Typical Electronic / Digital Aircraft Systems
General arrangement and BITE of typical systems, ACARS, EFIS, ECAM/EICAS, FBW, FMS, GPS, IRS, TCAS, EGPWS, central maintenance systems, cabin systems and integrated modular avionics.
Typical digital aircraft systems, summary notes
- EFIS presents flight and navigation data on the PFD and ND. ECAM (Electronic Centralised Aircraft Monitor) is the AIRBUS engine, warning and system display; EICAS (Engine Indicating and Crew Alerting System) is the BOEING equivalent.
- FMS (Flight Management System) combines navigation, performance and guidance: the CDU/MCDU is the crew interface, and the flight management computer feeds the autopilot and flight director along the programmed route.
- IRS/ADIRS: inertial reference uses laser gyros and accelerometers to give attitude, heading and position without external reference; combined with air data it forms the ADIRU that feeds almost every other system.
- GPS/GNSS provides position by ranging on satellites and is normally blended with inertial data; RAIM or SBAS augmentation provides the integrity monitoring required for approach.
- FBW (fly-by-wire) replaces mechanical control runs with electrical signalling to computers that command the actuators, with envelope protection and multiple redundant channels.
- TCAS gives traffic and resolution advisories from transponder interrogation; EGPWS/TAWS warns of terrain using a terrain database and GPS position; the weather radar overlays returns on the ND.
- ACARS is the digital datalink for routine air-ground messages; CMC/CMS is the central maintenance computer that collects and correlates BITE fault data from every system.
- IMA (Integrated Modular Avionics) replaces many federated LRUs with shared processing cabinets running partitioned applications over an AFDX network, fewer boxes, more software configuration control.
- ⚠ Exam trap: ECAM is Airbus, EICAS is Boeing. Both do the same job; the manufacturer is what the question is testing.
- Manufacturer convention
- ECAM = Airbus · EICAS = Boeing
- Data sources
- ADIRU → air data + inertial → EFIS, FMS, autopilot
A crew reports the ND loses map data while the PFD attitude remains correct. Which source is suspect?
The navigation source rather than the attitude source, most likely the FMS/flight management computer or its bus to the symbol generator. The inertial attitude reference is still feeding the PFD normally, which is why attitude is unaffected.
What is the maintenance advantage of a central maintenance computer over reading each LRU's own BITE?
It correlates faults reported by many systems into a single prioritised message, distinguishing the root-cause failure from the cascade of downstream systems that merely lost their input, which shortens troubleshooting and reduces no-fault-found removals.
Aircraft digital systems concept map
Typical Electronic / Digital Aircraft Systems
Typical digital aircraft systems quiz
Typical Electronic / Digital Aircraft Systems, quiz
1. On an Airbus, the system presenting engine and warning data is:
ECAMEICASEFIS2. EICAS is the equivalent system fitted by:
BoeingAirbusEmbraer only3. The crew interface to the flight management system is the:
CDU / MCDUDisplay switching panelMode control panel4. An inertial reference system determines attitude and position using:
Gyros and accelerometers, with no external referenceSatellite rangingRadio navigation beacons5. TCAS obtains information about conflicting traffic by:
Interrogating other aircraft's transpondersReading the weather radar returnReceiving ATC datalink messages6. ACARS is used for:
Digital air-ground message datalinkTerrain warningAutopilot engagement7. The purpose of a central maintenance computer is to:
Correlate BITE fault data from many systems into prioritised messagesStore the flight data recorder parametersLoad navigation databases8. Integrated Modular Avionics (IMA) replaces many separate LRUs with:
Shared processing cabinets running partitioned applicationsA single analogue computerDuplicated federated computers9. In a fly-by-wire system, the pilot's control input is:
Signalled electrically to computers that command the actuatorsTransmitted by cables and pulleysApplied hydraulically without computation10. The ND loses map data while the PFD attitude remains correct. The suspect source is the:
Flight management computer or its busInertial reference unitStandby attitude indicator