Decoding squawk codes


#1

What do the gurus recommend I use to decode squawk codes on my windows machine? I want to use the output from virtualradar and decode the squawk codes.


#2

Using the word “decode” is a little misleading. Squawk codes do not really “encode” anything other than providing ATC with an arbitrary and temporary identifier, or the VFR/emergency status of the flight if not being tracked.


#3

Thank you. I am assuming that these random codes do transmit some information about the state of the aircraft, or am I completely off?


#4

If the plane is on a flight plan or talking to ATC (air traffic control), then they will be told to squawk a unique code that is not being used by any other planes in that sector. The specific value of the squawk code is mostly meaningless. A plane will probably not get the same squawk code even if they repeated the same flight, since it is just the next available code at the time. For allocation purposes, there are blocks of numbers given for local flights or longer-distance flights. A flight sometimes may be required to change squawk codes as they are passed between controllers, or the flight gets additional clearance ahead, or if the old squawk code was already in use by another plane in the sector it is about to fly into.

When the plane is flying VFR and not talking to ATC, then it will generally just be squawking the standard code 1200. There are other values in the case of an emergency, radio failure, or hijack but those conditions don’t happen very frequently.

There are some official assignments for special meanings, but in general those meanings were just bureaucratic decision making with overly optimistic intentions that don’t get used outside of a very small district. https://en.wikipedia.org/wiki/Transponder_(aeronautics)#Code_assignments