Aces High Bulletin Board
General Forums => Aces High General Discussion => Topic started by: Pyro on May 20, 2003, 02:00:09 PM
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We're doing some revision regarding roll rate mechanics and the actual roll rates of planes. Basically, we're changing some things to make the effects of aileron input in stalls more accurate on a plane by plane basis. We're also changing the structure of the system to make it a lot easier to precisely hit the numbers we're trying to model. With these changes, I'll be going over every plane and fixing any irregularities that I find. If you feel there is a specific inaccuracy in the roll characteristics of a specific plane, please let me know here with what's and why's. If you have some specific data to present or reference, that would be the most helpful.
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Thanks for the Info Pyro. It's great to have some input.
Will you be modeling Adverse Yaw in normal and situations with missing ailerons?
What about the airflow moving infront of the aileron control surface negating performance? This was something that was designed for in the P-51 with an internal flap that was supposed to keep the airflow over the control surface instead of going between the space between the wing and the Aileron. -- Had a tremendous effect on perfomance and speed.
Right now in most planes I can lose a piece of wing and still make it home with lots of rudder, With Adverse Yaw I would have to be doubly carefull with the rudder and my power management lest the yaw pull the plane into a flat spin.
Good to know your going plane by plane tho. Good Q.A. :)
2Hawks
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It is always terrific to hear news from the developers!!! :)
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ps) I believe there were some discussions on how the Spitfires roll a little too fast. Can anybody elaborate on that?
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Pyro, this is an official demand to start whining? ;)
ramzey
ps. hands off from spit!!!!
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*pokes Spitfire wings*
:D
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*saws spitfire wingtips off* Yay! now it has an uber roll rate:D
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I always used to think rollrates of AH planes modeled quite correctly (at least to my limitted knowledge).
Still have one comment to make, about p38. Hope, it will be useful.
From "America's 100 thousands", by Francis H. Dean, page 160
"The p38 was a large heavy fighter not suited for quick snap or slam-bang maneuvers, and had a particularly slow initila responce in roll due to a high laterl inertial characteristic. The problem was a slow start into a rolland thus an inability to switch quickly form one attitude to another, as in reversino from a turn in one direction to one in the other. As one pilot said "It was disconcerting to havve a fighter barreling in on you, crank the wheel over hard, and just have p-38 sit there. Then, after it slowly rolled the first five or ten degrees of bank it would turn quickly, but the hesitation was sweat-producing. Many combat losses, particularly in North Africa, were attributed to this creaky initial rate of roll. Another pilot noted "The first ten degrees of bank came very slow". Power boosted ailerons, introduced the same time as dive recover flaps, gave the p-38 pilot a lot more "muscle" to improve roll characteristics at high speeds, but did nothing to improve them at low or moderate speeds where maximum roll performance was dependent only on full aileron deflection instead of pilot effort."
I noticed a small inertial in p-38 roll in AH, but it is not large enough to make much difference in fight. What described here shall be more noticable.
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I've read in several historical accounts that the 190D9 had a slower roll rate than the FWA's.
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guys, charts, documents, proofs
it work like that, not "by the feelings"
ramzey
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And it does roll slower than the A's in AH.
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Adverse yaw is present in the current model. The magnitude of it may very well differ with the changes we're making, but HT is also unhappy with the way the slip indicator currently functions and wants to change that.
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Originally posted by ramzey
guys, charts, documents, proofs
it work like that, not "by the feelings"
ramzey
Charts of rollrate?
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data is better word?
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You don't necessarily need documented data for what I'm asking, although that is certainly preferable, but you should be able to state a reasoned hypothesis with some supporting evidence. What Fariz posted is a good example. I'm not saying that whatever is posted will result in a change that way, but it is your opportunity make sure that I'm not overlooking any pertinent information.
