Features December 2015 Issue
Radar Contact: Dealing with Air Traffic Control Without A Transponder
Losing your transponder mid-flight isn't the end of the world, or your trip. Thanks to some ATC workarounds, no squawk is usually no problem.
There are two types of radar used in air traffic control: primary and secondary. Primary is commonly referred to as “skin paint.” Radio waves shoot out from a rotating radar antenna, bounce off the “skin” of whatever they hit, and return to the antenna. These only determine a target’s location via its range and bearing from the antenna. The distance that location changes in the time between antenna sweeps is used to calculate its speed.