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#1
10-11-2011, 09:32 PM
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Quote:
Last edited by Ataros; 10-11-2011 at 09:37 PM. 
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#2
10-11-2011, 10:42 PM
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"What is the historical 109 turnrate?" .... same problem as always it depends whose data you believe !. It also depends on how the turn is being flown in each aircraft. You after Sustained or instantaneous ?
These charts are reasonable for sustained turn performance: http://www.spitfireperformance.com/spit109turn.gif Spit V 109 Turn times.
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#3
10-11-2011, 11:07 PM
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That is an interesting chart, IvanK, but a bit difficult to read as the time scale is logarithmic.
The tendency is that in terms of turn rates full circle both planes were quite close with perhaps a very small advantage for the spit (perhaps 2s as absolut max generously estimated optically. Would have to print it out and measure it to be more precise) at medium velocities. The spit will rule at slow speeds. For high velocities theres a minor advantage for the 109 in terms of turn rate.
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#4
10-12-2011, 12:56 PM
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- first: on the ground of the knowledge of both nation at the time of the test/calculation (1940) - Secondly : on the base of the contradictions that a modern analysis would tell us First pt : If British engineer in 1940 had let an elliptical winged (EW) fighter be the most advanced defense they had allowed to be put on the frontline, for sure they were not aware of the advance Germans had made in that grounds. Remind that EW are the panacea only when dealing with inviscid flows etc... etc... Look at max Cl of both plane, max Pow and wing loading. I know that I can be annoying but those value and the fact that the wing thickness of the spit is lower tell us that there SHLD be an inversion in turn radius as the speed decrease. in other terms the spit shld turn tighter at high speed but hve a greater radius of turn when the speed is low. In other words they couldn't hve found any other value as their assumptions were made on false grounds. Last edited by TomcatViP; 10-12-2011 at 01:02 PM.
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#5
10-12-2011, 02:43 PM
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Sounds counter intuitive to me.
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#6
10-12-2011, 03:42 PM
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It's a rather long reply needed here indeed.
I think I did alrdy give an answer. To make it short here : 1st we are talking of turn radius as we are dealing with cte speed turn 2nd it's almost certain that at much of the speed range the SPit had an instant turn speed greater than the 109 as here Wing area rules (at comparable wingspan, nose authority etc.. etc... ) 3rd at cte speed, the drag generated by the wing in a turn attitude (AoA) and power to weight ratio are the keys. Simple calculation give you a result dependent only of Wing surface and Power to weight ratio as they are based on simpler theory that does not apply to high speed fighter and high G ( high AoA) turns. In their calculation they are in effect minoring the drag of the Spit wing.
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#7
10-12-2011, 05:55 PM
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My guess anyhow is that what is of importance in the chart IvanK posted is the turn time for a full circle. According to IvanK's chart the turn rate between the spit and the 109 is pretty close. This does not say anything about turn radius. If somebody could help be decypher the chart wrt turn radius I'd be happy to listen.
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#8
10-12-2011, 06:42 PM
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How to read the chart :
Choose a speed for a plane -> then select your G level / bank angle - > read the time to 360° *-> then compare to the other plane *You can also read the nearest dotted line that give you the nearest computed radius but as the speed V=d/t if you hve V (cte) and t then d is alrdy in your hands Alternatively you can follow a firm line that stand for a level turn (cte height) -> you can then see how much G/ bank angle is needed at a given speed for a given plane and what wld be the radius of turn. Last edited by TomcatViP; 10-12-2011 at 06:54 PM.
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#9
10-12-2011, 08:44 PM
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 I dont agree that their assumptions were made on false grounds. Everything I have read in these reports indicates to me that the boffins doing this work were really on top of their game. Here is some of the data they were using in this report obtained from a physical specimen BF109E3:   The USN also produced a comprehensive study on turn performance on the F2B (Buffalo) that is equally involved and again is based on straight out EM theory applied to the turn problem and again chock full of fan plots. Here is another chart from the same source source document as the original Fan plot came from (AVIA 5/2394 "Messerschmitt Me.109 Handling and Manoeuvrability Tests" which is a pretty exhaustive 63 page document. This chart provides similar data to the fan plot but perhaps in a more easily digestible format as both Spitfire and 109 plots are overlayed on the same chart. 
Last edited by IvanK; 10-12-2011 at 09:32 PM.
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