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http://www.hitechcreations.com/forums/showthread.php?s=&threadid=56342
190 revisited
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i try tipying in google some keywords looking for p-38 roll rate original documents and details and Reading the result i say to myself:
"heheh Find it!!"
try to imagine my face opening that links.....
link p-38 Chart (http://www.lightningbikes.com/p38.htm)
:eek: :eek: DAMNED NET!!!:rolleyes:
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Fariz said:
The p38 was a large heavy fighter not suited for quick snap or slam-bang maneuvers, and had a particularly slow initila responce in roll due to a high laterl inertial characteristic
This of course makes perfect sense due to the heavy engines out some distance from the axis of rotation. But I'm curious to know if there are any reports of this problem also coming into effect when trying to STOP a roll. Inertia isn't something you get rid of, you can only overcome it. So once you got the P38 rolling, you'd think it would also have taken a while to get it to stop, forcing the pilots to "pull some lead" on their desired stopping roll angle.
I know a guy who was shot down in a P38 over North Africa. I'll see if I can get anything from him on this subject.
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Here is the P-38L with boost.
(http://mywebpages.comcast.net/markw4/KelseyRoll.jpg)
And here is the original with others
(http://mywebpages.comcast.net/markw4/ahtroll.gif)
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>The p38 was a large heavy fighter not suited for quick snap or
>slam-bang maneuvers, and had a particularly slow initila
>responce in roll due to a high laterl inertial characteristic
You mean "polar of moment". Much of the weight displaced on a P-38 is not close to its center of gravity but located outwards such as with the dual engines and the twin tail booms and the heavy nose mounted guns and ammo. In normal single engine fighters, you have the center fusalage then the engine up front with maybe fuel tanks at the wing roots. Still weight is displaced down the centerline of the fusalage. Nevertheless in the P-38, the tail booms weight is marginal compared to the weight of the two Allison Engines though the Turbos and exhaust ducting and radiators are located there (oil cooler upfront below prop). Then the landing gear as well, front-aft.
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Here is some F4U roll data.
(http://mywebpages.comcast.net/markw4/F4UROLL.jpg)
The 400MPH figure for the F4U is a limit of 1/4 stick throw at 400MPH because of an aileron overbalance/Vibration.
Annecdotally from AHT "you couldn't really feel it unless you push hard against the stops". What the actual roll rate is with a full throw I have no idea.
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Originally posted by ramzey
data is better word?
No, chart is ok. Just not everything can be shown by chart. The second one by F4UDOA is from the same source, America 100 thousand. Just what I described above is not reflected by charts, they gave some "average" rollrate speed (degrees per second/alt). To reflect inertia you need (degrees/seconds) for each measured alt. Have not seen such charts.
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you can ask here Pyro : http://pub131.ezboard.com/ballboutwarfare
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What do you mean Fariz?
How else can you measure roll? Unless your saying that there is a deley from the time you move the control to the time the A/C starts rolling and then you start timing the roll?
I think that is roll inertia and is included in the 360 degree roll time already especially in the P-38. Otherwise you would have a deley that I don't think is realistic. Somewhat like WB3 ala MushBirds.
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It appears that there is a problem with older NACA roll rate charts. It seems that they measured peak roll rate at one speed and then calculated chart using this rate and controll force limits. That P-40 roll rate graph in the AHT is a good example; wing twist and spongines of the controll system does not show up in the chart. Reports showing this can be found from here (http://mitglied.lycos.de/luftwaffe1/index2.html) (P-36, P-40, Spit and Hurri report vs P-40F report, also P-63 report shows this).
RAE and NACA measured peak roll rate using special equipment like gyro etc. This means that differences in the acceleration or deacceleration of the roll does not show up in the charts.
gripen
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Originally posted by F4UDOA
What do you mean Fariz?
How else can you measure roll? Unless your saying that there is a deley from the time you move the control to the time the A/C starts rolling and then you start timing the roll?
I think that is roll inertia and is included in the 360 degree roll time already especially in the P-38. Otherwise you would have a deley that I don't think is realistic. Somewhat like WB3 ala MushBirds.
That is what I mean, it is some "relactunce" in plane responce. At most planes it will be neglectable, but for some shall play role.
Normally roll numbers measure time for a full roll then devide it to 360, and give degrees per second. But this way initial responce time can't be reflected. To reflect it you need to show how many time it took plane to take 45 degreed, then how many to get 90 degrees etc. I have not seen such data.
