Definitions — Page 15, Lesson 18

I want to walk you through the first set of definitions and abbreviations you'll need to know as you begin your aviation communications training. These are the building blocks you'll see again and again throughout your career, and they must be learned for exams. Let's start with the note at the top: the abbreviations listed here are normally spoken using the constituent letters — so you say "A-C-C," not a word — except those marked with an asterisk, which are spoken as complete words. Keep that in mind as we go through them. First, ACC stands for Area Control Centre or area control. This is the facility that manages aircraft once they're en route between airports. ADF is Automatic Direction Finding equipment — a radio navigation aid that points toward a ground station. ADR means Advisory Route. This is a route where air traffic services provide advice but not full control. AFIS, with an asterisk, is Aerodrome Flight Information Service — spoken as a word, "AY-fiss." It provides information to aircraft at an aerodrome but not full control. AGL means Above Ground Level — height measured from the ground directly below the aircraft. AIP is the Aeronautical Information Publication — the official document containing all the permanent aeronautical information for a country. AIRAC, with an asterisk, stands for Aeronautical Information Regulation and Control — spoken as "AY-rack." It's the system that ensures changes to aeronautical information are published on common dates. AIS is Aeronautical Information Services — the overall service that provides aeronautical data and information. AMSL means Above Mean Sea Level — height measured from average sea level, which is different from AGL. ATC is Air Traffic Control in general — the service that prevents collisions and expedites traffic flow. ATD means Actual Time of Departure — the real time you leave the ground or the gate. ATIS, with an asterisk, is Automatic Terminal Information Service — spoken as "AY-tiss." It's a continuous broadcast of recorded aeronautical information at busy airports. ATS stands for Air Traffic Services — the umbrella term covering all air traffic control, flight information, and alerting services. ATZ is Aerodrome Traffic Zone — a defined airspace around an aerodrome for the protection of traffic. CAVOK, with an asterisk, is spoken as "CAV-oh-kay." It means visibility, cloud, and present weather are better than prescribed values or conditions — essentially, perfect flying weather. CTR is Control Zone — controlled airspace around an airport extending from the surface upward. DME is Distance Measuring Equipment — a radio navigation aid that tells you how far you are from a ground station. EET means Estimated Elapsed Time — the time you expect a flight segment to take. ETA is Estimated Time of Arrival or Estimating Arrival — when you expect to arrive. ETD is Estimated Time of Departure or Estimating Departure — when you expect to depart. FIC is Flight Information Centre — the facility that provides flight information service. FIR is Flight Information Region — the largest division of airspace, where flight information and alerting services are provided. FIS is Flight Information Service — the service that provides information useful for safe and efficient flight. GCA is Ground Controlled Approach system or Ground Controlled Approach — a radar-based system where a controller guides you to the runway. HF is High Frequency, operating from 3 to 30 MHz — used for long-range communications. H24 means Continuous day and night service — 24 hours a day. IFR is Instrument Flight Rules — the rules for flying solely by reference to instruments. ILS is Instrument Landing System — the precision approach guidance system that gives you lateral and vertical guidance to the runway. IMC is Instrument Meteorological Conditions — weather conditions requiring you to fly by instruments. INFO, with an asterisk, is Information — spoken as "IN-foh." INS is Inertial Navigational System — a self-contained navigation system using accelerometers and gyroscopes. MET, with an asterisk, is Meteorological or Meteorology — spoken as "met." MLS is Microwave Landing System — an alternative precision landing system using microwave frequencies. MNPS means Minimum Navigation Performance Specifications — standards for navigation accuracy in certain airspace, like the North Atlantic. NDB is Non-Directional radio Beacon — a ground-based radio transmitter that provides bearing information. And finally, NIL means nothing — it's used in reports to indicate that a particular element is absent or zero. These are your foundational abbreviations. Take your time learning them — they'll be the language you speak every time you're on the radio or reading a flight document.