Spit IIa

[TomcatViP]

Originally Posted by IvanK

"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.

Those curves are contestable regarding how the both planes shld hve performed:
- 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.

[Skoshi Tiger]

Originally Posted by TomcatViP

in other terms the spit shld turn tighter at high speed but hve a greater radius of turn when the speed is low.

What do you mean by the term 'tighter'? Degrees per second or radius?

Sounds counter intuitive to me.

[TomcatViP]

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.

Originally Posted by TomcatViP

Those curves are contestable regarding how the both planes shld hve performed:
- 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.

I must admit that I had some difficulties reading the graph in terms of turn radius at it seemed to me that whatever g-line I regarded both spit and 109 would have had approximately the same turn radius. As this is probably not true I dismissed my way of reading the chart with respect to turn radius.

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.

[TomcatViP]

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.

[IvanK]

Originally Posted by TomcatViP

Those curves are contestable regarding how the both planes shld hve performed:
- 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.

The chart is one of the earliest plan Fan plots (or "Dog house plot" in US terms) that I have seen. As such its straight Energy Manoeuvrability theory that is Excess Power (ps) applied to the turning problem. As such it takes into account the total Airframe engine combination so Wing loading,planform,wing section etc is part and parcel of plot. The actual RAE derivation of these charts is discussed in great detail in AVIA 6/2366 RAE report "Notes on the dogfight" A more detailed version of the Spit fan plot chart from this report is shown below. In this case the study also takes into account various extrapolated wing areas and therefore wing loading etc.



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.

[fruitbat]

Thanks for posting IvanK, really interesting stuff.

Resumee:

The Spit has a turn radius of 700 ft (about 215m) and the 109 slightly below 900 ft (275 m). The turn rate is at medium and high speed similar (slight advantage for spit at medium speed, tendency vice-versa for high speed). Good advantage for spit at low speed. Altitude loss higher for 109 during full circle (nearly 0 for spit at medium speed, 5° for 109 at medium speed)

Does not feel that way in game ...

[GF_Mastiff]

Originally Posted by 41Sqn_Stormcrow

Resumee:

The Spit has a turn radius of 700 ft (about 215m) and the 109 slightly below 900 ft (275 m). The turn rate is at medium and high speed similar (slight advantage for spit at medium speed, tendency vice-versa for high speed). Good advantage for spit at low speed. Altitude loss higher for 109 during full circle (nearly 0 for spit at medium speed, 5° for 109 at medium speed)

Does not feel that way in game ...

no it doesnt I fly the spitIa and the 109s keep in a turn at medium speed the spit can not out turn them. or instant climb like the 109s E4s.

[CWMV]

Originally Posted by GF_Mastiff

no it doesnt I fly the spitIa and the 109s keep in a turn at medium speed the spit can not out turn them. or instant climb like the 109s E4s.

In truth you need to realize that you piloting ability, or lack there of, are more likely the reason why you cant conquer the 109's.

You in game experience simply does not hold up to numbers, so if you have some charts post them, please! Otherwise your "The 109's are sooo much better than me" just show your a bad pilot.