Plain English Meaning
A specific brand of flight guidance system, made by Sperry, that tracks how the airplane is tilted and turned in every direction and tells the pilot which way to steer to follow a planned path.
Full Definition
A flight director system manufactured by Sperry that senses and displays the aircraft's attitude in all three axes — pitch (nose up/down), roll (wing up/down), and yaw (nose left/right) — and provides steering commands to the pilot through an attitude director indicator. It serves as the attitude reference and command-generating component of an integrated installation.