edit 2: Here they are in no particular order if, like Nighthawk2174, you really want to view them. https://imgur.com/a/dHuhFrB Be warned they are in no particular order. (I might change that, but no promises)

Edited June 24, 2018 by IASGATG

[nighthawk2174]

Sorry for the wall of images below, if someone knows how I can do some sort of "spoiler" hide button or something please let me know.

 

The first series shows the vanilla AIM-7M fired at sea level, 30kft and 50kft, showing the base relative maximum range as defined previously. It shows that at sea level the missile is has a range of 10nmi instead of 14nmi. At 30kft it's about 24nmi instead of 25nmi. Lastly at 50kft it is 50nmi instead of 38nmi. The missile is too slow, even at 30kft, and especially at lower altitudes, whilst is too fast at extreme altitudes.

 

The second series is my modified version, which is not perfect by any means, but attempts to provide better low level performance without over performing at higher altitudes. It shows that at sea level the missile is has a range of 13nmi instead of 14nmi. At 30kft it's about 25nmi. Lastly at 50kft it is 50nmi instead of 38nmi.

 

Edit: It's 14 huge pictures, nevermind, please take my word for it. It's a big mess if I try and upload it. :(

 

Maybe drop them on imigur and put out the link? I would be interested in seeing these images!

[Lenux]

I don't understand how to launch the AiM 7F missiles ( F 18 Hornet )

Could anyone explain, please ?

Thank you

[razo+r]

I don't understand how to launch the AiM 7F missiles ( F 18 Hornet )

Could anyone explain, please ?

Thank you

 

Look here or read the manual:

[Chizh]

Hey Chizh buddy. I've been given permission to show this which should clear everything up.

 

Thanks!

It is very helpful.

 

What's interesting is that the vanilla 7M actually outperforms in the 50kft shot slightly. It arrives at M2.2 I believe? Instead of M2.0 (For the 38nm shot). It's the low altitude shots that the missile falls very short in. Basically the transonic drag is too high and the M4 drag is too low. Ive done my best to bend the curve to fit these variables and after about 55 iterations I got pretty close, still slightly too fast at 50kft. Probably because the drag reduction for the motor being lit isn't represented so I have to make the missile too slippery.

Could you share your script version with changed Drag params for 7M and 7F?

[Lenux]

I don't know, maybe it's a bug or because of the Early Access, but i can't launch a single AiM 7

[Lenux]

Look here or read the manual:

 

I watched this video 2-3 times

Between 0.40 - 0.50 , i don't have this same menu, on the left side ( SIZE / HELO / LOFT )

Am I doing something wrong ??

[IASGATG]

Thanks!

It is very helpful.

 

 

Could you share your script version with changed Drag params for 7M and 7F?

 

Sent. :)

[nighthawk2174]

Nice, hopefully, this will cause something to change soon!

[antagonist]

I watched this video 2-3 times

Between 0.40 - 0.50 , i don't have this same menu, on the left side ( SIZE / HELO / LOFT )

Am I doing something wrong ??

 

You're not required to have the Stores page open on any MFCD to be able to launch or release weapons. You only need it to give you an overview of what you still have onboard and to set up how you'd like to ruin the other guys' day, generally speaking.

 

Just plain launching the AIM-7 can be done by selecting it (which also immediately puts you into A/A mode), locking a target with your radar inn any mode, then pulling the trigger once you're lined up.

 

This is not the Weapon Release button, that one's for A/G ordnance exclusively.

[Lenux]

Antagonist, I tried many times, as you described

I'm not sure if I understand correctly : so, it's not possible to launch a AiM 7 missile, when there is no enemies on the target??

I have no issues, with any other missiles, rockets, bombs

Edited June 25, 2018 by Lenux

[antagonist]

Antagonist, I tried many times, as you described

I'm not sure if I understand correctly : so, it's not possible to launch a AiM 7 missile, when there is no enemies on the target??

I have no issues, with any other missiles, rockets, bombs

 

The Sparrow should be capable of LOAL. I haven't tried personally, but it should be possible to launch it without having a target locked, i.e. in FLOOD mode (not implemented yet) or with the radar in RWS, then locking a target afterwards.

[shagrat]

Antagonist, I tried many times, as you described

I'm not sure if I understand correctly : so, it's not possible to launch a AiM 7 missile, when there is no enemies on the target??

I have no issues, with any other missiles, rockets, bombs

A guided missile, by design, needs to know a target/contact/radar return it is supposed to guide towards.

As the current early access does not (yet) have FLOOD mode and as far as I understood from some experts here, the AIM-7 variants we have in DCS don't support Lock-on-after-launch (LOAL), you will need to lock a radar contact before you launch the missile.

[Chizh]

Sent. :)

Thanks!

