MAINJAFAD, listened to the link you provided and a new piece of information put up by Brown
Brown - On the question of the all moving tailplane, certainly the United States knew about it, but I've no evidence of them having actually flown a full scale flying tailplane, but I flew such a tailplane on a Spitfire in October/November 1944
NACA modified the XP-42 with an all flying tailplane March 1943 and made its first flight the same month in the hands of Langley test pilot John P. "Jack" Reeder. NASA photo.
