BG - you can call me YWIW and I fear that I will be flattening out the bumps and creases of runway 22 at Cranfield for the next couple of months at least... The ball is one of these instruments thingies that can be used to moderate the instructors breathing - too far to the left and he breathes in quickly, too far to the right and he reaches for a chute. Funny as we are only taxing....