Mandate 2020, ADS-B: Laying the Groundwork for A.I. in the Sky
As it stands right now all aircraft are tracked via radar. Most aircraft are equipped with a special radio (called a transponder) that transmits a 4 digit code, called mode ‘A’ for civilian flight or mode ‘3’ for military flights (this is called ‘squawking’). The air traffic controller assigns the code he or she wants the flight crew to squawk. It is this code is what helps air traffic control track that particular aircraft on their radar displays. The code can change as the plane gets handed off from one air traffic authority to the next one along their route. In most cases aircraft will also send out a different 4 digit code for their altitude (this is called mode ‘C’). These 4 digit codes (called replies) are sent out when the transponder receives a special signal (called an interrogation) from, what is called ‘secondary radar’, primary radar being the radar that actually tracks the airplane (you know that blip on the screen). Eventually a new mode was added, called mode ‘Select...