at least in the Moskau gameshow videos there were 4 different Spitfire versions available as flyable.
lets guess one is a Mk.II and the second a Mk.I with CSP.
they will propably have the 12lb boost.
the other two Mk.I (perhaps one with a fixed wooden propeller the other one with a 2-pitch one) propably not.
time will tell........
at least i dont want be in Olegs shoes who had to decide what perfomance charts he wanted use for his game Spits and 109s . There a lot around in books and internet![]()
The Spitfire figure you should be using is the faint line marked 12 lbs, as that was universal during the BoB.I've just converted that to Imperial, and then put it in Excel. I've then read the approximate altitude points off the Spitfire graph, and recorded the relevant speeds. I then subtracted the Spit speed from the 109's at each altitude:
Alt ft -----Diff favour 109
0 ............. 2.83
3,281 ........ 2.26
6,562 ........ 2.69
9,843 ........ 3.11
13,123 ...... 3.54
16,404 ..... -0.14
19,685 ..... -9.14
22,966 ..... -19.67
According to the chart, that's 314 mph at sea level, which is 505 km/h.
I'm happy to be corrected on that if it's wrong. Please feel free to update the table accordingly if you think the 12 lb curve is the right one.
I didn't use it because it's obviously a later addition to that chart. The chart is already dated a year after the BoB, so I'm not sure why that would be. Secondly, I didn't use it because I thought the data a bit dubious. It puts the critical alt for the 12 lb version at 11,500 feet. This seems a little low. Without some other corroborating source to hand I decided to go with the curve I felt more certain of.
But if you're confident that 359 mph at 11,500 feet is right, by all means please correct the table to reflect that.
I'm not sure if the 12 lbs figure is calculated or not, but I see no reason to doubt it. The critical alt is as it should be.
100 octane allowed the engine to run at 12 lbs boost, up from the previous 6.25 lbs. As there were no changes to the supercharger, 6.25lbs can be maintained to a much higher altitude than 12 lbs.
Modifying your table for 12 lbs:
Alt ft -----Diff favour 109
0 ............. -45
3,281 ........ -44
6,562 ........ -43
9,843 ........ -45
13,123 ...... -36
16,404 ..... -28
19,685 ..... -9.14
22,966 ..... -19.67
I can't vouch for the 109 figures, though, just going on what's in the charts provided.
Not sure,but if I had a 109 behind me,I would have turned it on and left it on until it went bang!Originally posted by csThor:
Just curious ... what are the limits? I mean how long could +12lbs be extracted from the engine? I figure for 1940 this was causing a serious strain for the engine and I guess it had to be limited to just a few minutes.![]()
Pilot's Notes Merlin II, III and IV (4th Edition, April 1940)from Rolls-Royce Limited state:Originally posted by csThor:
Just curious ... what are the limits? I mean how long could +12lbs be extracted from the engine? I figure for 1940 this was causing a serious strain for the engine and I guess it had to be limited to just a few minutes.
"An endeavour should be made to limit the use of the increased boost pressure to periods of 5 minutes."