Maximum range of R-27ER in DCS

[Cmptohocah]

Su-27SK manual states that minimum and maximum ranges for the R-27ER missile (for a co-alt target and for a range of altitudes from 0 to 10km) are:

2km and 65.5km respectively in PPS (HPRF) mode.

 

I did a test in DCS where I am firing an R-27ER at a co-alt target coming head on and the missile falls short at a distance of around 63km, which is even less than the manual says.

 

There is no mention of the airspeed of the launching aircraft and the target in the manual, so I have assumed a value of 0.8M. Perhaps someone can confirm/disprove this.

 

Target is IL-76MD flying at 10.000km at 0.78M and I have launched form an Su-27 at 10.000m and around 0.82M.

 

Tacview and DCS track are attached.

Tacview-20210105-175712-DCS-R-27ER-testing.zip.acmi R-27ER-testing.trk

[TaxDollarsAtWork]

About that part of the manual, it has been brought up a few times but do we know what the termination parameters were?

Is this 65km shot considered an R aero shot or is this a MAR/E-Pole shot?

 

We do have another chart if I'm not mistaken with fly off ranges which might help determining this but it also has the same lack of context.

[Cmptohocah]

15 minutes ago, TaxDollarsAtWork said:

About that part of the manual, it has been brought up a few times but do we know what the termination parameters were?

Is this 65km shot considered an R aero shot or is this a MAR/E-Pole shot?

Could you please explain what "R aero" and "MAR/E-Pole" shots mean?

[GGTharos]

1 hour ago, Cmptohocah said:

Su-27SK manual states that minimum and maximum ranges for the R-27ER missile (for a co-alt target and for a range of altitudes from 0 to 10km) are:

2km and 65.5km respectively in PPS (HPRF) mode.

 

I did a test in DCS where I am firing an R-27ER at a co-alt target coming head on and the missile falls short at a distance of around 63km, which is even less than the manual says.

 

There is no mention of the airspeed of the launching aircraft and the target in the manual, so I have assumed a value of 0.8M. Perhaps someone can confirm/disprove this.

 

900kph launch, 1100kph target.   I think it's all true airspeed, at 10km altitude.  CFD of the R-27 has been pushed back early and often unfortunately ... I suspect these missiles will 'fall short' further than the Rmax, since the Rmax should be some type of guarantee.

[TaxDollarsAtWork]

1 minute ago, GGTharos said:

 

900kph launch, 1100kph target.   I think it's all true airspeed, at 10km altitude.  CFD of the R-27 has been pushed back early and often unfortunately ... I suspect these missiles will 'fall short' further than the Rmax, since the Rmax should be some type of guarantee.

But at what speed would the missiles be hitting at this 66km range?

What maneuvers if any is the target doing?

[TaxDollarsAtWork]

49 minutes ago, Cmptohocah said:

Could you please explain what "R aero" and "MAR/E-Pole" shots mean?

R Aero stands for the absolute maximum kinetic range on a target provided the target doesn't change direction or react at all.

Usually when people mention the R-27ER has 125km range that's an R aero figure probably tested at about 15km alt.

 

But it makes me wonder shouldn't R aero at around 10km alt be around 80km then?

That's just speculation but anyway.

 

Minimum Abort Range (MAR) is the lowest range some one can execute an abort maneuver where they turn cold and defeat any and every possible on coming launch.

Edited January 5, 2021 by TaxDollarsAtWork

[GGTharos]

31 minutes ago, TaxDollarsAtWork said:

But at what speed would the missiles be hitting at this 66km range?

What maneuvers if any is the target doing?

 

Sure, I agree, but as you know:

That's a CFD question.

 

I would personally expect it to have a 4-5g ability for a second or three at that range/point, but I'm basing this on the sparrow specs so you know, YMMV for the specification of the R-27.

Edited January 5, 2021 by GGTharos

[FoxAlfa]

We are all wating on R-27/R-77 rework... and it looks we will wait more.... till then, I think we all agree that the current implementation lacks 'fidelity' in certain areas.

[Cmptohocah]

1 hour ago, TaxDollarsAtWork said:

But at what speed would the missiles be hitting at this 66km range?

What maneuvers if any is the target doing?

For me the max range is the maximum distance that missile will hit (under certain conditions as mentioned) without the target maneuvering.

 

1 hour ago, GGTharos said:

 

900kph launch, 1100kph target.   I think it's all true airspeed, at 10km altitude.  CFD of the R-27 has been pushed back early and often unfortunately ... I suspect these missiles will 'fall short' further than the Rmax, since the Rmax should be some type of guarantee.

 

Where did you get 900km/h and 1100km/h values from?

No matter what the CFD says, if the manual states that this is the max range, someone surely did research and testing, before they wrote it there. It's just the question of the speeds at this point.

Edited January 5, 2021 by Cmptohocah

[FoxAlfa]

2 hours ago, Cmptohocah said:

Where did you get 900km/h and 1100km/h values from?

