Bf109 test data

[41Sqn_Banks]

Originally Posted by Kurfürst

BTW ain't the Spitfire's FM based on the Spitfire prototype? No problem with this one, eh?

Nope. The speed charts posted by BlackSix are based on the performance test of N3171 (http://www.spitfireperformance.com/n3171.html). Interesting notes on engine power of this aircraft:

The results show that the maximum level speed is reached with the airscrew controlling at 2800 engine r.p.m. On increasing the r.p.m. to 3000 the speed was reduced, on the average by 4 m.p.h.

For the particular engine fitted there is a reduction of 17 b.h.p. at constant boost (+6¼ lb) when the r.p.m. are increased from 2800 to 3000. The loss of speed is therefore probably due to the loss of power accompanied by a slight decrease in airscrew efficiency. The matter is being further investigated by Messrs.Rolls-Royce and Messrs.Rotols. It will be noted that reducing the R.P.M. from 3000 to 2800 lowers the full throttle height by 2000 feet.

4.3 Engine Power. The engine installed in the aeroplane develops slightly less power under test bed conditions than that in K.9793, the aeroplane fitted with the 2-pitch airscrew. This could have the effect of reducing the top level speed by about 2 m.p.h.

...


2. There is a drop of 13 m.p.h in maximum level speed compared with the 2-pitch airscrew aeroplane but of this, 8 m.p.h. can be attributed to sources other than the airscrew.

3. Below full throttle height an increase in speed of about 4 m.p.h. can be attained by controlling the engine R.P.M. at 2800 instead of 3000.

[Kurfürst]

Well the figures people have been asking for the Spitfire, 285-290 mph or so at SL, are strikingly similar to those achieved with the Spitfire prototype. Which if I got the spiriti of the thread right, means that our Spitfire should realistically do about 250-260 mph tops. It's a PROTOTYPE and all that you know...

I am also asking that because N3171 trials did not measure speed near SL (or under 8000 feet) at all.

So on what are complaints about the lack of SL speed of the Spitfire as based again? A trial that did not even measure SL speeds or that infamous crayon curve?

I am very cynical here of course, but in that context, it's a somewhat difficult to understand the extremely demanding attitude displayed by some for the 109E performance on the other hand.

I mean if a crayon drawing will do for the +12 Spitfire surely four seperate timed runs on a record course with calibrated and recorded instruments, a bench tested engine, with the results being corrected for Normaltag and the nominal engine output and guaranteed by manufacturer will do for a 109, would it not.

[41Sqn_Banks]

Originally Posted by Kurfürst

Well the figures people have been asking for the Spitfire, 285-290 mph or so at SL, are strikingly similar to those achieved with the Spitfire prototype. Which if I got the spiriti of the thread right, means that our Spitfire should realistically do about 250-260 mph tops. It's a PROTOTYPE and all that you know...

I am also asking that because N3171 trials did not measure speed near SL (or under 8000 feet) at all.

So on what are complaints about the lack of SL speed of the Spitfire as based again? A trial that did not even measure SL speeds or that infamous crayon curve?

I am very cynical here of course, but in that context, it's a somewhat difficult to understand the extremely demanding attitude displayed by some for the 109E performance on the other hand.

I mean if a crayon drawing will do for the +12 Spitfire surely four seperate timed runs on a record course with calibrated and recorded instruments, a bench tested engine, with the results being corrected for Normaltag and the nominal engine output and guaranteed by manufacturer will do for a 109, would it not.

I must have missed the speed charts for Prototype K.5054, the earliest I know is the test of the the production aircraft K.9787 (http://www.spitfireperformance.com/k9787.html) which has 291 mph at sea level.