Squawk Codes
General
SSR codes fall into two groups; discrete and non-discrete. These groupings are a function of the ground radar/flight data processing system rather than the SSR system itself.
A non-discrete code is any code ending in '00' (e.g. 2000). Non-discrete codes may be used ('squawked') by more than one aircraft at a time and some non-discrete codes are allocated as general codes to certain classes of operation. For example, the standard SSR code for VFR aircraft in Australia is 1200 (formerly 2000). Some non-discrete codes are also allocated for emergency use; for example, 7700 denotes 'Mayday' and 7600 'Radio Failure'.
A discrete code, in contrast, is one which may only be assigned to a single aircraft at a time (codes may be re-used when no longer required by the original user). Any code not ending in '00' is considered non-discrete. As an aside, modern flight data processing systems may actually allow the simultaneous use of the same discrete code in certain circumstances.
In Australia for many years all high-capacity Regular Public Transport aircraft were allocated a 'skin' code. This was a discrete code allocated to the individual aircraft hull. The aircraft's transponder therefore never needed to be changed while the aircraft was operating in Australian airspace. This simple system was too difficult for the new TAAATS equipment, so it was discontinued from 1998.
Code |
Assignment |
|
| 0000 |
SSR data unreliable |
| 0001-0017 |
Air Ambulance Emergency Medivac - Helicopter |
| 0020-0027 |
Air Ambulance Emergency Medivac |
| 0030-0037 |
Radar Flight Evaluation / Sector Calibration |
| 0040-0057 |
MET research flight |
| 0060-0077 |
Aircraft Paradropping |
| 0100-0177 |
Royal Flights |
| 0200-0277 |
Royal Flights - Helicopter |
| 0300-0777 |
Not allocated yet |
|
| 1000 |
NATO Fighter Ops. |
| 1001-1077 |
Not allocated yet |
| 1100 |
NATO Fighter Ops. |
| 1101-1177 |
Not allocated yet |
| 1200 |
Standard VFR in Australia,US. - In Europe Standard VFR is 7000 or 2000 - (Standard FS Squawk) |
| 1201-1777 |
Not allocated yet |
|
| 2000 |
Standard VFR in Europe - In US. standard VFR code is 1200 |
| 2001-2777 |
IFR Flights in Australia - VFR Flights in Europe |
|
| 3000 |
NATO Fighter Ops. |
| 3001-3777 |
Not allocated yet |
|
| 4000 |
NATO Fighter Ops. |
| 4001-4777 |
Not allocated yet |
|
| 5000 |
NATO Fighter Ops. |
| 5001-5777 |
Not allocated yet |
|
| 6000 |
NATO Fighter Ops. |
| 6001-6777 |
Not allocated yet |
|
| 7000 |
Standard VFR in Europe - In US. standard VFR code is 1200 |
| 7001-7017 |
Aerobactic flights |
| 7020-7037 |
Police Flights |
| 7040-7477 |
VFR flights |
| 7500 |
Hi-Jacking |
| 7501-7527 |
Aircraft engaged in police air support operations |
| 7530-7557 |
Aircraft engaged in police air support operations - Helicopters |
| 7600 |
Radio Failure |
| 7700 |
Emergency |
| 7701-7727 |
Aircraft engaged in actual SAR Operations |
| 7730-7757 |
Aircraft engaged in actual SAR Operations - Helicopters |
| 7760-7776 |
Ground Transponders Tests/Trials |
