BoB Spitfire 100 Octane fuel

[winny]

Originally Posted by klem

I'm not sure where we're going with this Kwiatek.

The conclusion says that there is a drop in max speed with the Rotol vs 2-pitch. I think thats what A2A are saying.

In Tests 18th Aug - December 12th 1938 K.9787 MerlinII, DH5-20 returned 361mph at 18,000 feet, boost +6.4.

That report you linked says that Merlin III engined MkI N.1371 with Rotol achieved 353.5 (~354)mph TAS at 20,000 feet/3,000 rpm/Boost dropped off to 5.25. Actually thats the top speed at altitude A2A are claiming for their Ia.

This seems to be what the devs should be looking at:
http://www.spitfireperformance.com/spit1vrs109e.html

Anyway, we could go round and round for ever.....

There is a slight problem with k9787 ( 1st production Spitfire ) as a reference for mk 1a's. It was much lighter than a mk 1 in BoB trim. All up weight of k9787 was only 5819 lb, mk 1 in BoB trim 6155 lb ( source Alfred Price Spitfire in combat). It didn't have the bullet proof windscreen, which cost 6 mph, the IFF aerials cost about 2 mph, no armour plate.. Etc.

Top speed according to price of a fully equipped mk 1 in the summer of 1940 was nearer 350 mph. It's a minefield!