Spit Mk1 Boost?

[IvanK]

Originally Posted by lane

IvanK: The Inspection and Test Certificate posted by Kwiatek is taken from Aeroplane and Armament Experimental Establishment’s report on Spitfire II P.7280, Merlin XII - Rotol Constant Speed Airscrew, Comparative Performance Trials, First Part of A.&.A.E.E./692,e dated 27th September, 1940. You will note that the rated power listed matches that of a Merlin XII. I always assumed "Mark III" on the Certificate was a typographical error.

Thanks Lane, I have that report in full. All other pages refer to the engine as Merlin XII. The AVIA ref for this report in the UK National Archives is AVIA 18/1574
I am with you Lane, I think it refers to Merlin XII, the Merlin III looks like a typo on that single page