APP, DEP, CTR Positions & Responsibilities

By MattChase

Prerequisites
It is recommended you read the material on the Airport Air Traffic Control page before beginning this lesson.

Introduction
On the ground, the responsibilities of Air Traffic Control are relatively simple, and structured. In the air, things can get a little more confusing. The aim of this document is to help you understand the responsibilities of the various controllers you'll meet while airborne, and what to expect while under their control.

The three most common controllers you'll see in the air are Approach, Departure, and Centre. These three are generally considered to be 'radar controllers'. They are primarily responsible for maintaining separation in designated airspace. These control positions can have varying names (such as Radar, Control, Director) but most of the time their responsibilities are the same.

Approach (_APP)
As the name suggests, the Approach controller is generally responsible for providing control services to aircraft arriving (approaching) a certain airport. This may include, but not limited to, radar vectors to join finals, traffic advisories, and clearing aircraft for approach. The Approach controller may also perform Tower duties if they are offline. Approach controllers are designated with _APP, example: SEA_APP is Seattle Approach.

The aim of the Approach Controller is to sequence arriving aircraft for landing, while maintaining separation. In order to maintain separation and establish sequencing between aircraft, Approach may choose to use:

• Speed restrictions (eg, Decrease Speed 200 knots.)
• Altitude requirements (eg, maintain 3000 until established.)
• Vectors (eg, Turn Right Heading 340.)
• Circuit instructions (eg, Join Downwind Runway 09.)
• Approach Clearances (eg, Cleared the ILS Approach, Runway 15.)
• Orbit (A full 360 turn)
• Other various methods of control.

It is important, particularly when busy, to follow instructions given by these controllers; a single mistake by one aircraft can ruin an entire sequence of arrivals.

Departure (_DEP)
The Departure controller is generally responsible for providing control services to aircraft departing a certain airport. This may include, but not limited to, climb instructions, track lengthening, and instructions to join the flight planned route. The Departure controller will be the first to identify your aircraft on radar. The Departure controller may also perform Tower duties if they are offline. Departure controllers are designated with _DEP, example: CYOW_DEP is Ottawa Departure.

The aim of the Departure controller is to maintain separation between aircraft moving towards the first fix in their flight plan. To accomplish this, the Departure controller may issue:

• Speed restrictions (eg, Increase Speed 230 knots.)
• Altitude requirements (eg, Climb 8000, Cross XYZ at 5000.)
• Vectors (eg, Turn Right Heading 340 to join flight planned route.)
• Other various methods of control.

Airspace
Normally, both Approach and Departure are limited to an area known as a 'TMA', or Terminal Control Area. The TMA is a zone surrounding an airport, set up to protect arriving and departing aircraft. The size of a TMA varies greatly between different airports, going from as close as 20nm to as far as 60nm away from the airport. Frequently, this TMA can cover more than one airport, meaning that an approach controller for one airport may also be providing Approach Services for nearby airports. Approach and Departure may also control low-flying aircraft that are transiting through their airspace. Remaining vigilant of nearby controllers is important; the airport you are departing may be controlled by another approach controller!

On occasions, you may find that aircraft arriving at an airport are sent to the Departure frequency. This is normally because of an aircraft arriving in the direction that traffic is departing, and it is easier to maintain separation with all aircraft on the same frequency. This can happen frequently in the real world, and can happen online also. It is important to stay aware of this; occasionally pilots will get concerned over being handed over to what seems the 'wrong' controller, but it is generally nothing to worry about.

Navaids
Occasionally, ATC uses Navaid tracking instructions to allow the pilot to track a particular course, maybe to join a VOR Approach. Some common phrases you may hear include:
"Intercept the XYZ 180 Radial Inbound"
"Track the XYZ 10 DME Arc"
"Overhead ABC, Track the 270 Radial Outbound"

To follow these instructions, you need to able to use standard navigational equipment. We have a lesson on it, Navigation Aids.

These instructions are generally rare, so don't be afraid of connecting without knowing understanding these instructions fully. After all, VATSIM is a learning environment, and you don't become an airline pilot overnight! Just remember,



Advanced - Director
The Director is an Advanced ATC position in use at many major airports around the world. Their Sector ID online varies, but their core goal is the same. They are responsible for maintaining separation for aircraft on final. They own a small amount of airspace, and their primary task is setting up aircraft for final approach.

When flying into an airport with Director online, be quick with your radio calls, follow all instructions carefully and anticipate what will happen next. If you are getting handed-off to another controller, think ahead and tune your standby radio so when needed, you can switch to the other frequency quickly.

Centre (_CTR)
The Centre controller is responsible for providing control services to aircraft located in their FIR or Sector (see below), but are not in a TMA. This is primarily aircraft en route, but can also include aircraft arriving and departing smaller airports that don't have a TMA zone around them. Normally, Centre controls up to FL600, and covers right down the airspace floor, which varies greatly by location. In various parts of the world, the _CTR controller can also be referred to as 'Radar' or 'Control'. Centre controllers may also assume the duties of Approach/Departure when they are offline. Centre Controllers are designated with _CTR, example: FZZA_CTR is Kinshasa Centre.

