OBJECTIVES:
- Explain objectives of ATC
- Understand the difference between a service and a unit?
- ATC positions in VATSim vs. real-life
Air Traffic Services
After getting online, you will need to obtain all the information and authorizations you need to make your flight. People will tell you what to do, how not to crash into other planes, what runway is being used, what air-routes you have to follow, give information about the weather, send out people for search and rescue if you crash, etc...
This is called Air Traffic Service and is offered by an Air Traffic Service Provider. In real life, almost every country has such an organisation.
In our virtual world VATSim is the organisation that does this worldwide.
The aim of the Service is to provide pilots with one or more of the following:
- Air Traffic Control (ATC) service to prevent collisions and to organise traffic efficiently:
- on taxiways, runways and in the airspace around the airfield (called Control Zone or CTR), known as Aerodrome Control service;
- between arriving and departing aircraft in a Terminal Control Area (TMA) to and from one or more aerodromes, called Approach Control service;
- between en-route aircraft in Control Areas (CTA) and along Airways (AWY), this is Area Control service
- Flight Information service (FIS) by giving useful information and advise for the safe and efficient conduct of flight such as the status of navaids, bad weather, closed airfields etc.
- Alerting service by assisting aircraft in difficulties and by initiating Search and Rescue (SAR).
Air Traffic Control Units
Air Traffic Control Units are specialised in providing one of the Air Traffic Control services mentioned above, but also responsible for Flight Information Service and Alerting Service to pilots.
The Air Traffic Control Unit that is typically responsible for:
- Aerodrome Control Service is called the Aerodrome Control Tower (TWR)
- Approach Control Service is called the Approach Control Unit (APP)
- Area Control Service is called the Area Control Center (ACC) or Upper Area Control Center (UAC)
illustration showing the units as explained above
Air Traffic Control Positions
Because of the workload, separate ATC positions may be opened within each ATC Unit. Each of these positions is given a name and is assigned a specific task.
Before starting his flight, a pilot must contact the Air Traffic Control position of the ATC Unit that is controlling the airspace or airfield he will be using.
As an ATC, you have to choose the correct ATC position before connecting to the VATSim network with Euroscope or VRC.
You are logged in as an active controller, only if you use one of the following extensions:
...._DEL, ...._GND, ...._TWR, ...._APP, ...._ARR, ...._DEP, ...._CTR or ...._FSS.
When traffic is getting very dense, ATC may even decide to split ATC positions in sub-positions according to one of the 4 main compass directions. The extentions will then be like ...._N_CTR, ...._W_GND, etc...
screenshot of Servinfo showing online positions
However, if you only want to observe, you can connect as an observer, whereby you choose OBS as extension (...._OBS).
Aerodrome Control Tower positions
xxxx_DEL (example: LFPO_Delivery)
When all other Tower positions are manned on a busy VATSim-day, Delivery (DEL) will be the first ATC that pilots will contact before engine start.
Delivery (DEL) gives the departure clearance after having checked that the flight plan is correct and he approves start-up.
The departure clearance shall include the Standard Instrument Departure (SID) (only for IFR traffic) and a squawk code.
screenshot showing aircraft prior contacting Delivery
xxxx_GND (example: SBBR_Ground)
Ground (GND) handles all aircraft on the ground, except that on the active runway(s).
Whenever an aircraft needs to enter or cross an active runway, this has to be coordinated first with the Tower.
- For departures, the transfer to tower (TWR) is done when the aircraft approaches the holding point.
- For arrivals, the transfer will be done from tower (TWR) after the aircraft has vacated the runway.
For further details, see the Chapter about "Surface Movement Control - GROUND"
screenshot showing aircraft taxiing
XXXX_TWR (example: SCEL_Tower)
Tower (TWR) handles all aircraft on the active runway(s) and airborne aircraft that are visual with the runway within the airspace around the aerodrome. This airspace is called the Control Zone (CTR). This includes VFR traffic and helicopters.
Note: In real life CTR stands for Control Zone. Unfortunately in VATSim it is used for Area Control.
TWR “owns” the runways and gives take-off and landing clearances. Tower is also responsible for the separation of aircraft on the ILS.
- For departures, the transfer to departure control (DEP) or approach control (APP) is done directly after take-off, if IFR traffic. VFR traffic remains under control of TWR until leaving the local Control Zone.
Note: See the note under XXXX_APP
- For arrivals, APP should hand off the traffic to TWR once established on the ILS.
