NACA-RM-L54C05

Abstract

INTRODUCTION <br>The reduced lift capabilities of conventional high-lift devices when applied to sweptback-wing aircraft constitute a severe low-speed performance problem. Means for improving the maximum lift capabilities of the sweptback wing are being investigated extensively by the National Advisory Committee for Aeronautics. <br>One method now receiving attention is that of blowing a high-velocity (that is, a velocity that is high relative to the magnitude of the free-stream velocity) jet of air over the trailing-edge flap with the primary aim of adding sufficient energy locally as to either eliminate or at least reduce the tendency for flow separation over the flap . This method of boundary-layer control appears to be especially attractive for application to jet-powered aircraft inasmuch as a high-pressure source of air would be readily available. <br>Early German two-dimensional tests, such as those reported in reference 1, indicated that large increases in lift coefficient could be obtained by blowing a high-energy stream of air over a trailing-edge flap. A French investigation (ref. 2) extended the blowing technique to application on a moderately sweptback wing (31.3^&#176;) in conjunction with suction at about the midchord of the wing. In these French tests, approximately the rear 45 percent of&#160;the wing chord was divided into two chordwise segments which could be deflected. As in the case of the earlier two-dimensional tests , the results appeared to be very promising; however, analysis of the effects due to blowing is necessarily limited since only a few tests were conducted with blowing alone over the trailing-edge flap (zero suction at the midchord of the wing). <br>In view of the possibility, then, of increasing wing lift by means of blowing over the trailing-edge flap, the method has been extended to the case of a highly swept, thin wing. Tests have been conducted In the Langley full-scale tunnel on a semispan 49.lo sweptback wing having NACA 65A006 airfoil sections, an aspect ratio of 3.78, and a taper ratio of 0.59. Preliminary tests were conducted with a low-capacity blower and are presented in reference 3. Because of the very low pressure rise and quantity of flow of the blower, no significant results were obtained. The investigation reported herein is a continuation of the full-scale-tunnel blowing tests but with a multistage, large-flow-capacity blower. The tests were made with and without a slat- and fences installed and with and without blow- over a trailing-edge flap or trailing-edge flap and aileron. Tests were ale0 made to determine the rolling effectiveness produced by blow-air over the aileron. In addition, some chordwise pressure distributions were obtained at the midspan of the trailing-edge flap in order to study the load change that occurred as a result of the blowing method of boundary-layer control. <br>The tests were made at Reynolds numbers of 2.9 x 10⁶, 4.4 x 10 ⁶ , and 6.1 x 10⁶ corresponding to Mach numbers of 0 .O5, 0.O7, and 0 .10, respectively.