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Mode S Transponder and ADS-B relationship

Asked by: 925 views Aircraft Systems, Commercial Pilot, FAA Regulations, Flight Instructor, General Aviation, Instrument Rating

Mode S transponder is basically a equipment that does the work of Mode C + TCAS(TA+RA) and what I have learned on ADS-B is that the ADS-B out and in is broadcasted and received through UAT antenna. I also noticed that the aircraft must be equipped with WAAS or suitable GPS to get information about position, ground track, speed to broadcast them through UAT.

Now, my question is that, Mode S being able to do the TCAS, does it have any linkage between ADS-B?

Does ADS-B need Mode S transponder in order to broadcast its information and receive nearby traffics ?


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2 Answers

  1. Kris Kortokrax on Jul 31, 2016

    A mode S transponder does not “do the work of Mode C + TCAS.”

    You can satisfy your curiosity by referring to AC 20-131A (which describes TCAS and Mode S transponders), AC 20-165B (which describes ADS-B), AC 91-114A (ADS-B Operations) and AC-120-55C (which discusses TCAS II).

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  2. Best Answer

    John D Collins on Jul 31, 2016

    Mode S is a type of transponder that supports selective addressing of the transponder. The S comes from the word Selective. ADS-B is based on two technologies, UAT and 1090ES. UAT is an independent system that uses the frequency of 978 MHz. 1090ES is an extension of the mode S transponder that supports ADS-B Out on 1090 MHz.

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