Flight Director Systems — Page 340, Lesson 391

We're starting a brand-new chapter today: Flight Director Systems. Before we talk about a single instrument, I want to give you the vocabulary keys to the whole auto-flight world, because every mode, every annunciator, and every acronym you'll see on the panel is defined right here in this glossary. Let me walk you through the core building blocks. The A/P is the Autopilot. The A/T is the Autothrottle, which manages engine thrust. A/L is Autoland. The ADC is the Air Data Computer — that's the box that computes speed and altitude from pitot and static pressure. The ADI, or EADI, is the Attitude Director Indicator, the Electronic version being the EADI — that's your primary attitude display. The AFCP is the Auto-flight Control Panel, also called the MCP, the Mode Control Panel — that's where you select the modes. The AFCS is the Auto-flight Control System, the AFDS is the Auto-flight Director System, and the AFS is the Auto-flight System. Notice how these three are distinct: the AFCS is the overall system, the AFDS is the director portion, and the AFS is the umbrella term. Now, the modes. ALT ACQ is Altitude Acquire. APP is Approach. HDG is Heading. LVL CHG is Level Change. SPD is Speed. V/S is Vertical Speed. VNAV is Vertical Navigation, and it can be in SPD or PTH — Path or Speed mode. LNAV is Lateral Navigation. LOC is Localizer. VOR is VOR tracking, or the VHF omni-range beacon, depending on context. TO/GA is Take-off / Go-around. TRK is Track. And GA is Go-around, or Gear Altitude, again depending on context. Let's talk about the computers and sensors. The FCC is the Flight Control Computer. The FDC is the Flight Director Computer. The FMC is the Flight Management Computer. The FMGS is the Flight Management and Guidance System. The FADEC is the Full Authority Digital Engine Control. The PMC is the Power Management Computer. The TMS is the Thrust Management System. The CADC is the Central Air Data Computer. The DG or DI is the Directional Gyro or Direction Indicator. The VG is the Vertical Gyro. The IRS is the Inertial Reference System, and INS is the Inertial Navigation System. Now the displays and annunciators. The FMA is the Flight Mode Annunciator — that's the strip that tells you what the system is actually doing. The TMA is the Thrust Mode Annunciator. The PFD is the Primary Flight Display — that's the EADI including speed, altitude, and VSI tapes, and commonly a compass and annunciator panel. The ND is the Navigational Display. The HSI or EHSI is the Horizontal Situation Indicator, electronic version being EHSI. The CDI is the Course Deviation Indicator, the bar. The CDU is the Control and Display Unit. The ECAM is the Electronic Centralized Aircraft Monitoring, and EICAS is the Engine Instruments and Crew Alerting System — those are the two big monitoring systems. Let me hit the remaining specific terms. CWS is Control Wheel Steering. TCS is Touch Control Steering. CMD is Command, or Autopilot Engage. MI is Magnetic Indicator. RA is Radio Altitude. AoA is Angle of Attack. EPR is Engine Pressure Ratio. TLA is Throttle Lever Angle. N1 is the rpm of the first stage of compression — normally the fan in a high bypass engine — expressed as a percentage. QDM is the "Q" code for a magnetic heading to fly assuming zero wind. And finally, LAND 2 is fail-passive, while LAND 3 is fail-operational — those are your autoland capability levels. That's the full glossary. Every one of these will come back as we build the flight director picture, so keep this list as your reference sheet.