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Jaws2002
08-22-2006, 04:36 PM
http://www.rrgstudios.com/img/1946/40_full.jpg

Hashmark13
08-22-2006, 04:44 PM
I hope it's flyable.

Beware, '46 addon haters will flame this to a crisp.

waffen-79
08-22-2006, 04:48 PM
Originally posted by Hashmark13:
I hope it's flyable.

Beware, '46 addon haters will flame this to a crisp.

indeed, I just hope for the flyable Ar-234, anything else is a welcome BONUS

Jaws2002
08-22-2006, 05:24 PM
Originally posted by Hashmark13:
I hope it's flyable.

Beware, '46 addon haters will flame this to a crisp.

http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif

Well, they can bring their biplanes and try to shoot it down. http://forums.ubi.com/images/smilies/mockface.gif

Feathered_IV
08-22-2006, 06:27 PM
Humph! You'll never see over the bar in front of the gunsite http://forums.ubi.com/images/smilies/mockface.gif

orkan_3d
08-22-2006, 08:52 PM
I allways loved planes with surprised fishlike faces.

http://forums.ubi.com/images/smilies/16x16_smiley-surprised.gif http://forums.ubi.com/groupee_common/emoticons/icon_redface.gif http://forums.ubi.com/groupee_common/emoticons/icon_eek.gif http://forums.ubi.com/images/smilies/16x16_smiley-surprised.gif

Jaws2002
08-22-2006, 08:54 PM
Originally posted by Feathered_IV:
Humph! You'll never see over the bar in front of the gunsite http://forums.ubi.com/images/smilies/mockface.gif

With those toys, I won't need a gunsight. http://forums.ubi.com/images/smilies/metal.gif

PBNA-Boosher
08-22-2006, 09:03 PM
SWEET! We got the guided missiles!

ElAurens
08-22-2006, 09:25 PM
*YAWN* Jets...
pffftttt......

Deedsundone
08-23-2006, 01:37 AM
The resemblance is uncanny. http://forums.ubi.com/images/smilies/16x16_smiley-happy.gif
http://i25.photobucket.com/albums/c84/S-8/tunnan.jpg

Viper2005_
08-23-2006, 02:23 AM
The most interesting feature of Ta-183 is that the tail is only used for trim. Pitch control is provided by elevons, which has some interesting knock on effects (tipstall/pitchup likely if excessive forward stick is applied at high alpha)...

This may of course be solved by trimming nose down.

Then the aeroplane is likely to be quite resistant to tipstall, which is more than can be said of most early swept wing jets...

p-11.cAce
08-23-2006, 03:02 AM
http://forums.ubi.com/images/smilies/clap.gif I love the jets in the sim already and think a few more early jets would be great!

stathem
08-23-2006, 04:28 AM
If those X-4s are tuned to go off acoustically by the note of a four-engined bomber, they're not going to be a right lot of use against Mig-9s. - or indeed anything, since the Western allies don't exist in the VVS46 add-on.

NAFP_supah
08-23-2006, 04:38 AM
I see a jet, I see a guided Missile ... I sence my F-104G Coming along!

MEGILE
08-23-2006, 04:42 AM
Mig-9 vs. TA-183 is gonna be cool..

Maddox could do korea so easily... http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

BaronUnderpants
08-23-2006, 04:52 AM
Originally posted by Deedsundone:
The resemblance is uncanny. http://forums.ubi.com/images/smilies/16x16_smiley-happy.gif
http://i25.photobucket.com/albums/c84/S-8/tunnan.jpg


Maby Oleg used the FM of the J-29 or atleast some of it. Biggest differance would be the tail.

Blottogg
08-23-2006, 06:33 AM
Deedsundone, that's kind of like saying the Mirage 2000 is uncannily reminiscent of the F-102 because they're both deltas. Those subtle differences are important. Among the many other differences between the Tunnan and the 183, the Tunnan has wing fences and a leading edge dog-tooth to help prevent the spanwise flow and tip stall Viper2005 talked about.

Viper, I didn't know the tail was a trim surface only. I'm not sure if you'd be able to trim the 183 out of a stall, especially if tip stall progressed into a deep stall, with the tail getting submerged in the dirty air coming off the wing. The tail doesn't have much surface area, though it's got a longer moment arm than the wingtips (I think the engineers would have had a rude introduction to the phenomenon of aeroelasticity with that long swept tail, too.) Perhaps if the stall progressed inboard far enough, the loss of lift would let the nose drop regardless of trim setting on the tail. One of the many questions that no doubt would have been answered in wind tunnel/flight test, had the design progressed that far.

P.S. I re-read you post and realized you're not talking about trimming out of the stall, but rather trimming nose down to limit the AoA enough to prevent local tip AoA from reaching stall, even with elevons at "full droop". That would work, but is kind of the Ercoupe method of stall control, not giving the pilot enough pitch authority to get into trouble. I'm guessing you'd have to limit AoA to the 12-14 degree range. The left edge of the doghouse plot would move right, meaning the airplane would turn poorly at slow to medium speeds. Takeoff and landing speed would be faster, too.

Viper2005_
08-23-2006, 07:01 AM
Originally posted by stathem:
If those X-4s are tuned to go off acoustically by the note of a four-engined bomber, they're not going to be a right lot of use against Mig-9s. - or indeed anything, since the Western allies don't exist in the VVS46 add-on.

