When was Va invented?
 

Hi folks, I have been digging around the CARs CFRs and related ACs on Va Vo Vp Vc Vb etc. yes that old chestnut... I haven't been able to locate the reg that introduces Va as a requirement for publication in POHs. CAR 3 era aircraft look to have their design maneuvering speed termed Vp. Wondering how Va ended up in their flight manuals.