Whats a squawk code?? and how does it work

Question

and can someone give me a list of all of them that are used in the US please

Answer 1

Brandon your request for all codes is suspicious but since you've been a member for awhile I will err on trust.

What you are talking about is IFF,  'Identification Friend or Foe'  This was a means ot ground based and aircraft based transponders automatically corresponding to identify this was friend or foe..  It progressed to Radar's using it for position information but that's not your question.

An aircraft will be assigned a code to identify it in any anonymous group of other aircraft.  Squawk has been used for decades maybe because it you pull a ducks tail it will Squawk!  Ducks are the best navigators in fowl weather

Answer 2

A squawk code is a code put into a unit called a "transponder" which is part of the secondary surveillance radar (SSR) system. ATC issues you this code and enters the relevant data for your aircraft into their radar system so they can see your aircraft as more than just a blip on their radar.

The actual working of the transponder system is simple. The SSR transmitter continuously broadcasts an interrogation signal, when your aircraft receives that signal it replies with its transponder code (plus any other information encoded into it, frequently altitude readout).

You can see the list of non-discrete codes issued by ATC at http://www.faa.gov/airports_airtraffic/a...

Answer 3

It is a "radar transponder" code.  --Not an "ATC transponder" code.

Answer 4

I'll go just a bit further on this...

The ATC interrogation is on a frequency of 1030 MHz, and is two pulses spaced 8 uS (microseconds) apart. Alticoder interrogation pulses are spaced 21 uS apart.

That aircraft transponder sends back the reply signal at 1090MHz, which consists of accurately spaced information pulses between two framing pulses (reply train). The reply train framing pulses are spaced 20.3 us apart. Information (reply) pulses are spaced in between the framing pulses.

There are 12 reply pulses consisting A1, A2, A4, B1, B2, B4, C1, C2, C4, D1, D2, D4. The pulses are selected by the transponder squawk code that is dialed in. For instance, as mentioned above, code 7600 would use reply pulses A1, A2, A4, B2 & B4. If you add those numbers up, it gives you 7 for the A code and 6 for the B code. The C and D codes are zero since no pulses are used. Tada, 7600 is replied to the ATC.

For the alticoder, The D1 and D2 pulses are not used, and the D4 pulse is used only above 30,800 feet. The other codes are used to denote the altitude you are at. We call this the gray code, and any number of pulses are used at different altitudes for every 100' change.

If the emergency code (7700) is selected, the A1, A2, A4, B1, B2, B4 are used, followed by three extra sets of framing pulses with no reply

pulses inside them.

There is one extra pulse (x pulse) that can be used, but it is for

military drones. It would set between the A4 and B1 pulse.

Not that you aren't confused enough, but the codes are not laid out in

the reply train as written above. We used to look at the reply on an

oscilloscope in the shop to make sure all codes were there. A complete reply train for code 7777 would consist of:

Framing pulse,C1,A1,C2,A2,C4,A4,B1,D1,B2,D2,B4,D... Pulse.

IFF was one of my favorite systems to work in the shop. Most technicians hated it, mostly because of the I.F. bandpass alignment.

I've never heard of 4000 as being a military code, but it may be. The military has modes 1 and 2 to use for other applications. Our Mode 3a is the same as a civilian transponder, and Mode C is the alticoder.

Answer 5

Air Traffic Control (ATC) has two types of radar, primary and secondary.  Primary radar is basic radar and does not require special instruments in the aircraft.  Secondary radar requires that aircraft have a transponder to be seen.  The transponder communicates with the radar system.  A code that it put in the transponder of an airplane so Air Traffic Control can positively identify them.  1200 is the standard VFR code that is used when not talking to ATC.  When a plane contacts ATC they will assign a squawk code to identify the plane.  This code is four digits and can be any combination of numbers from 1 to 7.  

So your list would be 1111, 1211, 1311, 7117, 1753, 7145, 1574 etc.  4 digits of 1-7.  

Answer 6

Squawk codes are used to identify aircraft through their transponder to Air Traffic Control ATC through passive radar. The transponder sends a signal when interrogated by passive radar from ATC. This signal is the squawk code. (the transponder may send more information that is not related to squawk code also depended on what mode transponder and altimeter is installed.) The squawk code consists of a 4 digit code each digit having the range of 1-7.

Commonly used codes include

Any code the ATC may assign besides 7777 which is never used.

7700

Emergency in flight

7600

Communication Failure

7500

Hijacking

1200

This code is used during Visual flight rules when no other code has been designated



      

Answer 7

There are actually quite a few other reserved transponder squalk codes. For example, 4000 is reserved for military use.

1201-1204 are sometimes used to indicate an aircraft that is flying VFR on a particular route. For example, if there is a VFR flyway through congested airspace, you may be required to squalk 1204 to indicate to controllers that you aren't an intruder and intend to remain in the flyway. (Essentially, the flyway is class Bravo with a special exception.)

In Pheonix, there was (is?) a special agreement (called Sharp Echo) between news organizations and ATC to allow them to fly their helicopters, without communicating with ATC, in what was otherwise class B. A special squalk code was assigned to indicate to controllers that the aircraft was aware of the agreement and intended to stay at the permitted altitudes.

There are quite a few examples of such special codes.

Answer 8

A fairly good response here from many other contributors on the basics of the transponder and it's interrogation by ATC radar. I might just add that Mode "S" which no one has mentioned also further identifies the aircraft from which the squawk code is received assigned or generic. Any aircraft operated in controlled airspace is first issued a discreet code prior to clearance into the airspace. The transponder must always be on when the aircraft is airborne unless requested by ATC. This electronic reply to interrogation is also used in technology for on-board traffic warning devices. Many aircraft today still operate without radios, transponders or other hardwired equipment but they can only fly into controlled airspace with prior approval of a route and destination by the controlling agency. There are of course provisions for continued flight in the event of equipment failure.

Answer 9

Most airplanes are fitted with a device called an ATC Transponder, which detects the radar beam from an airport or enroute surveillance radar station.  When the transponder picks up the beam, it sends out a 4-digit code number in the form of a radio signal carrying the code number as a digital number.  Most transponders are also connected to an "encoding altimeter," and can send the airplane's altitude as well as the 4-digit code.

Sending out this code is called "squawking," so the code is called a "squawk code."

The pilot of the airplane can enter the 4-digit code through the dials on the front of the transponder, which is mounted in the airplane's instrument panel.  Whenever you contact Air Traffic Control (ATC) you will be assigned a squawk code by the controller.

There are certain standard codes; for example, the code 1200 means "I am flying visually on my own and not calling on ATC services."  Pilots call this "squawking a dozen."

There are other codes that mean, "My radios aren't working" or "I have been hijacked."  Aside from those few, there really isn't a list.  A squawk code can be any four digits in the range 0-7.

A computer connected to the ATC controller's radar console picks up the codes and displays associated information on the radar screen so that it follows the airplane around on the screen.  This gives the controller much clearer information than just the "blip" on the screen that they had with the older radar equipment.

For much more information including pictures, tables, and diagrams, try an internet search on "ATC transponder" or "squawk codes."