Aces High Bulletin Board
General Forums => Aces High General Discussion => Topic started by: Karnak on June 01, 2001, 09:28:00 PM
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I have noticed that there is a lot of contention being caused by this chart in the AH forum. Is the NACA chart really the absolute reference for roll rates?
Is it correct in all cases? What condition were the aircraft in that were used for these tests (When R.R.S.Tuck gave a demostration in the US owned Spitfire MkV in 1941 he said that it was very sloppy because everybody in the USAAF had had a go at her)? What mark of Zero was used? Probably the A6M2, that is what most of our testing was done on. Does the A6M2 have the exact same roll behavior as the A6M5? I don't know, do any of you? The Typhoon's roll rate is now pretty close to the NACA chart, but I have a difficult time believing that a fighter aircraft would even get close to production with the kind of roll rate the Tiffie now has, let alone have more than 3,000 produced.
Why is so much trust put in this one source? Are there other sources that give a different picture on any of these aircraft?
(http://www.users.bigpond.net.au/phoenix/images/rollrates.jpg)
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We few, we happy few, we band of brothers;
For he to-day that sheds his blood with me
Shall be my brother
Bring the Mosquito FB.MkVI Series 2 to Aces High!!!
Sisu
-Karnak
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Tho I fly the 109 a lot I have never seen my self as a luftwobble and I honestly dont go around seeing AH as some sort of allied vs axis drama where we try to screw each other around. So please try not to take is at that.
And I fly many different countries planes from time to time, and I like flying them all.
However im getting a little annoyed with this Typhoon roll rate uproar of late. Many of the people complaining about it are the "GIVE US HARD DATA" types who seem to live by some test numbers and this and that.
But now that data shows that one of their
planes has a modeling error, well the data MUST be incorrect. No way could their favorite fighter have a, gasp, shock, horror, poor perfomance area.
So clearly the data is at fault, it was obviously compiled by a gang of one handed half-blind, illiterate, retarded monkeys of questionable parentage.
What you guys are saying, or at least appear to be saying, is that this chart is valid EXCEPT for the inconvenient facts about the typhoon. Because it seems to me that its pretty accurate for all the planes 190s, 51s,zeros etc.. But it must be inaccurate for Typhoon beecause its so darn inconvenient that it rolls so poorly in RL.
Well then I say its very inconvenient that Zeros are slow, so all speed data on A6M is incorrect or at least suspect.
I think its inconvenient that B17s arent faster than fighters so certainly B17 test data is in error.
I think its inconvenient that such and such is not to my liking whatever test data involved must be questionable.
OK OK nuf sarcasm (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif), but I hope you guys get my point, many of you scream "HARD DATA FACTS FIGURES" but now that that such details inconveniece your tactics and flying, all of a sudden these FACTS become questionable.
Please dont take this as some sort of anti-Typhoon pilot tirade as I know full well that it wont be made or killed by its rolling but frankly you guys should just get used to it as it seems these tests put the Typhoon in its correct light as the unmanouverable fast attack plane it was.
Again I hope to make it clear this is just a general staement on how I feel on this issue, and I dont intend it to be insulting or abrasive to anyone.
thanks, GRUNHERZ
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GRUNHERZ,
You will note, I hope, that I backed you up on the Typhoon roll rate.
If this is the only data we have, we have to go with it regardless of "feel". But I can still express my doubts on the data even as we use it. I am not saying that it should be made to roll better unless there is more hard data that says that it should.
What I have noticed is that Luftwaffe fans are using this data to attack from both the perspective that 190s roll too slowly and that Spits and Zeros (an Axis aircraft) roll to fast.
HTC saw fit to fix the Typhoon according to the NACA data, but not the 190s, Spits and Zero. I wonder if they have data on 190s, Spits and Zeros that is different than the NACA data.
BTW, I have to admit that when I fly 190s I would dearly like them to roll better when at speed.
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We few, we happy few, we band of brothers;
For he to-day that sheds his blood with me
Shall be my brother
Bring the Mosquito FB.MkVI Series 2 to Aces High!!!
Sisu
-Karnak
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Yep Karnak I saw that, and thanks. My reply wasnt directed at your post specifically rather just expressing my concern on how a lot of these "FACTS" folks are up in arms over the Tiffie thing. The NACA charts were first shown in January I think and it has taken HTC some 5 months to implement it in the Tiffie FM, so its a good chance it wasnt some rash whimsical thing they changed with no supporting evidence. Tifie guys just cool down if ots correct as NACA data shows then learn to fly with it or if not HTC will get around to it. In the meantime fly some other planes if the Tiffie isnt good 4 u, have fun and all that I think. (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
You see what Im trying to articulate here?