I am not advocating any way of modeling planes, because my knowledge in this field is very limitted. It was asked if there is something which may help them to model roll, I posted some info. :)
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heh, fly with force feedback stick. That imo simulates the inertia to counter the current roll rate of the plane.
As always, the trick is in the wrist.
:D
*hides under a rock*
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It appears that there is a problem with older NACA roll rate charts. It seems that they measured peak roll rate at one speed and then calculated chart using this rate and controll force limits. That P-40 roll rate graph in the AHT is a good example; wing twist and spongines of the controll system does not show up in the chart. Reports showing this can be found from here (P-36, P-40, Spit and Hurri report vs P-40F report, also P-63 report shows this).
RAE and NACA measured peak roll rate using special equipment like gyro etc. This means that differences in the acceleration or deacceleration of the roll does not show up in the charts.
gripen
What he said. Unless you belive that p40 rolled at 160dps at 360mph.
The 109e should get re-examined. If theres any plane that rolls worse in ah I have found it.
(http://bellsouthpwp.net/w/o/wotans/Info/bank45.gif)
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Batz,
I have read annecdotal reports of the 109 out rolling the P-51 at approximately 200MPH. Your chart would seem to support that showing a 4 sec 90 DPS roll at 200MPH then dropping to 8 econds at 300mph. However the 300MPH roll is worse than the current AH model and the Spitfire is even worse than the 109.
Do you have the rest of that report? I think it is on the Spit test web site.
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yep its on the spit web site but from tests done with the ah 109e-4 it appeared to roll to slow above 300mph. Test of the mk 1 appeared that the spit rolled a bit to good.
I use word like appeared because I found it difficult to test roll accurately. I think wilbuz and urchin tested it as well and came to a similiar conclusion. It may very well be correct in ah.
I am only talking about the 109 emil.
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Hey pyro,
How do you model flight? How do you represent aerodynamic forces and moments.... and how did you get the moments of inertia necessary for the dynamical equations, I have found information on more modern airplanes (see NASA CR-2144: Aircraft Handling Qualities Data
Linearized aero data for the NT-33A, F-104A, F-4C, X-15, HL-10, Jetstar, CV-880M, B-747, C-5A, and XB-70.) but I have no idea how you would get this type of info for these old airplanes. My guess is you probably have to use the DATCOM (The USAF Stability and Control Digital Datcom. AFFDL-TR-79-3032 ) but still I don't think you can calculate moment of inertia stuff from that. I guess it wouldnt be that hard if you knew individual airplane component weights (ie how much does the wing weigh, the vstab and h stab, fuselage, engine, etcera) but again I have never seen this data listed for ww2 airplanes. I am sure you have good sources though ;)
Well I guess we need to know what input information you need. Like has been said, simply maximum roll rate information isn't gonna help that much since air combat is dynamic, not steady state :)
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oh and if you need anything from NASA Langley I'll be there 2 weeks in June and all of July with full access to the library so if theres any old reports you need let me know. they have the most complete Aerospace library in America.
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Thanks for the input. Please be sure to reference any data that you post so that it remains in context.
Zig, the moments of inertia are problematic since we only have this data on a few planes and had to use that to make estimates on all the others. I don't follow your reasoning on why roll rate information is not helpful. I can assure you that it is. If you are trying to recreate an equation and accurately fill in all the variables, why would you only concern yourself with one side of the equation? It sounds like you subscribe to a school of thought in this genre that believes these planes should be modeled on inputs alone and the output will naturally fall out accurately. I can tell you that such an approach is naive and any real accuracy derived from that method is more or less coincidental because you either don't know all the variables or don't know all the variables precisely. Even if your engine was so advanced that it considered the effect of the fit and finish of every single rivet on the plane - you would not have the necessary input data to insure an accurate output. See chaos theory and butterfly effect.
You can look at the equation a * b * c = d and say that it's not necessary to know the value of d when you know the values of a, b, and c. That is correct, but it is not correct when there is a margin of error in any of those values. And if a, b, or c, are derived values, a small difference early on can cascade into a much larger one.
