Understanding Vatsim: Airport Control And Center Controllers

Virtual pilots on VATSIM (Virtual Air Traffic Simulation Network) can connect their flight simulators to a shared network and experience realistic communication and procedures with the help of VATSIM's trained virtual Air Traffic Controllers. The network, which was founded in 2001, has grown to become the largest online flight simulator community, with over 100,000 active users. In this community, the ATC (Air Traffic Control) works on a top-down principle, where a center controller oversees the airspace above a specific airport and provides ATC services to all towered airports within their jurisdiction. If a center controller is the only one online, pilots will need to request clearance from them, and the subsequent instructions will depend on whether the field is towered or untowered.

Center controllers are responsible for all airports in their area

However, it is important to note that center controllers may not always cover all airports in their area, as their areas of responsibility can vary. For example, a center controller responsible for a certain sector may only cover a few airports within that sector, while other airports within the same sector are considered uncontrolled and pilots will need to handle their own taxi and takeoff.

In some cases, such as with larger airports, center controllers may provide "top-down service", where they provide ATC services for the larger airports while smaller airports within their sector are considered uncontrolled. This can vary depending on the specific VATSIM division and their policies.

To determine whether a center controller oversees a particular airport, pilots can use resources such as map.vatsim.net or vatglasses.uk to verify the controller's area of responsibility. These tools can help pilots understand the specific airports and sectors controlled by a center controller and make informed decisions about their flight plans and communication with air traffic control.

If no controller is present, pilots go to Unicom

In the absence of air traffic control, pilots are required to ensure self-information in flight and on the ground. This is known as Traffic Information Broadcasts by Aircraft (TIBA) or self-announcing procedures. This is a mandatory procedure and is done through UNICOM (Universal Communications).

UNICOM is the VHF broadcast frequency, set to 122.800 MHz, which is selected to send TIBA, or self-announcing procedures for pilots. It is used to report aircraft positions and pilot intentions when no active and relevant air traffic controller is available and connected. Both voice and text can be used on UNICOM, and all messages must be in English.

UNICOM allows pilots to be informed of the presence of nearby aircraft movement and to know the intentions of each aircraft, whether on the ground or in flight. This is known as Situational Awareness. To achieve this, pilots must submit their intentions on UNICOM in advance, either by voice or text, so that everyone can correctly anticipate the actions of others.

In summary, UNICOM is a vital tool for pilots to maintain situational awareness and ensure safe operations when no air traffic controller is present.

The top-down principle: the next controller up will provide ATC services

The top-down principle is a fundamental concept in air traffic control (ATC). It dictates that the next controller up in the hierarchy will provide ATC services if the current controller is unavailable or unable to do so. This ensures a seamless and efficient flow of air traffic and helps maintain safety.

In the context of VATSIM (Virtual Air Traffic Simulation Network), the top-down principle is crucial for pilots to understand. If a pilot needs an IFR clearance and the only controller online is the center controller, the pilot should contact the center controller for their clearance. The subsequent steps depend on whether the field is towered or untowered. If it's a towered field, the center controller will also provide taxi, takeoff, and departure instructions. On the other hand, if it's an untowered field, the center controller will give an IFR release and switch the pilot to Unicom to handle taxi and takeoff, and then the pilot calls the center controller back once in the air.

The top-down principle also applies to the broader ATC system. For example, if a pilot is at an airport with no controller online, they should check the map to see if they are underneath Class B airspace or an approach frequency. If so, those controllers will provide the necessary clearances and instructions. If not, the pilot contacts the center controller, but only if the center's airspace covers the airport. If there is no controller available to provide clearances, the pilot will depart under uncontrolled conditions until they enter controlled airspace, at which point they can contact the appropriate controller.

It's important to note that the top-down principle is not solely based on proximity to a controller. Instead, it prioritises the next controller up in the hierarchy, ensuring a structured and organised approach to ATC services. This hierarchy includes positions such as ground, tower, departure/approach, and center controllers, each with their own specific responsibilities and areas of control.

By following the top-down principle, pilots can navigate the ATC system effectively, ensuring they receive the necessary clearances and instructions while also maintaining safety and adhering to standard procedures.

Pilots should check who's online above their departure airport

Pilots should always check who is online above their departure airport. This is because the ATC (Air Traffic Control) works on a top-down system, meaning that the highest-ranking controller will control everything below them.

Pilots should first check if a controller at their airport is online. If ground or clearance delivery frequency is online, they will be the pilot's first stop, and will get them their clearance even if no one else is online. If neither of these are online, or the airport is uncontrolled, pilots should then check the map. If the airport is underneath a Class B airspace, or relevant approach frequency, they will provide clearances and instructions. If there is no one available to give clearances, pilots will depart under uncontrolled conditions until they enter another airspace. Once they've entered an area of controlled airspace where a controller is online, they can then contact them and get their clearance en route.

In short, pilots should check to see who's online above their departure airport in the following order: Ground --> Tower --> Departure/Approach --> Center --> Uncontrolled.

VATSIM is a shared network for pilots to connect with Air Traffic Controllers

VATSIM, or Virtual Air Traffic Simulation Network, is an online flight simulation network that allows virtual pilots to connect their flight simulators to a shared network. It was founded in 2001 and has since built a community of over 100,000 active users, making it the largest online flight simulator community. VATSIM provides a realistic flying experience with communication and procedures handled by trained virtual Air Traffic Controllers.

The network operates on a top-down principle, where a center controller oversees all the airspace and airports within their jurisdiction. If a lower-level controller, such as a tower or ground controller, is not available at a specific airport, the center controller will take over and provide services for that airport. This ensures that pilots always have a point of contact for clearances and instructions, even if the airport is not directly controlled by a local controller.

However, it is important to note that not all airports are covered by VATSIM controllers. In some cases, pilots may find themselves in an uncontrolled airspace where they need to rely on Unicom for communication. This typically happens when there are no controllers available at the airport or in the surrounding area.

VATSIM's shared network provides a unique opportunity for pilots to experience realistic air traffic control and communicate with other pilots and controllers in a simulated environment. It offers a structured and organized approach to online flight simulation, enhancing the overall experience for users.

VATSIM's trained virtual Air Traffic Controllers play a crucial role in maintaining the realism and accuracy of the simulation. They handle various responsibilities, including providing clearances, taxi instructions, takeoff and departure instructions, and ensuring safe and efficient airspace management.

Frequently asked questions