Types of controller in air traffic control system

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Air Traffic Control System

1.1. Overview

The air traffic control system (ATC), a part of the airspace system, has a responsibility to manage the complex mixture of air traffic from general, commercial, corporate and military aviation [Futureatc]. Air traffic control system is a name of service which provides guideline to aircraft, prevents collision and manages secure and orderly traffic flow. It is a vast network consisting of equipment and people, which ensure the safe operation of aircrafts [6].

Every service which is offered by ATC system has two main objectives, the first one is to avoid the aircraft collision and second one is to maximize the effectiveness of the system, so that safe journey of the aircraft can be made possible without any delays [7]. The term collision refers to both mid-air and ground collision. The effectiveness of a system means the departure and landing of any aircraft without any collision.

The core part of ATC system is an air traffic controller. Air traffic controllers coordinate the movement of air traffic to make certain that planes stay a safe distance apart. Their immediate concern is safety but controllers also direct planes efficiently to minimize delays. There are number of aircrafts which needs the supervision of the air traffic control system, for example, small private, military, large commercial aircrafts etc. ATC system provides verity of service to aircraft like weather updates, flight profile information, emergency relief services and navigational etc. ATC is a system in which services are continuously provided to aircrafts by the ground-based controllers [9].

The ATC system is a very complex and large domain and it is difficult to model the whole ATC system. We modeled the controllers of ATC system. These controllers guide the aircraft before takeoff and after landing. For the purpose, we divide the task into four controllers, gate, ramp, ground and local controllers.

1.2. Controller

It is responsibility of air traffic controller to make safe travel from take off to landing. The air traffic controller is highly skilled, qualified and experienced person who keeps track of planes flying within their assigned area and make certain that they are at safe distances apart. An air traffic controller collaborates with other controllers to hand off an aircraft which has safely flown within controlled airspace. After successfully hand off the aircraft communicates with other airspace controller.

The primary objective of ATC system is the safety of aircrafts and its passenger. To ensure the safety we must satisfy that there is no conflicting situation in any stage of the aircraft departure and arrival procedure. The air traffic controllers play important role to avoiding the collision of aircrafts. Controllers in all types of air traffic control facilities develop strategic plans for traffic flow, monitor theses plans with visual inputs to update their "big picture" of the traffic flow. And communicate heavily with aircrafts and other controllers to ensure continued safety and efficiency [Futureatc].

1.2.1. Gate Controller

The gate controller is the first object that controls the aircraft when aircraft is departuring and the last object when aircraft is arriving. The gate controller is responsible for the following activities.

At departure time it

* assigns gate to aircraft

* makes the availability of gate and

· grants pushback clearance.

At arrival time it

* assigns gate to aircraft

* makes the availability of gate and

* allows to pass from the gate.

1.2.2. Ramp Controller

The center point for the efficient, safe and expeditious movement on ground of aircraft ingress and egress within the confines of the ramp. It serves as liaison between the airport operations staff, tenants and the federal aviation administration.

At departure time it

* provides clearance for ramp and

* sequencing at ramp.

At arrival time it

* provides clearance for ramp and

* sequencing at ramp

1.2.3. Ground Controller

The ground controller is responsible for the ground movement of aircraft, taxiing or vehicles operating on taxiways or inactive runways. The ground controller can issue clearances only to those aircraft and vehicles, which are under its control.

Runway incursion prevention is a primary responsibility of the ground controller. Runway incursion means that occurrence of anything at an aerodrome, for example, invalid presence of vehicle, aircraft or person on protected area of surface which is specified for landing and takeoff of aircraft. More than 400 runway incursions are recorded in 2002. For issuing a clearance to an aircraft or vehicle to cross an active runway, the ground controller must first gain permission from the local controller responsible for that runway [10]. The ground controller has the following activities.

At departure time it

* provides departure information to aircraft

* assigns runway with the help of local controller to aircraft

* issues taxi clearance and

* arranges departure queue.

At arrival time it

* issues taxi clearance

* arranges arrival queue and

* grants permission to enter taxiway.

1.2.4. Local Controller

The one major responsibility of the local controller is to provide separation between arriving and departing aircraft. Another major responsibility of the local controller is to safely sequence arrivals and departures. This controller also relays instrument flight rules clearances and taxi instructions. The local controller also issues takeoff and landing clearances and provides assistance to other flights flying through their local area [10]. The local controller informs the pilot about conditions at the airport, such as weather, speed and direction of wind, and visibility. The local controller also issues runway clearance for the pilot to take off. It has the following activities.

At departure time it

* gives permission to ground controller to assign runway to aircraft

* selects for departure

* grants departure clearance

* provides instruction in emergency situations and

* gives recovery instructions.

At arrival time it

* assigns runway

* makes the availability of runway

· grants permission for landing and

· informs about emergencies.

Clearance Delivery Controller: The clearance delivery controller is one, which is subpart of the local controller. It is responsible for obtaining and relaying departure clearances to pilots [10]. Here we are not considering it as different controller, therefore we assume that local controller does these all activities. The clearance delivery controller checks to see that the route indicated for the flight requested conforms to established preferential routes. If there are departure restrictions that would supercede the requested clearance, then the clearance delivery controller may temporarily amend the clearance [10].

1.3. Aircraft

The primary component of the air traffic control system is aircraft. An aircraft is a vehicle, which is able to fly by being supported by the air [15]. The helicopters commercial, airbus military aviation, private aero plane, and special purpose general avionics all belongs to category of aircraft. Depending on the type of aircraft its speed and altitude limitation are different. Aircraft can communicate with air traffic controller with its unique identifier called call sign. The aircraft perform the following activities.

At departure time it

* requests to assign gate to gate controller

* requests to push back clearance to gate controller

* push backs to enter ramp area

* requests to leave ramp

* leaves ramp area to enter taxiway

* requests to taxi clearance

* taxing

* enters at runway

* requests for departure clearance

* makes departure

* deviates from the departure (departure is canceled)

* recovers original track and

* finally makes depart.

At arrival time it

* requests for assign runway

* requests for landing

* starts landing

* deviates from the landing (landing is canceled)

* recovers plan

* requests for taxi clearance

* enters at taxiway

* requests to enter ramp

* enters at ramp

* requests for gate assignment

* passes through gate and

* finally arrived.

1.3.1. Ramp Areas

Ramp is that place at the airport where different activities are performs on aircraft like loading and unloading of baggage, aircraft push back and towing, a mail and cargo services, aircraft marshaling. Aircraft services are also provided here like fuel facility maintenance, cabin cleaning and deicing.

1.3.2. Taxiway

A taxiway is a path on an airport connecting runways with ramps, hangars, terminals and other facilities. They mostly have hard surface such as asphalt or concrete, although smaller airports sometimes use gravel or grass [15].

1.3.3. Taxiing

Taxiing refers to the movement of an aircraft on the ground, under its own power. The aircraft usually moves on wheels, but the term also includes aircraft with floats. On the other hand, taxiing is the controlled movement of the airplane under its own power while on the ground [31].

1.3.4. Runway

A runway is a strip of land at an airport on which aircraft can take off and land and forms part of the maneuvering area. Runways may be a manmade surface (often asphalt, concrete, or a mixture of both) or a natural surface (grass, dirt, or gravel) [13].