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Zigrat,
Among NACA papers look for the Confidental Bulletins of the Aeronautical Research Committee (Stability and Control Sub-Committee handled aileron stuff), Memorandum Reports for the AAF (MR and CMR, NACA tested practically all fighters used by AF) and Advance Confidential Reports (ACR). Seems that confidential bulletins are not listed in their database but I believe they have those in their archives (I've seen quite lot of that stuff in PRO). Generally you must go through truck load of papers to find something interesting.
gripen
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IMO, roll rate is secondary compared to roll inertia/acceleration.
As an exageration, imagine what good at scissors would be a plane with a roll rate of 360d/s but spending 1 minute untill that rate is achieved and that needs another two minutes to get that rate in the opposite way.
It is the same that level top speed vs level acceleration. Just imagine two sims modeling the P51B, both with same top speeds at sea level, the first achieving it in 5 minutes and the second in 10 minutes.
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Pyro,
Can you please help me out with something I've been trying to figure out for a long time.
Why do some people think that if you center a stick while a plane is rolling, that a WWII aircraft will take up to 45-90 degrees of continued roll to stop rolling.
I know that when I roll my little aeroplane in real life and I center the stick, that the plane stops rolling VERY quickly.
What gave people the idea that a plane continues to roll so far after centering the stick?
I have seen gun camera footage of a combat P51 being shot at, initiating an imediate aileron reversal of roll.... ie the roll response was immediate and crisp.
It seems like on the internet, people think either a plane responds to stick imput immediatly or that it takes a lag period before ailerons actually work once already in a roll.
Why is this?
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hey pyro,
no i definitely think that knowing the answer helps to get the equation.. i know it definitely made my homework problems a lot easier when i could back solve since the final result was in the back of the book! so i dont disagree with anything you wrote :)
My point was more along the lines of the p-38 roll issue that was previously mentioned. Roll data such as in the chart posted by f4udoa has little relevence with regard to dp/dt (time range of change of angular velocity along the body x axis) since it really only gives the maximum roll rate and this has nothing to do with roll inertia, only with aileron effectiveness( mostly dealing with aileron size, hinge moment, wing torsional stiffness (ie when does reversal occur) and available control power (cockpit considerations) and the roll damping term Clp (mostly dependent on planform shape). Its similar to the concept that just because a plane is fast doesnt mean it climbs well. There is no real way to back out moments of inertia from maximum roll rate data alone. You could however use that data to estimate aileron power information since that DATCOM and the paper referenced below give methods for calculating Clp. (page 20)
For explanation of the different stability derivates and explanations on how to estimate them see http://naca.larc.nasa.gov/reports/1952/naca-report-1098/naca-report-1098.pdf . I think the methods in the DATCOM are the ones currently accepted by industry and used in aircraft conceptual design.
I apologize if you took me the wrong way but I guess i probably do have a bias since I work in aircraft conceptual and preliminary design where you draw an airplane and have to figure out "how will this thing fly" .. Actually many airplanes since we need to evaluate thousands of designs using automated tools for optimization purposes. We are happy if we get close in the early stages of the design process, where you are modeling planes that actually flew and will have many many complaints if someone finds your model differs from such and such chart by 2%. I think your job is harder in many ways.
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Zig, p38 happens to be one plane we do have moments on.
But you are correct about no simple way to estimate moments from flight data, unless you have a time to max roll rate chart, don't belive i've ever seen one.
But we do have the moments on a number of planes. And with enof samples of different planes ,others can be estimated fairly accuratly. Now if you also look at the effect of moments being off 10% by estimating them, you will see that the net effect is almost none existant.
HiTech
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HT, Pyro-
I have full access to the Grumman Library, which would include all the original specs on the F-6F, F-4F, and TBF.
We also have a large amount of the original work on the Republic P-47.
If you need me to look something up on these aircraft, and can give me an idea as to what values you need, I'll be happy to do so.
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Hitech,
You have flown or flown in a P-51D (You bastard;) ) what was the feel of it?
I have flown at Air Combat USA. My experiance was that if you had your hand on the Yoke and even thought about a roll you were going to do one. I don't think those A/C were any less unstable in the rolling plane than the P-51. In fact the only perceived hesitation in the controls would probably be the distance neccesary to move the controls before you get response. And that is negated by joystick calibration in the virtual world.
