From the start, aircraft designers faced the challenge of overcoming heavy control loads. Large control surfaces require lots of force, and unless the pilots spend their off hours at the gym, they can be a limiting factor. One of the earliest solutions was the aileron horn, a tab that juts off the end of the wing. It was popularized by the Fokker Dr. I in WWI, and is still in use today on the venerable ATR-72 turboprop.