R-27ET HUD Range Indication

[159th_Falcon]

First of all one for the mods, no idea what subforum this subject belongs in. Hence im posting it in the general section for bugs and problems in DCS World.

 

I had already noticed the issue in multiplayer but now managed to test it.

(AI wasn't very co-operative)

 

Problem is that the Rmax and Rtr indications of the R-27ET are either incorrect

OR

the R-27ET is not performing as it should

OR

a combination of the above.

 

Performed a test, target F15C flying 1000 meters ASL @ 1300 km/h

Hunter, SU-33, controlled by me trailing at the same altitude.

 

First i let the distance grow to beyond Rmax when my speed is about 1340 km/h.

Then i wait till i am inside Rmax, whit an speed of about 1350 km/h and launch the first ET.

Watch it in F6 view and as soon as its speed drops below 1300 km/h i pause the game.

Go into F10 map view and use the ruler to find out how close it came to the target.

Not very, more then 5 km away still.

 

So i keep the burners on to close the gap till about 8km distance. By this time speed is about 1420 km/h giving the ET a bit of an extra push.

 

Surprise, by the time the ET drops below 1300km/h its still 1 km away, despite being launched just 8 km away.

 

All can be seen in the attached track.

 

Also tried launching the ER (no track) at 8 km distance at similar speed and it did not have any trouble bringing down the F15C.

When i look in the encyclopedia, both missiles are quoted to have the same max speed and the same range.

Which seems sensible seems the biggest difference between the two is the seeker head.

 

Anyway, please fix this by either;

A increasing speed/range on the 27ET

B decreasing indicated launch range on the HUD

C combination of the above.

 

Oh, forgot to mention, for the ET the Rmax and Rtr in this situation are indicated as being identical.

27ET.Rtr.trk

[Dudikoff]

When i look in the encyclopedia, both missiles are quoted to have the same max speed and the same range. Which seems sensible seems the biggest difference between the two is the seeker head.

 

Maybe the encyclopedia entry is wrong as I'd expect that the T/TE have somewhat reduced speed/range compared with R/RE due to the blunt seeker head shape?

 

Not really an aerodynamics engineer to be able to judge how significant role it should play, so just guessing here, but I'd assume it's noticeable, at least at lower altitudes (as in this case, e.g. 1000m AGL)?

Edited July 22, 2013 by Dudikoff

[159th_Falcon]

Good point. And i wouldn't mind if the two end up being a bit different in performance.

 

What i do mind though is that the HUD indication does not represent the range of the weapon.

 

(and at the moment the difference in range between ER and ET is rather large)

[Dudikoff]

What i do mind though is that the HUD indication does not represent the range of the weapon.

 

Of course, I don't know how it's actually implemented, so my post is totally useless from the bug perspective (probably from most if not all perspectives, too).

 

I was just commenting on a possible reason for the range discrepancy between TE and RE models as I'm curious if this would be significant and if it's modeled or planned to be.. IIRC, there was a thread in which this was discussed, but I can't remember the conclusion or if there were any DEV comments. Feel like a broken phone here..

[159th_Falcon]

Roger, anyway, this thread can be deleted since v1.2.5 just came out and i will run the test again in that.

 

If needed ill make a new bug report.

[*Rage*]

I'd be interested in you're findings too Falcon since I've noticed the ET has subpar kinetic performance compared to the ER. The tail chase ABing target scenario should be where it excels.

[159th_Falcon]

Just a short heads-up. I did redo the test. Then found out about the problems whit the 1.2.5 release.

 

So ill redo it again if/when a patch/hotfix is released.

 

ET still seems to have significant less range then ER.

But, when i watched ET in F6 view i don't believe i ever saw the 2nd stage motor activating.

 

Anyway, will be revisited.

 

And now i'm wondering why this is in the lock-on forum.

Ah well, mod moved it here so must be right.

[159th_Falcon]

As promised, just tested again in V 1.2.5.15865

 

Setting;

Target 1000 meters ASL

Target speed 1290 km/h

 

Chase plane 1000 meters ASL

Chase speed between 1320 and 1420 km/h

 

Result;

ET launch from max range ~ 13-14 km, falls way short. (~5km)

ET launch from ~ 8 km range almost reaches the target, probably could have IF;

i didn't fire an ER 7 seconds after the ET.

 

If you replay the track file you can see the ER overtaking the ET before the ET reaches the target, once the two missiles are close enough the proximity fuse takes over.

 

The two explode couple hundred meters behind the target.

 

My guess is that the R-27ET is using the R-27T motor instead of the Dual Stage ET one.

 

You can see this in the track, ET only has initial ignition,

ER has initial followed by a second ignition x seconds later.

 

Hope the track provides some good info for the testers/dev's

 

~S~

v1.2.515865.R27ET.Rtr.trk

[TaliG]

Hi! Please take a look the deferences currently modelled in our sim...

File is located at:

C:\Program Files\Eagle Dynamics\DCS World\Config\Weapons missiles_data.lua

Edited July 26, 2013 by TaliG

[TaliG]

So at the moment I think ET and ER are performing EXACTLY as they are modelled to perform:thumbup:

 

:music_whistling:

[Kuky]

I think the shape of ET (rounded) makes it little more draggier then ER

[*Rage*]

So at the moment I think ET and ER are performing EXACTLY as they are modelled to perform:thumbup:

 

:music_whistling:

 

But are they modelled correctly? How much does the rounded cone affect speed/range?

[159th_Falcon]

I think the shape of ET (rounded) makes it little more draggier then ER

A little, yes maybe.

