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Holtzauge
06-10-2010, 01:33 PM
Scenario: Both a/c start at 4 km and 400 Km/h TAS. Both dive at 30 degrees and initiate a 3 g pullout at 2 Km into a 30 degree climb.

1) What will happen? Will Fw pull away, stay ahead all the time? Will Spit pull away, stay ahead all the time? Will they exchange position during the chase? If so where and when?

2) How long will it take to reach pullout time for each aircraft?

3) Who will end up highest at stall? What will be the end altitude for each a/c?

4) What will be the total duration of flight for each a/c before stalling

5) What will be the scenario at 10, 20 30, 40 50, 60 ........X s ? Who is first and how close is the other a/c?

I will post two C++ simulation charts:

1) A diagram showing delta distance between Fw and Spit as a function of time until the first stalls

2) A diagram showing altitude as a function of time and speed as a function of time for each a/c

Results will be posted when we have enough speculation and contenders, hopefully on Saturday.

If not then I'll just skip it. So humor me!

I think this should be fun: First we will see who get's the most correct answers and second we can all look forward to a loooooooooong debate about how the scenario is wrong, red underlined quotes from books, atmospheric and EAS conversions and how it is that what the pilot had for breakfast influences the outcome.

There is no price for getting the most correct answers other than the unparalleled honour of being the sharpest knife in the Ubizoo drawer. http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

EDIT: Added that start speed is TAS

JtD
06-10-2010, 03:11 PM
That could have been a good one for the flight physics quiz I didn't manage to give a bump for a good week now. http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

I'd say, just going by my guts, the Spitfire is going to pull ahead initially because of better acceleration, the 190 is going to catch up in the later stages of the dive, might even pull ahead, will lose a lot more speed in the pullout, and will then lose out in the climb, where the Spitfire will certainly catch up with it and outclimb it. I'd expect the Spit to get up clearly beyond 4000m, the Fw to just get to that altitude.

If you insist, I'll do a bit more thinking (maybe experimenting, too) tomorrow.

Out of curiosity, which performance figures are you going to use? Would of course be nicer to see 1.65 ata in the comparison.

JtD
06-11-2010, 08:37 AM
150 hits and just one guess? C'mon guys, this is the fun part!

Holtzauge
06-11-2010, 09:24 AM
Originally posted by JtD:
Out of curiosity, which performance figures are you going to use? Would of course be nicer to see 1.65 ata in the comparison.

I have to go with what I have: BMW801 data for 1.42 ata from a chart I have estimating this at 1800 Hp SL and Merlin 66 +18 boost with 1675 Hp SL.

As you know from the by now legendary Fw 190 180 degree turn discussions, 1.65 ata could be included but is not since Kettenhunde has refused to share the data he has on this with us.

Xiolablu3
06-13-2010, 03:59 AM
Well I would certainly say that the FW190 would pull away during the dive.

Thats sourced from every combat pilot on the Western front who ever faced the FW190 in the Spitfire.

Also the FW190 will get even further ahead in the zoom climb 'part' of the climb.

The only question is can the Spitfire catch up with it superior climb once the 'powered climb to stall' portion starts?

I just dont know. I would think the FW190 will be a long way ahead after the dive and zoom climb.

JuHa-
06-13-2010, 05:57 AM
The big difference in reached height will happen after the Fw190 stalls out at 190km/h IAS, as the Spit will be able to climb until ...120km/h IAS. Otherwise, Fw190 likely will lead a bit before the pull-up. Maybe http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

Holtzauge
06-13-2010, 09:02 AM
One of you (not saying which one) has it pegged down pretty well. http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

Now how much ahead will one be in front of the other and when? Is it 10, 50, 100, 200, 300 or more?

ElAurens
06-13-2010, 09:11 AM
I would suggest that the results obtained with our pixel planes will be different from real world results, as in our sim we have various scripted autopilot tools to perform these maneuvers to perfection, whereas in the real world of WW2 aviation even the best recording devices were flawed and no pilot could ever achieve repeatable results with any degree of accuracy. And in the real world encounter, the losing pilot would be dead.

