Harsh light results when the sun is low (i.e. early morning, late afternoon, and in winter). If possible, avoid capturing when the sun is low (i.e. fly around noon when the sun is near its zenith). Particularly undesirable are backlit situations (i.e. the camera pointing into the sun, which can also cause lens flare). If you have to capture during winter at high latitudes, preferably fly on an overcast day with diffuse light.
If you cannot avoid capturing in high-contrast conditions, expose so that the brightest parts of the tower are as bright as possible (but without overexposing them).