Definitions — Page 11, Lesson 14

I want to walk you through the definitions that form the foundation of aviation communications and air traffic control. These are terms you'll use every single day as a professional pilot, so let's take them one at a time. Let's start with Apron. An apron is a defined area on a land aerodrome — that means an airport on the ground, not a water aerodrome. It's intended to accommodate aircraft for specific purposes: loading and unloading passengers, mail, or cargo; fuelling; parking; or maintenance. So when you taxi to the gate or to a remote stand, you're on the apron. Next, Area control centre. This is a unit established to provide air traffic control service to controlled flights under its jurisdiction. In everyday language, this is the facility that handles aircraft once they're en route, between departure and arrival — not the tower at the airport, but the centre that manages the airspace in between. Automatic terminal information service — we call it ATIS. This is the provision of current, routine information to arriving and departing aircraft. It works by means of continuous and repetitive broadcasts throughout the day, or a specified portion of the day. So when you tune into the ATIS frequency at an airport, you hear a recorded message that repeats over and over, giving you the weather, runways in use, and other essential information. Now, Blind transmission. This is a specific situation where one station is receiving no reply. It could be that just his own receiver is not working, so he transmits 'blind', hoping that Control can hear him. More formally, it's a transmission from one station to another station in circumstances where communication cannot be established, but where it is believed that the called station is able to receive the transmission. So if your transmitter works but your receiver fails, you might send a blind transmission — you can't hear them, but you hope they can hear you. Broadcast is different. A broadcast is a transmission of information relating to air navigation that is not addressed to a specific station or stations. So when you make a position report on a frequency that other aircraft are monitoring, or when you broadcast a safety alert, that's a broadcast — it's for anyone listening, not for a specific controller or aircraft. Clearance limit. This is the point at which an aircraft is granted an air traffic control clearance. When ATC gives you a clearance, they specify a limit — that's the point you're cleared to. For example, "Cleared to the ABC VOR" — that VOR is your clearance limit. Control Area. This is a controlled airspace extending upwards from a specified limit above the surface of the earth. So it doesn't start at the ground — it starts at some altitude above the surface, like 2,000 feet, and goes up from there. Controlled airspace is a broader term. It's an airspace of defined dimensions within which air traffic control service is provided for controlled flights. So both Control Areas and Control Zones are types of controlled airspace. Control Zone is a specific type of controlled airspace. It extends upwards from the surface — from the ground — to a specified upper level. So unlike a Control Area, a Control Zone starts at the ground. This is typically around an airport. Estimated time of arrival, or ETA. This is the time at which the pilot estimates that the aircraft will be over a specified location. Not necessarily the destination — it could be any point along the route. Expected approach time, or EAT. This is the time at which ATC expects that an arriving aircraft, following a delay, will arrive at the holding point to complete its approach for a landing. So if you're in a holding pattern because of traffic, ATC will give you an EAT — the time they expect you to leave the hold and start your approach. Flight plan. This is specified information provided to air traffic services units, relative to an intended flight, or path of a flight, of an aircraft. It includes your route, altitude, speed, fuel, and other details that ATC needs to manage your flight. Heading. The direction in which the longitudinal axis of an aircraft is pointed, usually expressed in degrees North — and that can be true north, magnetic north, compass north, or grid north. So heading is where the nose is pointing, not necessarily where the aircraft is actually tracking over the ground. Holding point. A specified location, identified by visual or other means, in the vicinity of which the position of an aircraft in flight is maintained, in accordance with air traffic control clearances. This is the point you fly to in a holding pattern. Holding procedure. A predetermined manoeuvre which keeps an aircraft within a specified airspace whilst awaiting further clearance. That's the racetrack pattern you fly — the standard holding pattern. IFR flight. A flight conducted in accordance with instrument flight rules. That means you're flying by reference to instruments rather than visual reference to the ground. Instrument meteorological conditions, or IMC. These are meteorological conditions expressed in terms of visibility, distance, cloud, and ceiling, less than the minima specified for visual meteorological conditions. In simple terms, IMC is weather that's below VMC minima — you can't fly visually, so you must fly under IFR. These definitions are the building blocks. Every clearance, every procedure, every communication you make will rely on these terms being crystal clear in your mind.