It's not actually that simple.

The fuze is tuned to detonate the warhead at a certain distance from the design target assuming a certain range rate (it uses the doppler effect remember?).

Change the tone of the target's engine noise and you'll change the fuzing parameters, but you won't prevent initiation.

In other words, for any given range rate you'll see a different detonation range, or for any given detonation range you'll see a different range rate.

The chances are that it will be quite a forgiving optimisation.

Wright 1820 turns at 2600 rpm (ie 43 Hz), with a reduction gear ratio of 16:9, such that the maximum prop rpm is 1463 or so.

That gives 24 Hz.

Multiply by 3 blades to give a bladepass frequency of 72 Hz or so.

Now consider a Mustang. 3000 rpm through a 0.479 reduction gear (V-1650-7) gives 1437 prop rpm, which is 24 Hz.

Multiply by 4 blades to give a bladepass frequency of 96 Hz.

Now consider the doppler effect

fr/fs = (1-n*vr/c)/(1-n*vs/c)

fr = frequency detected
fs = frequency of source
vr = velocity of detector
vs = velocity of source
c = local speed of sound
n = unit vector from s to r

Let's start with a B-17, which we shall attack from the rear. We can assume a 180 mph cruise speed. Thus fs = 80 m/s.
We'll assume a standard day at 25,000 feet, so c = 310 m/s.
The missile would appear to reach a maximum speed of about Mach 1, so let's assume Mach 0.9 at "impact". That's about 280 m/s for vr. We've already calculated that fs = 72 Hz. n = cos theta where theta = angle from nose of missile to target.

So, now we can plug those numbers in:

fr/72 = (1 - - 0.9)/(1 - -0.26) = 108 Hz.

If the target is missed, the missile will hear a different situation since n now = -1.

fr/72 = (1 + - 0.9)/(1 + - 0.26) = 9.7 Hz.

Pretty dramatic isn't it?

Now, let's attack headon (this changes a sign):

fr/72 = (1 - - 0.9)/(1 - + 0.26) = 1.9/0.75
thus fr = 72*1.9/0.75 = 184 Hz.

If the target is missed, the missile will hear

fr/72 = (1 + - 0.9)/(1 + + 0.26) = 5.7 Hz

Of course, what actually happens is that n varies as the cosine of the angle between the missile and the target. So, as the missile approaches, the angle increases, and n decreases from 1 to zero at the point of closest approach, and then heads off towards -1 as the missile zooms off into the wild blue yonder).

Since the missile is cracking along at a fair old rate, it must be detonated before the point of closest approach. Therefore we can say that the fuse is tuned for a frequency in the range produced by the design target when 1>n>0.

If you feel that way inclined, you can sit down and work out the geometry for yourself...

The point is that the fuse must be tuned to a frequency higher than that of the bomber's engine note because the design closing velocity is large and n > 0.

As such, it's easy to see that if you throw the missile at a different target such as a P-51:

i) The fuze will always function provided that the doppler shifted engine note is in the correct frequency band and is loud enough.

ii) The Mustang's higher-pitched engine note is likely to be at least partially compensated for in the tail-chase case by its faster cruise speed.

iii) In the head-on case, the fuze is likely to detonate the missile late, and the target may escape. The fuze delay was designed to carry the missile from 40 m at initiation to 5 m at detonation, which is about 0.175 s at the design closing speed of about 200 m/s (tailchase attack against B-17). A P-51 flying at 400 mph headon would increase this closing speed to 460 m/s, which would obviously more than double the fuzing distance.

This incidently implies a 5 m miss distance, so you can draw a triangle and work out that the miss angle at initiation is 7 degrees or so. This gives n = 0.99...

So, we may assume that the fuse was probably tuned based upon the assumption that n = 1.

This leaves considerable room for manoeuvre.

If, in the design case attacking a B-17, the fuze initiates at n=0.99, then we may say with confidence that it will initiate against a P-51 when n<0.99.

How much less? Well, it's not too difficult to perform the calculations if you feel that way inclined.

Suffice it to say that the fuze would most likely function against a wide variety of targets, though the results would vary depending upon the relationship between n, range rate and target hardness.

And that of course is based upon the assumption that the fuse was finely tuned. The chances are that it would operate over a band of perhaps +/- 10 Hz or so in order to account for variations in range rate, which greatly simplifies the problem. The limiting factor would likely be amplitude rather than frequency...

TgD Thunderbolt56
08-23-2006, 07:03 AM
The wait itself could be mind-numbing. We're still waiting for the IL-10 Manchurian add-on that was supposed to be out over a month ago. Any add-on will be cool though and these last two should be a nice farewell for FB+PF.


TB

stathem
08-23-2006, 07:09 AM
Originally posted by Viper2005_:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by stathem:
If those X-4s are tuned to go off acoustically by the note of a four-engined bomber, they're not going to be a right lot of use against Mig-9s. - or indeed anything, since the Western allies don't exist in the VVS46 add-on.

It's not actually that simple.

The fuze is tuned to detonate the warhead at a certain distance from the design target assuming a certain range rate (it uses the doppler effect remember?).

Change the tone of the target's engine noise and you'll change the fuzing parameters, but you won't prevent initiation.

