Which AFCS subsystem is primarily responsible for automatic stability augmentation, especially for roll and yaw?

• A. SAS
• B. Stabilator
• C. FPS
• D. Flight Director

Answer: (A)

Automatic stability augmentation is about automatically damping disturbances to keep the helicopter steady without the pilot’s constant input. The subsystem dedicated to this task, especially for roll and yaw motions, is the Stability Augmentation System. It senses how fast and in what direction the aircraft is rotating about the roll and yaw axes and then trims the flight controls to counter those motions, reducing oscillations and making the aircraft easier to control in gusty conditions.

Other subsystems have different primary roles. The Stabilator mainly handles pitch stability by automatically adjusting the horizontal stabilizer to keep the nose from pitching undesirably. Flight Path Stabilization works to maintain a chosen flight path, which can involve coordinated roll and pitch commands, but its focus is path maintenance rather than pure damping of roll and yaw. The Flight Director provides guidance cues to the pilot (or autopilot) but doesn’t automatically dampen the aircraft on its own.