whoever modelled the La7....

[gripen]

Badboy,
I'm merely pointing out that real world data in the case of the P-51 (or other planes with similar profiles) shows different shape of flight envelope than in the case of the planes with older profiles. You can see the phenomena from the sources I claimed above. And if we look your AH data above (La-7, P-51D, Fw 190D) we can't see that phenomena (all curves are similar). It should be noted that phenomena (different shape of Clmax curve) shows up at entire speed range so it is not limited to compressebility speeds as you are trying to prove above (typical jet vs typical prop graph). So, there is indeed something wrong in the P-51 vs other comparison you posted above if compared to real world data.

Anyway, your data clearly states that it's for a simulation (AH) so I have nothing to complain in that case but dtango posted data without a claim about source.

gripen

[Hristo]

As for low speed handling. Lame-5Fn and Lame-7 had leading edge slats, just like 109. This is not visible in AH, but modeled in Il-2.

[Xjazz]

Great work Badboy!



How about 15k and/or 30k EM analysis with the D9 added to the La7 v P-51?

[straffo]

Originally posted by funkedup
I'm not prepared to start telling HTC that all of their painstakingly prepared mathematical models are faulty.

pfff
in fact it's quite easy : just change your usual RAF ride for a 109 or a 190 during one month and you would be ready to do so

[dtango]

gripen:

I thought I stated that my performance information came from flight tests of AH a/c as I was replying to funked.  The objective of my EM chart certainly wasn't meant to check AH FM's but to help explain how that pesky La-7 does what it does .

Anyhow your point is taken.  I am very much using a simplified model for the lift limit calculations for the flight envelope simply based on AH stall speed of an a/c.

Thanks for both reports.  Digested the first.  Interesting data.  If HTC modelled the P-51D with data from the 1st report, there would be a lot of screaming for sure from pony haters!  Of course there's some puzzling stuff there as well.  But I guess that's real life.  Admittedly some of it is over my head.   Haven't looked over the 2nd since it's a bit longer.

Tango, XO
412th FS Braunco Mustangs

[Spritle]

Did anyone read the article at simhq a few weeks ago about EM diagrams?  It compared the EM diagrams from the AH P-51D to the Microsoft Combat Flight Sim P-51D.  Now at first this might sound ridiculous, but what the article tried to explain is this.  Even though the diagrams were different both P-51D's performed similarly against their respective opponents from each game.  Does that make since?  

So if you compare the EM diagram from the AH P-51D to that of the AH Fw190 there is some ratio of difference.  As long as the same ratio existed between the MSCFS P-51D vs. MSCFS Fw190 then it really didn't matter that the EM diagrams don't match cross platform, as the aircraft would perform correctly against one another within the same game.  This is especially true since you can't fly an AH P-51D against a MSCFS Fw190.  

So really it's not THAT important that the flight models have 100% fidelity compared to their real world counterparts, but rather that they maintain their historical difference with their SIMULATED adversaries.  This would indicate that there needs to be some base EM diagram that ALL other aircraft models MUST maintain their historical difference against.  

This makes the already difficult task of comparing real world test data for an aircraft to AH flight numbers for a different aircraft and then stating “there is an error” impossible.  Instead ALL real world data MUST be converted to SIM data based on that BASELINE EM diagram mentioned earlier.

Here is the link to the article.

http://www.simhq.com/simhq3/sims/air_combat/skills/

Spritle

[dtango]

Spritle - Don't know if you knew or not but Badboy who is posting here wrote that article.

Tango, XO
412th FS Braunco Mustangs

[Tilt]

Originally posted by Mitsu
La-7 is an outstanding fighter...I agree about it.
but I feel AH's one is wrong in something....

In real life, La-7 was bad (unstable) at takeoff/landing.
Doesn't it mean La7 had a bad handling at slow speed?
and it had a tight tapered wing, doesn't it have bad wing-tip stalls?
AH's one is really stable at low speed....easy handling...too easy to recover from spin. I feel it is strange.

In the second place, La-7 can accelerate to the top speed like a rocket. But its engine diameter is big. Doesn't it have a large profile drag? (I mean drag setting might have error in La-7...)

