PPRuNe Forums - Mode S Transponder

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Danial9874

28th June 2025 16:41

Mode S Transponder

Hello guys, I know that the Mode S is a secondary surveillance and communication system which supports Air Traffic Control (ATC). Each Mode S transponder equipped aircraft is assigned a unique address code. Using this unique code, interrogations can be directed to a particular aircraft and replies can be unambiguously identified. But, who provide/ allocate the Mode S codes to aircraft ? ICAO ? National Airworthiness Authority ?

EXDAC

28th June 2025 17:02

https://www.icao.int/WACAF/Documents...Assignment.pdf

DaveReidUK

28th June 2025 18:57

Quote:

Originally Posted by Danial9874 (Post 11912563)

But, who provide/ allocate the Mode S codes to aircraft ? ICAO ? National Airworthiness Authority ?

Both.

ICAO allocates a range of addresses to each country. The country's NCAA (or equivalent) assigns addresses to individual aircraft.

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