Electronic Instrument Systems
Familiarisation with the layout of an electronic flight instrument system, which data appears on the primary flight display and which on the navigation display.
Electronic instrument systems, summary notes
- EFIS (Electronic Flight Instrument System) replaced the electromechanical "basic six" with two integrated displays per pilot, driven by symbol generators (SGs) that gather data from the air data computers, inertial reference units and radio-navigation receivers and paint it as symbology.
- The EADI/PFD (Electronic Attitude Director Indicator / Primary Flight Display) carries the ATTITUDE group: artificial horizon, flight-director bars, airspeed and altitude tapes, vertical speed, Mach, radio altitude, the rising runway and the ILS localiser/glideslope deviation scales.
- The EHSI/ND (Electronic Horizontal Situation Indicator / Navigation Display) carries the NAVIGATION group: compass rose or arc, track and heading, waypoints, VOR/ADF bearing pointers, wind vector, and overlaid weather radar and terrain (EGPWS) returns. Typical selectable modes are ROSE, ARC, MAP and PLAN.
- Each display unit is interchangeable and reconfigurable: if one DU fails, its content can be transferred to the surviving DU (composite mode), and a display switching panel selects the alternate symbol generator.
- Standby instruments, an ISIS (Integrated Standby Instrument System) or separate attitude, airspeed and altimeter, remain independent of EFIS so a total EFIS loss still leaves flyable instrumentation.
- ⚠ Exam trap: weather radar and the map are on the ND/EHSI, never on the PFD/EADI. The PFD shows what the aircraft is doing; the ND shows where it is going.
A symbol generator fails in flight. What is the effect on the affected pilot's displays, and what action restores a usable picture?
Both of that pilot's display units lose their symbology because a single SG drives them. Selecting the alternate/opposite symbol generator on the display switching panel re-drives the units from a healthy SG; if only one display unit remains serviceable, composite mode combines the essential attitude and navigation symbology onto that single unit.
EFIS concept map
Electronic Instrument Systems
Electronic instrument systems quiz
Electronic Instrument Systems, quiz (Level 1)
1. EFIS stands for:
Electronic Flight Instrument SystemEngine Fuel Indicating SystemEmergency Flight Information Set2. The primary flight display shows mainly:
Attitude, airspeed and altitudeThe route and weatherEngine oil pressure3. The navigation display shows mainly:
Where the aircraft is going, track, waypoints and weatherEngine vibration levelsCabin temperature4. An artificial horizon is presented on the:
Primary flight displayNavigation displayEngine display5. Standby instruments are fitted so that the crew:
Still has attitude, airspeed and altitude if the EFIS failsCan navigate without radio aidsCan monitor the engines6. Compared with older electromechanical instruments, EFIS displays are:
Able to show many parameters on fewer screensHeavier and simplerUnable to show navigation data7. If one EFIS display unit fails, the crew can normally:
Transfer the essential display onto the remaining unitOnly continue on standby instrumentsDo nothing until landing8. Weather radar returns are normally shown on the:
Navigation displayPrimary flight displayStandby altimeter