In other words, for any given range rate you'll see a different detonation range, or for any given detonation range you'll see a different range rate.

The chances are that it will be quite a forgiving optimisation.

Wright 1820 turns at 2600 rpm (ie 43 Hz), with a reduction gear ratio of 16:9, such that the maximum prop rpm is 1463 or so.

That gives 24 Hz.

Multiply by 3 blades to give a bladepass frequency of 72 Hz or so.

Now consider a Mustang. 3000 rpm through a 0.479 reduction gear (V-1650-7) gives 1437 prop rpm, which is 24 Hz.

Multiply by 4 blades to give a bladepass frequency of 96 Hz.

Now consider the doppler effect

fr/fs = (1-n*vr/c)/(1-n*vs/c)

fr = frequency detected
fs = frequency of source
vr = velocity of detector
vs = velocity of source
c = local speed of sound
n = unit vector from s to r

Let's start with a B-17, which we shall attack from the rear. We can assume a 180 mph cruise speed. Thus fs = 80 m/s.
We'll assume a standard day at 25,000 feet, so c = 310 m/s.
The missile would appear to reach a maximum speed of about Mach 1, so let's assume Mach 0.9 at "impact". That's about 280 m/s for vr. We've already calculated that fs = 72 Hz. n = cos theta where theta = angle from nose of missile to target.

So, now we can plug those numbers in:

fr/72 = (1 - - 0.9)/(1 - -0.26) = 108 Hz.

If the target is missed, the missile will hear a different situation since n now = -1.

fr/72 = (1 + - 0.9)/(1 + - 0.26) = 9.7 Hz.

Pretty dramatic isn't it?

Now, let's attack headon (this changes a sign):

fr/72 = (1 - - 0.9)/(1 - + 0.26) = 1.9/0.75
thus fr = 72*1.9/0.75 = 184 Hz.

If the target is missed, the missile will hear

fr/72 = (1 + - 0.9)/(1 + + 0.26) = 5.7 Hz

Of course, what actually happens is that n varies as the cosine of the angle between the missile and the target. So, as the missile approaches, the angle increases, and n decreases from 1 to zero at the point of closest approach, and then heads off towards -1 as the missile zooms off into the wild blue yonder).

Since the missile is cracking along at a fair old rate, it must be detonated before the point of closest approach. Therefore we can say that the fuse is tuned for a frequency in the range produced by the design target when 1>n>0.

If you feel that way inclined, you can sit down and work out the geometry for yourself...

The point is that the fuse must be tuned to a frequency higher than that of the bomber's engine note because the design closing velocity is large and n > 0.

As such, it's easy to see that if you throw the missile at a different target such as a P-51:

i) The fuze will always function provided that the doppler shifted engine note is in the correct frequency band and is loud enough.

ii) The Mustang's higher-pitched engine note is likely to be at least partially compensated for in the tail-chase case by its faster cruise speed.

iii) In the head-on case, the fuze is likely to detonate the missile late, and the target may escape. The fuze delay was designed to carry the missile from 40 m at initiation to 5 m at detonation, which is about 0.175 s at the design closing speed of about 200 m/s (tailchase attack against B-17). A P-51 flying at 400 mph headon would increase this closing speed to 460 m/s, which would obviously more than double the fuzing distance.

This incidently implies a 5 m miss distance, so you can draw a triangle and work out that the miss angle at initiation is 7 degrees or so. This gives n = 0.99...

So, we may assume that the fuse was probably tuned based upon the assumption that n = 1.

This leaves considerable room for manoeuvre.

If, in the design case attacking a B-17, the fuze initiates at n=0.99, then we may say with confidence that it will initiate against a P-51 when n<0.99.

How much less? Well, it's not too difficult to perform the calculations if you feel that way inclined.

Suffice it to say that the fuze would most likely function against a wide variety of targets, though the results would vary depending upon the relationship between n, range rate and target hardness.

And that of course is based upon the assumption that the fuse was finely tuned. The chances are that it would operate over a band of perhaps +/- 10 Hz or so in order to account for variations in range rate, which greatly simplifies the problem. The limiting factor would likely be amplitude rather than frequency... </div></BLOCKQUOTE>

Viper, you have too much time on your hands. You really need a job. http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

Viper2005_
08-23-2006, 07:19 AM
Originally posted by Blottogg:
Deedsundone, that's kind of like saying the Mirage 2000 is uncannily reminiscent of the F-102 because they're both deltas. Those subtle differences are important. Among the many other differences between the Tunnan and the 183, the Tunnan has wing fences and a leading edge dog-tooth to help prevent the spanwise flow and tip stall Viper2005 talked about.

Viper, I didn't know the tail was a trim surface only. I'm not sure if you'd be able to trim the 183 out of a stall, especially if tip stall progressed into a deep stall, with the tail getting submerged in the dirty air coming off the wing. The tail doesn't have much surface area, though it's got a longer moment arm than the wingtips (I think the engineers would have had a rude introduction to the phenomenon of aeroelasticity with that long swept tail, too.) Perhaps if the stall progressed inboard far enough, the loss of lift would let the nose drop regardless of trim setting on the tail. One of the many questions that no doubt would have been answered in wind tunnel/flight test, had the design progressed that far.