For further details, see the Chapter about "Aerodrome Control - TOWER"
screenshot showing aircraft in contact with TWR
Approach Control Unit positions
XXXX_APP (example: KBOS_APP)
Approach (APP) normally handles arriving aircraft from the Initial Approach Fix (IAF) towards the ILS for landing and airborne aircraft after they are handed off by the TWR until they can be transferred to the next ATC postion.
Approach (APP) could handle aircraft leaving or arriving at and from one or several airports at the same time.
For further details, see the Chapter about "DEParture - ARRival - APProach"
screenshot showing APP position inEuroscope or VRC with departing and arriving traffic
At some airports, the different tasks of APProach are split between a DEParture controller and an ARRival controller. The purpose is to relieve the work-load of the approach controller by separately handling all departures on a separate frequency. By doing so, the APProach controller can better handle the arrivals, but has to change his position name to ARRival Controller.
It is the controller at the APP position who decides when the traffic load requires his position to be split into ARRival and DEParture positions.
XXXX_ARR and XXXX_DEP positions MAY NOT BE ACTIVATED SEPARATELY!
XXXX_ARR (example OEJN_ARR)
Arrival (ARR) normally only handles arriving aircraft from the Initial Approach Fix (IAF) towards the ILS for landing. The ARR position shall only be opened together with the DEP position that is serving the same TMA.
ARR will hand off traffic to TWR when established on ILS or when the aircraft is visual with the runway (visual approach) and if clear of other traffic it controls.
For arrivals, transfer to ARR is normally done by Area Control (CTR) while descending and preferable before reaching the IAF.
For further details, see the Chapter about "DEParture - ARRival - APProach"
screenshot showing ARR position inEuroscope or VRC with aircraft being vectored to ILS
XXXX_DEP (example ZSNJ_DEP)
Departure (DEP) handles all departing aircraft after they are airborne and handed off by the TWR. The DEP position shall only be opened together with the ARR position that is serving the same TMA.
Transfer to the Area Control (ACC or in VATSim CTR) is done while climbing, preferable before reaching the upper limit of the APP area or the SID point.
Note: When DEP is not active, APP shall perform all the tasks of DEP as well. See note under XXXX_APP
For further details, see the Chapter about quot;DEParture - ARRival - APProach"
screenshot showing climbing aircraft at DEP position inEuroscope or VRC or in FS with airport in background
(Upper) Area Control Center positions
XXXX_CTR (example: DAAA_CTR)
Area Control (ACC) or in VATSim 'CTR' owns all airspace within his Flight Information Region (FIR) that is not controlled by any APP or TWR.
An FIR is a wide area of airspace in which Countries are responsible for the provision of the Air Traffic Services (ATS).
ACC (CTR) controls the aircraft while (over flying) en route or climbing or descending from or into an airfield situated in its Flight Information Region (FIR).
Departures (IFR) from local airfields are transferred from DEP or APP before reaching the upper limit of the TMA (Terminal Control Area) or the SID point.
IFR arrivals are transferred to APP before reaching the appropriate IAF (Initial Approach Fix) or the agreed transfer point.
In VATSim Area Controllers often have to deal additionally with GND/TWR/APP control for controlled airfields located in their area of responsibility, when no local active controller is logged in there. This could be difficult to manage properly and often cause students to be soon overloaded.
Note: If there is an Upper Area Control (UAC) sector active above the normal ACC (CTR), its tasks are basically the same as for the ACC (CTR), but in the Upper Airspace. However, traffic will not be directed for APP, since there is always the ACC in between.
screenshot showing CTR position inEuroscope or VRC with en-route traffic above FL100
Flight Information Center position
XXXX_FSS (example: EBBU_FSS)
In VATSim the main purpose of the FSS unit is to provide advise and information, including traffic information to VFR and IFR traffic outside controlled airspace, or for handling particular (non-controlled) areas, e.g. connected to Oceanic Control.
A Flight Information Center (FIC) or in VATSim Flight Service Station (FSS) provides traffic in large areas with en route traffic information, VFR search and rescue services, assists lost aircraft and aircraft in emergency situations, relays ATC clearances, advises about Notices to Airmen (NOTAMs), broadcast aviation weather and informs about the status of NAVAID's.
In addition, at selected locations, FSS's provide En Route Flight Advisory Service (Flight Watch), relay weather observations, issue airport advisories, and advise Customs and Immigration of transborder flights.
For further details, see the Chapter about "FIS - Flight Information Service"
screenshot showing light aircaft flying VFR below 5000 feet over a highway, river, coastline...