But did you watch the track?

The ER overtakes the ET whit a SIGNIFICANT speed difference.

(ER was fired 7 seconds AFTER ET, remember?)

 

I'm no expert, but i wouldn't expect a whole lot more drag due to the rounded nose cone of the ET.

 

But are they modelled correctly? How much does the rounded cone affect speed/range?

 

No more then 5% orso if i had to hazard a guess. There's much more to a rocket's drag then the nose cone alone.

[GGTharos]

I'm no expert, but i wouldn't expect a whole lot more drag due to the rounded nose cone of the ET.

 

You should, it's a big difference - BUT, it all depends on some things :)

 

No more then 5% orso if i had to hazard a guess. There's much more to a rocket's drag then the nose cone alone.

Nope (assuming you have the same rocket motor) ... nose fineness drives range on a missile.

 

That said, there's rounded noses where the nose is a hemisphere that is the diameter of the missile - that's the draggiest - like say, the AIM-4, and there's rounded noses where the hemisphere is mounted in what is partly a sharp nose, which is far less draggy and depending on how much you can reduce the diameter, the drag will be very similar or even practically the same as that of a radar guided missile radome.

 

The reason you should expect a certain distance from an ET is the usage diagrams :)

Edited July 27, 2013 by GGTharos

[Kuky]

A little, yes maybe.

But did you watch the track?

The ER overtakes the ET whit a SIGNIFICANT speed difference.

(ER was fired 7 seconds AFTER ET, remember?)

 

That is to be expected because you didn't launch both missiles at exact same time (and to test them correctly both missiles need to be fired from same point/line at the same time, like a race). The missile engine only burns few seconds, I don't know now what time ET engine burns but lets assume its 7 sec... in that time just when the first missile engine burns out you fire the second missile... during this 7sec your aircraft will have traveled some distance already and given second missile a "head start" because it now starts long after first missile (starting position) and it now accelerates while first missile is already decelerating... so it's expected that second missile when it passes the first missile will have probably just have its engine stop... it will be at max speed, while first missile has decelerated somewhat... so yes... speed difference at that moment will be high.

 

You can test with 2 same missiles also... fire 1st then fire second missile when first missile eninge stops burning... same thing will happen... 2nd missile will overtake 1st missile and have more speed at time of "takeover"

[TaliG]

I made some tests last knight.

Conditions was:

Su33 at 24000feet 500knt

No target, unauthorised ballistic, straight lunch towards the same heading.

Both missiles lunched from the same point (separate missions for each missile)

and repeated the test at least 10 times for each missile.

I measured the distance antil the missiles hit the ground.

Results:

ER: 26nm average from lunch to ground impact

ET: 20nm -//- -//- -//-

These are Ballistic , eg the missiles falls to the ground.

 

Wikipedia and other sources state that maximum distance at optimal conditions are 130km for ER and 120km for ET. These numbers are impossible to catch even with 2 rocket motors onboard.

 

What do I have to do to achieve even half the number that wiki states?

[Kuky]

OK, these optimal conditions stated as 130Km is not actual missile distance... it's max distance from launching aircraft to target aircraft at time of launch... taking into account that target will not maneuver The distance which missile will fly (and have enough energy to maneuver with target) is much much less. And also this distance stated might not be correct with real life... and this is one area where really accurate sources are hard to get mostly due to being classified and not widely available to public.

[TaliG]

Understood.

From the tests I made, the difference in covered distance between the 2 missiles is ~15%.

So if we can assume that the spherical head has a 15% reduction in aerodynamics than the conical,

then we have a pretty good model here and nothing is wrong with ET.

:confused:

[karambiatos]

if there is a difference in the performance fine, but why isnt it represented on the range tape on the HUD, i believe that was falcons original question.

[159th_Falcon]

^^^^ That's correct.

 

Well, two question's actually.

One was the range tape not showing correctly.

And / Or

ET does not have enough range.

[TaliG]

^^^^ That's correct.

 

Well, two question's actually.

One was the range tape not showing correctly.

And / Or

ET does not have enough range.

If the 15%performance deference is correct then the hud tape is also correct (cannotmeasure this exactly) because there is no huge deference in the distance representation between ER and ET.

May be you mean that the launch authorization does not come when you expected.

This is because the hit seeker cannot lock to the target, eg not enough heat radiation due to aspect ratio of the target...

This can be overcome with the ''archer'' technic.

If you know your targets speed and ''3d'' direction, then you can make a rough calculation of where your target will be after 5-8 seconds, override launch permission and fire the towards this direction...If you are correct and your target passes through that point then ET will be capable of acquiring the target and enough power to hit it.

If you wait for launch authorisation then you will propably end up launching to close to the targe where a 73 would me a better choice:smilewink:

 

It always works for me on AI targets which are very predictable.

[159th_Falcon]

Please everyone, just watch the track and you will see why either, and i say it again;

Hud range tape is incorrect

actual missile range is incorrect

combination of the above.

[Wags]

We are aware and it's already in our database.

[159th_Falcon]

All i wanted to hear. :thumbup:

[pepin1234]

One interesting test could be shot the R-27ET and the ER at the same time, same altitud and the ER shot against a heading target with no maneuvers. You need 2 more pilots. One will be the target heading at 1000m and the other beside you launching the ER together with you. Then you can see how downgraded could be the ET. At every 5 km flight stage you can see the speed diference between both missiles with same rocket/Body.

 

The only you should know, how long time the cooler of the ET seeker to get over (not sure if battery too)