The subject which I have to discuss to-day is one which can be treated from a standpoint of the scientist or from that of the practical engineer. I am going to try to discuss it from the latter point of view.
The testing of the behaviour of aeroplanes in flight, to which I want to draw attention, does not deal with research on stability and control, it only deals with checking the flying characteristics with regard to the requirements which should be fulfilled.
In the Dutch requirements for a certificate of airworthiness for civil aircraft there are several detail rules, which all tend to state that the aeroplane should be stable and well controllable within the whole region of flight, and for all conditions which may occur in normal and special use.