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According to the NACA table, 190 should roll quite a bit better at low and middle speeds.
At high speeds it should roll somewhat slower than it rolls now.
Overall, though, 190 should have better roll rate (just compare the area of gained rollrate to the area of lost rollrate, as Mandoble pointed out).
Speaking of 190 defence, at high speeds 190 has other options than to just roll. So reduced rollrate won't be as important.
At lower speeds, when that Spitfire is on your six and firing, you pretty much count on roll rate only. I'd be very happy to have some 15deg/sec more to it.
Now everytime a Spit gets me at 250 IAS I can blame AH roll modeling, with 190 being to slow in roll and Spit being to fast.
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Karnak,
You have a bogus chart, it is missing the top performance line.
Here is the actual NACA chart
(http://w3.cablespeed.com/~nexus/nexusrules.jpg)
Nexus (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)
[This message has been edited by DmdNexus (edited 06-02-2001).]
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Karnak - I've asked the same questions you're putting forward several times.
Data with no explanation as to how it was collected or the conditions under which the experiment was performed is as meaningful as arguments based on 'feel'.
I.e. not very meaningful at all.
This is a basic scientific tenet.
I'm not saying the data is bogus for any of the aircraft, but I'd like to see the test conditions. Purely out of interest.
[This message has been edited by Dowding (edited 06-02-2001).]
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I have noticed that there is a lot of contention being caused by this chart in the AH forum. Is the NACA chart really the absolute reference for roll rates?
Until now itīs the best source imo.
Is it correct in all cases?
What mark of Zero was used?
In the original report, they mention that the curve for the zero is added without exact knowledge of the force limits
What i personally donīt want to believe is the peak of the rollrate of the fw-190 . I mean, several different sources speak about extremly light aillerions even in a high speed flight. Would those pilots write this when the fw-190 reached 50pounds stickforce already at 250mph??? Naa, I donīt believe it. German sources say you could fully deflect even in a very high speed flight your stick , but the rollrate was limited due to wing deformation.
Maybe the fw-190 was tested with 30pounds stickforce or even less. I really would like to see the origin of the fw-190 data.
niklas
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Niklas,
Wouldn't that make it effectively useless as a refence for the Zero's roll rate? The AH Zero doesn't roll very fast, and rolls quite badly when it is going at any kind of speed, perhaps it is accurate as it stands now.
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We few, we happy few, we band of brothers;
For he to-day that sheds his blood with me
Shall be my brother
Bring the Mosquito FB.MkVI Series 2 to Aces High!!!
Sisu
-Karnak
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Dowding, here ya go (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
NACA REPORT (http://naca.larc.nasa.gov/reports/1947/naca-report-868/naca-report-868.pdf)
From memory, the test was conducted as follows;
Trim to straight and level flight.. 5 rolls to the left, 5 rolls to the right - 50lb stickforce used.
Further info is in the report (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
[This message has been edited by Jekyll (edited 06-02-2001).]
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the chart is right on. I am sad to admit, but Spitfire rolls to fast in AcesHigh, while 190 rolls to slow (http://bbs.hitechcreations.com/smf/Smileys/default/frown.gif)
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Grun there reason the question has popped up about the NACA chart is that the tiffie roll rate does seem a bit out there.
Check my posts in response to flying the tiffie. You'll note in ALL of them I say the reduced roll rate won't affect me that much. And it doesn't.
The issue here is that with the new roll rate from the NACA data, a few people are starting to disbelieve the NACA data is accurate. Why? Because a tiffie cannot hold level trimmed flight with 1 DT sub 200kias, or the same with 1 x 1000lber sub 240kias.
Slow roll rate is one thing, NO roll rate is another. Nowhere in history does it say 'tiffies sucked coz they rolled worse than a 747'. So people are naturally looking at this data and questioning it.
My guess is the tiffie should roll half-way between what it is and was. If you look at similar planes of that size, ron surfaces etc.
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Vulcan, don't forget that you cannot simply compare aircraft of the same size, or aircraft which 'looked' the same.
An example. Compare the Tempest and the Typhoon. Similar looking aircraft, right?
Yet roll performance is very different. In the Typhoon there were integral fueltanks built into the wings. The Tempest, with its thin wing, had no space for such tanks. The increased moment of inertia for the Typhoon may well have had much to do with its historically 'slow' rollrate.
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Thanks for the source Jekyll. Very interesting reading. (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
Surely there must be a corroborating source out there - RAF trials perhaps?
