Definitions — Page 24, Lesson 37

Let’s start with taxiing. Taxiing is the movement of an aircraft on the surface of an aerodrome under its own power, excluding take-off and landing. So the moment the aircraft is moving on the ground using its own engines, that’s taxiing — but the actual take-off roll and the landing roll are not considered taxiing. Now, a taxiway. A taxiway is a defined path on a land aerodrome, established for the taxiing of an aircraft, and intended to provide a link between one part of the aerodrome and another. So it’s the designated route that connects, say, the runway to the apron. There are three specific types of taxiways I want you to know. First, the aircraft stand taxi-lane. That’s a portion of an apron designated as a taxiway, intended to provide access to aircraft stands only. So it’s the little path that gets you right up to the parking spot, and nowhere else. Second, the apron taxiway. That’s a portion of a taxiway system located on an apron, intended to provide a through taxi route across the apron. So instead of just accessing a stand, this one lets you cross the apron to get to the other side. Third, the rapid exit taxiway. This is a taxiway connected to a runway at an acute angle, designed to allow landing aeroplanes to turn off at higher speeds than are achieved on other exit taxiways, thereby minimizing runway occupancy times. So it’s that angled exit that lets a landing aircraft leave the runway quickly, freeing the runway sooner for the next arrival. Next, the Terminal Control Area, abbreviated TCA. A TCA is a control area normally established at the confluence of ATS routes in the vicinity of one or more major aerodromes. So it’s the controlled airspace set up where air traffic service routes come together near big airports. Now, Total Estimated Elapsed Time. This one has two definitions depending on the flight rules. For IFR flights — that’s instrument flight rules — it’s the estimated time required from take-off to arrive over that designated point, defined by reference to navigation aids, from which it is intended that an instrument approach procedure will be commenced. Or, if no navigation aid is associated with the destination aerodrome, to arrive over the destination aerodrome itself. For VFR flights — visual flight rules — it’s simply the estimated time required from take-off to arrive over the destination aerodrome. Next, Track. Track is the projection on the Earth’s surface of the path of an aircraft, the direction of which path at any point is usually expressed in degrees from North — true, magnetic, or grid. So it’s the actual path over the ground, measured in degrees from one of those three north references. Now, Traffic Avoidance Service. This is advice provided by an air traffic service unit specifying manoeuvres to assist a pilot to avoid a collision. So the controller tells you exactly what to do — turn left, turn right, climb, descend — to avoid hitting someone. Then Traffic Information. This is information issued by an air traffic service unit to alert a pilot to other known or observed air traffic which may be in proximity to the position or intended route of flight, and to help the pilot avoid a collision. So unlike the avoidance service, which tells you what manoeuvres to make, traffic information just alerts you that other traffic is near, so you can take action yourself. Next, Transition Altitude. This is the altitude at or below which the vertical position of an aircraft is controlled by reference to altitudes. So below this altitude, you use altitude — height above mean sea level. Above it, you switch to flight levels. Now, an Unidentified Aircraft. This is one of which the Air Traffic Control Unit is aware, but of which the identity is not known. So the controller knows there’s an aircraft there, but doesn’t know who it is. Next, VFR. That’s the symbol used to designate the visual flight rules. And a VFR Flight is a flight conducted in accordance with the visual flight rules. Then Visibility. Visibility is the ability, as determined by atmospheric conditions and expressed in units of distance, to see and identify prominent unlighted objects by day and prominent lighted objects by night. So it’s how far you can see, measured in distance units, and it applies to unlighted objects in daylight and lighted objects at night. Next, Visual Meteorological Conditions, abbreviated VMC. These are meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling equal to or better than specified minima. So VMC is defined by three things — how far you can see, how far you are from cloud, and the ceiling — all meeting certain minimum values. And finally, VMC is also the symbol used to designate visual meteorological conditions. Now, I want to show you a couple of figures that tie this together. shows the aerodrome reference code, which relates to runway and taxiway dimensions. And shows declared distances, which are the distances published for runway use. These will help you visualise how taxiways and runways fit together on an aerodrome. That covers the definitions in this section. Let me know if you want me to expand on any of them.