P.S. I re-read you post and realized you're not talking about trimming out of the stall, but rather trimming nose down to limit the AoA enough to prevent local tip AoA from reaching stall, even with elevons at "full droop". That would work, but is kind of the Ercoupe method of stall control, not giving the pilot enough pitch authority to get into trouble. I'm guessing you'd have to limit AoA to the 12-14 degree range. The left edge of the doghouse plot would move right, meaning the airplane would turn poorly at slow to medium speeds. Takeoff and landing speed would be faster, too.

The elevons will probably only tipstall you if you're pushing forward hard whilst at highish alpha. Whilst you're pulling, they act to prevent tipstall, which is a very nice touch.

But if you push the limits then this feature could get you into trouble. With "up" elevon, the wing is effectively washed out, and won't tipstall. Take the elevon off (or even worse, apply "down" elevon) in order to recover, and you'll tipstall.

This is especially dangerous since it will lead to a pitch reversal. Ouch!

So, if you're pushing the limits, the best way to recover from a turn might be to maintain back pressure on the stick and use the trim to ease the alpha down. As the alpha comes down you can relax back pressure, and eventually start pushing, whilst meanwhile neutralising the trim again. In otherwords, I'm talking about a dynamic use of trim to access the edges of the envelope here, not an attempt to provide envelope protection by simply limiting control authority.

You'd see the same behaviour in reverse under negative g, but few would push that hard under normal circumstances. Having said that, it opens up the spectre of an inverted spin if something like a stall turn or roll off the top is botched. I suspect there would have been some interesting health warnings in the POH...

Idiosyncratic trimmer usesage was quite common on early transonic aircraft, with the X-1 and F-86 being classic examples. So, whilst this aeroplane would likely be pretty dangerous near the edges of the envelope, and might give modern pilots considerable pause for thought, by mid 40s to mid 50s standards it would probably have fit in...

MEGILE
08-23-2006, 07:24 AM
Originally posted by Viper2005_:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by stathem:
If those X-4s are tuned to go off acoustically by the note of a four-engined bomber, they're not going to be a right lot of use against Mig-9s. - or indeed anything, since the Western allies don't exist in the VVS46 add-on.

It's not actually that simple.

The fuze is tuned to detonate the warhead at a certain distance from the design target assuming a certain range rate (it uses the doppler effect remember?).

Change the tone of the target's engine noise and you'll change the fuzing parameters, but you won't prevent initiation.

In other words, for any given range rate you'll see a different detonation range, or for any given detonation range you'll see a different range rate.

The chances are that it will be quite a forgiving optimisation.

Wright 1820 turns at 2600 rpm (ie 43 Hz), with a reduction gear ratio of 16:9, such that the maximum prop rpm is 1463 or so.

That gives 24 Hz.

Multiply by 3 blades to give a bladepass frequency of 72 Hz or so.

Now consider a Mustang. 3000 rpm through a 0.479 reduction gear (V-1650-7) gives 1437 prop rpm, which is 24 Hz.

Multiply by 4 blades to give a bladepass frequency of 96 Hz.

Now consider the doppler effect

fr/fs = (1-n*vr/c)/(1-n*vs/c)

fr = frequency detected
fs = frequency of source
vr = velocity of detector
vs = velocity of source
c = local speed of sound
n = unit vector from s to r

Let's start with a B-17, which we shall attack from the rear. We can assume a 180 mph cruise speed. Thus fs = 80 m/s.
We'll assume a standard day at 25,000 feet, so c = 310 m/s.
The missile would appear to reach a maximum speed of about Mach 1, so let's assume Mach 0.9 at "impact". That's about 280 m/s for vr. We've already calculated that fs = 72 Hz. n = cos theta where theta = angle from nose of missile to target.

So, now we can plug those numbers in:

fr/72 = (1 - - 0.9)/(1 - -0.26) = 108 Hz.

If the target is missed, the missile will hear a different situation since n now = -1.

fr/72 = (1 + - 0.9)/(1 + - 0.26) = 9.7 Hz.

Pretty dramatic isn't it?

Now, let's attack headon (this changes a sign):

fr/72 = (1 - - 0.9)/(1 - + 0.26) = 1.9/0.75
thus fr = 72*1.9/0.75 = 184 Hz.

If the target is missed, the missile will hear

fr/72 = (1 + - 0.9)/(1 + + 0.26) = 5.7 Hz

Of course, what actually happens is that n varies as the cosine of the angle between the missile and the target. So, as the missile approaches, the angle increases, and n decreases from 1 to zero at the point of closest approach, and then heads off towards -1 as the missile zooms off into the wild blue yonder).

Since the missile is cracking along at a fair old rate, it must be detonated before the point of closest approach. Therefore we can say that the fuse is tuned for a frequency in the range produced by the design target when 1>n>0.

If you feel that way inclined, you can sit down and work out the geometry for yourself...

The point is that the fuse must be tuned to a frequency higher than that of the bomber's engine note because the design closing velocity is large and n > 0.

As such, it's easy to see that if you throw the missile at a different target such as a P-51:

i) The fuze will always function provided that the doppler shifted engine note is in the correct frequency band and is loud enough.

ii) The Mustang's higher-pitched engine note is likely to be at least partially compensated for in the tail-chase case by its faster cruise speed.

iii) In the head-on case, the fuze is likely to detonate the missile late, and the target may escape. The fuze delay was designed to carry the missile from 40 m at initiation to 5 m at detonation, which is about 0.175 s at the design closing speed of about 200 m/s (tailchase attack against B-17). A P-51 flying at 400 mph headon would increase this closing speed to 460 m/s, which would obviously more than double the fuzing distance.

