INTRODUCTION

This Item illustrates the practical use of those excrescence drag Data Items, see Table 2.1, that are particularly pertinent to the types of excrescence commonly found on wings.

In order to illustrate the application (Section 3) of the excrescence drag Items applicable to wings the case of a subsonic transport aircraft in the cruise condition has been chosen, and the excrescence drag arising from a number of wing components (controls, removable panels etc.) is calculated (Section 4).

Each component is the subject of a separate example and the various contributions to the excrescence drag of the component are calculated and itemised for two calculation cases. Calculation Case (i) deals with an ideal situation in which there are no avoidable surface mismatches or sealing problems, and Calculation Case (ii) deals with the effects of possible surface mismatches or poor sealing. The itemised drag contributions for each component are used to highlight those areas of detail design and installation that are likely to contribute most to avoidable drag. Conclusions from the calculations are summarised in Section 5.