Hi Parmigiano,
>I think that fear of mass desertion was not the main point: my interpretation is that if I have to develop and deploy a new fighter I also count on a surprise effect. If the enemy already can evaluate this machine even before I can field it in numbers, I lose this advantage and this can influence my decision to invest on the project.
Hm, I don't think that was a factor in WW2. The Allies were ware of the long-nose Fw 190 almost two years before it actually went into production, and as far as I can tell, they had no advantage from that at all.
(In fact, tactical evaluation of captured aircraft so often gave misleading results that sometimes, I wonder who actually benefitted more ... the captor or the underestimated enemy
I'd admit that the psychological impact would be greater if the new type arrives un-announced, though - as it was the case with the first Fw 190s in 1941.
Regards,
Henning (HoHun)