Crumpp: Posting the NAVWEPS chart and showing the relationship between 21 s, 68 deg bank angle and the 115.6KEAS*1.37 shows you have no idea about what you are doing: That chart just shows the relationship between these variables in a stationary turn.
You use the unsupported preconception that the Spitfire can hold a sustained turn bank angle of 68 deg at 20,000 ft and this is where you go wrong. The RAE report R&M 2349 by Morgan & Morris actually states the bank angle for the Spitfire at 20,000 ft which is 51 degress, not the 68 degrees you pulled out of a hat. Now instead enter the RAE turn speed of 141 mph TAS and bank angle of 51 deg in that same chart. This gives us 11.4 deg/s. This is equivalent to a turn time of 31.5, not 21 s. You see now?
In addition, I really like the circular argument you use to MIG-3U's question about the impact of power: First you assert that the Spitfire will have a turn time of 21 s at 20,000 ft without any power analysis whatsoever, period. Now you suddenly claim it's dependant on which Merlin version was used, compressibility corrections etc. Are you perhaps beginning to feel the heat and want back away from the 21 s claim?
Which brings us to the question of proof: I don't think you understand how this works: You have made a claim that the Spitfire turn time at 20,000 ft is 21 s. If you want to convince us then YOU need to provide proof of this either through references or calculations showing where the RAE who claim 31.5 s got this wrong. I wish you good luck with that.
Personally, I'm comfortable with my simulation result of 31.65 s and seeing that this is in line with the Royal Aircraft Establishment result I'm placing my money on Mr Morgan & Morris and their figure of 31.5 s and I will not hold my breath until I see your "proof" for the 21 s claim.
I can add that the C++ code which validity you question (and that I use to come to the same conclusion about the Spitfire turn performance at 20,000 ft as Mr Morgan & Morris of the RAE) is an extension of the code I wrote for my Masters Thesis which was analysis of fighter jet performance and the influence of external stores on speed, climb and turn rate performance etc. This is actually a bit more complicated than analysing the Spitfire by the way since the external stores really mess up the area ruling and leads to complications, especially in the transonic range. However, seeing you are an expert in everything from 100 octane usage during BoB to turn rates I guess this falls far below the level of your extensive expertize.
I also notice that you are now "employed full time in aviation as a pilot" which was interesting to learn because previously, while you have generously shared your experiences and anecdotes of a life as a private pilot, posted pictures of small privare aircraft that you own etc., you have made no earlier mention of this that I recall. Would be interesting to hear which type of aircraft you fly on a commercial basis? Do you fly passenger or cargo services?
While you were quick to question my formal education, I notice that you have still not replied regarding your own credentials. When you do, In addition to the info about when you got your Msc and your experience in the aeronautical industry please add some info about what you did for your Masters Thesis. Based on your penchant and reliance on charts like the NAVWEPS, was it something to do with nomograms perhaps?