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Originally posted by Dowding:
Surely there must be a corroborating source out there - RAF trials perhaps?
[/B]
The sources of that NACA report were discused some time ago in the rec.aviation.military
See my post under typhoon discussion and use google with search words: NACA report 868 roll
Gripen
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From the looks of it, things like adverse yaw were not accounted for? The dihedral would play a large part in that. For example, a 10 degree yaw with 5 degrees of dihedral could take 1 whole degree off the helix angle in the roll (0.017 rad). Based on that, the results could be anywhere from 25-35% off the mark. Also, look at the slope of the lines, from the minimum speed to that where maximum roll rate occurs. Ideally, it should be linear with speed. The fw-190 is very close. The Typhoon isn't, recording a roll rate that is 86% of that expected at 250 mph. I suppose that stretching of control cable could explain that, but it still starts off with a low helix angle. Why would that be? It could be due to the wing being 50% thicker than most wings, meaning that the upper and lower surfaces of the wing converge at the trailing edge at a steeper angle. The steeper that angle is, the closer the airflow is to separating from that part of the wing. This means the ailerons can't deflect as much without stalling. On the plus side, the thick wing should give lots of stall warning as the separation point gradually creeps forward on the wing as the angle of attack is increased.
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wells, this page is the start of the description of the flight test procedure: http://naca.larc.nasa.gov/reports/1947/naca-report-868/index.cgi?page11.gif (http://naca.larc.nasa.gov/reports/1947/naca-report-868/index.cgi?page11.gif)
This chart shows the comparison of helix angles(the next page is the angular velocity comparison): http://naca.larc.nasa.gov/reports/1947/naca-report-868/index.cgi?page41.gif (http://naca.larc.nasa.gov/reports/1947/naca-report-868/index.cgi?page41.gif)
Pages 39 and 40 describe the purpose of including the charts. And on page 76 there is a chart showing details of the aileron setups for the tested a/c.
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From pg 40 of the report...pretty much sums it up!
The wide variations in the performance of airplanes having Frise ailerons may be an indication of the well-known fact that Frise ailerons are extremely sensitive to each of a large number of design parameters.
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the chart is right on. I am sad to admit, but Spitfire rolls to fast in AcesHigh, while 190 rolls to slow
This was not written by me.
To the amazinhunk who wrote it:
I hope HTC logged your IP and that they ban your ass.
At least learn to spell in English before trying to impersonate me.
And I have been saying the Spit rolls too fast since long before many of the current crop of Luftwhiners even knew about this sim, so it's not like you've accomplished anything.
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I don't think its absolute rollrate performance that is troubling the 190 drivers. Does it really matter if the 190 is 8% too slow in roll at such and such speed? Probably not.
It's the relative roll performance which appears to be the problem. I've heard it suggested that the 190 rollrate has been turned down to avoid warp-rolling issues - it just rolls too durn fast in real life for our imperfect internet to keep up with.
So just to show the postion, here is extracted data from the same rollrate chart, expressed in a different way.
I took the NACA and AH data for planeset comparison, basically 190 -v- the world. Worked out the rollrate differences based on NACA data, the rollrate differences based on AH data and subtracted one from the other to find the difference in performance.
(http://www.users.bigpond.net.au/phoenix/images/difference.jpg)
So, for example, look at the Spitfire at 225 IAS. The difference is roughly -23 degrees. That means that at that speed the Fw190 rolls 23 degrees/sec too slowly AS COMPARED TO THE SPITFIRE.
Not absolute roll performance.. relative roll performance.
Now, I don't know whether the original NACA report is accurate: for all I know the NACA team might have been sitting on a shady veranda, sipping Margueritas when they should have been out testing aircraft. So the value of the comparison is going to be affected by the reliability of the NACA source material.
As you can see, I haven't bothered to compare all the AH planes. Frankly, it bores me to even attempt it. I'd have to re-test the P51B, perhaps the P47D-11 etc and I just dont have the time to do so.
I've already posted the link to the excel spreadsheet containing all the test results. If anyone else wants to do the tests, be my guest.
But I'll say one thing before I go: If this roll performance issue had been one which disadvantaged the P51, the Spitfire, the P47 or (God forbid) the F4U, it would have been fixed months ago.
[This message has been edited by Jekyll (edited 06-05-2001).]
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Again, an excelent graph Jekyll <S>!
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If this roll performance issue had been one which disadvantaged the P51, the Spitfire, the P47 or (God forbid) the F4U, it would have been fixed months ago.
You really believe that BS?