This incidently implies a 5 m miss distance, so you can draw a triangle and work out that the miss angle at initiation is 7 degrees or so. This gives n = 0.99...

So, we may assume that the fuse was probably tuned based upon the assumption that n = 1.

This leaves considerable room for manoeuvre.

If, in the design case attacking a B-17, the fuze initiates at n=0.99, then we may say with confidence that it will initiate against a P-51 when n<0.99.

How much less? Well, it's not too difficult to perform the calculations if you feel that way inclined.

Suffice it to say that the fuze would most likely function against a wide variety of targets, though the results would vary depending upon the relationship between n, range rate and target hardness.

And that of course is based upon the assumption that the fuse was finely tuned. The chances are that it would operate over a band of perhaps +/- 10 Hz or so in order to account for variations in range rate, which greatly simplifies the problem. The limiting factor would likely be amplitude rather than frequency... </div></BLOCKQUOTE>

wtf Viper my head just exploded

Blottogg
08-23-2006, 07:39 PM
Nice explanation to both items, Viper. You aren't taking an acoustics course this semester, are you?

The acoustic proximity sensor is interesting, and one of the things I wonder about is how they managed to tune the microphone to detect the target frequency range over what must have been a lot of ambient broad-spectrum noise from the rocket motor and airflow.

An unintuitive countermeasure would have been for the bomber pilot to go to coarse pitch. This would have decreased fr, possibly detonating the missile early. Pretending they were a P-51, the bomber guys could alternatively have gone to fine pitch, hoping that the higher frequency delayed missile detonation until after it passed (both take the target out of the anticipated frequency band you point out as necessary in your condition i)). Either technique could leave them vulnerable to a guns follow-up, if they lost too much speed while monkeying with the pitch levers. I doubt the sim engine will be able to model any of this in any case, most likely detonating the missile within a fixed distance from a target. If the modeling is very trick, the missile will only detonate in proximity to a bomber, saving your inept Ai wingmen when they inevitably fly in front of you when you fire/guide the missile.

I'd forgotten that the only time both elevons are fully down is with full stick forward, which is unlikely during the turn as you said, though either maximum commanded roll rate or rudder rolling at high AoA could lead to some interesting departures too. The scenario you paint of counter intuitively recovering from high alpha flight would no doubt have taken either a lot of specific training during conversion to type, or perhaps the conservative AoA limits I suggested, to keep the pilot from getting to the point of recovery in the first place. Imagine turning hard, trying to get that gun shot on an escort fighter, only to realize you're trapped in lag. No problem until you push forward to lag off and extend (perhaps with some roll control included to reverse the turn away from the guy you were chasing), only to find that your push forward was the last straw, stalling the tip(s). Depending on how close you were to stall during the turn, and how hard you pushed forward (both affecting what, if any, reduction in nose rate you achieved) the jet may just rate through the stall and fly away. Otherwise, like you said you've got to counter intuitively pull back on the stick and fly the jet to lower AoA with the trim (again, provided the tail has enough clean air and authority.) And doing the same while inverted (pushing hard while at the top of a loop like you mention, maybe chasing a snapshot at the top of an Immelman) would be even more disorienting from the cockpit. Lacking enough training in recovery techniques, the accident rate would have been appalling (even worse than other early jets), before considering "normal" swept wing idiosyncrasies like slipping. Imagine the first rookie coming in a little high on final, who puts in a boot full of rudder and opposite roll like he did in his old 109. A snap-roll while fully configured and close to the ground would have been spectacular and brief.

Now I'm curious to fly this thing, if nothing else just to see how the Il-2 engine models it.

Sintubin
08-23-2006, 07:58 PM
Originally posted by Viper2005_:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by stathem:
If those X-4s are tuned to go off acoustically by the note of a four-engined bomber, they're not going to be a right lot of use against Mig-9s. - or indeed anything, since the Western allies don't exist in the VVS46 add-on.

It's not actually that simple.

The fuze is tuned to detonate the warhead at a certain distance from the design target assuming a certain range rate (it uses the doppler effect remember?).

Change the tone of the target's engine noise and you'll change the fuzing parameters, but you won't prevent initiation.

In other words, for any given range rate you'll see a different detonation range, or for any given detonation range you'll see a different range rate.

The chances are that it will be quite a forgiving optimisation.

Wright 1820 turns at 2600 rpm (ie 43 Hz), with a reduction gear ratio of 16:9, such that the maximum prop rpm is 1463 or so.

That gives 24 Hz.

Multiply by 3 blades to give a bladepass frequency of 72 Hz or so.

Now consider a Mustang. 3000 rpm through a 0.479 reduction gear (V-1650-7) gives 1437 prop rpm, which is 24 Hz.

Multiply by 4 blades to give a bladepass frequency of 96 Hz.

