Effect of boost control cutout prior to +12 psi boost modifications

[Viper2000]

Originally Posted by ICDP

Read what I said again. My point was that at 12,000ft or 24,000ft it is easier to keep an engine cool than at SL. Had the test been done at SL the temperatures would have been much higher.

This doesn't follow. The air temperature is lower, but so too is the air density.

The worst case for cooling is generally likely to be minimum speed at FTH.

Above FTH the power decreases in proportion to air density, but the problem is reduced because:

• FTH is likely to be <11 km and so the air temperature continues to decrease during the climb.
• minimum TAS will be higher, and mean TAS will also be higher because airframe drag is less.

BTW, the last time I tested the Spitfire II it was just wrong, and if anything was faster than it should be with a Merlin XII at +12, with the wrong FTH.

Speed is a pretty meaningless metric IMO. It's much better to plot a TAS vs altitude graph and then take the error to be the area of the gap between the lines of real test data and sim data. Of course, this should be an absolute figure, because +ve and -ve errors obviously don't cancel each other out.

In the end, this thread wasn't intended to be an argument about +12 boost.

It was intended to point out that given that we have 87 octane boost indications, we should have 87 octane boost cutout behaviour, which was very different from 100 octane boost cutout behaviour. IMO it's worth simulating this simply because it's interesting.

Obviously we should have 100 octane fuel and +12 boost, but that's for another thread (indeed it's pretty sad that such a thread should be needed at all, but obviously it is).

*edited to remove engine wear stuff to Kurfürst's thread*