Differential Aileron travel

The difference between the upward and downward travel of an aileron. An aileron moves a greater number of degrees upward than downward to counteract adverse yaw. The downward-moving aileron produces both induced and parasite drag, but the upward-moving aileron produces only parasite drag. To prevent the combined drag causing the nose of the airplane to start to move toward the down aileron, the up aileron travels a greater distance, producing enough additional parasite drag to overcome the induced drag caused by the down aileron.