Now consider the doppler effect

fr/fs = (1-n*vr/c)/(1-n*vs/c)

fr = frequency detected
fs = frequency of source
vr = velocity of detector
vs = velocity of source
c = local speed of sound
n = unit vector from s to r

Let's start with a B-17, which we shall attack from the rear. We can assume a 180 mph cruise speed. Thus fs = 80 m/s.
We'll assume a standard day at 25,000 feet, so c = 310 m/s.
The missile would appear to reach a maximum speed of about Mach 1, so let's assume Mach 0.9 at "impact". That's about 280 m/s for vr. We've already calculated that fs = 72 Hz. n = cos theta where theta = angle from nose of missile to target.

So, now we can plug those numbers in:

fr/72 = (1 - - 0.9)/(1 - -0.26) = 108 Hz.

If the target is missed, the missile will hear a different situation since n now = -1.

fr/72 = (1 + - 0.9)/(1 + - 0.26) = 9.7 Hz.

Pretty dramatic isn't it?

Now, let's attack headon (this changes a sign):

fr/72 = (1 - - 0.9)/(1 - + 0.26) = 1.9/0.75
thus fr = 72*1.9/0.75 = 184 Hz.

If the target is missed, the missile will hear

fr/72 = (1 + - 0.9)/(1 + + 0.26) = 5.7 Hz

Of course, what actually happens is that n varies as the cosine of the angle between the missile and the target. So, as the missile approaches, the angle increases, and n decreases from 1 to zero at the point of closest approach, and then heads off towards -1 as the missile zooms off into the wild blue yonder).

Since the missile is cracking along at a fair old rate, it must be detonated before the point of closest approach. Therefore we can say that the fuse is tuned for a frequency in the range produced by the design target when 1>n>0.

If you feel that way inclined, you can sit down and work out the geometry for yourself...

The point is that the fuse must be tuned to a frequency higher than that of the bomber's engine note because the design closing velocity is large and n > 0.

As such, it's easy to see that if you throw the missile at a different target such as a P-51:

i) The fuze will always function provided that the doppler shifted engine note is in the correct frequency band and is loud enough.

ii) The Mustang's higher-pitched engine note is likely to be at least partially compensated for in the tail-chase case by its faster cruise speed.

iii) In the head-on case, the fuze is likely to detonate the missile late, and the target may escape. The fuze delay was designed to carry the missile from 40 m at initiation to 5 m at detonation, which is about 0.175 s at the design closing speed of about 200 m/s (tailchase attack against B-17). A P-51 flying at 400 mph headon would increase this closing speed to 460 m/s, which would obviously more than double the fuzing distance.

This incidently implies a 5 m miss distance, so you can draw a triangle and work out that the miss angle at initiation is 7 degrees or so. This gives n = 0.99...

So, we may assume that the fuse was probably tuned based upon the assumption that n = 1.

This leaves considerable room for manoeuvre.

If, in the design case attacking a B-17, the fuze initiates at n=0.99, then we may say with confidence that it will initiate against a P-51 when n<0.99.

How much less? Well, it's not too difficult to perform the calculations if you feel that way inclined.

Suffice it to say that the fuze would most likely function against a wide variety of targets, though the results would vary depending upon the relationship between n, range rate and target hardness.

And that of course is based upon the assumption that the fuse was finely tuned. The chances are that it would operate over a band of perhaps +/- 10 Hz or so in order to account for variations in range rate, which greatly simplifies the problem. The limiting factor would likely be amplitude rather than frequency... </div></BLOCKQUOTE>

Exact wat i woulded to say but you where first

http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif

Gubru
08-23-2006, 08:45 PM
Any idea when this will be out? http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

reisen52
08-23-2006, 09:20 PM
Originally posted by Viper2005_:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by stathem:
If those X-4s are tuned to go off acoustically by the note of a four-engined bomber, they're not going to be a right lot of use against Mig-9s. - or indeed anything, since the Western allies don't exist in the VVS46 add-on.

It's not actually that simple.

The fuze is tuned to detonate the warhead at a certain distance from the design target assuming a certain range rate (it uses the doppler effect remember?).

Change the tone of the target's engine noise and you'll change the fuzing parameters, but you won't prevent initiation.

In other words, for any given range rate you'll see a different detonation range, or for any given detonation range you'll see a different range rate.

The chances are that it will be quite a forgiving optimisation.

Wright 1820 turns at 2600 rpm (ie 43 Hz), with a reduction gear ratio of 16:9, such that the maximum prop rpm is 1463 or so.

That gives 24 Hz.

Multiply by 3 blades to give a bladepass frequency of 72 Hz or so.

Now consider a Mustang. 3000 rpm through a 0.479 reduction gear (V-1650-7) gives 1437 prop rpm, which is 24 Hz.

Multiply by 4 blades to give a bladepass frequency of 96 Hz.

Now consider the doppler effect

fr/fs = (1-n*vr/c)/(1-n*vs/c)

fr = frequency detected
fs = frequency of source
vr = velocity of detector
vs = velocity of source
c = local speed of sound
n = unit vector from s to r

Let's start with a B-17, which we shall attack from the rear. We can assume a 180 mph cruise speed. Thus fs = 80 m/s.
We'll assume a standard day at 25,000 feet, so c = 310 m/s.
The missile would appear to reach a maximum speed of about Mach 1, so let's assume Mach 0.9 at "impact". That's about 280 m/s for vr. We've already calculated that fs = 72 Hz. n = cos theta where theta = angle from nose of missile to target.

