Artificial Horizon, Directional Gyro, and Autopilots
The history of intentional blind flying began with Jimmy Doolittle’s flight in a Consolidated NY-2 in September 1929. The airplane was equipped with two gyroscopic instruments, a gyro horizon and a directional gyro. Both have free gyroscopic wheels, which tend to preserve their position in inertial space. The wheels are mounted in double gimbals so that the airplane is free to rotate about them. The relative rotation is displayed on the instrument faces. Legal IFR flight in an airplane with a standard-category U. S. airworthiness certificate requires airplanes to be equipped with these instruments.
Recent developments in inertial navigation with strapped-down laser gyros and attitude determination by the Global Positioning System (GPS) provide synthetic versions of the artificial horizon and directional gyro. Autopilots use these instruments or their synthetic versions in automatic blind flying.