squawk code

[Chananya Freedman]

Hello there. 

Can somebody please explain to me what a "squawk code" is and what its purpose is.  For example, on a clearance frequency, I would hear "Expect flight level 230 10 minutes after departure;  departure frequency 124.6 squawk 4640."  Can somebody explain to me what the end of that quote means?  for some reason, I think that the numbers equal a beacon frequency, but I do not see a decimal point.  Can someone clear up my confusion?  thanks,

Chananya

[delta092b]

Squawk code is unique  transponder code assisgned to the aircraft that identifies it on the controllers Radar systems. You will sometimes here "squawk with ident" which will then flash/glow/highlight the aircraft on the controllers screen (useful when there are lots of aircraft).

It can also be used to help in emergency situations as the aircraft can squawk emergency codes to indicate general emergencies, hijacking, loss of radio etc.

[Chananya Freedman]

what is the initial squawk?  Is that like a beacon frequency.  If so, why no decimal?

Chananya

[pgarside]

A squack code is any four didgit number which a pilot enters into the airplanes transponder.  There is no decimal because it is not a frequency, but simply a code which helps atc keep track of information about that particular plane.  Every time there is a flight plan filed, there must be a transponder code along with it, which is unique to that airplane (except for most airplanes flying under visual flight rules, because they will all most always be squacking 1200 in the United States).

Wikipedia has a good article on transponder codes which i found, along with a good picture of a transponder (although the picture seems to be of an older model cessna)

http://en.wikipedia.org/wiki/Transponder_(aviation)

[Casper87]

Squawk codes shown on a radar screen. A couple are code-callsign converted, the rest arent.

[JALTO]

What type of technology or process is involved  on ATC's end when a pilot is assigned a code while in flight.  I've noticed when someone requests flight following ATC is able to assign a code without hesitation.  Is there a majic hat of flight numbers right next to them

Jalto

[KSYR-pjr]

This subject reminded me of a brief, educational exchange I heard on a NY airspace frequency last week. 

I found the exchange in the archives and posted the clip to this thread in the Audio Clips forum.

[Casper87]

JALTO,

Not sure about the US (but I can only assume its similar) but in the UK there is a published list of squawk codes and their relevant uses and the agencies which use them.
I.e Cardiff Radar use a block between 3601 and 3643, and 3646-3657

[djmodifyd]

we have different blocks of codes
0401-77 is for local ifr
0331 is local vfr departure...and 0301-30 is for local popup vfr (departure would be departing from the airport...popup would be somewhere in our airspace such as from a satellite airport)


if someone calls up..such as "cessna 12345 is with you 30n, would like vfr flight following to XXX"
i just have to type in S345 then hit enter...and the computer pops up a code...

that is how we are able to basically just spit out a code so quickly...since we just have to type in those 4 letters then hit enter.