The influence of hole orientation on the aerodynamics of battle damaged wings

2012-07-13T11:05:56Z (GMT) by Peter M. Render T.W. Pickhaver
Wind tunnel tests were carried out on an NASA LS(1)-0417MOD aerofoil with a circular hole simulating gunfire damage. To represent different attack directions, the inclination of the hole axis relative to the aerofoil chord was varied. The hole had a diameter of 20% of the aerofoil chord and its axis was centred at half chord. The aerofoil spanned the wind tunnel to create approximate two-dimensional conditions and balance measurements were carried out at a Reynolds number of 500, 000. Surface flow visualisation and pressure measurements were also carried out. The aerofoil model incorporated a cavity to represent the internal geometry of an aircraft’s wing. Compared to an undamaged wing the addition of damage increased drag, reduced lift and gave a more negative pitching moment. The effects increased with incidence. Adding negative obliquity, where the upper surface hole was moved forward and the lower hole rearwards, increased the magnitude of these effects. Except when combined with extreme negative obliquity, adding skew, where the holes were offset in a spanwise direction, had little measurable effect in terms of aerodynamic coefficients. However, adding skew introduced asymmetry to the flow through the damage.