Do you plan on building a deley in the roll of all of the fighters on AcesHigh?
Please do not make this feel like MushBirds 3.
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as it is in ah currently.
Unlike wbs.
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I follow you Zig. There's nothing tricky about the way the model works. It works as you would expect it to. The ailerons change the effective AoA of that portion of the wing and the resultant forces generate the effect. Looking at a typical roll rate chart for these planes, roll rate will increase with speed up to an apex and then fall off as stick force becomes a limiting factor. Once the data is plugged into the model, the plane should be closely match the part of the chart to the apex. If it doesn't then that tells me that something is off and I have to massage the variables to produce the desired output. Once you get past the optimal speed, roll rate is decreasing because maximum stick deflection can no longer be achieved. At that point, I'm looking at the backside of the roll rate curve and using that to input to the model that maximum lateral stick movement for that speed. In this case, the inputs for limiting stick deflection are solely based on the desired output. It is a lot of inputs to make and any mistakes made there are not readily apparent. It also means that if I later find something amiss on the front side of the curve and correct it, it throws everything off on the back side. One of the changes that I alluded to is that we're changing the input to the other side of the equation. Instead of stating what the maximum stick input is at a particular speed, the maximum roll rate will be used instead and the model will fill in the necessary stick input. That will give us a higher degree of accuracy and make errors less likely. We're also making changes to get rid of some limitations that introduce small errors that have to be overcome elsewhere. An example of this is that the current model assumes aileron travel is equal in both directions. That's not the case on many planes and modeling it that way could lead to some minor undesired characteristics.
As HT said, moments of inertia are nice to have but not something we really sweat. We had a good starting point and having an exact number is not needed because even a huge change can be barely perceptible. You really just need to get in the ballpark with it.
I don't know why some people feel there should be a tremendous amount of roll inertia in these planes. For me to impart a large amount on a typical single engine fighter, I would have to increase the MoI's an order or more of magnitude. It was something that we talked about prior to HT taking his P-51 flight because I thought that it should be present to a noticeable degree(I'm not talking about a big bellybutton lag, but rather the absense of crispness). Anyway, his flight laid those doubts about the model to rest. I guess the reason some people subscribe to that idea is because it seems to make sense intuitively. It's much easier to visualize mass than force.
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Originally posted by blackwitch
I've read in several historical accounts that the 190D9 had a slower roll rate than the FWA's.
and...you think its wrong in AH?
The roll rate on the 190A's was far suoerior to any other aircraft and the 190d9 was a little slower than the A's I believe .This still however was far better than most aircraft at least up to 400 mph +.Are you saying you think the roll rate of the 190d9 is too fast in AH or too slow? Have you tested it to see if it is?
From tests ive done i would say the 190's are all slightly slower than the charts.Also they perhaps dont match up to several 'historical accounts' ive read as in:
Oberleutnant Oskar-Walter Romm 15. staffel JG3
'As an air superiority and interceptor fighter the fw190d-9 handled better than the Fw190A; it was faster and had a superior rate of climb.During dogfights at altitudes of between about 10,000 and 24,000 ft, usual when engaging Russians, I found I could pull the fw190D into a tight turn and still retain my speed advantage.In the descent the 'Dora-9' picked up speed much more rapidly that the A type; in the dive it could leave the russian yak-3 and yak-9 fighter standing.'
However, as is often pointed out accounts from pilots dont count ;)
anyhow im just jumping in to defend the 190D just in case you are out to get it :D
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No... I like the D9 see mine here...
http://www.whitewitchweb.clara.co.uk/all_images/fw190d9/index.htm
I was just answering pyro's thread starting comment with..
I've read in several historical accounts that the 190D9 had a slower roll rate than the FWA's.
That's all :)
p.s. "If" I had one criticism on the AH D9 it would be that the colour on the wings is "mostly" wrong
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Hey pyro,
yeah I totally understand. Do you model aileron reversal? I have never experienced it in aces high but IIRC many of the early planes of WW2 experienced it (I think the spit Mk I especially) where right aileron gives left roll above a certain airspeed
I also agree that exact figures for roll inertia are probably not necessary. If you know it for a P-51 that number will probably be reasonably accurate for a Me-109 with a little massaging. If your 10% off like you said it may mean that it takes 2.2 seconds to reach maximum roll rate rather than 2 seconds but IMO that type of difference is rather trivial.
