Auto Flight System Presentation Of Airbus(A321,A320.A319,A318)

 AUTO FLIGHT SYSTEM PRESENTATION OF AIRBUS


GENERAL
The Auto Flight System (AFS) is divided into four main parts:
- Flight Management (FM),
- Flight Guidance (FG),
- Flight Augmentation,
- Fault Isolation and Detection System (FIDS).
The first two functions are accomplished by the Flight Management and
Guidance Computers (FMGCs). The other two functions are accomplished
by the Flight Augmentation Computers (FACs).
The AFS calculates the position of the aircraft using several aircraft
sensors.
In addition, the system has the capability of storing flight plans in its
memory, which are predetermined by the airline. A flight plan describes
a complete flight from departure to arrival, it includes vertical information
and all intermediate waypoints. Knowing the position of the aircraft and
the desired flight plan (chosen by the pilot), the AFS is able to compute
the orders sent to the flight controls and engines so that the aircraft can
follow the flight plan.

                               GENERAL

                                    GENERAL


FLIGHT MANAGEMENT/FLIGHT GUIDANCE
The FM part has several functions linked to the flight plan such as lateral
and vertical guidance associated with performance computation.
The FG part has 3 functions:
- Autopilot (AP),
- Flight Director (FD),
- Autothrust (A/THR).
The FMGC functions, FM and FG are controlled from the MCDUs and
the Flight Control Unit (FCU).
Basically, the MCDUs provide the long term interface between the crew
and the FMGCs (e.g. flight plan selection and modification) while the
FCU provides the short term interface (e.g. engagement of the autopilot,
flight director and A/THR functions).
Besides the MCDUs and the FCU, the main displays presenting Flight
Management and Guidance information are the EFIS displays.

            FLIGHT MANAGEMENT/FLIGHT GUIDANCE


FLIGHT MANAGEMENT/FLIGHT GUIDANCE (continued)
AUTOPILOT/FLIGHT DIRECTOR
The main AP and FD functions are:
- stabilization of the aircraft around its center of gravity when the
AP/FD system holds vertical speed or flight path angle and heading
or track,
- acquisition and holding of a flight path,
- guidance of the aircraft after take off,
- automatic landing and go around.
The AP function gives orders to control:
- the position of the control surfaces on the three axes (pitch, roll and
yaw),
- the nose wheel steering.
The FD function generates optimum guidance orders used in manual
controls. The FD is also used to monitor the AP when it is engaged.
The FD symbols are displayed on the PFDs.


FLIGHT MANAGEMENT/FLIGHT GUIDANCE - AUTOPILOT/FLIGHT DIRECTOR


FLIGHT MANAGEMENT/FLIGHT GUIDANCE (continued)
AUTOTHRUST
The A/THR system fulfills the following functions through the control
of the thrust:
- speed or mach hold (either FMGCs computed or from throttle levers
position),
- thrust hold (either FMGS computed or from throttle lever position),
- thrust reduction during descent and during flare in final approach,
- protection against insufficient speed linked to excessive angle of
attack.
To fulfill the A/THR functions, the FMGCs communicate with the
Full Authority Digital Engine Control (FADEC) via the FCU and the
Engine Interface Units (EIUs).

     FLIGHT MANAGEMENT/FLIGHT GUIDANCE - AUTOTHRUST


FLIGHT AUGMENTATION
The flight augmentation part fulfills the following functions:
- rudder trim,
- yaw damper,
- rudder travel limitation,
- flight envelope protection,
- FIDS.
For flight envelope protection, the FAC computes:
- the various speeds for aircraft operation (e.g. flaps limit speed),
- the excessive angle of attack and windshear detection,
- the low energy warning, indicating to the crew that the aircraft is quickly
decelerating and that thrust will have to be increased to recover a positive
flight path angle through pitch control.
The FIDS function is only active in FAC 1. FAC 1 is connected to the
BITE of all the AFS computers and communicates to the Centralized
Fault Display System (CFDS).

 
                   FLIGHT AUGMENTATION


PANEL LOCATION/CONTROL AND INDICATING
The different panels used for AFS control and indicating are described
in this topic.
MCDUs
Two MCDUs are located on the center pedestal.
The MCDU is the primary entry/display interface between the pilot
and the FM part of the FMGC.
The MCDUs exchange information not directly but via the FMGCs.

