AIM-7 Performance

[OnlyforDCS]

I think people are still a little bit confused regarding with how missile modeling works in DCS. From what I've been able to gather Ill try and summarize it as succintly as possible. (Please feel free to correct any of my mistakes IASGATG & GGTharos):

 

1) Missiles have terminal guidance, inertial and radio correction flight phases. (Depending on make and type some have one or more of these )

 

2) Because of the way the code works missiles always maneuver at their max. G limits regardless of their flight phase.

For example: Say a particular missile needs to loft, instead of lofting at a steady 3 or 4gs, the missile guidance logic will make it do a series of small high g corrections, which will end up giving the same flight profile but will introduce significant ammounts of drag.

Another example In the case of the Aim7m: You fire the missile at range, the target starts maneuvering. Instead of initially following the target with steady low g turns, the missile's fins will do quick fast max g inducing corrections. This will end up giving it the exact same flight path, however as in the first example with siginficant ammounts of added drag.

 

3) There is something odd about atmospheric modeling in DCS and how it interacts with missiles. This is not a guidance problem as IASGATG stated, to put it into as few words as possible: in high and fast situations (with non maneuvering targets) missiles have the range that they should, however down low they are significantly draggier than their RL counterparts.

Edited June 15, 2018 by OnlyforDCS

[blkspade]

Is there?

 

Didn't Razbam make their own missiles? Aren't Heatblur making their own? Both are different to EDs implementations. I'm not arguing for one side or another. Just the lack of consistency as it appears to me.

 

I think you misunderstood the question, which is something I answered before it was asked. There is only one version of every missile, which is platform agnostic. So the same missile performs exactly the same on all the planes capable of employing it. That's what they were asking.

[BitMaster]

I think people are still a little bit confused regarding with how missile modeling works in DCS. From what I've been able to gather Ill try and summarize it as succintly as possible. (Please feel free to correct any of my mistakes IASGATG & GGTharos):

 

1) Missiles have terminal guidance, inertial and radio correction flight phases. (Depending on make and type some have one or more of these )

 

2) Because of the way the code works missiles always maneuver at their max. G limits regardless of their flight phase.

For example: Say a particular missile needs to loft, instead of lofting at a steady 3 or 4gs, the missile guidance logic will make it do a series of small high g corrections, which will end up giving the same flight profile but will introduce significant ammounts of drag.

Another example In the case of the Aim7m: You fire the missile at range, the target starts maneuvering. Instead of initially following the target with steady low g turns, the missile's fins will do quick fast max g inducing corrections. This will end up giving it the exact same flight path, however as in the first example with siginficant ammounts of added drag.

 

3) There is something odd about atmospheric modeling in DCS and how it interacts with missiles. This is not a guidance problem as IASGATG stated, to put it into as few words as possible: in high and fast situations (with non maneuvering targets) missiles have the range that they should, however down low they are significantly draggier than their RL counterparts.

 

 

 

 

In short, the DCS missiles are digitally steered, like a controller w/o sticks and a PS3.

 

 

Either 0 or 100% deflection.

 

 

 

 

ED, we are in the year 2018, the Hornet is out and this shall be the missiles ?

 

 

 

I am a bit confused on how this shall match the overall praised detail and realism, fidelity and what not else.

 

 

Digital ? cmon ! You can do much better

[IASGATG]

There are two phases. A loft phase where the missile attempts to keep the target and a specific angle relative to the horizon. It maintains this until a specified distance to target, at which point it ends and instantly enters what you're calling the terminal phase. In the terminal phase, the missile attempts to keep a specific angle of lead pursuit. Only if the missile is coded to have the right seeker head and the loft code is enabled with the variables completed will it loft. If it is not set it will be terminal off the rail. There is no control to adjust the terminal guidance laws.

[Sonoda Umi]

There is still a problem: Range of AIM-7M not excessing 5nm at appx. 15000ft.

Another question: the initial speed of AA-10 is faster than AIM-7 - is that true in the real life?

[GGTharos]

Your first problem doesn't mean anything at all - we don't know the launch parameters, meaning launcher/target positions, speeds etc.

 

 

Your second question: Yes. The R-27R has an all-boost motor that propels it to a somewhat higher speed than the AIM-7 can reach with its boost-sustain motor. However, the sustain motor on the AIM-7 burns so long that it achieves a higher average speed than the R-27R in most cases.