Finally i agree about crisp response. If you look at the magnitude of the roll damping term you will see its pretty darn big, and for most airplanes unless they have big wing tip tanks or something else out there when aileron input is removed they should go to zero roll rate rather quickly.
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I quess you have allready got RAE TN 1231? (available from the PRO as AVIA 6/10353 and DSIR 23/12865) It's contains a simple method to calculate real times to bank plane but all planes in the comparison were single engined. It also contain time/roll velocity charts for the Fw 190.
gripen
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Yes on ail. reversal zigrat. It just falls out of the model from lift curves.
HiTech
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Here is a thought. Contact some pilots that have warbirds and ask them to run some tests.
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This sounds like the right way to work a problem, manipulate that side of the equation where any uncertainties result in smaller effects. Engineers do this all the time, as do economists.
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Originally posted by Pyro
I follow you Zig. There's nothing tricky about the way the model works. It works as you would expect it to. The ailerons change the effective AoA of that portion of the wing and the resultant forces generate the effect. Looking at a typical roll rate chart for these planes, roll rate will increase with speed up to an apex and then fall off as stick force becomes a limiting factor. Once the data is plugged into the model, the plane should be closely match the part of the chart to the apex. If it doesn't then that tells me that something is off and I have to massage the variables to produce the desired output. Once you get past the optimal speed, roll rate is decreasing because maximum stick deflection can no longer be achieved. At that point, I'm looking at the backside of the roll rate curve and using that to input to the model that maximum lateral stick movement for that speed. In this case, the inputs for limiting stick deflection are solely based on the desired output. It is a lot of inputs to make and any mistakes made there are not readily apparent. It also means that if I later find something amiss on the front side of the curve and correct it, it throws everything off on the back side. One of the changes that I alluded to is that we're changing the input to the other side of the equation. Instead of stating what the maximum stick input is at a particular speed, the maximum roll rate will be used instead and the model will fill in the necessary stick input. That will give us a higher degree of accuracy and make errors less likely. We're also making changes to get rid of some limitations that introduce small errors that have to be overcome elsewhere. An example of this is that the current model assumes aileron travel is equal in both directions. That's not the case on many planes and modeling it that way could lead to some minor undesired characteristics.
As HT said, moments of inertia are nice to have but not something we really sweat. We had a good starting point and having an exact number is not needed because even a huge change can be barely perceptible. You really just need to get in the ballpark with it.
I don't know why some people feel there should be a tremendous amount of roll inertia in these planes. For me to impart a large amount on a typical single engine fighter, I would have to increase the MoI's an order or more of magnitude. It was something that we talked about prior to HT taking his P-51 flight because I thought that it should be present to a noticeable degree(I'm not talking about a big bellybutton lag, but rather the absense of crispness). Anyway, his flight laid those doubts about the model to rest. I guess the reason some people subscribe to that idea is because it seems to make sense intuitively. It's much easier to visualize mass than force.
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Zig, HT misunderstood your question. High speed roll reversal is not modeled.
Gripen, I don't believe I've ever seen that report. Do you have a copy perchance?
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ah thanks pyro thats what i thought.. since you would need to model structural deformation too which isn't that fun!
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Originally posted by Zigrat
I also agree that exact figures for roll inertia are probably not necessary. If you know it for a P-51 that number will probably be reasonably accurate for a Me-109 with a little massaging.
This has no sense at all for me, you are comparing something with big and heavy wings (fuel tanks and machineguns there) with something with small and "empty" wings. If exact figures for roll inertia are not necessary, then exact figures for acceleration/climb/speed etc are secondary ...
When you roll, what you are moving are just the wings against the air flow, big wings offers more resistance to movement, heavy (big mass) wings too, heavy and big ones much more. I wonder how was the roll rate (if any) of P38 at speeds below 150 mph.
