HIGH-LIFT devices for improving safety in flight recently have assumed increasing importance because of the higher and higher performances demanded of both commercial and military airplanes, increases in size and weight, and rises in wing loadings, Mr. Wenzinger points out. In addition, he draws attention to the necessity for keeping landing speeds down to a reasonsonable figure, and for devising arrangements for assisting the take-off of large and heavily loaded airplanes because of the limitations of length of present-day runways.
Summarizing the extensive investigations of lift-increasing devices carried out by the National Advisory Committee for Aeronautics during the past 10 years, the author stresses their effect on lift. Two general classes are considered: those located at the leading edge of the wing, and those located near the trailing edge. Several combinations of both are included.
The author concludes that the slotted types of flap appear to be the most promising on the basis of the aerodynamic characteristics listed, in particular the NACA arrangement of the double-slotted flap.