[Talisman]

Originally Posted by 41Sqn_Banks

I'm sure you are referring to this page.
Note the header where it reads "Amended in Vol. I by A.L. 31 and P.N. by A.L./L". This means the content of the page was changed at a later date.
Judging from the date of the previous A.L. 30, which was issued December 1943, I would guess it is from early 1944 if not later.

The page without amendments looks like this: http://forum.1cpublishing.eu/attachm...9&d=1332086948

Note the "List of Contents" page from June 1940. Para 1 of Section 2 didn't contain "Engine data" but "Introductory notes".

http://forum.1cpublishing.eu/attachm...7&d=1332086792
http://forum.1cpublishing.eu/attachm...8&d=1332086871

See this post for more details: http://forum.1cpublishing.eu/showpos...&postcount=677

Of course this doesn't mean that +12 "Emergency boost" was cleared not before early 1944. I would guess it was cleared in November 1940 at the same time as the Merlin XX.

Thanks for posting. Wikipedia says:
Merlin XII (RM 3S)
1,150 hp (860 kW); fitted with Coffman engine starter; first version to use 70/30% water/glycol coolant rather than 100% glycol. Reinforced construction, able to use constant boost pressure of up to +12 psi using 100 octane fuel; Used in Spitfire Mk.II.[76] First production Merlin XII, 2 September 1939.[18]

First production Merlin XII Sep 1939 and trial data from the link is dated May 1940, so I would hope RAF pilots were provided with an emergency boost capability, and other improvements, by the time the first Spit Mk II sqn was fully operational later in the year, or they would have had less capability than the Spit MkI. Amendments to RAF Air Pubs show a vertical line in the margin to mark the place the amended information has been inserted on the pages that are effected; I do not see any vertical lines on the page for the latest amendment. Still perhaps someone will be able to clarify the point you raise. Perhaps some combat reports from Spit MkII sqns will help if any of them mention operating the boost cut-out.

Talisman