Quote:
Originally Posted by JtD
Now how would they technically do that, make the boost of 12" drop off quickly instead of having it follow the outside pressure? What did the automatic boost control cut out do on the Spitfire II if not disable automatic boost control?
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As I understand, the cut out as its name suggest disabled to automatic boost control and gave direct control to the pilot over the boost. Maximum forward position on the throttle was set to open the cross section for +12 lbs at SL, and naturally this fell off with altitude; the pilot would have to open even further to compensate, which was however physically impossible - the throttle could not be pushed even further, it was already in the end position.
This graph suggest (see boost falling) that +12 fell back to +9 within about 2500 feet. This would also suggest that using the boost cutout was quite useless above that altitude, since it gave you the same performance as not using it at all.
http://www.spitfireperformance.com/p7280-speed.jpg
Come to think of it, it seems to work exactly the same as the 109E's 1-minute rating, altough that latter was automated.
05-13-2012, 12:02 PM
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