No matter what the CFD says, if the manual states that this is the max range, someone surely did research and testing, before they wrote it there. It's just the question of the speeds at this point.

The 900 km/h and 1100 km/h are fighter and target speeds/envelopes for the graphs... it is written on them, at least on version I have. 

This is exectly why we need CFDs to figure out the drag... and with drag and full mass known... it is easy to get the speeds... and I am sure with proper modeling the manual ranges will be archived no problem.

Edited January 6, 2021 by FoxAlfa

[GGTharos]

2 hours ago, Cmptohocah said:

For me the max range is the maximum distance that missile will hit (under certain conditions as mentioned) without the target maneuvering.

 

But this basically says nothing.  What are the conditions under which the missile can still hit the target?

 

I mean, are we looking for 1/10?  7/10?  (In the case of the R-27 it is 7/10) ... what does the missile need to be able to do to get that 7/10?

[TaxDollarsAtWork]

1 hour ago, FoxAlfa said:

The 900 km/h and 1100 km/h are fighter and target speeds/envelopes for the graphs... it is written on them, at least on version I have. 

This is exectly why we need CFDs to figure out the drag... and with drag and full mass known... it is easy to get the speeds... and I am sure with proper modeling the manual ranges will be archived no problem.

 

Yes but what speeds does the R-27 pass/hit the target at in those conditions this has to be some kind of pre-briefed shot I don't really believe this to be an R aero figure with some slack in there maybe its an E pole shot or R opt

Edited January 6, 2021 by TaxDollarsAtWork

[Cmptohocah]

7 hours ago, GGTharos said:

 

But this basically says nothing.  What are the conditions under which the missile can still hit the target?

 

I mean, are we looking for 1/10?  7/10?  (In the case of the R-27 it is 7/10) ... what does the missile need to be able to do to get that 7/10?

How come it says nothing?

It says: "Dear Flanker driver, if you have a target at this distance and this altitude (assuming that your speed and the target's speed are X and Y the weather conditions are windless and the temperature is standard for this altitude), rest assured that you will get a LA and most probably hit the target, provided it does not maneuver. We did some tests and research and have decided that this is the maximum distance at which we are happy with the results."

 

I don't know what is inside the "black box" and if the ER can hit something at 200km (exaggeration) or not, but it really doesn't mater. Someone took all the different parameters into account and decided that they are happy with the missile performance at X distance and provided the pilot with this value.

What does "1/10" "7/10" mean? Fired to kill ratio?

Conditions are:

• X speed of the launching platform
• Y speed of the target (constant)
• pressure altitude
• no-wind, constant OAT
• no-maneuvering

The missile needs to reach the target and explode, at least in DCS as the missiles are contact-based.

 

6 hours ago, TaxDollarsAtWork said:

Yes but what speeds does the R-27 pass/hit the target at in those conditions this has to be some kind of pre-briefed shot I don't really believe this to be an R aero figure with some slack in there maybe its an E pole shot or R opt

 

 

At what ever speed is needed to support the weight of an R-27ER that has its fuel burned out, in case of current guidance in DCS it's a straight and level flight at 1G, to reach (touch in DCS) the target and deliver the payload.

7 hours ago, FoxAlfa said:

The 900 km/h and 1100 km/h are fighter and target speeds/envelopes for the graphs... it is written on them, at least on version I have. 

 

Cool, so I will use those speeds to re-do the test. Thanks to both you and @GGTharos.

[TaxDollarsAtWork]

3 minutes ago, Cmptohocah said:

How come it says nothing?

It says: "Dear Flanker driver, if you have a target at this distance and this altitude (assuming that your speed and the target's speed are X and Y the weather conditions are windless and the temperature is standard for this altitude), rest assured that you will get a LA and most probably hit the target, provided it does not maneuver. We did some tests and research and have decided that this is the maximum distance at which we are happy with the results."

 

I don't know what is inside the "black box" and if the ER can hit something at 200km (exaggeration) or not, but it really doesn't mater. Someone took all the different parameters into account and decided that they are happy with the missile performance at X distance and provided the pilot with this value.

What does "1/10" "7/10" mean? Fired to kill ratio?

Conditions are:

• X speed of the launching platform
• Y speed of the target (constant)
• pressure altitude
• no-wind, constant OAT
• no-maneuvering

The missile needs to reach the target and explode, at least in DCS as the missiles are contact-based.

 

 

At what ever speed is needed to support the weight of an R-27ER that has its fuel burned out, in case of current guidance in DCS it's a straight and level flight at 1G, to reach (touch in DCS) the target and deliver the payload.

Speed at that point even in a straight line test tells us a lot about how energetic the missile is.

Maybe they wanted Mach 4 (as an exaggeration) at impact for this chart

Maybe they wanted 500kmh at impact

 

Knowing termination parameters is important to get an accurate picture of a missile's range

 

[Cmptohocah]

1 minute ago, TaxDollarsAtWork said:

Speed at that point even in a straight line test tells us a lot about how energetic the missile is.

