Looking for Spitfire I sustained turn rate charts

[Charge]

1. The Merlin is quite more powerful than the DB
(109E and Spit I on 87 oct)

2 The Wing of the Spitfire in question generates quite some more lift than the wing of the 109 given roughly the same thrust.


Just a few thoughts Angus:

1. But it wasn't, at least according to numbers. The propellors were of different shape and probably rotated at slightly different speed. But what was their efficiency ->generated thrust?

2. Depends on the AoA? I'd imagine the 109 wing generate very good figures for lift in small AoA due to its NACA profile where as Spitfires wing is better when AoA increases because of its wing area alone. I'd also like to see the effects of the washout in Spits lift figures in level flight. The wing tips can't generate much lift as the AoI is different for the root and tip? So their drag figures, too, are quite different in different speeds and angles?

I'd also imagine the angle of climb have a significant effect on results your calculations may give.

-C+

[Crumpp]

Came across this and thought of this thread.



Hope this helps.

Crumpp

[Angus]

Lovely, excellent.

Now I just have to read the darned thing.

[Badboy]

Originally posted by Crumpp
Came across this and thought of this thread.
Crumpp

In my last message I posted a link to another thread in which I posted the url to those diagrams at the fourthfightergroup site:

http://www.fourthfightergroup.com/eagles/spit109turn.gif

They are simply a different style of EM diagram sometimes seen in reports dated that far back, but contain almost identical information to the ones I produce, just presented in a different way.  

Quite a long time ago now, I decided to reproduce the same type of analysis used in that diagram and piggy back it onto the work I've already done for the Aces High aircraft. Now when I produce an EM analysis for any aircraft, I automatically get both types of diagram. There are advantages and disadvantages to both methods. The diagrams I've been producing were not conceived until the 1960s and they have the advantage that they can be overlaid with one another for a far easier comparison. The disadvantage with the type of EM diagram that originated in the late 30s is that they can't be overlaid. So for example, here is an overlay of the AH Spitfire MkI and the Me109e

 
 
The main advantage to producing the type of EM diagrams seen in those early reports is that they can be compared with the ones that exist for the real aircraft. For example, the Spitfire in the diagram above has this diagram:



But let's compare that with the diagram for the real Spitfire MkI.



Here we can see that both the real Spitfire and the AH Spitfire have the same corner velocity at that altitude and configuration, so let's compare a turn. Just for example I've selected a 5g turn at the corner speed of 250mph. I've indicated on the diagram for the real Spitfire that it would need to descend at 16 degrees below the horizon to sustain that turn and it would turn a full circle in about 14.5 seconds with a radius of about 850ft. You can see from the diagram for the AH Spitfire that it would also make the same turn in about 14.5 seconds with a radius of 850ft, and that it would need to descend at an angle of 23 degrees below the horizon, a descending turn only 6 degrees steeper than the real aircraft. But the turn rates and radii for the turn, along with the corner speed are amazingly close. The difference in the angle of descent is probably due to differences in engine power available at that altitude between the real world tests and Aces High, and perhaps some differences in weight.

It is interesting that both diagrams are essentially the same shape, and that they agree quite closely in many respects, indicating that the flight model in Aces High has accounted for all of the aerodynamic factors that would influence the shape of the curves to any significant degree. A worthy achievement indeed. Kudos to HTC.

This is even more significant, because I've made a similar comparison with the Spitfire and 109e from other simulations, and so far Aces High has first place for accuracy.  I was thinking of writing up the whole comparison for an article on SimHQ, but other projects have pushed back in the que.

Hope that helps...

Badboy

[TimRas]

Excellent work Badboy.

[HoHun]

Hi Badboy,

My Spitfire I turn calculation agrees with the WW2 chart quite well in turn rate at 12000 ft, but I get a much higher turn speed and accordingly a larger radius. (About 190 mph vs. 160 mph.)

Since I've used the NACA report lift coefficient for the Spitfire which is a bit lower than the British value, that appears normal. Since the NACA value is measured data opposed to the "assumed" data in the WW2 turn rate graph you linked, I feel I'm erring on the side of caution here ;-)

Regards,

Henning (HoHun)

[Badboy]

Originally posted by HoHun
Hi Badboy,

My Spitfire I turn calculation agrees with the WW2 chart quite well in turn rate at 12000 ft, but I get a much higher turn speed and accordingly a larger radius. (About 190 mph vs. 160 mph.)

Since I've used the NACA report lift coefficient for the Spitfire which is a bit lower than the British value, that appears normal. Since the NACA value is measured data opposed to the "assumed" data in the WW2 turn rate graph you linked, I feel I'm erring on the side of caution here ;-)

Regards,

Henning (HoHun)

Hi HoHun

Nice to talk to you again…

I know the graph posted does say that those lift coefficient values are assumed, and that is unfortunate, because I know they are not… At least not in the sense of being guessed at. I read the reports a long time ago, but recal that those values were arrived at after in flight and wind tunnel measurements were used to produce an empirical relationship. I’ve seen the data, the resulting graph, and equation. The in-flight measurements were obtained using swivelling pitot and suspended static heads, and stalls were done at both full throttle and gliding in order to determine the stall boundaries used on the graph. I think they used the word “assumed” to indicate that the intermediate values were not measured directly, but resulted from calculations based on the resulting empirical formulae. I checked the calculations back when I read it, and I think they are likely to yield far better results than using a constant Clmax value, and I use similar methods in my own work.  

I’m just mentioning that because I’ve seen the graph used in previous threads, where it was negatively criticised on the basis of that word, which I admit is misleading. I didn’t say anything before, because I’ve discovered there really isn’t any point bringing facts into a discussion when the participants have some other axe to grind.  

So it is perhaps unfortunate that the authors of that report used that word, because although they did some very excellent work at the time, they weren’t to know that some 60 years later the appearance of that word on their graph would be used in arguments on a flight sim’ board to invalidate it for reasons of gamesmanship… Not accusing anyone here, just saying. Bottom line... My vote goes to Farnborough not NACA :-)

Badboy

[HoHun]

Hi Badboy :-)

>I know the graph posted does say that those lift coefficient values are assumed, and that is unfortunate, because I know they are not… At least not in the sense of being guessed at.

Roger that, and I actually I assumed they were assumed as quoted for a very good reason :-)

Still, for the NACA data, I had the full report along with the test procedures, and was certain the measured Clmax was indeed achieved under Gs. Do you know whether this was the case for the British tests, too?

>I checked the calculations back when I read it, and I think they are likely to yield far better results than using a constant Clmax value, and I use similar methods in my own work.  

Well, I'm using a constant Clmax, but since I picked the Clmax for the acceleration that coincedes with the best turn rate, the error will only catch up with me in some other place ;-)

>So it is perhaps unfortunate that the authors of that report used that word

I agree. Though it's correct terminology, it implies more uncertainty about the Clmax than there actually was.

>Bottom line... My vote goes to Farnborough not NACA :-)

I stick with NACA for now, but I'm ready to admit we're operating at the limits of what is possible in retrospect accuracy anyway :-)

Regards,

Henning (HoHun)

[Wotan]

Here's a little something to keep the allied farmbois panties bunched...

http://mnemeth1.brinkster.net/movies/EAA_Interviews.wmv

[Crumpp]

They are simply a different style of EM diagram sometimes seen in reports dated that far back, but contain almost identical information to the ones I produce, just presented in a different way.

I did not follow your link.  That diagram was sent to me through another source.  Nice work, Badboy.

Crumpp

[Angus]

Whoa, nice link Wotan.
Do you know what 109G the guy is referring to?
1500 lbs ligter than the Mustang anyway.