Definitions — Page 24, Lesson 24

I want to walk you through the definitions section of your communications manual. This is the start of a new topic — the standard abbreviations and acronyms used in aeronautical communications. These are not optional vocabulary; they are the precise, regulated shorthand that every pilot and air traffic service unit uses to exchange information quickly and without ambiguity. Let's go through them in order. We begin with ATN — Aeronautical Telecommunication Network. This is the global data network that supports air-ground and ground-ground communication for air traffic management. Next, ATOTN — Air Traffic Operation Telephone Network. This is a dedicated telephone network used specifically for operational coordination between air traffic service units. ATP — At (time or place). You will see this in messages to specify a particular time or location. ATS — Air Traffic Service. This is the umbrella term for services such as air traffic control, flight information, and alerting. ATSU — Air Traffic Service Unit. This refers to any facility that provides air traffic services, like a control tower or area control centre. ATTN — Attention. Used in messages to draw the recipient's focus to a particular item. ATZ — Aerodrome Traffic Zone. This is a defined volume of airspace around an aerodrome, established for the protection of aerodrome traffic. AUG — August. Simple month abbreviation. AUTH — Authorized OR Authorization. Context tells you which meaning applies. AUW — All Up Weight. This is the total weight of the aircraft, including everything on board, at any given moment. AUX — Auxiliary. As in auxiliary power unit or auxiliary systems. AVASIS — Abbreviated Visual Approach Slope Indicator System. This is a simplified version of the standard visual approach slope indicator, used to help pilots maintain the correct glidepath on approach. AVBL — Available OR Availability. Again, context determines the meaning. AVG — Average. AVGAS — Aviation Gasoline. This is the fuel used by piston-engine aircraft. AVTUR — Aviation Turbine Fuel. This is the fuel used by turbine-engine aircraft, commonly known as kerosene-based jet fuel. AWTA — Advise at What Time Available. You will use this in messages when you need to know when a resource or service will become available. AWY — Airway. A designated air route with defined dimensions, typically between navigation fixes. AZM — Azimuth. This is a horizontal direction measured clockwise from true north, usually in degrees. Moving to the letter B. B — Blue. Used in colour coding, for example on runway lights or instrument markings. BA — Braking Action. This is a report of the effectiveness of braking on a runway surface, typically given as good, medium, or poor. BAA — British Airports Authority plc. A specific airport authority. BASE — Cloud Base. This is the height of the lowest part of a cloud layer above ground level. BCFG — Fog Patches. A weather phenomenon where fog is not continuous but occurs in patches. BCN — Beacon (aeronautical ground light). A visual navigational aid, such as an aerodrome beacon or a rotating beacon. BCST — Broadcast. A transmission intended for all stations to receive, not directed to a specific recipient. BDRY — Boundary. Typically refers to an airspace or control zone boundary. BECMG — Becoming. Used in meteorological forecasts to indicate a change to a new condition. BFR — Before. BKN — Broken. In aviation meteorology, this describes a cloud amount of 5/8 to 7/8 of the sky covered. BL... — Blowing. This is followed by a code for the substance being blown: DU for Dust, SA for Sand, or SN for Snow. For example, BLDU means blowing dust. BLDG — Building. As in a structure, not the verb. BLO — Below Clouds. Used in flight planning or reports to indicate operation beneath a cloud layer. BLW — Below. BOMB — Bombing. A military activity notification. BR — Mist. A weather phenomenon with visibility greater than 1000 metres but less than 5000 metres, caused by suspended water droplets. BRF — Short (used to indicate the type of approach desired or required). For example, a short approach or a short landing. BRG — Bearing. The direction from one point to another, measured in degrees from north. BRKG — Braking. Related to braking action reports. B-RNAV — Basic Area Navigation, pronounced 'AR-NAV'. This is a navigation specification that allows aircraft to fly directly between waypoints without needing to overfly ground-based navigation aids. The 'B' stands for Basic. BS — Commercial Broadcasting Station. A non-aviation radio station. BTL — Between Layers. Used to describe a position or flight level between two cloud layers. BTN — Between. Now the letter C. C — Centre (runway identification). When a runway has a centre runway, it is identified with the letter C, for example Runway 27C. CAA — Civil Aviation Authority. The national regulatory body for civil aviation in the UK. CANP — Civil Aircraft Notification Procedure. The process for notifying authorities of civil aircraft movements. CAP — Civil Aviation Publication. A series of publications issued by the CAA. CAS — Calibrated Airspeed. This is the indicated airspeed corrected for instrument and position errors. It is the speed you read on the airspeed indicator after those corrections. CAT — Category. Used in many contexts, such as instrument approach categories or aircraft categories. CAT — Clear Air Turbulence. Turbulence encountered in cloudless air, typically at high altitudes, often associated with jet streams. CATZ — Combined Aerodrome Traffic Zone. A zone that combines the traffic zones of two or more closely located aerodromes. CAVOK — Pronounced 'KAV-OH-KAY'. This stands for Ceiling And Visibility OK. It means visibility, cloud, and present weather are better than prescribed values or conditions. Specifically, visibility is 10 kilometres or more, no cloud below 5000 feet or the highest minimum sector altitude, and no significant weather phenomena. CB — Pronounced 'CEE BEE'. This is the abbreviation for Cumulonimbus, the towering cloud associated with thunderstorms, heavy rain, hail, and severe turbulence. CBR — Cloud Base Recorder, also known as a ceilometer. This is an instrument that measures the height of the cloud base. CC — Counter Clockwise. A direction of rotation. CC — Cirrocumulus. A high-level cloud type, appearing as small white patches or ripples. CCA — Corrected Meteorological Message. This is a message type designator used when a meteorological report needs correction. You may also see CCB, CCC, and so on, in sequence for multiple corrections. CD — Candela. The SI unit of luminous intensity, used to measure the brightness of lights, such as runway lights or approach lights. CDN — This abbreviation is cut off in the excerpt, but it typically stands for Coordination. We will cover the rest when we continue. These definitions are your foundation. Every time you read a NOTAM, a meteorological report, or an ATC clearance, you will encounter these abbreviations. Learn them as exact terms, not approximations.