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But your graph Crumpp bears little resemblance to the RAE chart.
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Do some math....
The RAE chart is at 12,000 feet and was taken off one data point. It did puzzle me as our radius and other data aligns. It puzzled me until I stated getting into the details of the chart.
According to that chart, the Spitfire Mk 1 is capable of reaching 340mph (+) at 12,000 feet on 1050 bhp.
The RAE graph found in AVIA 6/2394 is a performance estimate from September 1940.
A flight report from March 1940 gives the power at 12,000 feet:
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Normal B.H.P 950/990 at Rated Altitude 12,250 ft
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And lists the Vmax for the type as 326 mph TAS.
http://www.spitfireperformance.com/n3171.html
The AVIA 6/2394 does not fit the only +12lbs estimate we have for level speeds.
http://www.spitfireperformance.com/s...-rae-12lbs.jpg
This estimate shows 359mph TAS at 12,000 feet.
That is over a 5% error from the speed found in AVIA 6/2394. It would be unusual for such a large estimate error in an established design.
I don't know what Spitfire data they used but I suspect it was for an improved high altitude version as we saw before in a similar report previously posted on these forums in which you were involved in the discussion.
All that can be said is we don't know the details and the ones we do know, do not fit any existing service model at the time.
When we plug in the data from the Spitfire Mk I serving in the RAF during the BoB, we get a different result.
Another anomaly is the CLmax. In order to get a CLmax of 1.87 on the Spitfire, you have to drop the stall speed far below what the Spitfire POH list's to a scant 62 knots.
At the 76mph Vs (69mph IAS Vs + 7mph PEC) found in the POH, we get a CLmax of 1.69 which is far below the 1.87 Gates uses in the report.
I am pretty sure Gates was not using a standard Spitfire Mk I for his base data in the estimate. It does not align with one.
Calculate Sea level CL max:
CL = Lift/(dynamic pressure * Reference Area)
Dynamic Pressure = density ratio * Velocity^2 / 295
Dynamic pressure = (1 * 66^2)/295 = 14.76610169psf
CL = 6050lbs / (14.76610169psf * 242sqft) = 1.693067034
Lift = CLqS
Lift = 1.87 * 14.76610169psf * 242sqft = 6682 lbs of Lift generated.