Spit Mk1 Boost?

[TomcatViP]

calm down pls

[Kwiatek]

[IvanK]

Whats the title of this Test document Kwaitek or its AVIA Ref No ?

This does not reflect the In service Boost ratings for the Merlin III. Its unusual in that In service MERLIN III climb rating was + 6.25Lbs boost not as +9 shown here. If its genuine then I believe its a 1 off RAE trial report investigating the feasibility of rating the Merlin to +9Lbs climb in preparation for this rating in the Merlin XII. Merlin XII as fitted to Spitfire MKII had +9 Climb

MERLIN III LIMITS from Spit I Pilots notes

[Kwiatek]

I dont know IvanK - i just found these single document some time ago. But it is clearly for MErlin III testing with 100 octan fuel - data is from 28.02.1940.

Document which you posted is of course for Merlin III with 87 octan fuel only - not for 100 Octan fuel.

Here is for Merlin XII for both 87 and 100 Octan fuel used:

[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.

[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

[Kwiatek]

Hmm interesting so you got IvanK linkl for these report?

I got also such documents for 12 lbs limitation of Merlin III:







But i think most know these documents.

[IvanK]

12lbs Boost was available to both the Merlin III and the Merlin XII (running 100 Octane) when Boostcutout was activated. In the case of the Merlin III a couple of mods were also required to allow 12Lbs Boost. This has been debated at length in the forum.

Only the Merlin XII had the +9lbs limit Full throttle. (Boostcutout not activated)
The Merlin III Limit was +6.25Lbs Boost. 9Boostcutout not activated)

I don't have links to the docs. I spent a bunch of time in the UK archives researching and copying them. Pretty much every RAE report is available there.
Bits and pieces of these docs are available online at Spitfire Performance testing and WWII Aircraft performance http://www.wwiiaircraftperformance.org/

[Kurfürst]

Originally Posted by IvanK

Whats the title of this Test document Kwaitek or its AVIA Ref No ?

This does not reflect the In service Boost ratings for the Merlin III. Its unusual in that In service MERLIN III climb rating was + 6.25Lbs boost not as +9 shown here. If its genuine then I believe its a 1 off RAE trial report investigating the feasibility of rating the Merlin to +9Lbs climb in preparation for this rating in the Merlin XII. Merlin XII as fitted to Spitfire MKII had +9 Climb

My take would be that Kwiatek's paper shows an early rating, valid for the first quarter/half of 1940, with +9 lbs being the initial maximum cleared for generic flying, and +12 only for takeoff when necessary. This seems to be quite typical when introducing higher ratings for an engine.