Flight investigation of boundary-layer transition and profile drag of an experimental low-drag wing installed on a figher-type airplane

NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of advance research results to an authorized group requiring them for the war effort.They were previously held under a security status but are now unclassified.Some of these reports were not technically edited.All have been reproduced without change in order to expedite general distribution.L -NACA ACR No. L5C08a surface.With a standa-rd-finish,-a minimum profile-drag coefficient of 0.0063 was obtained.The results obtained in turns with the smooth surface showed an increase of about 6 to ll|.percent in the profile-drag coefficient above that obtained in normal flight at lower Mach numbers and corresponding lift coefficients; whereas, with the standard finish, no increase was observed..The results on the smooth upper surface of the wing section in the slipstream indicated that, with normal engine operation, the most rearward position of transition was between 20 and 25 percent chord.The attempt to measure the profile drag of the smooth upper surface by means of a. half-wake trailing-edge rake was not successful because a large lateral component of boundary-layer flow existed at the trailing edge of this section 1 .