The goal of Centre controllers is to separate aircraft on crossing routes, and to sequence aircraft so they can be processed by an Approach or Departure controller. To accomplish this, the Centre controller may use:

• Speed restrictions (eg, Maintain Mach .80.)
• Altitude requirements (eg, Climb FL360, Cross XYZ at FL350.)
• Cruise altitude changes (eg, Climb and maintain FL330.)
• Track Alteration (eg, Track Direct XYZ for Track Shortening.)
• Traffic Advisories (eg, Traffic is at your 2 o'clock, 5 miles...)
• Holds (See Below.)
• Other various methods of control.

It is important, when being controlled by Centre, to monitor the frequency at all times. While it may not seem like there is an aircraft near you, Centre controllers are taking care of the 'bigger picture' and are trying to eliminate conflicts before they begin.

As mentioned above, Centre controllers may also provide control services for airports not inside a TMA, or airports located outside controlled airspace. How Centre treats these aircraft is different for every region, but in most cases, clear and definitive instructions are given, such as 'Depart at own discretion, call airborne' or 'No Reported IFR Traffic, call holding short'. When on the ground at one of these airports, and unsure about the correct procedure, simply ASK! The controller would rather help out a learner, than deal with a pilot who didn't contact him.

Holds
Holds are used by Centre control when an airport is extremely busy and the Approach controller has no more room for aircraft. Holds can be a tricky maneuver to perform, so it is recommended you read the document Introduction to Holding before flying into rush hour traffic.

Step Climbs and Track Shortening
While flying, you'll often find that Centre controllers can be your best friend in the air. If you want to change altitude in cruise, Centre can help. Simply ask for an amended cruise altitude, and Centre, providing it doesn't create a conflict or violates procedure, will try to clear it.

You may also find that Centre controllers use a technique known as 'Track Shortening'. For the pilot, this may mean being cleared direct to another way point on the flight plan, in order to minimise the distance travelled. This can save time and is often mutually beneficial to both parties. If you are looking for track shortening, ask the Centre controller and they will attempt to accommodate you.


Advanced - Procedural (Non-Radar) Airspace.
In many areas of the world, radar coverage is a luxury, too expensive to ensure total coverage. As a result, there may be many Centres which have no radar coverage at all. When flying through non-radar airspace, there are different rules that apply. For a complete description of Non-Radar Control, see Oceanic Airspace Procedures.

Sectors
When busy, it can be beneficial for the controllers to split their airspace into 'sectors'. Sectors are designed to minimise workload, and often sectors have the controllers covering specific duties. The Sector ID is normally located between the ICAO code and the position suffix. Such as SCEZ_N_CTR. A look at some common Sector ID's is below.

• ICAO_N_CTR: Controls aircraft in the North of the FIR.
• ICAO_E_APP: Controls aircraft arriving from the East.
• ICAO_W_DEP: Controls aircraft departing to the West
• ICAO_S_CTR: Controls aircraft in the South of the FIR, or is a Student Controller.
• ICAO_I_APP: An Instructor, normally assisting a Student controller.
• ICAO_H_CTR: 'High Sector'. Controls aircraft in the FIR above a certain altitude.
• ICAO_L_CTR: 'Low Sector'. Controls aircraft in the FIR under a certain altitude.

In many places, the sectors follow a unique naming scheme that can make it hard to determine what area the controller is responsible for on first glance. Examples include:

• CHI_35_CTR.
• BN-TRT_CTR
• LPPO_T_CTR.
• NZCH-A_CTR.
• WSSS_F_APP.
• NY_CAM_DEP.
• SOLENT_APP.
• SY-RIS_APP.

Who to contact?
When approaching controlled airspace, and there are multiple sectors online, it is easy to get confused which sector you should contact. With some sector ID's, you may be able to work it out yourself (Such as I'm coming in from the west, I should contact ICAO_W_CTR), but with other Sector ID's, you may need to either;

• Check the relevant FIR/ARTCC/VACC's website, and look for detailed material and an explanation of sectors and their responsibilities. They should be easy to find under 'Airspace Maps' or 'Sector Diagrams'.
• Check the Controller Info and look for any information that may assist, such as 'Heathrow Director', 'Covering West of Los Angeles', or 'Covering Newark Arrivals Only'.) These descriptions are often the most accurate and painless way to find the correct sector for you.
• Ask the Controller! If worst comes to worst, and you have no idea who to contact, simply take your best guess, and call with your position. If you're wrong, the controller should advise who the correct controller is. If you're right, note it down. You never know when you'll need it. This is not recommended during periods of extreme traffic, however, and should only be used as a last resort.

If there is only one controller online however, it is likely that they will be covering the entire TMA or FIR, rather than the sector in their call sign. So, MEM_05_CTR would cover all of the KZME airspace, as opposed to just the '05' Sector.

Advanced: FSS (Flight Service Station)
Flight Service Station is another controller you're likely to see online. For a complete explanation on this position, see Flight Service Station

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