Radar Contact: Dealing with Air Traffic Control Without A Transponder

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 targets 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.

Key Takeaways:

• Even with a failed transponder, Air Traffic Control (ATC) can still provide IFR service by relying on primary radar ("skin paint") and employing "back to basics" identification techniques.
• ATC uses multiple methods to identify aircraft without transponders, such as coordination with control towers for departing flights, pilot-provided position reports, and instructing pilots to execute identifying turns.
• Once identified, the flight requires increased manual coordination: pilots must verbally report all altitude changes, and ATC sectors perform verbal handoffs instead of automated ones, making the flight more labor-intensive but still feasible.

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