This paper discusses the various aspects of flow separation on wings and aerofoils at subcritical Mach numbers. It is shown that in general the onset of non-linearities in the aerodynamic characteristics, for plane constant-section wings, can be related to the initiation of regions of flow separation somewhere on the wing and often near the wing tip.
Empirical correlations are produced, tor plane wings of constant symmetrical section, enabling estimates to be made of the lift coefficient for onset of separation at either the leading or trailing edge of the wing.
A correlation of stall types on aerofoils, due to Gault, is extended in application to the estimation of initial stall and separation types for plane wings of constant symmetrical section. Suggestions for extending the application of this correlation to the estimation of section stall type for cambered, twisted and non-constant section wings are made.