[Chizh]

As the current early access does not (yet) have FLOOD mode and as far as I understood from some experts here, the AIM-7 variants we have in DCS don't support Lock-on-after-launch (LOAL), you will need to lock a radar contact before you launch the missile.

FLOOD mode implemented in DCS many years ago in F-15C.

There are not the issue of missile rather a Hornet weapon system. Will be implemented. Please wait.

[GGTharos]

To be very pendantic, the missile itself support LOAL (like all SARH AAMs, it MUST) but it does not support 'practical LOAL' ie. mid-course datalink.

 

What does it mean? It means that the missile must lock onto its target very shortly after launch, and this is exactly what happens with sparrow RL:

 

When the trigger is 'pulled', the missile is:

 

Tuned by the attacking radar to the correct waveform

Given initial steering/english BIAS data and a target doppler search range

Rocket motor fires, missile ejected

Missile keeps seeker 'cold' for a short time since it would be blinded by mothership radar

Initial steering/bias commands are executed

Seeker turns on, begins search and tries to look in a particular direction and lock onto a doppler return within the designated range

If the above fails, the missile 'throws open the flood gates' and tries to find a target within a much wider range of frequencies

 

(the 'doppler range' is really a range of frequencies offset from mothership's own radar frequency, ie. we're looking for a target with a particular, narrow set of closure values)

 

That's my limited understanding of the process, and it is why FLOOD works. When the missile is launched without a target, FLOOD mode is entered automatically and the missile uses the wide doppler gate to find a target. You can probably imagine how that fares if there are multiple targets, including countermeasures in the air.

 

 

What Sparrow needs to be LOAL the way we think of it, is a datalink and guidance that blends this datalink in. That would be the AIM-7P.

 

A guided missile, by design, needs to know a target/contact/radar return it is supposed to guide towards.

As the current early access does not (yet) have FLOOD mode and as far as I understood from some experts here, the AIM-7 variants we have in DCS don't support Lock-on-after-launch (LOAL), you will need to lock a radar contact before you launch the missile.

Edited June 25, 2018 by GGTharos

[antagonist]

FLOOD mode implemented in DCS many years ago in F-15C.

There are not the issue of missile rather a Hornet weapon system. Will be implemented. Please wait.

 

Yeah, I think he was asking specifically regarding the Hornet, not the Eagle.

[shagrat]

To be very pendantic, the missile itself support LOAL (like all SARH AAMs, it MUST) but it does not support 'practical LOAL' ie. mid-course datalink.

 

What does it mean? It means that the missile must lock onto its target very shortly after launch, and this is exactly what happens with sparrow RL:

 

When the trigger is 'pulled', the missile is:

 

Tuned by the attacking radar to the correct waveform

Given initial steering/english BIAS data and a target doppler search range

Rocket motor fires, missile ejected

Missile keeps seeker 'cold' for a short time since it would be blinded by mothership radar

Initial steering/bias commands are executed

Seeker turns on, begins search and tries to look in a particular direction and lock onto a doppler return within the designated range

If the above fails, the missile 'throws open the flood gates' and tries to find a target within a much wider range of frequencies

 

(the 'doppler range' is really a range of frequencies offset from mothership's own radar frequency, ie. we're looking for a target with a particular, narrow set of closure values)

 

That's my limited understanding of the process, and it is why FLOOD works. When the missile is launched without a target, FLOOD mode is entered automatically and the missile uses the wide doppler gate to find a target. You can probably imagine how that fares if there are multiple targets, including countermeasures in the air.

 

 

What Sparrow needs to be LOAL the way we think of it, is a datalink and guidance that blends this datalink in. That would be the AIM-7P.

Yeah, that is the detailed version... For practical purposes I consider a LOAL Mode like with modernized SARH missiles, that can be thrown in the roughly correct direction and start guiding when close® to the target by picking up a late activated radar lock.

(Edit: when the data link points out a specific target/course to target)

 

...and yes, I was specific to the Hornet, and to the current implementation.

As we have a heavy WIP there will be lots of stuff added. Puls frequencies, FLOOD mode etc.

 

Give the devs some time to work on that stuff. ;)

Edited June 25, 2018 by shagrat

[Chizh]

Yeah, I think he was asking specifically regarding the Hornet, not the Eagle.

This thread is named AIM-7 Performance not F/A-18 issues.

[Nealius]

AIM-7M: Can't hit anything beyond 2nm

 

I flew a good number of missions today trying out the AIM-7M on some unarmed Phantoms doing an orbit over the ocean. It didn't matter if I was high aspect, low aspect, maintained lock throughout the engagement, or what, none of my missiles would hit unless I fired within 2nm. Even at 3-4nm the missile would track fine until about halfway to the target, when it would suddenly veer 90° to the right and miss. This would repeat frequently. My radar held a solid lock all throughout. Is anyone else experiencing horrible Pk with the Sparrow?