Bug 174 on 12lbs boost. Review please.

[41Sqn_Banks]

Kurfürst I'm not saying it was +12 boost, only that the boost must have been higher than +9, as it wouldn't make sense to use the cut-out without getting any benefit. I don't think there is so far any definite proof for the exact emergency boost value of the Spitfire II in 1940. However the fact that earlier (Merlin III), similar (Merlin XX) and later (Merlin 45) engines had +12 emergency boost in 1940 (the Merlin 45 of course in 1941), and the fact that +12 boost is documented for the Merlin XII for 1942(?) is a strong indicator that +12 boost was the emergency limitation of the Merlin XII.

BTW in RAF terminology "All-out" is not equal to "emergency". This can be seen in the Spitfire V test report: http://www.spitfireperformance.com/aa878.html

Max. for all-out level flight (normal rating)(5 minute limit) +9
Max. for all-out level in special emergency (prior to increase to +16) +12
Max. for climb and level flight (combat rating)(3 min. limit) +16

Of course this is not a Merlin XII engine but it shows that there could be different boost limitations for "all-out normal rating" and "all-out emergency".