I wonder if anyone can shed light on the historical aspect i.e. at what point in the History of Flight / Aerodynamics/ Aviation Regulation did 1.3 start appearing? It might shed some light on why 1.3 was chosen and if it was to be applied to a specific aircraft group or to aircraft in general.
Assuming ,as sounds most sensible , it relates to energy reserves available for the flare does that mean it is valid across aircraft groups (i.e everything is more or less proportionate and holds true whether 747 or 152) or is it primarily relevant to large aircraft only in which case what values should be used for the other groups?
TIM