Maybe they wanted Mach 4 (as an exaggeration) at impact for this chart

Maybe they wanted 500kmh at impact

 

Knowing termination parameters is important to get an accurate picture of a missile's range

 

 

I understand, but the entire point of my post is that it fails to reach the target in DCS completely. Having said that, I do need to repeat the test with the quoted 900 and 1100km/h values, for the launching platform and the target, respectfully.

Wether the lift is too low for the current speed at this distance, or the drag coefficient is too high, or any combination of those, I can't really tell.

[Cmptohocah]

@GGTharos @FoxAlfa,
if you guys were referring to this graph here --> 

Then the speed of both the target and the fighter is 1100km/h (dashed line) for the max distance of 65km. 

[GGTharos]

You're right, my mistake going off of memory.

[BlackPixxel]

R-27R chart was the one with 700/900 and 900/1100 for target/shooter

[Cmptohocah]

Did another test at 900km/h TAS and the missile max effective range in DCS is identical to the one marked on the graph above (solid lines). I could not verify the dashed ones, but I assume they fit the chart also. I have done test at 1, 5 and 10km altitude.

 

Turns out that my initial assumption of 0.8M was wrong.

[BlackPixxel]

I think the graphs are what ED took as reference when doing the old FM. They would change the different coefficients by hand until it fit the graph.

 

Which leads of course to bad results, as the graphs has some reserve for target maneuvering. How much is unknown.

Edited January 6, 2021 by BlackPixxel

[Fri13]

On 1/6/2021 at 8:43 PM, BlackPixxel said:

I think the graphs are what ED took as reference when doing the old FM. They would change the different coefficients by hand until it fit the graph.

Which leads of course to bad results, as the graphs has some reserve for target maneuvering. How much is unknown.

 

I don't believe those has much given for the maneuvering, as you can't really start to add factors in for maneuvers because there are way too many of them. Like change speed or angle slightly at launch moment and you just eliminated the longest range shot.

These are anyways just for missile max kinematic flight range.

[FoxAlfa]

1 hour ago, Fri13 said:

 

I don't believe those has much given for the maneuvering, as you can't really start to add factors in for maneuvers because there are way too many of them. Like change speed or angle slightly at launch moment and you just eliminated the longest range shot.

These are anyways just for missile max kinematic flight range.

 

 

 

 

I disagree, this are 'recommended' max engagement envelopes for the pilots.
MiG-29 manual even instructs pilot to fire the first missile at that range and second at R2 (R-non escape zone)   

You wouldn't recommend with at least some accommodations for increased PK....
which in max kinematic is not possible, so it is reasonable to assume that max kinematic is bigger.

All in all we need CFDs and proper autopilot updates, without them we are very much in the area of speculation.
 

Edited January 7, 2021 by FoxAlfa

[Cmptohocah]

51 minutes ago, FoxAlfa said:

 

I disagree, this are 'recommended' max engagement envelopes for the pilots.
MiG-29 manual even instructs pilot to fire the first missile at that range and second at R2 (R-non escape zone)   

You wouldn't recommend with at least some accommodations for increased PK....
which in max kinematic is not possible, so it is reasonable to assume that max kinematic is bigger.

All in all we need CFDs and proper autopilot updates, without them we are very much in the area of speculation.
 

 

As @Fri13 mentioned, it would not be practical to determine anything other than a max range for a non-maneuvering target.

 

Also, MiG-29s manual makes sense in that regard, 'cause if the target does not change its flight path it will grant you a kill with minimum possible risk to your self. In RL RWRs are not super dependeable target location devices like in DCS, so if the target has not picked up the launch it might get splashed.

 

Our RWRs are just to good. They see and know everything and never make a mistake. Not to mention ECM.

[GGTharos]

They're quite dependable for telling you that you're being attacked.  Their angular and range accuracy and the ability to use them as ISR platforms is the inaccurate part.

[dundun92]

1 hour ago, Cmptohocah said:

Also, MiG-29s manual makes sense in that regard, 'cause if the target does not change its flight path it will grant you a kill with minimum possible risk to your self.

But what if the bandit pilot sneezes and accidentally moves the control stick half an inch and causes a slight flight patch deviation ? What if the wind changes direction by a little bit? What if you fired it 0.5° off of the ASE circle? What if you rolled a bit during launch, and the time the missile took to correct meant that the missile had to make a slightly larger turn to get onto the target, giving it slightly less energy (assuming the missile does this sort of manuever)? Do you really want to instruct pilots to be firing at a range where something like that trashes the shot? There has to be some sort of margin, even if its not that big, but the question is how much? Until we know that you have to treat DLZ ranges like this as Raero at a minimum, but with potential to be higher.

Edited January 8, 2021 by dundun92