The R-27ER has a very powerful boost-sustain motor, it will be faster in all cases.

 

 

 

There is still a problem: Range of AIM-7M not excessing 5nm at appx. 15000ft.

Another question: the initial speed of AA-10 is faster than AIM-7 - is that true in the real life?

[j-tk]

I've found the only current work around to this until ED is able to focus more on it is to keep your nose pointed dead on the enemy aircraft. It seems the code for the semi-active radar of the sparrow is where the bug lies, but I'm near 100% hit rate if I let the missile ride my nose beam in.

[Sonoda Umi]

Your first problem doesn't mean anything at all - we don't know the launch parameters, meaning launcher/target positions, speeds etc.

 

 

Your second question: Yes. The R-27R has an all-boost motor that propels it to a somewhat higher speed than the AIM-7 can reach with its boost-sustain motor. However, the sustain motor on the AIM-7 burns so long that it achieves a higher average speed than the R-27R in most cases.

The R-27ER has a very powerful boost-sustain motor, it will be faster in all cases.

 

I.E.

Instant Mission AIM-7 Shooting

Target: IL-76

Target Range: 10NM to 15NM

Contrast Speed: 100+knot

Hit ETA: appx. 110s

 

The missile lost after I shot it in 40s, and the kinetic energy of missile was almost zero.(The actual shooting range not excess 5NM)

[GGTharos]

What is a 'contrast speed'? These parameters are incomplete.

 

 

Target/shooter distance, speed, altitude, aspect, and initial bearing for the shot are needed.

[Sonoda Umi]

What is a 'contrast speed'? These parameters are incomplete.

 

 

Target/shooter distance, speed, altitude, aspect, and initial bearing for the shot are needed.

 

In other word, I had 100+ knot speed faster than IL-76

[GGTharos]

That doesn't mean anything. It could be at 0kts and you could be at 100, regardless of how ridiculous this sounds :)

 

The parameters that I have listed are what's needed. Not 'a different way of saying those parameters' or 'things I think I should say' ... those exact parameters.

[Nerd1000]

 

2) Because of the way the code works missiles always maneuver at their max. G limits regardless of their flight phase.

For example: Say a particular missile needs to loft, instead of lofting at a steady 3 or 4gs, the missile guidance logic will make it do a series of small high g corrections, which will end up giving the same flight profile but will introduce significant ammounts of drag.

Another example In the case of the Aim7m: You fire the missile at range, the target starts maneuvering. Instead of initially following the target with steady low g turns, the missile's fins will do quick fast max g inducing corrections. This will end up giving it the exact same flight path, however as in the first example with siginficant ammounts of added drag.

 

Missiles don't always maneuver at max G (if you watch one in F6 view this will be obvious). The issue is that there is only one guidance law available to them, to wit Proportional Navigation (PN.) PN works by having the missile attempt to keep the target at a constant bearing and elevation off its nose (as this means that the missile and target are on a collision course.) If the target's bearing is moving right to left the missile will turn left until the bearing is constant again. The steering input is proportional to the error (fast changes in bearing will result in larger control inputs), so if the target turn gently the missile will use a proportional input (less than max G) to maintain the collision course. DCS may include augmented PN (where the missile can account for and lead into the target's turns, allowing it to 'cut the corner' when pursuing a maneuvering target) for more advanced missiles, but I'm not certain on that front.

 

PN works well in the terminal phase, but in the boost and coast phases of a BVR missile's flight it causes the missile to turn violently in an attempt to 'lead' the target any time the target changes course. There are other guidance laws that work better in this case: one option would be to calculate steering inputs for both PN and Pure Pursuit (PP = the missile tries to fly directly towards the target) then take a weighted average of them as the input sent to the controls. The missile would start by flying PP, and mix in increasing amounts of PN as the range to the target decreased.

[Baitball]

Frustrations with the AIM7

 

I've been trying to get better with the sparrow and no matter what I do, I usually get these results:

 

1. Target locked BVR and tracking by following the green dot (20nm+ out)

2. Target begins turn and I follow lock via the green dot

3. Target turns towards me, or keeps moving approximately perpendicular to me (5-20nm)

4. I don't get the fire cue on the HUD until around 10nm or less

5. He locks me and fires instantly

 

*target stated above ranges from small fighters to large turboprops and jets

 

 

It seems obnoxiously unrealistic that I could acquire a lock from 20-40nm out and not be able to get a fire cue until below 10nm or so. I am visual by around 15nm and using ACM instead of BVR gets me an almost instant fire cue. What am I doing wrong?

