## Glossary 

Active waypoint. The waypoint being used by the FMS/RNAV as the reference navigation point for course guidance. 

ADAHRS. See air data attitude and heading reference system. 

ADC.  See air data computer. 

ADS-B.  See automatic dependent surveillance—broadcast. 

Advanced avionics information system. Any cockpit electronic (avionics) system designed to provide information or data to the pilot about aircraft status or position, planned routing, surrounding terrain, traffic, weather, fuel, etc. Advanced avionics systems are generally evidenced by visual displays of integrated information in lieu of mechanical or stand alone instruments for one or two data sets each. 

AHRS.  See Attitude Heading Reference System. 

Air Data Attitude and Heading Reference System (ADAHRS). An integrated flight instrument system that combines the functions of an air data computer (the “AD” short for ADC) and an Attitude Heading Reference System (AHRS) into one unit. 

Air Data Computer (ADC).  The system that receives ram air, static air, and temperature information from sensors, and provides information such as altitude, indicated airspeed, vertical speed, and wind direction and velocity to other cockpit systems. 

Altitude alerting system. The system that allows the pilot to receive a visual and/or auditory alert when the airplane approaches or deviates from a preselected altitude. 

Altitude capture. An autopilot function that enables the autopilot to level the airplane at a selected altitude automatically. 

Altitude function.  An autopilot function that maintains the present altitude of the airplane. 

Annunciator panel.  Grouping of annunciator lights that is usually accompanied with a test switch, which when pressed illuminates all the lights to confirm they are in working order. 

Approach mode/function.  An autopilot function or mode that allows the pilot to capture and track any VOR radial or localizer with a higher degree of accuracy. 

Area navigation (RNAV). A method of navigation that permits operations along any desired flightpath within the area of coverage of station‑referenced navigation aids (e.g., GPS, VOR/DME, DME/DME, eLORAN), or within the limits of a self‑contained navigation system (INS, doppler radar), or any combination. 

Armed.  A system mode or function that is set to become actively engaged at a later time, when certain conditions are met. 

Attenuation.  See radar attenuation. 

Attitude Heading Reference System (AHRS). An integrated flight instrument system that provides attitude, heading, rate of turn, and slip/skid information. 

Automatic dependent surveillance—broadcast (ADS-B). A surveillance system in which an aircraft or vehicle to be detected is fitted with cooperative equipment in the form of a data link transmitter. The aircraft or vehicle periodically broadcasts its GPS‑derived position and other information (e.g., velocity) over the data link, which is received by a ground-based transmitter/ receiver (transceiver) for processing and display at an air traffic control facility. 

Automatic mode change.  Any change in mode or system status initiated by the system, rather than by a deliberate mode change action taken by the pilot. 

