I built this entirely on my own, in an attempt to design a flying engine that did not use any sticky pistons. I tested this engine against the ones I saw on the wiki and in videos, and this outpaced them by a large margin. To start, simply use flint to update the piston at the back of the engine (It's the one that's basically buried). To stop, I recommend putting an obsidian block in front of the upper portion of the engine. Putting it somewhere else might break the engine. Most engines use 3 segments, and a sticky piston to retrieve the third segment, wasting a lot of time going back and forth. My engine only uses normal pistons, and has only two segments, which only go forward, drastically increasing efficiency.