Spit IIA Speed in game test

[41Sqn_Banks]

Originally Posted by Kurfürst

Banks, what is the date of this manual? I see it has been amended so its contents are at a later date than the original. When did this amendment came into force?

It's from the same manual where the unamended engine limitations page from you is taken, i.e. the "unamended" version (though as can be seen there is an amendment included). If you have a really unamended version maybe you can show the corresponding pages.

Secondly, then how did the boost override work on the Mk II in 1940?

Did it overode automatic boost control and the pilot had to adjust boos manually, according to altitude?

Of course, the cut-out did disable the boost control, thus the pilot had to adjust boost with altitude. The only question that remains is if it maximum boost was limited (like modified Merlin III) or not (like unmodified Merlin III).

Also note this post: http://forum.1cpublishing.eu/showpos...&postcount=365

It shows that there were two different "All out" boost limits for Merlin 45, one regular rating (+9) and one for emergency (+12, later +16).

I just want to remind you that I was on your side in this case until there the combat reports were discovered that show the use of emergency boost/cut-out. I don't see a definite proof so far that the emergency boost was +12, however it's the only plausible value, everything below or above would be very very unlikely.

[Kurfürst]

Originally Posted by 41Sqn_Banks

I just want to remind you that I was on your side in this case until there the combat reports were discovered that show the use of emergency boost/cut-out. I don't see a definite proof so far that the emergency boost was +12, however it's the only plausible value, everything below or above would be very very unlikely.

I have reviewed the paper and the manual again.

My conclusion, based on the July 1940 Spitfire II manual is that the references to emergency boost simply refer to +9 lbs, which was the all out limit to be used "in emergency". See attached manual. Therefore, early references from August 1940 to emergency boost refer to +9 lbs / 3000 rpm.

Controlled +12 lbs could be obtained by pushing through the gate for take off purposes only, and would fall off quickly with altitude. Boost graphs indicate it would be back to +9 by 3-4000 feet.

The Boost-cut out emergency control is simply an override for the automatic boost control. It should be noted that references to use of boost cut out do not appear until November 1940. Pilot can then control boost manually, and should be careful not to overstep the limitation of +9 lbs. He may choose to go over +9, as the Boost-cut out emergency control system technically permits it.

If doing so, great engine wear and risk of engine failure is risked. The officially sanctioned use of +12 with a limitation of 3 minutes or 1000 feet, whichever was shorter, was there for a reason.

He also has to manually adjust boost according for changes in altitude (at low altitude, extreme over-boost may occur as the throttle fully forward would result in about +17 lbs boost, and likely immediate destruction of the engine). Decrease of altitude will result in boost increase, increase in altitude will result in boost decrease. I am looking forward to Spitfire II pilots trying to get this right in a fight...

In short, its somewhat similar to manual overrevving practice on the DB 601 on 109/110.