Spit/109 sea level speed comparisons in 1.08 beta patch

[NZtyphoon]

Originally Posted by Crumpp

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:



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.

And what do we see on the 109 data? Estimate on chart = 1,200 Bhp at 2,400 rpm 15,000 feet, TAS 340 mph + at 12,000 which Crumpp, conveniently has ignored, whereas the true output was about 960 ps 2,300 rpm at about 3,500 metres

http://www.wwiiaircraftperformance.o...oct40-pg22.jpg

So Gates was also using an unusually powerful 109 for the chart as well. I suspect it was probably an experimental high-altitude 109E.

Question is what data did Crumpp use to compile his chart? There's no engine rating shown, no take of weights, nor anything else to indicate on what basis Crumpp's "calculations" were made. For any proper analysis Crumpp's chart is totally useless.