And dead men tell no tales.

M_Gunz
06-13-2010, 10:39 AM
Originally posted by ElAurens:
as in our sim we have various scripted autopilot tools to perform these maneuvers to perfection,

The same way every time is not the saying perfect every time is it?

JuHa-
06-13-2010, 11:16 AM
Fw190 will lead by 200m after the dive, just entering the pull-up.

Holtzauge
06-13-2010, 11:16 AM
Originally posted by ElAurens:
I would suggest that the results obtained with our pixel planes will be different from real world results, as in our sim we have various scripted autopilot tools to perform these maneuvers to perfection, whereas in the real world of WW2 aviation even the best recording devices were flawed and no pilot could ever achieve repeatable results with any degree of accuracy.

True, there are a lot things that would vary IRL depending on the pilot but OTOH by tweaking the modelling based various sources of speed and climb data etc in the end you have a model that can be used to explore other parts of the flight envelope with most likely a pretty good degree of accuracy. At least to the level of being able to compare how different aircraft would fare against each other and what are the strength and weaknesses of each design.

For example, I think the results I will post are are for some counter intuitive (and they certainly were for me when I fist saw them). But when you look closer at the numbers, there is a logical explanation for the results and I believe this modelling would carry over to reality as well but maybe there will be some debate about that http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

Holtzauge
06-13-2010, 11:36 AM
Originally posted by JuHa-:
Fw190 will lead by 200m after the dive, just entering the pull-up.

Good going! Now we have some numbers!

JtD, M_Gunz, El_Aurens and Xia: Care to make some guesses with numbers as well?

JtD
06-13-2010, 11:52 AM
After
10 sec: Spit ahead by 50
20 sec: Fw ahead by 50 (about start of pull out time)
30 sec: Fw ahead by 50 (shortly after pull out)
40 sec: co-alt
50 sec: Spit ahead by 50
60 sec: Spit far ahead and above.

All numbers +/- 100m. http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

Holtzauge
06-14-2010, 10:51 AM
It seems Kettenhunde has declined my invitation to participate in this poll http://forums.ubi.com/images/smilies/bigtears.gif

I presume this is because he is so tied up trying to figure out how zoom works in the "Getting away from spit..." thread. But I cannot fault his priorities: It's neccessary to learn to walk before you run http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

Holtzauge
06-14-2010, 12:00 PM
Ok, so here are the results. Looks like JtD won!(Provided we turn a blind eye to the +/- 100m hedgeing of the bet that is)

Did you by any chance "cheat" by using Devicelink? http://forums.ubi.com/images/smilies/winky.gif

http://img.photobucket.com/albums/v210/Holtzauge/Fw190A8SpitfireMk9400kmh30degreediv.jpg

http://img.photobucket.com/albums/v210/Holtzauge/Fw190A8SpitfireMk9400kmh30degree-1.jpg

Since I have done these types simulations before I'm not as surprised as I was the first time when I thought there must be a mistake: All common knowledge and anecdotal evidence tells us how the Fw190 is superior to the Spitfire in a dive. So anything else must be wrong. Or is it? Are there exceptions to the rule?

However, when I analysed the results the more closely it all pans out: I checked the results with calculations by hand and due to the highter T/W ratio the Spitfire will accelerate faster than the Fw190 intitially IF the dive is initiate from low speeds. However, if both start the dive from higher speeds, the Fw190 will pull away from the beginning as common knowledge also tells us.

This also seems to be what most experinced Il2 jocks point out in this forum: When in an Fw190, always keep your speed up! Never get suckered into slowing down.

Concerning the results from the comparative Fw190A3 and Spitfire Mk9 tests that have been posted a number of times, IIRC the initial conditions are not stated so it's difficult to replicate the test. If the test was done (which seems reasonable from a practical perspective) by flying both a/c side by side and entering a dive without changing throttle setting, then the Fw190 would certainly win. This is also what I see in the C++ simulations: High weight is an advantage in the dive when you are at or close to the top speed at the current throttle setting.

