Line your Banshee up with a wall so that the wing you want to scrape off is opposite to the wall. Barrel roll into the wall and the wing will hit the wall. This will require a few attempts to completely scrape the wing off and will drain your shield (if available) on every hit. Another way is to simply fly at a corner pointing in the direction you are going, or a pillar. Make sure your wing is the only thing that hits the wall or pillar. Like the first method, this may take a few attempts and will drain your shield.