Nevertheless, this design hides a detail that is technically extraordinary. In front of the pilot’s face Leonardo drew a small, upside-down ampulla from which a small object is suspended. This is a bona fide attitude indicator (and probably the first in history)! The knocker would indicate to the pilot the machine’s inclination and the attitude of flight. When the machine was in rectilinear, horizontal flight, the pendant would not touch the edges of the bell.