However, if the dive is entered from a speed well below top speed and the throttle advanced to WEP as the dive is initiated, then the high T/W will pull away initially simply due to better acceleration.

Without having tested this in IL2, I'm still pretty sure you would get roughly the same results. However, I would expect slight differences since I have compressibility effects modelled and this is missing from stock Il2.

JtD
06-14-2010, 12:19 PM
Interesting, thanks for posting. Got the numbers right, but not the timing. The numbers I know from experience, I know it's a small difference. I wouldn't have expected the Fw to stay with the Spitfire up to 50 seconds into the maneuver, and that at 1.42 ata performance.

What I want to note about the "superior 190 acceleration", it's only been brought to my attention lately, it rarely says "higher", it usually says "better". A "higher" acceleration translates into a superior sustained climb rate, something we know the 190 does not have. A "better" acceleration might also be a "quicker" acceleration, meaning the aircraft responds to a throttle change quicker, thus starting earlier with the acceleration. This is, considering the 190's Kommandogerät, very likely true. Now if that translates into just one second of extra acceleration in the beginning, it can translate into an advantage of of 5-10 km/h - for free. This is something the other plane has to overcome first, then gain on, and only then it will start to catch up and only then it might eventually pull ahead.

I'd be curious to see the effect in your calculation, maybe you can have the 190 start at a speed of 400 km/h + 1 second level flight acceleration? Or maybe + 2 seconds?

Holtzauge
06-14-2010, 12:29 PM
It's interesting that you mentioned that. I have also been thinking about if the automatic controls in the Fw190 would be an advantage in this case. IRL combat this is surely so but what about the Fw180A3/SpitfireMk9 test? I would assume two experienced test pilots and I would not expect that much of a difference in time in getting the most out of the engines?

I still suspect it MAY be so that the dive results are comparative results from two a/c flying side by side co-alt and speed then nosing over in a dive. If the throttle settings are not adjusted as they go into a dive this would certainly put the Fw190 way ahead.

Pure speculation of course, but I find it hard to reconcile those test results with the simulations and what seems to be experience from Il2 as well. Maybe the differences are just down to test conditions.....

JuHa-
06-14-2010, 12:50 PM
Ach so! I was betting on my old results on Fw190A4 vs Spit5 acceleration tests http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

But the 'superior' acceleration of Fw190 vs Spit stems from the Faber tests, which was with different machines. IIRC. So the mk9 is pretty similar to A8 when it comes down to these scenarios!

Buzzsaw-
06-14-2010, 01:03 PM
Salute

The fact the 190A8 normally had a boost of 1.65 ata makes this somewhat irrelevant.

JtD
06-14-2010, 02:41 PM
I would assume two experienced test pilots and I would not expect that much of a difference in time in getting the most out of the engines?

Not sure that this would all be down to the pilot, could be the engine itself needed some time to adjust as well.

Kettenhunde
06-14-2010, 09:10 PM
4400Kg...

TinyTim
06-15-2010, 04:05 AM
Please excuse my ignorance, but I fail to see in what environment this testing was done.

C++ simulation

and

Without having tested this in IL2,

suggest that this C++ simulation isn't the same as IL-2 engine, or? If so, where does this C++ simulation come from, and why would it show us the real picture?

Please don't get me wrong, I'm not in any way doubting the results (they seem pretty spot on to me) - I'm just curious how this simulation was done.

Holtzauge
06-15-2010, 10:27 AM
Originally posted by TinyTim:
Please excuse my ignorance, but I fail to see in what environment this testing was done.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">C++ simulation

and

Without having tested this in IL2,

suggest that this C++ simulation isn't the same as IL-2 engine, or? If so, where does this C++ simulation come from, and why would it show us the real picture?

Please don't get me wrong, I'm not in any way doubting the results (they seem pretty spot on to me) - I'm just curious how this simulation was done. </div></BLOCKQUOTE>

The C++ simulation is derived from my master's thesis (done 20+ years ago http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif). Originaly it was written in the Simula language and only covered jet aircraft and it lay dormant for years until I started with WW2 sims. Then I started wondering about how aircraft behaved in the sims and I updated the code and rewrote it in C++ (there are a lot of good free C++ compilers availabe) to also cover prop aircraft.

