Thanks for your responses, I am pleased to see how rational and level-headed they have been. I usually post on aircraft modeling sites (the scale plastic variety), and if these guys were here they would demand to know how many times I have flown the real thing...
I will try to clarify the points I made about the Spitfire and NACA 868 in general.
Believe me, I am the last person who would dismiss the NACA chart 868; I think this is probably one of the greatest single discovery about WWII aircraft maneuverability ever made. The 109G is sadly absent, and thus its roll rate is still a matter of debate. 109F charts do exist, and show a much higher speed for the roll peak (350 MPH TAS) than usually assumed, with peak values ranging from 85° to 109° per second. I would peg the G at 70°-80°/sec at 350 MPH, worsening to 50°/sec below 250 MPH.
Note that the Zero roll rate is labelled "stick force unknown", and that this is critical, because all Zeroes had outstanding roll up to 200 MPH, being close to 100°-120°/sec(!) at a low 120-150 MPH, this always going down after, and ever more steeply after 250 MPH TAS...
[Of note with Japanese aircrafts is that most of their speeds are quoted at Military Power, NOT War Emergency Power. In comparison, the Japanese WEP was usually longer, for instance, than the 109G's 3 minutes (I suspect the 10 WEP minutes-capable MW-50 tank of the 109 often went unused for logistical reasons...). I estimate the Ki-84 topped out at 690-700 km/h, the A6M5 at 590-600 km/h, the Tojo is quoted in a report at 640 km/h. And so on...]
Getting back to NACA 868, you will note that the Spitfire Mark is not specified on the chart, while the specific model is specified for almost all the other, conveniently obsolescent, types. This should immediately draw our undivided attention; the year of the report was 1947, and there were still MANY Spitfires in active service with many nations friendly to American interests. Moreover, in Indochina and elsewhere, many of these Spitfires were in active combat, and keeping the info blurry on these and CURRENT British aircrafts might have been seen as the polite thing to do...
As for what the NACA 868 Spitfires actually were, an indication here with these clipped MK XII tests;
http://www.spitfireperformance.com/mk12roll.gif This from the excellent "WWII aircraft performance" site.
So the CLIPPED Mk XII ranges from 25° to 50° per second, roughly. 38°-25°/sec to right at 300-400 MPH, 50°-40°/sec to left at 300-400 MPH. The unclipped wing substracts about 6°-8°/sec. to the left at high speed and that's it. I ignored the poor performance of EN 221.
Note the unusual preference to dip the LEFT wing at higher speeds; most other aircrafts above 250 MPH have a preference to the RIGHT; but here the spiral of air spins in the OPPOSITE direction; the Griffon propeller turns the other way... Below 250 MPH, the reserve power of the engine turns UPSIDE-DOWN the preference, under acceleration, because this time the stronger TORQUE of the propeller twists opposite against a much weaker slipstream spiral. It is then that the Griffon torque wants to dip the RIGHT wing, again opposite to what most others fighters do at low speeds, and again for the same rotation direction reasons...
Some may find things to quibble, but my feeling is that the above Mk XII performance is probably slightly superior to what we can expect the real, heavier, Mk XIV to do, and is in fact more a mirror image of the MK IX... The Mk IX is slightly better than the MK XIV, if the Supermarine factory test pilot is to be believed, so my guess for the MK XIV would be a range of 40° to 20°/sec. instead of 50° to 25°/sec., from 300 to 400 MPH.
Obviously the 140°/sec of the NACA 868 chart are from another dimension; ie; fully re-designed wings of the post-war Marks...
Note that the Mk XIV was produced in fairly modest numbers, a clear sign to my eyes that it was not seen as a huge success.
Let's disgress for a moment, and consider the strange fact that a MK IX augmented to +25 lbs (colored 150 fuel) will OUT-CLIMB a MK XIV at +18 lbs, yet fails to gain 1 MPH from this extra 350 hp(!), being 40 MPH slower than the +18lbs MK XIV, despite having nearly the same power: ?!! : Radiator design, supposedly...
Does the slow roll rate mean the late Spitfires were crap? Not entirely. Take the ability to point the nose across the turn in a high speed "mushing" stall; very good offensively when the enemy numbers are dwindling, but bad defensively when they are numerous and behind you.
Much as I love the roll rate as a maneuver feature, in my game at least its importance is exaggerated. The Spitfire is probably the worst rolling pure day fighter of WWII; pilots flew around the problem quite well, and it did out-climb and out-accelerate ANYTHING, including ALL 109s... Where the Mark XIV was supreme was at high altitude, where its heavy ailerons may have lightened up and its climb rate was comparatively even more incredible. Other than this narrow high-altitude point defense role, I think it is fair to say that with its more rigid wings, the Me-109 had aged slightly better, if you discount its small, and diminishing, endurance...
Gaston.