How many levels of AFCS control are in sequence?

• A. 3
• B. 4
• C. 5
• D. 6

Answer: (C)

The idea is that AFCS runs in a progression from keeping the airplane stable to fully automatic flight. The first layer provides stabilization augmentation, damping out disturbances so the aircraft doesn’t become unstable. The next layer adds a basic attitude control loop that helps hold or return to a commanded attitude. The third level is the flight director, which gives guidance cues to steer toward a desired flight path. The fourth level is the autopilot, which can automatically fly the aircraft following those cues or direct attitude/heading/altitude commands. The final level handles power and flight path management, typically auto-throttle (and its integration with navigation/approach). Put together, there are five levels in sequence.