           PANEL LOCATION/CONTROL AND INDICATING - MCDUS


PANEL LOCATION/CONTROL AND INDICATING
(continued)
FLIGHT CONTROL UNIT
A FCU is installed on the glareshield.
The FCU front face includes an AFS control panel between two EFIS
control panels.
The AFS control panel allows and displays the AP and A/THR
engagement, and the selection of guidance modes and flight
parameters.
Each pilot has an EFIS control panel to select the display on his related
EFIS screens.
Speed, lateral guidance and level change can be selected by the pilot
after a "pull" action or managed by the flight management after a
"push" action. In that case, the parameter window shows dashes (- -
- -) and a white dot will indicate that the reference is managed.
An exception to this rule is when the V/S - FPA knob is pushed, a
level off is immediately commanded.

   PANEL LOCATION/CONTROL AND INDICATING - FLIGHT CONTROL UNIT


PANEL LOCATION/CONTROL AND INDICATING
(continued)
EFIS DISPLAYS
Four EFIS displays, i.e. two PFDs and two NDs, are located on the
main instrument panel.
Flight parameters are displayed on the PFDs while the flight plan and
navigation data are displayed on the NDs.

PANEL LOCATION/CONTROL AND INDICATING - EFIS DISPLAYS


PANEL LOCATION/CONTROL AND INDICATING
(continued)
PRIMARY FLIGHT DISPLAY
As the main guidance instrument, the PFD displays various speeds
and reference parameters used for short term flight guidance.
The Flight Mode Annunciator (FMA) is the top part of the PFD and
indicates:
- the AP, FD and A/THR engagement status,
- the AP/FD and A/THR modes,
- the landing category.

 PANEL LOCATION/CONTROL AND INDICATING - PRIMARY FLIGHT DISPLAY


PANEL LOCATION/CONTROL AND INDICATING
(continued)
SIDE STICKS
Two side sticks are respectively located on the CAPT lateral panel
and F/O lateral panel.
When the AP is engaged, the side sticks are locked in the neutral
position, by solenoids.
The AP is disengaged, and the side sticks become free, when the red
TAKEOVER & PRIORITY pushbutton on any side stick is pressed
or when a force above a certain threshold is applied on any side stick.

    PANEL LOCATION/CONTROL AND INDICATING - SIDE STICKS


PANEL LOCATION/CONTROL AND INDICATING
(continued)
THROTTLE LEVERS
The engines are manually controlled by throttle levers, which are
located on the center pedestal, or automatically controlled by the
A/THR system. Two red INSTINCTIVE DISCONNECT pushbuttons,
located on the throttle levers, allow the A/THR function to be
disengaged (push either one). Note that the throttle levers never move
automatically.

     PANEL LOCATION/CONTROL AND INDICATING - THROTTLE LEVERS


PANEL LOCATION/CONTROL AND INDICATING
(continued)
FLIGHT CONTROL PANELS
On the two flight control (FLT CTL) panels, located on the overhead
panel, there is a pushbutton to respectively disengage FAC 1 and 2.

   PANEL LOCATION/CONTROL AND INDICATING - FLIGHT CONTROL PANELS


COMPONENT LOCATION
The AFS computers are located in the aft avionics rack (80VU).

                COMPONENT LOCATION


MAINTENANCE/TEST FACILITIES
Using the MCDU, you can have access to the CFDS fault messages of
the AFS.
The BITE of each AFS computer including FCU and MCDUs, can be
interrogated via the FAC 1. AFS TEST and LAND TEST can be launched
from the MCDUs.

               MAINTENANCE/TEST FACILITIES


SAFETY PRECAUTIONS
Make sure that all circuits in maintenance are isolated before you apply
electrical power to the aircraft.
Before you pressurize/depressurize a hydraulic system:
- make sure that the travel ranges of the flight control surfaces are clear,
- check that the Flap/Slat lever agrees with the actual flap and slat surface
position,
- make sure that the Speed brake Selector is retracted and disarmed.
Put safety devices and warning notices before you start a task on or near:
- the flight controls,
- the flight control surfaces,
- the landing gear and the related doors,
- components that move.
Put warning notices in the cockpit to identify systems undergoing
maintenance work.


SAFETY PRECAUTIONS

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