The nice thing about running the numbers in a C++ simulation is that once you have a good correlation with IRL data like speed and climb you can use this to integrate also dynamic things like dives zooms and instantaneous turns. This is how I generate the data for the figures I post here.

Another nice thing is that gernerally there is a good correlation between data from IL2 and from my C++ simulations. My guess is that this applies in this BnZ scenario as well. I think JtD said his winning guess was based on experience from Il2.

As a final note on the results, I know Kettenhunde usually ends up arriving at totally different conclusions than me, JtD, FatCat, Wurkeri and Devicelink generated results from IL2 and vociferously proclaims that we are all wrong Ad nauseam.

This means he is either a stubborn fool or a genius. I guess you have to make your own mind up as to which is the case. http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

Holtzauge
06-15-2010, 10:31 AM
Originally posted by JuHa-:
Ach so! I was betting on my old results on Fw190A4 vs Spit5 acceleration tests http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

But the 'superior' acceleration of Fw190 vs Spit stems from the Faber tests, which was with different machines. IIRC. So the mk9 is pretty similar to A8 when it comes down to these scenarios!

When you say pretty similar does that mean in IL2? I do not fly that much in Il2 so my experince is limited and I'm curious how my simulation compares to IL2 behavior.

Holtzauge
06-15-2010, 10:47 AM
Originally posted by Buzzsaw-:
Salute

The fact the 190A8 normally had a boost of 1.65 ata makes this somewhat irrelevant.

I would have liked to simulate that but I lack 1.65 ata data so I have to make do with the 1.42 ata. I agree that this would probably reduce the difference since the T/W would be almost on par, especially if one assumes a weight of around 4300 Kg instead for the Fw190.

If one were to eliminate the T/W advantage in this way and also start off at a higher initial speed then I wager that the Fw190 would have a significant advantage and pull away rather rapidly.

Again, I guess that why a lot of experienced Il2 Fw190 jocks always maintain the importance of keeping your speed up.

I think my simulations shows the danger of getting suckered into slowing down for a kill in a Fw190 and then trying to dive out of trouble when things go wrong.

Since the C++ sim seems to reflect IL2 I can see this leading to some complaints in the forum about the FM being "wrong" when being caught by a Spitfire in a dive. http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

JtD
06-15-2010, 12:11 PM
According to the front page, Holtzauge made two posts after TinyTim, but I don't see them in here. Odd.

Edit: Now I do. Hm.

Holtzauge
06-15-2010, 01:13 PM
Originally posted by JtD:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I would assume two experienced test pilots and I would not expect that much of a difference in time in getting the most out of the engines?

Not sure that this would all be down to the pilot, could be the engine itself needed some time to adjust as well. </div></BLOCKQUOTE>

I was thinking about your idea to model the difference in engine responsiveness but frankly I have no idea how much quicker the Kommandogerät is compare to an average pilot with control levers.

I would assume that the Fw190 pilot just slams the Gashebel against the stop and that's it while the Spitfire needs a more manual approach but OTOH is this not just advancing the prop pitch and throttle lever forward together with maybe a slight relative difference learned from experience? Naturally this would require some fine tuning once the engine has revved up but I have difficulty seeing that the time to do this would have a major impact? However, if one engine had limitations in how fast you could spool up the engine and supercharger then I can see that making a difference. Does anyone have a clue how fast this is IRL? How many s for a BMW801 and how fast is a Merlin? Does the automatic control on the BMW mean it will rev up much faster? If so how much?

While I do not have the time right now, I could maybe later incorporate a "rev up time" for each aircraft if there is some data to go on that is.

Holtzauge
06-15-2010, 01:20 PM
Originally posted by JtD:
According to the front page, Holtzauge made two posts after TinyTim, but I don't see them in here. Odd.

Edit: Now I do. Hm.

I made the same reflection on your post above. The thread list had you as author of the last post but there was nothing in the thread for quite some time......