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I cant believe how helpful this thread has been. I have been wondering about the 'insta' response in a role that you get with AH. I needed to hear it from somebody else cause intuitively I just could not believe that was accurate....... but when I was just on my honeymoon in Kauai, HI, I happened to have my hand out the window driving to some insanely nice golf course and started playing airfoil with it. The slightest turn or twist instantly wiped my heavy bellybutton hand in another direction. Imagining the force exerted by an aileron much larger on a rather aerodynamic 'turn oriented' device traveling through the air at 250 miles an hour made me realize that any small input by an aileron on a wing would be immense!
I salute pyro for digging for this info, and explaining the modeling. Wonderful stuff. I was going to squeak about how little inirtia you felt in AH roles previous to my honeymoon.....
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Pyro,
I have the text part of the report, I'll try to scan it.
gripen
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I have the whole document scanned and zipped, If I can be of any help?
Neil.
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Neil,
You can help Pyro better than me! Another interesting RAE report at PRO is DSIR 23/13030. It's a quite long and theoretical report on aileron characters during maneuvers and probably something Pyro is looking for.
Somekind of study on flying characters of the Bf 109 (including aileron data) might come out before end of the year ;)
gripen
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I've noticed something about forward slips that just doesn't seem right, though I have no numbers to back me up. I use them regularly when landing, saves time by slowing ya down quickly.
The problem is that when I come out of the slip I always seem to lose lift. I don't think this should be the case. The forward slip should not only increase drag but also reduce lift due to less of the wing being presented to the air stream and turbulence induced over the wing by the fuselage.
Wondering if maybe the fuselage is generating more lift in the slip than appropriate?
I couldn't find the thread about slips. ;)
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Gripen,
thanks for the reference, I look fwd to seeing the 109 flying characteristics study.
BTW would you like the parts of the report you are missing, if so post your E-mail.
Neil.
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Neil,
Thanks! My e-mail is gripen39 at luukku dot com. I can mail you in return more PRO and other british archive references.
gripen
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Mandoble:
If one used P-51's inertia tensor for 109 and it made ~5% difference in roll acceleration - I say: "So what? Go with it!"
I don't think they are using the inertia tensors interchangeably anyway, it was just said that you can get the inertia tensor with in the ball park from one plane to another if you assume the structual part of a wing has same mass per volume unit and then use the actual dimensions of the plane in question.
// fats
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Spitfire 1 compared to 109 E seems to roll way too fast. I have some test reports made by the RAF of the 109 E4, comparing it to the Spit 1. Roll rate at 400mph to 45 degree roll took 4 seconds in both planes. About the same as in AH. However bellow that speed in AH the Spit 1 greatly outrolls a 109 E. In no reports does it say that this should be the case, it actually says that the 109 E had great maneuverabilty in low speeds.
This is a part of the test repor made by the Brittish.
"Ailerons
Aileron control is very good at low speeds, there is positive feel and a definite resistance to stick movement.
As speed rises the ailerons gradually become heavier but retain excellent response, being at their best between 150 and 200mph. Between 200 and 300mph they become noticeably heavier and over 300mph become too heavy for comfortable manoeuvering. Over 400mph the pilot can exert up to one fifth aileron using all his strength."
It allso says that lowering the flaps will make the ailerons much heavier and slightly less effecitve cause the ailerons come down 11 degrees with the flaps.
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Hi Neil,
I got the report. Thanks a bunch, that's a really great contribution.
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yay now pork the 109 ;)
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Don't know if this site will come through very well but it contains charts reportedly from Lockheed
http://home.att.net/~ww2aviation/P-38-3.html
If it doesn't come through let me know and i'll try and post the charts.
Oh it contains a ROLL RATE CHART!!!!!
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Can you provide a little more bibliographic information. I have no idea what this report is and how I can locate it. A web search for RAE (at least I know what RAE is) got me nowhere
Originally posted by gripen
Neil,
You can help Pyro better than me! Another interesting RAE report at PRO is DSIR 23/13030. It's a quite long and theoretical report on aileron characters during maneuvers and probably something Pyro is looking for.