[feefifofum]

Your altitude?

Target's altitude?

Closure rate?

 

These are the three main factors for when you'll receive a shoot cue. The sparrow wants to be fired at high altitude with a high closure rate. I've had success with 25nm shots at head-on, fighter sized targets from 32,000 feet, co-altitude with 1000+ knots of closure.

 

I've similarly had failures with shots inside of 6 miles against aggressively maneuvering targets at low altitudes and poor aspect. There are known issues with DCS missile performance that you can read any of the million pages-long threads about, but you can definitely achieve positive results farther out than 10 miles.

 

As far as your bandit being able to shoot first, that all depends on what you're up against.

[Baitball]

Your altitude?

Target's altitude?

Closure rate?

 

These are the three main factors for when you'll receive a shoot cue. The sparrow wants to be fired at high altitude with a high closure rate. I've had success with 25nm shots at head-on, fighter sized targets from 32,000 feet, co-altitude with 1000+ knots of closure.

 

I've similarly had failures with shots inside of 6 miles against aggressively maneuvering targets at low altitudes and poor aspect. There are known issues with DCS missile performance that you can read any of the million pages-long threads about, but you can definitely achieve positive results farther out than 10 miles.

 

As far as your bandit being able to shoot first, that all depends on what you're up against.

 

 

I have been shooting targets such as the MiG25, Su24, and F-5.

Target altitudes: anywhere from 11000' to 25000'+

Closure Rate: Anywhere from 500 to 1000+

 

When you say the sparrow wants to be fired at high altitude, do you mean I should be firing from a significantly higher elevation than my intended target? Or do you mean just an overall high altitude engagement?

[gabuzomeu]

I see a different behaviour between 7F (OK ish) and 7M (disster, runs away from target when closing in...)

or am I delusional? :-)

[Baitball]

I see a different behaviour between 7F (OK ish) and 7M (disster, runs away from target when closing in...)

or am I delusional? :-)

 

I will experiment with a mix of F and M models and report back. I have tried using the 7F before, but to be honest, I had the same results as with the M models.

[HawkDCS]

I raised a few questions here in this thread.

 

https://forums.eagle.ru/showthread.php?t=210940

[Baitball]

I raised a few questions here in this thread.

 

https://forums.eagle.ru/showthread.php?t=210940

 

 

 

Looks like this is almost a universal problem. I have probably properly locked, tracked, and fired over 150 7M's by now and I am having the same shoot cue not appearing until an incredible 5-8nm away, and even with the shoot cue at 15-20nm away, my kill rate has been....let's just say very low.

 

Thanks for the link!

[pete_auau]

iam getting the shoot cue all the time weather being 9nm out or 30 nm out my issues is they dont hit the target lol even though i have fired 4 at one:) guess i have to make them novice and usually they fill me with holes and have to retreat.

[StandingCow]

Just to throw my hat in the ring... myself and my wingmen have had similar experiences... right now the sparrow just isn't worth even taking, better to load up on heaters.

[shagrat]

Early Access, WIP, radar will be worked on during early access phase in subsequent updates... at least that is what Wags stated in the radar thread. Likely that has an impact on the AIM-7, as well.

[OnlyforDCS]

Missiles don't always maneuver at max G (if you watch one in F6 view this will be obvious).

 

Im pretty sure that they will always deflect their fins to maximum when maneuvering. That is what I mean when I say they maneuver at their max g limits. I.E. they will do short full deflections of their fins. Are you saying that they don't do this?

[OnlyforDCS]

Early Access, WIP, radar

 

Try the Aim7m on the F15C. You will see similar results.

[red_coreSix]

Im pretty sure that they will always deflect their fins to maximum when maneuvering. That is what I mean when I say they maneuver at their max g limits. I.E. they will do short full deflections of their fins. Are you saying that they don't do this?

 

What you're referring to is bang-bang guidance which is mostly used in early air-air missiles and some ATGMs. Modern missiles (our sparrows included) don't use this.