Thirdly, La-7 can fly and fight without 1/2 wing very easily.  Actually I shot down bandits with it. Is this model correct?

OK Mitsu out...Sorry for poor English.

P.S
This is whine though...I hate to see some pilots do a high -G loop in La-7. It's pretty weird....

agree with some of  Mitsu here........both La 5 and La7 had a very disconcerting landing and take of "bounce"(la 7 more so)......... Czech pilots used to Spitfires had to be trained not to correct for it as they did with lesser bounce from Spitfires...........

AH is in error re the stall speed IMHO.......the La7 pilot was instructed that the proper landing speed was 137 Km /hour thats approx 85mph........try it!  I do not know what the true departure point speed was for near level low alt but I am sure it was lower than the recomended landing speed!

Leading edge slats lowered the departure speed with the characturistic rapid departure at that lower point. But it was considered "easy" (by ex spitfire pilots) to recover.

Engine off drag seems low in all AH planes to me..........(un qualified opinion)

But the nose down engine off/throttled back acceleration of the La7 seems high  even tho it is the smallest and has the  lowest total drag of all the radial engined fighters.

Its elevator and rudder control surfaces were massive in comparison with wing and tail areas and would have an abnormal affect of drag during manouvering.

However Verm is correct IMO that the climb, accel and top speed are certainly not over modelled.......

If it were down to me (and of course it is not) I would be increasing both the drag and thrust side of the model....... but retaining the drop off in thrust with alt...and adding a bit more stability at below 100mph with a rapid departure and bouncy landing.

thx for the diagram badz........copied

[Badboy]

Originally posted by gripen
Badboy,
I'm merely pointing out that real world data in the case of the P-51 (or other planes with similar profiles) shows different shape of flight envelope than in the case of the planes with older profiles. You can see the phenomena from the sources I claimed above.

Gripen,

Of course I'm familiar with that material, almost any first year undergraduate would be perfectly aware of the dependence of the aerodynamic coefficients on Mach and Reynolds Number. However, you seem to be expecting that to have an influence on the EM diagram that should be obvious, I've pointed out that I have both types, including many real EM diagrams produced by the military and the difference isn't obvious at all.

And if we look your AH data above (La-7, P-51D, Fw 190D) we can't see that phenomena (all curves are similar). It should be noted that phenomena (different shape of Clmax curve) shows up at entire speed range so it is not limited to compressebility speeds as you are trying to prove above (typical jet vs typical prop graph). So, there is indeed something wrong in the P-51 vs other comparison you posted above if compared to real world data.

I wasn't trying to prove anything, indeed, why would I try to prove something that was already common knowledge? I have been referring to the variation in the aerodynamic coefficients as a function of Mach and Reynolds number, and although it might not sound like it, that's exactly what that report is discussing.  Those Mach effects are the result of compressible flow, and you appear to be misunderstanding the influence that would have on the EM analysis, and my explanation of it.  

The EM diagrams for the real aircraft are infact very similar to those shown here for Aces High, and I've already explained why. I don't know what difference you are expecting to see, and I suspect you don't either? The fact remains that even with all those factors included in the model, the similarity to the AH EM diagrams is almost breathtaking!

Badboy

[ra]

All this mathematical torque stuff is way over my head.  I'm lucky if I can tie my shoes without getting my finger stuck.

But isn't there a difference between calculating torque correctly and applying the resultant force to the FM?  I'm specifically thinking about the fact that we can take off from a CV in a F4U-4  without using any rudder correction at all.  The FM may calculate the torque #'s correctly, but whatever it does with those #'s doesn't seem to affect flight characteristics much.

ra

[dtango]

Badboy:

I think one of the things gripen was trying to point out from the 1st report was that according to the v-n type diagram in the report the P-51D lift-limit envelope is different from what we have on our EM charts. Here is the chart.  

I can't quite explain that since I'm a little perplexed as to how the specific graph in question was put together though the report I think basically says that the v-n diagram in question was based on flying the a/c to it's buffet/stall limits.  

