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Dihedral and sweep back can properly be compared only to the extent to which their action is similar in a side slip. In general the rolling moments due to side slip are about three to six times greater for a given dihedral angle than for an equal angle of sweep back.
The reduction of drag of an airfoil when the air stream is oscillating is called the Katzmayr effect. The purpose here is to offer a simple explanation of the cause of the Katzmayr effect.
The following contains information on the air forces on a wing produced by it's pitching at a finite rate of angular velocity. The condition of smooth flow at the region of the trailing edge is maintained. The wing then experiences the same lift as if moving with the momentary velocity of the rear edge.
Recent data have shown that certain forms or types of ailerons that are in extensive use are in reality quite inefficient and entirely unsuited for the high speeds now realized. The same data indicate that two forms (both shown here) are efficient and satisfactory in every way. The most important characteristics of ailerons are effectiveness under all flight conditions, small moments about the hinge, high efficiency (small yawing moment opposing turn), and simplicity in construction. Information required for the design of ailerons is given for chord, span, area, and plan form.
This report provides a list of landing locations for seaplanes on the Atlantic coast of the United States and the facilities and services located there.
A method of calculating the horizontal tail area for an airplane equipped with flaps is presented.. The general problem of tail design, the effects of flaps on the factors involved, and the manner in which the flaps change the requirements upon which the minimum horizontal tail area is based are discussed.
The proper landing of airplanes equipped with flaps, although probably no more difficult than landing without them, requires a different technique. The effects of flaps on the aerodynamics characteristics of a wing are given and, with the aid of figures and diagrams, a detailed comparison of the glide and landing of an airplane with and without flaps is made. The dangers attending improper execution and the importance of such factors as air speed fuselage attitude, glide-path angle, and control manipulation, upon all of which a pilot bases his judgement, are emphasized. Of most importance in connection with the use of flaps are: the maintenance of a sufficient margin of speed above the stall; a decisive use of the controls at the proper time; more cautious use of power during the approach glide; and, above all, the willingness to accept the steep nose-down attitude necessary in the glide resulting from the use of flaps.
Flight tests were made to demonstrate the particularity of employing fixed tabs in conjunction with a suitably designed differential linkage to reduce the force required to operate ailerons. The tests showed the system to be practicable with tabs of the inset type. The relative ineffectiveness of attached tabs for changing the aileron floating angle rendered them unsuitable. Experience gained in the investigation has indicated that the use of the system is limited to maximum deflections of one aileron relative to the other of less than 30 degrees and that the differential linkage should always be designed on the basis of the highest probable floating angle.
The analysis of box beams with shear deformation of the flanges can be reduced to the solution of a differential equation. The same equation is met in other problems of stress analysis. No analytical solutions of this equation can be given for practical cases, and numerical methods of evaluation must be used. Available methods are briefly discussed. Two numerical examples show the application of the step-by-step method of integration to shear-lag problems.
The analysis of various types of shell under combined bending and torsion is discussed. The calculation and the use of the shear center are touched upon as incidental problems. Twelve fully worked numerical examples are given in an appendix.
The shock expansion method of the NACA TN No. 1143 was used to determine the principal aerodynamic characteristics of two-dimensional supersonic airfoils. A discussion is given of the effect of thickness ratio, free-stream Mach number, angle of attack, camber, thickness distribution, and aileron deflection. The calculations indicated that the minimum drag of supersonic airfoils is obtained when the maximum thickness is behind the 0.50 chord. The center of pressure obtained for a symmetrical supersonic airfoil was found to be ahead of the 0.50 chord.
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