Can you please give me some explanations about autopilot and autoflight system?
Autoflight is the general term describing all of the following:
- Flight Director: A guidance system for the pilot and autopilot with various modes. See What is a "Flight Director"? for details.
- Autopilot: A system controlling the flight control surfaces to follow the flight director.
- Autothrottle / Autothrust: A system setting engine thrust automatically depending on the selected mode. See also What is Auto-thrust?.
For example, the Boeing 737 NG FCOM describes it as follows (Vol. 2, Chapter 4 - Automatic Flight):
The automatic flight system (AFS) consists of the autopilot flight director system (AFDS) and the autothrottle (A/T). The flight management computer (FMC) provides N1 limits and target N1 for the A/T and command airspeeds for the A/T and AFDS.
The AFDS and A/T are controlled using the AFDS mode control panel (MCP) and the FMC. Normally, the AFDS and A/T are controlled automatically by the FMC to fly an optimized lateral and vertical flight path through climb, cruise and descent.
AFS mode status is displayed on the flight mode annunciation on each pilot’s primary display.