Chapter 9. The system of automatic piloting

9.2. Fly-by-Wire system

The FBW system provides control of the position of the aircraft in the air.

The main functions of the FBW:

  • control of pitch, roll , yaw;
  • control of the lift force;
  • deviation interceptors according to the position of the ailerons;
  • evaluation of maximum permissible deviations and prevent their occurrence
  • the reduction of torque moment in case of failure of one engine;
  • reduce the effects of turbulence;
  • automatic change of the effectiveness of the ailerons depending on airspeed and other

The main elements of control of aircraft position in the air is shown in Fig. 136.

Fig. 136. Controls the position of the Aircraft

Flight control is accomplished by adjusting the angles of roll, pitch, and yaw.

Control of the pitch angle is adjustable rudder placed on the stabilizer, steering height - deviation of the wheel pilot from you (Fig. 137), and control of the angle of roll using ailerons and interceptors.

Fig. 137. The control of pitch angle

The ailerons are located on the ends of the wings symmetrically. If the rudder is deflected to the side, left and right ailerons are simultaneously deflected in different directions, making the plane begins to lean on the roll (Fig. 138). To enhance the effect of the ailerons apply the brakes, located on both sides of the wings. In case of a deviation of the steering wheel at certain angles together with deflection of the ailerons are activated corresponding interceptors.

Fig. 138. Control of roll angle

Control the angle of the course is performed through the action on the rudder. The rudder is deflected in proportion to the motion pilot’s pedal(Fig. 139).

Control lifting force is accomplished through the control position of the flaps, slats and air brakers. In addition, FBW changes position of deflecting elements to compensate the structural features of the aircraft. At this moment control elements of the pilot remains in the previous state.

The FBW system generates an alarm and does not allow to exceed deviations of such parameters : heading, pitch, and bank angles over the maximum permissible values For sensitive perception of deviation on controls, action force is created proportionally to the deviation. Controls of two pilots depend on each other. Deviation of one of them leads to a corresponding deviation of the second one in the same direction.

Fig. 139. Control the yaw angle

Deviations of the controls is transmitted to the moving parts with a manual transmission or an electrical signal. The transmission channel control deviations reserved.

The principle of operation of the flight management system shown in Fig. 140. In center of the system a computer is located. The action of the pilot on the controls is transmitted to the evaluator, which evaluates which elements will be decline and how. The deviation signals are transmitted to the system control deviant mechanism. Mechanical parts are declined by hydraulic or electric rotary mechanisms.

Fig. 140. The flight management system

The position of decline parts is controlled by special sensors that alert the control system of decline mechanism, the computer and provide information about the measured parameters to electronic display system

AVIONICS training course materials represented only in demonstrative mode. If it useful, all grammar mistakes will be corrected and more documents will be added. Let me know if you interest in avionics.
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Avionics training in details by
Ostroumov IvanOSTROUMOV Ivan, PhD
Associate Professor, www.sciary.com/ostroumov