XX TWo important effects due to the downwash 1 the angle of attack actually seen(or feel) by the local section is the angle between the chord line and the local relative wind. This angle is defined by a a cc =a-al 2 The local lift vector is in the direction perpendicular to the local relative wind. As a subsequence there is a drag created by the presence of downwash※ Two important effects due to the downwash. 1 the angle of attack actually seen(or feel) by the local section is the angle between the chord line and the local relative wind. This angle is defined by aeff  eff = −i 2 The local lift vector is in the direction perpendicular to the local relative wind. As a subsequence, there is a drag created by the presence of downwash