None or I have nothing to send you — Page 15, Lesson 19

I want to walk you through the definitions and message priority structure that form the foundation of aeronautical communications. Let's start with the terms you'll see in every flight document and radio exchange. First, NOTAM — that's a Notice to Air Missions. It's a notice containing information concerning the establishment, condition, or change in any aeronautical facility, service, procedure, or hazard. The key point is that timely knowledge of this information is essential to personnel concerned with flight operations. So if a runway light is out, a navigation aid is off the air, or there's a temporary hazard near the airport, it goes into a NOTAM. PAPIs — Precision Approach Path Indicators. These are the lights beside the runway that give you visual glidepath guidance during approach. QFE — this is the atmospheric pressure at aerodrome elevation, or at the runway threshold. When you set QFE on your altimeter, it reads zero on the ground at that aerodrome — it shows your height above that specific airfield. QNH — the altimeter subscale setting to obtain elevation when on the ground. So with QNH set, your altimeter reads the actual altitude of the airfield above mean sea level when you're sitting on the runway. RCC — Rescue Coordination Centre. This is the organisation that coordinates search and rescue efforts if an aircraft is in distress. RNAV — Area Navigation. This allows you to fly any desired flight path within the coverage of ground- or space-based navigation aids, rather than being limited to flying directly to or from a specific ground station. RVR — Runway Visual Range. This is the distance a pilot can see along the runway, measured by special instruments. It's critical for low-visibility takeoffs and landings. SELCAL — Selective Calling. This is a system that permits the selective calling of individual aircraft over radiotelephone channels, linking a ground station with the aircraft. Instead of the pilot having to monitor the frequency constantly, the ground station sends a coded signal that triggers a visual or aural alert in the cockpit — only that specific aircraft's SELCAL code responds. SID — Standard Instrument Departure. This is a published procedure that takes you from the departure runway onto the en-route structure. SIGMET — information concerning en-route weather phenomena which may affect the safety of aircraft operations. Things like severe turbulence, icing, volcanic ash, or thunderstorms. SNOWTAM — a special series NOTAM notifying the presence or removal of hazardous conditions due to snow, ice, slush, or standing water associated with snow, ice, and slush on the movement area. It uses a specific format so that the information is immediately recognisable and standardised. SPECIAL — Special meteorological report, in abbreviated plain language. This is issued when weather conditions change significantly between routine reports. SSR — Secondary Surveillance Radar. This is the radar system that interrogates the transponder in your aircraft and receives a reply with altitude, identity, and other data. SST — Supersonic Transport. An aircraft designed to fly faster than the speed of sound. STAR — Standard Instrument Arrival. A published procedure that brings you from the en-route structure down to the initial approach fix for landing. TACAN — UHF tactical air navigational aid. It provides both bearing and distance information, primarily used by military aircraft but also available for civil use in some areas. TAF — Aerodrome Forecast. A weather forecast for a specific airport, covering a period typically 24 to 30 hours. TMA — Terminal Control Area. The controlled airspace around major airports where approach and departure traffic is managed. UHF — Ultra High Frequency, from 300 to 3000 MHz. UIR — Upper Flight Information Region. The airspace above the normal Flight Information Region, where en-route traffic at high altitudes is managed. UTA — Upper Control Area. Controlled airspace above a certain altitude, typically above FL245 or FL195 depending on the region. UTC — Coordinated Universal Time. This is the time standard used in aviation worldwide — you'll set your clocks to UTC for all flight operations. VASIS — Visual Approach Slope Indicator System. Like PAPIs, these are lights that give you visual glidepath guidance, but VASIS uses a two-bar or three-bar system with red and white lights. VDF — Very High Frequency Direction Finding system. A ground station that can determine the bearing of your aircraft by listening to your VHF transmission. VFR — Visual Flight Rules. The set of regulations under which you fly by visual reference to the ground and other aircraft, with specific weather minima. VHF — Very High Frequency, from 30 to 300 MHz. This is the primary frequency band for air-to-ground voice communications. VIP — Very Important Person. VMC — Visual Meteorological Conditions. Weather conditions that meet or exceed the minima for VFR flight. VOLMET — Meteorological information for aircraft in flight. These are regular broadcasts of weather reports and forecasts for airports along your route. VOR — VHF Omnidirectional Radio Range. A ground-based navigation aid that provides bearing information to the aircraft. VORTAC — a combination of VOR and TACAN in one facility, giving you both VHF bearing and UHF distance and bearing. Now, let's move to the Categories of Messages. This is critical for understanding radio discipline. By convention, messages are placed into categories so that if several need to be sent, the highest priority messages are sent first. This also applies to normal radio communications — for example, an aircraft emergency call takes priority over a request for landing. The order of priority, from highest to lowest, is: First, Distress — the call sign is MAYDAY. This is a condition of being threatened by serious and/or imminent danger and of requiring immediate assistance. If you're on fire, losing control, or about to crash, that's MAYDAY. Second, Urgency — the call sign is PAN PAN. This is a condition concerning the safety of an aircraft, but it does not require immediate assistance. This also includes messages preceded by the medical transports signal — PAN PAN MEDICAL. So if you have a sick passenger but the aircraft itself is fine, that's PAN PAN. Third, Direction Finding — communications relating to Direction Finding. If you need a ground station to give you a bearing because you're unsure of your position, that goes here. Fourth, Flight Safety — messages of immediate concern to an aircraft in flight. This includes meteorological advice of immediate concern to aircraft in flight or about to depart, and other messages to aircraft in flight or about to depart. Fifth, Meteorological Messages — reports, forecasts, and warnings. Sixth and lowest priority, Flight Regularity — messages regarding the operation or maintenance of facilities, servicing, changes in requirements for passengers and crew, non-routine landings, aircraft parts or materials, and changes in aircraft operating schedules. This priority structure ensures that when the frequency is busy, the most critical safety-related communications get through first. As a professional pilot, you must know these categories and use the correct priority for every transmission you make.