So, now we can plug those numbers in:

fr/72 = (1 - - 0.9)/(1 - -0.26) = 108 Hz.

If the target is missed, the missile will hear a different situation since n now = -1.

fr/72 = (1 + - 0.9)/(1 + - 0.26) = 9.7 Hz.

Pretty dramatic isn't it?

Now, let's attack headon (this changes a sign):

fr/72 = (1 - - 0.9)/(1 - + 0.26) = 1.9/0.75
thus fr = 72*1.9/0.75 = 184 Hz.

If the target is missed, the missile will hear

fr/72 = (1 + - 0.9)/(1 + + 0.26) = 5.7 Hz

Of course, what actually happens is that n varies as the cosine of the angle between the missile and the target. So, as the missile approaches, the angle increases, and n decreases from 1 to zero at the point of closest approach, and then heads off towards -1 as the missile zooms off into the wild blue yonder).

Since the missile is cracking along at a fair old rate, it must be detonated before the point of closest approach. Therefore we can say that the fuse is tuned for a frequency in the range produced by the design target when 1>n>0.

If you feel that way inclined, you can sit down and work out the geometry for yourself...

The point is that the fuse must be tuned to a frequency higher than that of the bomber's engine note because the design closing velocity is large and n > 0.

As such, it's easy to see that if you throw the missile at a different target such as a P-51:

i) The fuze will always function provided that the doppler shifted engine note is in the correct frequency band and is loud enough.

ii) The Mustang's higher-pitched engine note is likely to be at least partially compensated for in the tail-chase case by its faster cruise speed.

iii) In the head-on case, the fuze is likely to detonate the missile late, and the target may escape. The fuze delay was designed to carry the missile from 40 m at initiation to 5 m at detonation, which is about 0.175 s at the design closing speed of about 200 m/s (tailchase attack against B-17). A P-51 flying at 400 mph headon would increase this closing speed to 460 m/s, which would obviously more than double the fuzing distance.

This incidently implies a 5 m miss distance, so you can draw a triangle and work out that the miss angle at initiation is 7 degrees or so. This gives n = 0.99...

So, we may assume that the fuse was probably tuned based upon the assumption that n = 1.

This leaves considerable room for manoeuvre.

If, in the design case attacking a B-17, the fuze initiates at n=0.99, then we may say with confidence that it will initiate against a P-51 when n<0.99.

How much less? Well, it's not too difficult to perform the calculations if you feel that way inclined.

Suffice it to say that the fuze would most likely function against a wide variety of targets, though the results would vary depending upon the relationship between n, range rate and target hardness.

And that of course is based upon the assumption that the fuse was finely tuned. The chances are that it would operate over a band of perhaps +/- 10 Hz or so in order to account for variations in range rate, which greatly simplifies the problem. The limiting factor would likely be amplitude rather than frequency... </div></BLOCKQUOTE>

Interesting stuff...too bad in real life it only took them another 40 years or so to make reliable A2A missiles.

Zeke

Akronnick
08-23-2006, 10:19 PM
There's a reason they're called MISSiles, if they worked, they'd be called HITiles.

Viper2005_
08-24-2006, 03:28 PM
No acoustics for me - just wikipedia.

http://en.wikipedia.org/wiki/Doppler_effect

No microphone required:

http://www.luft46.com/missile/x4-2.gif

The Plastic Diaphragm is centered in the missile, and is connected by means of a lever arrangement to a needle-like pointer whose mass is much smaller than that of the diaphragm. Two opposing openings (covered by a fine mesh screen) in the missiles body allow sound to enter to the diaphragm, and when the missile passes through the the transition region of the Doppler frequency shift, the vibrations of the diaphragm excite resonances in the needle, the needle touches an electric contact, completes the circuit and fires the igniter.

Taken from www.luft46.com (http://www.luft46.com)

Having read both it's not too hard to have a stab at the basic maths.

The wind noise is likely to be rather higher pitched and as you say broader in spectrum than the main bladepass harmonic coming from the bomber. It's very unlikely to cause a false positive (unless it excites a high order harmonic). In addition, since the sound pickup is in the nose of the missile, and the mach number is high, the aerodynamic noise coming off the missile body, wings and fins will be quiet, and anyway it's likely to be squashed down to a fairly low frequency. Provided that a bit of tunnel time is taken to avoid resonance at an unfortunate frequency (given that a liquid fuel rocket is used, injector resonance is a potential issue). Obviously the fuse must be isolated from the structure...

I considered the rpm trick. The trouble with it is that in service the missile would have been deployed against bomber formations, and unless the whole formation applied the countermeasure it wouldn't work too well. In fact, the countermeasure would play into the attackers' hands since the objective of the missile was to protect the attacker from the devastating crossfire of the combat box.

Large rpm changes would break up the formation, and then the stragglers would be easy meat. Remember that a 10% loss rate is the limit of acceptability.

The R4M was based upon the same logic. The blasted things would miss more often than not, but they'd likely scare the bombers out of formation. The same logic was applied by NATO with various folding fin or spin stabilised a2a rockets in the 1950s. They hardly ever hit anything, but that wasn't the point, just as most rounds fired by troops on the ground never hit anything, but merely serve to keep the enemy's head down!

In the context of a bomber formation, the chances are that the missile would continue until it met a bomber which had neglected to reduce rpm.

