NACA-ARR-L5F30 REV A

Abstract

INTRODUCTION <br>One of the devices employed for balancing control surfaces, especially ailerons, of modern high-speed airplanes is the sealed internal balance (fig. 1), Much Of the experimental work that has been done in the development of the sealed internal balance has been summarized in reference 1, which includes a brief consideration of seal effects, In reference 1 (and in all previous internal-balance work), the balancing effect of a seal in an internal-balance arrangement was accounted for by an approximate method That is, by assuming the balance chord to be the distance from the control-surface' hinge axis to the center of the sealed nose gap, regardless of seal width. <br>An analytical investigation to determine the contribution of the seal to the balancing moment of a sealed internal-balance arrangement indicated that the approximate method was generally in error over most of the flap-deflection range (reference 2). This analysis also indicated that variation of either the seal width, the sealed-gap width, or the shape of the wing structure forward of the overhang has an important effect on the balancing moment contributed by the seal. <br>The present investigation is an extension of the investigation reported in reference 2 and was begun in order to check experimentally the fabric-seal analysis reported therein. The present investigation covered a larger deflection range than was covered in reference 2; in addition, the effect on the seal moments of a con-fining balance-chamber roof (the contour of the airfoil) and an off-center attachment of the seal to the wing structure were determined. <br>The moment contributed by the seal in each of the configurations tested is presented as a fraction of the moment of the thin-plate overhang over the complete deflection range. A comparison is made of the seal moments obtained experimentally and analytically (reference 2) with seals and sealed nose gaps of similar size in the, presence of each of the three different types of internal wing structure with no vertical restrictions. In addition, a comparison is made between the experimentally determined and the computed hinge-moment coefficients of an internally balanced aileron, and an example is presented to show the relative accuracy of hinge-moment data computed by the approximate method and those computed from the results of the present investigation.