Somekind of study on flying characters of the Bf 109 (including aileron data) might come out before end of the year ;)
gripen
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P36, P40, Spit and Hurri Rollrate comparison:
http://members.tripod.de/luftwaffe1/aircraft/usaaf/rollrate.pdf
Link comes from this interesting page:
http://mitglied.lycos.de/luftwaffe1/index2.html
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Joeblogs,
http://www.pro.gov.uk/
then click on catalogues and then then online catalogues procat, then click search or enter reference in the top r/h box.
Neil.
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Here is a goodie for you:
"I have mentioned how badly I felt about the aierons of the Spitfire at the time of the Battle of Britain. In October 1940 I flew a captured 109E; to my surprise and relief I found the aileron control of the German fighter every bit as bad - if not worse - at high speeds as that of the Spitfire I and II with fabric covered ailerons. They were very good at low and medium speed, but 400 mph and above they were almost immovable. I thought the Me 109E performed well, particularly on the climb at altitude, and that it had good stalling characteristics under g except that the leading edge slats kept snapping in and out. But it had no rudder trimmer - which gave it a heavy footload at high speed - while the cockpit, the canopy and the rearward vision were much worse than in the Spitfire. Had I flown the Me 109 earlier, I would have treated the aeroplane with less respect in combat"
(Jeffrey Quill, RAF test pilot)
BTW, this thread never mentions the a6m. Now if AH has an error in roll rate and high speed performance, there it really is!
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Originally posted by Neil Stirling1
Joeblogs,
http://www.pro.gov.uk/
then click on catalogues and then then online catalogues procat, then click search or enter reference in the top r/h box.
Neil.
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Originally posted by Angus
BTW, this thread never mentions the a6m. Now if AH has an error in roll rate and high speed performance, there it really is!
The zeek rolls at high speeds? I think the moon has a faster roll rate than the zeek at speed
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I have never found any actual test data with respect to Lavochkin roll rates.
Obviously some crude assumptions can be made when looking at the wing profile, the size, position and total deflection of the aelerons
Few pilots flew both western and Russian planes and the only anecdotal evidence I have is from those Czech pilots who left their RAF Spitfires in January 44 to fly La5FN's later in July of the same year.
By comparison the Lavochkins instrumentation suffers heavy critique (no artificial horizon no gryo compass etc etc) but apart from its bounce during landing the Czech pilots hailed the la5Fn as highly (excellent) manouverable in all plains and a delight to fly.
This is hardly a description of roll rate but one would expect a roll rate at least superior to the Spit from such a comment.
It is possible that the Czechs flew later La5FN's which were fitted with all metal (steel /dural composite) aelerons with improved linkages to the same. But I would doubt it. Indeed these were newly trialed on the La7 prototype in March 44 and fitted to the first la7's in production in early May. It would be surprising if the Czechs were given brand new La5FN's after their initial training.
I mention this because the new design of aeleron reduced total aeleron weight by 100kgs and radically reduced the stick forces required between the former la5Fn (wood /metal/cloth composite aeleron) and the later la7. The la5fn had a two handed (Spitfire type) control stick whilst the La 7 had a single handed (messerschmidt type ) joy stick. Hence from a pilots perspective stick forces during roll were significantly reduced during the development of the la7.
In summary this (admitedly very anecdotal evidence) would support the view that the La5Fn rolled at least as well as the Spitfire during normal combat manouvering and that the reduced stick forces of the la7 allowed the pilot to roll the la7 better still where the stick forces of the la5Fn were found to be restrictive. (presumably at higher speeds)
The question would be which Spitfire?
One of the pilots to give this account was Frantisek Faitjl DFC who was a squadron leader in 313 squadron.......
http://cz-raf.hyperlink.cz/bio/fajtl.html
You will note that until his departure this squadron flew latterly the Mk V (C & B) with a few Mk VII.
http://cz-raf.hyperlink.cz/units/313.html
If as this page suggests Faijtl is still alive then he may be an invaluable source of comparitive data few persons have experienced he also flew the la7 after the war.
The other pilot to compare the two aircraft was W/O Ladislav Valousek who flew with 310 Squadron
http://cz-raf.hyperlink.cz/units/staff310.html
They had similar experience of the MkV ( C & B ) with some HF Mk VI
http://cz-raf.hyperlink.cz/units/310.html