I know - groan. But I have a dead serious, non-loaded question for those of you with slicker marbles than me. Not trying to continue that density altitude slip thread. Too many tangents, and nothing accomplished. This question is honestly something I've never thought about in my years of blissful ignorance of such convoluted sideslip complexity. I cannot for the life of me think of a reason to ever perform this "drill", but I'm interested in the academics. Here it is - I'm trying to figure out how to recreate this "runway sideslip drill" exactly as shown in the picture below. I shot a new video below starting out in coordinated flight, tracking the right edge of the runway, and then entering a slip. I used enough rudder for the bank angle to prevent the airplane from turning or modifying its flight path. I could have continued this slip in that constant fight path state until I ran out of fuel. Now I know that this is not the runway slip exercise. Suppose from this starting position that I was trying to "side slip" the airplane and move it toward the left side of the runway, starting as I show in the video. Oops - too much rudder, or too little aileron. Nothing is happening. No flight path change. So how do we change our flight path from here? There are only two ways I can think of - either reduce the rudder deflection, or increase the aileron deflection. So in the video, I slightly reduce the right rudder deflection, but only enough to cause the airplane to do something different. Then I hold that input. I am still slipping. But unless I need to be locked in a padded cell, it sure appears to me that the airplane is turning (slipping turn) at a constant rate (curved flight path) and not simply adopting a new and constant flight path as shown in the picture. You can see my hand, and I did not make any further inputs with the stick from the initial slip. So looking back at the picture below, it shows the airplane starting in coordinated flight, fuselage aligned with the flight path, and then "side slipping" to the left along a straight, but diagonal flight path, moving the airplane laterally to the left. Then it shows a point at which "controls are neutralized", and boom - the airplane returns to the original flight path, in coordinated flight, just displaced a bit to the left. Never in my short 13 years of flying have I neutralized slip inputs to find the airplane's flight path instantaneously redirected as a result of removing the slip. In this video, I made the airplane move to the left across the runway in a turn, but when I neutralized the controls and exited the slip, the airplane was of course flying a new flight path, not aligned with the runway - and continued that way. Duh...because the airplane was turning. A turn was required in the opposite direction to return the airplane's flight path parallel to the runway. This "runway sideslip drill" is shown nowhere in the sacred FAA Handbook, but some seem to take it as gospel. It is also claimed that no turning is required in order to perform this drill and its two flight path changes - one to move the airplane in a new direction to the left, and another to return the flight path to the original direction. Can anyone explain this mysterious sideslip drill? I'm wondering if there's a good reason no videos can be found showing an aircraft replicating the movements depicted in this diagram. To me, it seems at odds with the laws of physics. But I'm open to education.