[Juha]

Hello Ruy
if you have the Morgan’s & Shacklady’s bible, look pages 53-54. Those Spitfires with DH 2-pitch propellers had their props converted to CS propellers with DH built conversion sets at sqns by DH teams and additionally 20 conversion sets per week were sent to Supermarine from 25 June 40 for the production line. As much of M’s & S ‘s book, this part is straight from old Flight article and tells the story on DH’s POV and forgets Rotol part of the story. But because of the massive installation of CS props to fighters was initiatived in late June 40, I doubt that US propellers had much impact during the BoB.

My impression is, based on fairly limited information, that some Spits, from Dec 39 onwards and some Hurricanes at least from Apr 40 onwards were equipped with Rotol CS props but when it was found out how dangerous opponent 109E was it was decided that all Spits, Hurris and Defiants were to have CS props and because of Rotol’s production capacity wasn’t big enough to satisfy this sudden rise of demand in the very short time allowed it was decided to satisfy most of the demand by DH conversion sets. Its entirely possible that Brits placed an order of CS props also to HS, but when would the props ordered in mid June at earliest arrive to Supermarine factory? I have not read on early Spits with HS props, but that means nothing. CS props are one of those important details on which there are not so much reliable info in aviation literature.

Juha

ADDITION: By summer 40 all new Spits, Hurris and Defiants were delivered from the factory with CS prop, either Rotol or DH, as standard equipment and the crash conversion program at sqns was estimated to be complated by 20 Jul 40 for Spitfires, after which fighters at MUs were to be converted.