AFDS controls Aircraft by via monitoring of speed, height and heading, and together with ILS and MLS provides take off and landing of Aircraft in autoflight mode. AFDS consists of computing unit, control panel and steering facilities (Pic. 141). Commonly, AFDS is using 2-3 computing blocks, which are perfoming calculation simultaneously. So that the required levels of system stability and reservation are reached. Pilot chooses the required modes of operation via control panel and inputs all required parameters. Also, special buttons are located on a steering wheel to perform emergency autopilot disengage, and autothrottle disengage button is located on a thrust controls.
Fig. 141. AFDS
AFDS provides control over flight parameters via three control channels: thrust control channel, vertical and lateral cotrol channels. The thrust control channel sends control commnads to the engine control system. The vertical control channel provides control of elevators, and the lateral control channel provides ailerons and rudder control via flight control system.
AFDS acts on the egine control system or on the FBW by setting of certain flight parameter. Thus, aerodynamic state of Aircraft is changing, which is controlling by acceleration, velocity and position sensors. So AFDS sets the value of a particular parameter to the required level [5].
Incoming information about flight parameters AFDS takes from:
- overall Aircraft's equipment control system;
- radioaltimiter;
- landing system;
- INS;
- altitude, speed parameters system;
- FMS
In the automatic mode AFDS provides:
- stabilization of an Aircraft according to the center of gravity;
- stabilization of barometric altitude;
- stabilization of heading;
- control of Aircraft's flight via FMS commands;
- control of Aircraft during final approach until decision height;
- stabilization of velocity and Mach number;
- prevention the breakdown of speed, overload, roll and pitch angles parameters beyond maximum setallowable limits;
- vertical and lateral guidance, etc.