It has been known for many years that the rectangular wing stalls first in the central region, burbling spreading gradually tipwards with further increase of incidence. This phenomenon is useful in connection with lateral control, because this control is retained for a while (though reduced) past the stall. Increased use of the1 tapered wing to-day raises the question of whether this phenomenon holds good with tapered wings. There is already some doubt on this score.
Note on page 750 * See an account of certain tests by Mr. Wenzienger, Aeroplane, 6th February, 1935.