The A320 ATA 34 Technical Notes provide brief and to-the-point information about the Airbus A320 Navigation Systems, including its components and their functions.

A320 NAVIGATION SYSTEMS

The Airbus A320 aircraft navigation systems provide the crew with the data required for flight within the most appropriate safety requirements. These data can be divided into four groups :

  1. Air Data/Inertial Reference System (ADIRS)
  2. Landing and taxing aids
  3. Independent position determining
  4. Dependent position determining

ADIRS

  • 3 Air Data/Inertial Reference Units (ADIRU) > ADIRU 1, ADIRU 2, ADIRU 3.
    • Air data function through its Air Data Reference (ADR) portion.
    • Attitude, heading and position function through its Inertial Reference (IR) portion.
  • Standby systems
    • ISIS
      • ISIS indicator replaces 3 conventional standby instruments –
      • Standby altimeter
      • Standby airspeed indicator
      • Standby horizon indicator
    • Standby Compass – for standby heading ……… (independent instrument)

Landing and Taxiing Aids

  • Paravisual Indicator (PVI) (optional system)
  • Head Up Display (HUD) (optional system)
  • Instrument Landing System (ILS) (optional system)  >>> MMR
    • The primary function of the Multi-Mode Receiver (MMR) is to receive and process Instrument Landing System (ILS) and Global Positioning System (GPS) signals.
    • The MMR also receives the approach data from the Global Navigation Satellite System (GNSS) Landing System (GLS) function.
    • The MMR is a navigation sensor with two internal receivers – ILS receiver & GPS receiver. >> (ILS receiver – Localizer and Glide/slope).
    • 2 MMRs – MMR1 and MMR2, linked to:
      • Localizer and Glide/slope antenna
      • GPS antenna

Independent Position Determining

  • Weather Radar (WXR) system
  • Radio Altimeter (RA)
  • TAWS – Generic Term
    • Ground Proximity Warning System (GPWS)
    • EGPWS
  • ACAS – Generic Term
    • Traffic Alert and Collision Avoidance System (TCAS)
    • Traffic and Terrain Collision Avoidance System (T2CAS)
    • Traffic and Terrain Collision Avoidance System (T3CAS)

Dependent Position Determining

  • Distance Measuring Equipment (DME)
  • Air Traffic Control (ATC)
  • Automatic Direction Finder (ADF)
  • VHF Omni-Range (VOR)
  • Global Positioning System (GPS) (optional system)

Additional Notes

  • Why pitot/static port both side (cross connection) – to minimize error.
    • Static – position error
  • Total 8 ADM – all are interchangeable
  • Pitot – 3
  • Static – 6
  • Pitot probe – total pressure
  • ISIS – direct connection to port not through ADM
    • Source – pitot – stby pitot probe / static – stby static probe
  • Laser gyro – total 3 – inside ADIRU (IR part).
    • 2 beam in each gyro – beam travel time
    • Error signal in terms of frequency
    • Frequency is inversely proportional to time.
  • IR inside
    • 1 ring laser gyro for each axis
    • 1 accelerometer for each axis
  • There is a separate 3 axis accelerometer for FDR. (do not confuse with accelerometer inside IR)
  • Water drain in stby static port – because direct source for ISIS.
  • Mode selector unit (MSU) of ADIRS (- ADIRS MODE)
    • NAV
    • ATT – only heading
  • ISIS
    • ATT/SPEED/ALT – Same place as in PFD.
  • BUGS + LS – press for at least 2 sec. >> maintenance mode.
  • LS – press to avail localizer and glidescope.
  • BUGS – for BUGS setting. Press bugs only.
  • Red flag – if system is inop. (eg. ATT , HDG in red)
  • Mean sea level – for altitude calculation
  • QNH – sea level atmospheric pressure
  • In NEO only – ISIS test can be done through MCDU.
  • GPS – 360 degree – divided into 6 >> each 60 degree
  • When GPS is active – no VOR/DME/ADF is required.
  • VOR/DME – single unit
  • All DME are installed with VOR at ground >> VOR + DME – all VOR station
  • If tune VOR – automatically tune DME, frequency are paired and installed at ground together.
  • VOR/DME on ND
    • VOR 2 – VOR sys 2
    • VIDP – Airport
    • 34 NM – given by DME
  • Minimum 4 satellite – GPS position (normally 6 are available)
  • MMR – 90 VU
  • ILS 1 – PFD 1 & ND 2
  • ILS 2 – PFD 2 & ND 1
  • GPS is primary navigation now.
  • GPS Monitor Page on MCDU
    • MERIT – 100 >> GPS accuracy is up to 100 meter
    • mode/set
    • NAV/6 – 6 satellite
    • TRK – heading
  • TAT 1 – only ADIRU 3. — stby
  • ADIRU 1 — TAT 1.
  • Normal
    • MMR 1 – ADIRU 1, 3 – GPS 1
    • MMR 2 – ADIRU 2 – GPS 2
  • If ADIRU 2 fails –
    • ADIRU 2 >> ADIRU 3
    • Switch for GPS 2 input
      • ATT heading selector knob switching (?)
  • FMGC
    • IR 1 & IR 2 – pure data – FMGC 1 & 2
    • Pure GPS data – FMGC 1 & 2
  • MMR > GPS data > ADIRU > FMGC
  • Weather radar transmitter with predictive windshear system function in option.
  • In old a/c – Map mode – map selection >>>> in WXR system
    • Ground picture (antenna will tilt down)
    • Now – EGPWS is doing the same function.
  • PWS – 5 NM (class range) – takeoff/landing
  • Precipitation rate –
    • > 50 mm/hr – turbulence
    • 12 – 50 mm/hr
  • Windshear indication on ND – Red & Black + warning on PFD
  • CAL knob – minimum position, use for testing.
  • WXR antenna
    • Holes for passing magnetic field
    • Waveguide – hollow tube – less distance required for waveguide, that’s why separate self in 90 VU.
    • Optical cable required less distance.
  • Multiscan – top/down & left/right
  • WXR related indication  – ND only
  • PWS related indication – ND + meaning (details) > on PFD
  • Aft side of WXR antenna – BOARD – for protection from return waves.
  • WXR stabilization signal from – ADIRU 1
  • PWS
    • below 2300 feet RA.
    • Aural warning through – FWC (windshear ahead)
  • If warning for the same time – PWS / TCAS & EGPWS >> PWS warning is inhibited.
  • RA auto ON – no switch
  • RTTR
  • RA indication on PFD.
  • Cooling fan – 2 for 2 RA transmitter
  • TA / RA advisory
    • 4 volume
    • Indication on ND
  • GPWS – database updated at every defined time.
  • GPWS system has no antenna. It takes data from sources and computes.
  • ELS >> ADS-B (is enhanced version) >>> ADS-B – IN/OUT
  • Many Airlines have ADS-B — OUT only.
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