Air Traffic Control

Raj Rohit Gottipolu Air traffic control: Air traffic control is the mechanism used for controlling and directing aircrafts on the ground and in the air. The ATC systems key purpose is to organize the flow of traffic so that any collisions of aircrafts can be prevented. Preventing Collisions: The approach used by ATC systems to prevent collisions is 'separation'. It is used for keeping an aircraft at a minimum distance from another to reduce the risk of collision. The security policy used for preventing collisions is called 'separation minima'. Pairs of aircraft which satisfy this policy are said to be separated. Separation is based on flight rules and class of airspace in which the aircraft is flying. Flight rules: There are three sets of flight rules under which an aircraft can be flown: 1. Visual flight rules (vfr): It is a set of regulations under which a pilot has to control aircraft's attitude, navigation and separation only by visual reference to the environment outside the cockpit. 2. Instrument flight rules (ifr):It is a set of regulations under which a pilot has to control the flight of an aircraft completely based on the aircraft instruments. 3. Special visual flight rules (svfr): Under these regulations, pilot has to fly the aircraft only in control zones. svfr is not used frequently and are considered similar to ifr. Classes of airspace: There are seven classes of airspace from A to G. Classes A to E come under controlled airspace, where ATC controls the separation between aircraft and classes F and G are uncontrolled airspace. All the aircraft are separated from each other in classes A and B. Class G doesn't need any aircraft to be separated. Separation of aircraft in rest of the classes depends on the flight rules. Types of separation: Separation is of two types. Vertical separation and Horizontal separation. Vertical separation: Any two aircraft must be separated by a minimum of 1000 feet vertically if they are flying between ground and a height of 29000 feet. Horizontal separation: If vertical separation doesn’t exist, there should be some horizontal separation. Horizontal separation is of many types. It includes:

Procedural separation, Lateral separation, Longitudinal separation, Radar separation and Reduced separation. Thus, the security policy used by ATC is flight rules and airspace and the security mechanism is to implement the separation between aircraft so that no collision will occur. Some aircraft will also have collision avoidance systems that act as a backup to ATC instructions.