Auto Flight System of A320 can be broadly divided into four sections:
- Input section
- Information section
- Computation and Processing
- Output section
INPUT SECTION
MCDU 1 – Multifunctional control and display unit, MCDU 2, FCU – flight control unit
INFORMATION SECTION
Navigation Information (Data), Performance Information (Data), ADIRS – air data and inertial reference system & GPS – global positioning system, Clock and Radio Navigation Aids.
COMPUTATION AND PROCESSING – FMGS/FMGC
Computation and Processing of data in A320 is done by two Flight Management and Guidance Systems (FMGS) which are identical. They receive input from various sensors (details given later), from Pilots and process same to deliver output.
FMGS performs the function of – FLIGHT MANAGEMENT, FLIGHT GUIDANCE AND FLIGHT AUGMENTATION
Flight Management part of FMGS controls:
- Navigation
- Flight Planning
- Performance Optimization
- Predictions
- Display Management
Flight Guidance part of FMGS controls:
- AP Commands – to automatically control pitch, roll and yaw
- FD Commands – for pilot to control pitch, roll and yaw
- Auto-thrust Commands – to automatically control thrust
Flight Augmentation part of FMDS controls:
- Flight Envelope Computation – example maximum speed in particular configuration
- Maneuvering Speed Computation – best speed to fly in given configuration
- Windshear detection
- Angle of attack protection
Working of FMGS (FMGC)
INPUT –
Both FMGCs take information from on-side sensors except in certain cases like validity comparison. Also information from MCDU1 and MCDU 2 goes to FMGC 1 and 2 respectively and they all information is crosschecked and synchronized.
Input from FCU is sent to both the FMGCs.
OUTPUT –
Both FMGCs commands respective FDs and APs and according to internal logic one FMGC is declared master which decides whether channel 1 or 2 is to be used for auto-thrust.
OUTPUT SECTION
EFIS – Electronic Flight Information System, FD/AP – Flight Directors, Auto-Pilot and A/THR – auto thrust.