What I can't explain either is if for instance the sea level chart is correct then the P-51D in that report has a much better instantaneous turn capability then what our EM charts indicate.  E.g. at sea level near mach .2 (~150 mph) the P-51D has a lift limit of 3g's according to the chart.  With this info using the simple equation of Vstall-turn = Vstall * sqrt (gload), I end up with a level stall speed for the P-51D at ~88mph ASL.

Still mulling over it all.

Tango, XO
412th FS Braunco Mustangs

[gripen]

Badboy,
We can clearly see that in your P-51/La-7/Fw 190D chart all slopes are very similar and ratio between planes stays constant at hole speed range. We also know that atleast the La-7 utilized NACA 230 series profile and IIRC the Fw 190 used NACA 2something profile too. If we look NACA data we can see that the P-51 had very different Clmax curve shape if compared to the planes which utilized NACA 230 profile. This difference should certainly show up as atleast varying ratio between planes ie as speed increases the P-51 does relatively better (real world data v-g curve comparison between the P-51 and P-38 or P-47 or F4U shows this difference quite clearly, data mostly from manuals). For one reason or another this difference does not show up in your comparison. BTW how many times I should explain this issue? Does this difference show up in your numerical values if we can't see it from the graph?

gripen

[bioconscripter]

I don't complain about the La-7. Every plane has disadvantages and advantages. I have never landed a La-7, a 109 is easier to land than La-7, and La-7 seems to have very high stall speed. Also, I cannot hit anyone with it's guns when they are moving around a lot, sure, it has powerfull guns but the guns don't shoot in a nice even stream but all over the place, not a lot of ammo either. And I don't see a lot of people flying the La-7, everybody seems to be flyings spits, typhoons or those japaneese planes.

[Badboy]

Originally posted by gripen
Badboy,
For one reason or another this difference does not show up in your comparison.

I’ve already explained that in a previous post.

BTW how many times I should explain this issue? Does this difference show up in your numerical values if we can't see it from the graph?

I’ve already explained that too. But if you want to verify it, I can only suggest you carry out your own EM analysis taking all those factors into account, and then, when you have results similar to mine, as indeed you will, you probably won’t even believe it then. But you will at least be able to re-read my previous posts and it may all make a little more sense to you.

Meanwhile, you can rest assured, the Aces High diagrams are both correct and accurate!

Badboy

[Badboy]

Originally posted by dtango
Badboy:
I think one of the things gripen was trying to point out from the 1st report was that according to the v-n type diagram in the report the P-51D lift-limit envelope is different from what we have on our EM charts. Here is the chart.  

Ohh boy, where to begin?

The first thing you must remember, is that the envelope shown on an EM diagram doesn’t have hard boundaries because an aircraft can fly outside of the envelope if forced to do so. In aircraft with manual pitch control, if enough control power exists, it is possible for the pilot to generate enough pitch acceleration to force a g overshoot, simply put, he can pull back fast enough on the stick to force the aircraft outside of the envelope, and generate greater loading than would be possible in steady state conditions. That is what’s happening in the report. Basically, the report isn’t showing you the type of v-n diagram you think it is, it isn’t showing you the aircraft envelope at all, and it isn’t showing you the lift limit, it is showing you a buffet boundary, that in most cases has been reached by taking the aircraft outside the envelope and then into post stall conditions.

I can't quite explain that since I'm a little perplexed as to how the specific graph in question was put together though the report I think basically says that the v-n diagram in question was based on flying the a/c to it's buffet/stall limits.

It was based on the buffet boundary, not the stall limit, there isn’t really any such thing as a stall “limit” it’s more like a region of the envelope, it is possible to fly in it, or beyond it, how far beyond the stall you go will depend on the pitch rate on the aircraft when you get there.

What I can't explain either is if for instance the sea level chart is correct then the P-51D in that report has a much better instantaneous turn capability then what our EM charts indicate.  E.g. at sea level near mach .2 (~150 mph) the P-51D has a lift limit of 3g's according to the chart.  With this info using the simple equation of Vstall-turn = Vstall * sqrt (gload), I end up with a level stall speed for the P-51D at ~88mph ASL.
Still mulling over it all.

You can’t base performance calculations on transient conditions that exist briefly outside the aircrafts normal envelope… Correction, you can, but it just wouldn’t have any useful meaning in terms of air combat.

Hope that helps

Badboy