Electronic Displays and Alerting Systems
Domain 8 covers the glass cockpit: display units and their symbol generators, the alerting hierarchy, and the warning systems - TCAS, EGPWS and stall/overspeed. Questions test reversion and failure logic, colour philosophy, and the priority of aural and visual alerts.
Displays
- PFD - attitude, speed and altitude tapes, FMA, flight path vector, ILS deviation.
- ND - heading or track rose, navigation data, weather, TCAS symbols.
- EICAS/ECAM - engine and system pages plus alert messages.
Symbols are generated by display management computers (DMC) or by symbol generators inside the display unit. A display unit failure triggers automatic reversion to a different display on a remaining unit, and the crew can also swap PFD and ND manually. Each display unit usually has its own power supply and cooling.
Alert hierarchy
- Level 3 / warning - red, master warning, aural (fire, stall, overspeed, configuration).
- Level 2 / caution - amber, master caution, single chime.
- Level 1 / advisory - cyan or white message, no aural.
Colour convention: red = act now, amber = act soon, green = normal, white or cyan = information, magenta = target or active.
Warning systems
EGPWS/TAWS gives aural and visual alerts for excessive descent rate, excessive terrain closure, altitude loss after takeoff, unsafe terrain clearance and excessive glideslope deviation, plus advisory callouts. A GPWS without a terrain database cannot see ahead. TCAS II issues TAs and RAs; an RA requires a prompt manoeuvre, typically within about 5 seconds, regardless of ATC, and the manoeuvres are coordinated between aircraft. Stall warning is normally a stick shaker plus an aural warning.
Worked example
An amber ENG OIL PRESS caption with a single chime and a master caution light is a level 2 caution, not a warning. The crew silences the master caution, reads the ECAM/EICAS message, and acts soon but not instantly. A red FIRE caption with a continuous bell and master warning is level 3.
Traps that cost marks
- Mixing up warning (red) and caution (amber).
- Forgetting that reversion is automatic on some types and manual on others.
- Treating an EGPWS look-ahead alert as identical to a GPWS mode 1 alert.
- Thinking an ATC clearance overrides an RA.