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Crump

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  1. RAE TN 1106 is about the Avro Vulcan and nothing to do with the Spitfire.... http://naca.central.cranfield.ac.uk/reports/arc/cp/1106.pdf Just post a copy of the report you are referencing so we can see the details.
  2. Could there be some confusion going on because of the fact aircraft have unusable fuel onboard? Generally if you look at the type certificate of an airplane, it will list the actual physical volume capacity of the tanks on a standard day. The cockpit gauges will generally read useable fuel and the weight and balance fuel portion will only reflect useable fuel. The difference between the two is the amount of unusable fuel that is left in the tank when the cockpit gauge reads empty. On the weight and balance, unusable fuel is included in the basic empty weight and CG location.
  3. Thank you for that but I do not need it. Again, still looking at where you are getting the 1.36 as the design Clmax...... Why don't you stop trying to get the thread locked and playing games. Just answer the question! Oh...you want the thread locked because it is getting uncomfortable as the details come out. You got nothing to fear Holtzauge, right?
  4. LOL... What don't you follow it with your MsC in Aeronautical engineering? Yes, I purposely used the general terms for what I what I was doing but it all follows common theory and the correct principles. Again, without the details of what JtD is doing it is impossible to say the degree of useful information being produced. My post was not to discourage him but rather to redirect his course from his own theories of "efficiency" Aircraft performance math dictates that turn performance is the result of power available to power required. If you want to determine the games propeller efficiency in a turn then you simply use the shaft horsepower of the engine minus the power required to reproduce the games turn performance times. Power required to reproduce game turn times / Shaft Horsepower of the engine = Games Propeller Efficiency That is all you have to do. Now whether that is games value is correct or not depends on the specific off the propeller design AND the theory being used. Momentum Theory.......Limited usefulness at predicting propeller efficiency is one of the basic limitations of its use....it only shows the upper end of theoretical maximum efficiency for an infinite number of blades. It is useful though in that it show us there is little to choose from regarding propeller designs and the common assumptions work just fine. Blade element theory is more accurate as is what most propeller designers use to predict the performance but one must know the details of the propeller design being evaluated. Like anything, wrong information can lead to wrong results such as one case I know of where the individual analyzed the tip of a propeller with a working radius of .7. If you compare propeller efficiency at a radius of .95 on a propeller with a working radius of .7.....of course it is not going to appear to be a very efficient design, LOL. Like you did not notice this had nothing to do with anything IL2 but just decided to cheer the guy on instead of helping him out? LOL https://forum.il2sturmovik.com/topic/26384-re-dev-report-138-vdm-propeller-some-historical-files/
  5. Problem is the foundation is flawed JtD. Induced drag is based upon Coefficient of Lift and your assumptions for the efficiency factor. Assume the wrong CLmax, propeller efficiency, and (span, oswald, aircraft, or wing) efficiency results in erroneous results. You are piling assumption upon assumption all wrapped in a method of your own creation. It is very likely to be ignored because of that. I would ignore it as it goes down many rabbit holes. Just use convention and do NOT make up your own theories. You will find that the VVS turn times agree very well with convention if the conditions are properly converted. TSAGi kind of knew what they were doing and were not learning it off the internet or going down rabbit holes. What are you doing regarding oswald's? There are good fairly simple techniques to estimate it. For example you can return a very reasonable estimate using some measured data from the design such as Taper Ratio, Aspect Ratio, wing span, and mean fuselage diameter. Take the FW-190 because we have very good engineering data on the design: Our inviscid efficiency: etheo = 1/(1+F(lambda) * Aspect Ratio) F(lambda) = Value determined by graph using the taper ratio of the design = .00375 (I can give you the graph as well as the entire theoretical mechanics). etheo = 1/(1+.00375 * 5.8) = 1/ 1.02175 = .97871 Now we need to correct the inviscid drag and factor in the viscid drag. Fuselage correction = 1 - 2{(mean diameter of the fuselage/wingspan)}^2 = 1 - 2{(4.36ft/34.5ft)}^2 = .968 Mach effects runs thru another formula but the net result at a Mach of .228 as 1. Our corrected Oswald's efficiency accounting for viscid, inviscid, and mach effects comes out too: e = etheo * Fuselage Correction * Mach effects = .97871 * .968 * 1 = .947 So convention tells us that oswald's efficiency for the FW-190 is ~.947 at turning velocity. Now, .85 is a very valid and normal assumption for the entire envelope. Mach effects will drop that efficiency as the velocity increases and that will be about the average over a subsonic designs envelope. The point being to be very cautious and use valid and normal assumptions. Use conventional theory properly as well the mathematical conventions required by it and do not make up your own theory. It seems to me that you are trying to work propeller efficiency backwards. There does not need to be any "theory" of our own making in that goal. Aircraft performance math dictates that turn performance is the result of power available to power required. If you want to determine the games propeller efficiency in a turn then you simply use the shaft horsepower of the engine minus the power required to reproduce the games turn performance times. Power required to reproduce game turn times / Shaft Horsepower of the engine = Games Propeller Efficiency That is all you have to do. .
  6. I do not know where Holtzauge gets the 1.36. In looking at RAE documents, I have found the Clmax as high as 1.82 for power on effects in a turn. That is what I am trying to find out. I agree that the design Clmax for the Spitfire is ~1.6. You can see that in the POH numbers: Weight 7150lbs Stall Speed = 78KIAS PEC = + 3.4Kts Normal wings = -5.2Kts 76 knots.... Well it requires 74 knots to equal a Clmax of 1.59 which well within the 3% margin of error for level speed measurement and agrees with engineering convention by meeting the NACA 2213 measured airfoil characteristics. That is not really the same airfoil but it is close.
  7. That is what your saying.... It is not a strawman Hotzauge. Nobody is "against" you. Just trying to figure out your logic is all.
  8. So we can say that in your opinion, only Supermarine could reach their design CLmax. Grumman, Messerschmitt, Curtiss, Focke Wulf, and everyone else are completely suspect or unable to do what you claim Supermarine did....achieve their design coefficients of lift. You do know being able to do that is a fundamental requirement of aeronautical engineering.
  9. The biggest advantage of the FW-190 in IL2 is that it can absorb some pretty good damage. It is kind of neat to watch all the damage graphics in the game in.
  10. He is using induced drag. It is his own creation and parameter loosely based on science. It has no relation to any actual aircraft efficiency factor.
  11. file:///C:/Users/Owner/Downloads/assets-European-Telemetry-and-Test-Conference-etc2014-34.-European-Telemetry-and-Test-Conference-6.3-etc2014%20(1).pdf
  12. Here we go: http://www.dtic.mil/dtic/tr/fulltext/u2/a280006.pdf That is in 1974 NASA terms which I am sure was far less accurate than 1940 RAE measurements.
  13. Quote it all you want. Probably why the RAE whined so much when the NACA said the Spitfire Clmax was so much lower than the RAE "measurement", LMAO!!
  14. Because Airspeed Measurement was soooooooooooo accurate....they decided to ignore it and go with this other extra step.... Have I got that Right Holtzauge?
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