A technique to predict the aerodynamic losses of battle damaged wings

Development of a technique to predict the effects of simulated battle damage on the aerodynamics of a three dimensional wing is described. A methodology for converting two dimensional lift, drag and pitching moment data to three dimensional values is developed. To test this methodology, wind tunnel testing was carried out on a three dimensional half model of the NASA LS(1)-0417MOD aerofoil, with simulated battle damage. The effective aspect ratio of the model was 6. A circular hole with a diameter of 20% of wing chord was used to simulate gunfiretype battle damage. To model different attack directions the axis of the hole was inclined along the chord and span. Three spanwise locations for the damage were tested. Testing was undertaken at a Reynolds Number of 1,000,000. Compared to an undamaged wing, the addition of damage caused an increase in drag, a decrease in lift and a more negative pitching moment. The effects increased with incidence and changed with hole orientation. These effects were reduced as the damage was moved towards the wing tip. Results from the predictive technique were compared with those from half model testing. The predicted lift loss was seen to be in close agreement with wind tunnel results, but the drag increase was under predicted. The biggest errors in the prediction occurred for the pitching moment, although the relatively low aspect ratio is believed to have an adverse effect on the comparison.