However, it is also worth pointing out that I've based my sums on 2600 rpm because that was a nice number I found on the web. The bombers probably didn't use full rated power in the cruise, which would affect both the design frequency of the fuse and the options available to the bombers (assuming that they worked out the fuse's MO). In the longer term a RADAR fuse would be a likely replacement or augmentation (as a sanity check).

Wingmen (and indeed the launch aircraft) would be protected from the warhead by setting up an arming delay of perhaps a second or so.

Remember that this missile was designed to engage bombers at "long" range with the primary objective of keeping the attacking fighter out of their guns envelope. As such, a fairly large minimum range wouldn't have been a problem.

I agree that the elevons could be troublesome, but of course there may have been washout...

Using the trimmer at high alpha is no different from rolling with rudder only in the Phantom, and pilots seem to have adapted to that without too much grief. It is often hard to remember just how much of flying comes down to training. You can get used to flying anything, and if you learn on it, you'll find it natural. If I told you that I was going to build a basic trainer that was directionally unstable on the ground you'd probably tell me that was a bad idea. Actually a flew a Stearman in July and can tell you that it isn't too difficult provided that your feet are awake...

Unconventional controls are only a problem if you make them a problem. Plenty of people fly weightshift microlights and are quite happy despite the fact that the controls work backwards. The French flew for many years with "backwards" throttles...

P-38L had no "feel" in roll and indeed its ailerons wouldn't even self-centre.

Many swept wing jets suffered from pitchup to varying degrees. Most high performance aeroplanes built before about 1955-60 have extremely nasty habbits when they approach MMO. And lots of them had high accident rates in service.

I'm sure that the Ta-183 would have had perhaps more than its fair share of problems as a result of being one of the first on the scene. But I suspect that it could have been made to work extremely well all things considered - Kurt Tank was genius, and more importantly he flew his aeroplanes. And that's always good for quality control!

However, dutch roll and inertia coupling type issues might have raised their ugly heads at some point in the programme, along with directional snaking at high Mach (flow separation from the canopy messing up the aerodynamics of the fin being a likely culprit). It's potentially a very interesting aeroplane, and I really hope that it's flyable (though I doubt IL2 could reproduce many of the quirks I would expect it to exhibit).

As for the missile reliability questions raised by others, I would point out that missile technology was extremely effective at shooting down bombers in the 1950s. Missiles got a bad name in Vietnam when they were asked to do a job for which they were not designed, namely attacking manoeuvring fighter targets. That they didn't work too well is far from surprising. In fact, the real surprise is that they worked at all...

X-4 would only have been as good as its pilot. In the right hands it would have been extremely effective; there's nothing to prevent it from scoring direct hits against fighters. In the wrong hands it wouldn't be able to hit the broad side of a barn door. The prox fuse was designed to take some of the skill out of it by removing the need for a direct hit. But even so the X-4 would require considerable skill to employ effectively against anything other than large bomber formations.

mgoyat
08-24-2006, 08:58 PM
It's a good thing the Ta-183 has an ejection seat http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

carguy_
08-25-2006, 06:14 AM
I wonder how do they think of the missile control.Controling it by the hat would be a good simulation of what the pilot had to do.It seems pretty hard if we take it has no sensitivity adjustment options.
I have a 2nd left over joystick.It could do great as a missile controller. http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

Blottogg
08-25-2006, 07:42 PM
True, rudder rolling a Phantom was just one of many quirks the pilots of 50's and 60's fighters adapted to. The only difference with the 183 would be using a secondary control (trim) instead of a primary control you already had in your hands (or feet.) Vought Cutlass drivers would probably have been able to make the transition to the 183 pretty easily (or with equal difficulty, depending on your point of view.)

The Germans knew they had to pass on the idiosyncracies of these new aircraft in one form or another to the neophytes. They managed to pass on the nuances of jet operation while the intructor stood on the wing and the student taxied. While that approach wouldn't work for instructing 183 stall recovery (though it paints a humorous mental picture), I'm sure the subject wouldn't have been ignored. Academics would certainly be preferable to the worst case test pilot scenario: "I've departed, and the conventional recovery methods aren't working, so I've got the rest of my life to try something else until I find something that works. Flaps (maybe, stalling the inboard section of the wings), gear (probably not), trim... hey this seems promising." Hopefully with enough altitude to allow for this experimentation.

Neat info on the Luft '46 site. An arming delay would be a good idea, even though the launch aircraft would have a different propellor frequency. A minimum launch range is a small price to pay in order to guard against a mis-tuned fuze. The fuze was a neat way of ignoring most of the broad spectrum noise. The site also shows the engagement envelope of the missile as being a little less than +/- 60 degrees off the target's tail. Given the "banana" trajectory of a forward quarter launch, the limit is probably due to end-game manuverability/guidance limitations as much as fuzing shortcomings. And yes, a radar fuze would probably have been a better long-term solution, though earlier versions of those still had problems accomodating both low and high closure rates across a variety of intercept angles. And being set off in proximity to chaff, as well as the target.

Perhaps if we keep speculating long enough, Ubi will release 4.07 just to shut us up?

Viper2005_
08-25-2006, 08:46 PM
The trick would be to use radar and acoustics in concert. That way you get a sanity check and the poor thing won't go bang without good reason.