ENR 1.6  ATS Surveillance Services and Procedures

1   CIVIL

1.1   Transponder requirement

The carriage and operation of Mode S transponders with basic functionality is mandatory in the Brussels FIR/UIR for all aircraft operating:

  • in civil class C airspace;
  • in civil class D airspace;
  • in class G airspace for VFR flights at night.

The carriage and operation of a serviceable transponder - capable of replying to Mode A and C interrogations - is mandatory in the Brussels FIR/UIR for all aircraft operating in military controlled airspace.

An exemption to these rules may be granted, provided that the request is made before the flight, to the authority having jurisdiction over the airspace concerned.

Note: Pilots are reminded about the importance of having a well-functioning transponder to be switched on in the Belgian part of the Brussels FIR/UIR; ATC is allowed when possible to refuse aircraft without a well-functioning one.

1.2   Standard SSR Operating Procedures

Except when encountering a state of emergency, pilots shall operate transponders and select modes and codes in accordance with ATC instructions. In particular, when entering the Brussels FIR, pilots who have already received specific instructions from ATC concerning the setting of the transponder shall maintain that setting until otherwise instructed.

IFR flights about to enter the Brussels FIR that have not received specific instructions from ATC concerning the setting of the transponder shall operate the transponder on Mode A and C, Code 2000 before entry and maintain that code setting until otherwise instructed.

In order to improve radar detection of non-controlled flights, VFR flights in the Brussels FIR shall select Mode A and C, Code 7000, unless otherwise instructed.

In accordance with ICAO Doc 8168 (PANS-OPS). Volume I, Part II, Section 3, chapter 1.3, the flight crew of aircraft equipped with Mode S transponders shall set the aircraft identification in the transponder. This setting shall correspond to the aircraft identification specified in item 7 of the ICAO flight plan, or if no flight plan has been filed, the aircraft registration. in order to be interpreted properly, there must be no spaces between the designator letters and flight number, nor any additional/superfluous zeros preceding the flight number. In case the aircraft identification can be entered manually, entry should be part of the start-up procedures.

Correct setting of aircraft identification is essential for identification and correlation (of radar track with flight plan data). An incorrect setting of the aircraft identification will be reported to the Belgian Civil Aviation Authority.

Note 1: For Mode S transponder ground operation at EBBR, see EBBR AD 2.20, § 1.4.

Note 2: For Mode S transponder ground operation at ELLX, see ELLX AD 2.20, § 1.1.

1.3   Emergency Procedure

If the pilot of an aircraft encountering a state of emergency has previously been directed by ATC to operate the transponder on a specific code, this code setting shall be maintained until otherwise advised.

In all other circumstances, the transponder shall be set to Mode A and C, Code 7700. Notwithstanding the standard procedure (see above), a pilot may select Mode A and C, Code 7700 whenever the nature of the emergency is such that this appears to be the most suitable course of action.

Pilots of aircraft in flight subjected to unlawful interference shall endeavour to set the transponder to Mode A and C, Code 7500 to make the situation known, unless circumstances warrant the use of Code 7700.

Note: Continuous monitoring of responses on Mode A and C, Code 7500 and 7700 is provided.

1.4   Radio Communication Failure Procedure

In the event of an aircraft radio receiver failure, Mode A and C, Code 7600 shall be selected and established procedures followed. Subsequent control of the aircraft will be based on those procedures.

Note: Continuous monitoring of response on Mode A and C, Code 7600 is provided.

1.5   Transponder Failure
1.5.1   Failure Before Intended Departure

If the transponder fails before intended departure and cannot be repaired, pilot shall:

  • inform ATS as soon as possible, preferably before the submission of a flight plan;
  • plan to proceed, as directly as possible, to the nearest suitable aerodrome where repair can be made;
  • insert in item 10 of the ICAO flight plan form under “SSR” the letter “N” for complete unserviceability of the transponder or, in the case of partial failure, the letter corresponding to the remaining transponder capability.
1.5.2   Failure After Departure

If the transponder fails after departure, pilots may expect that ATC units will endeavour to provide services for continuation of the flight to the aerodrome of first intended landing in accordance with the flight plan. After landing, pilots shall make every effort to have the transponder restored to normal operation. If repair cannot be effected, pilots shall comply with the provisions described in § 1.5.1 above.

1.6   System of SSR Code Assignment
1.6.1   In Belgium

Codes will be assigned in accordance with the SSR code allocation list for the ICAO EUR Region, which is based on the Originating Region Code Assignment Method (ORCAM).

Codes protected for international transit, transit codes, which are assigned to overflying or inbound flights, will be retained by ATC.

Code 1000 will be assigned or retained to indicate an eligible (flagged by the IFPS) IFR flight, where the downlinked aircraft identification is validated as matching the aircraft identification entered in the flight plan.

Departing International IFR Flights
0101 - 0117departing traffic
7101 - 7167departing traffic
4401 - 4427departing traffic inbound the United Kingdom, the Netherlands, Ireland, Greenland, Iceland, Canada or the United States, and departing traffic re-entering Belgium.
1000eligible (flagged by the IFPS) departing traffic
Domestic Flights
4450 - 4457codes assigned by Brussels ACC/APP
5101 - 5167codes assigned by Brussels APP
6301 - 6313codes assigned by Brussels TWR
6314 - 6327codes assigned by Charleroi TWR/APP
6330 - 6343codes assigned by Liège TWR/APP
6344 - 6361codes assigned by Oostende TWR/APP
6362 - 6377codes assigned by Antwerpen TWR
VFR Flights
0041 - 0057codes assigned by Brussels INFO
1.6.2   In Luxembourg
Departing International IFR Flights
3501 - 3507Departing traffic
5650 - 5657Departing traffic
7170 - 7177Departing traffic
7570 - 7577Departing traffic
Flights remaining in Luxembourg TMA below FL 165
and solely controlled by Luxembourg APP
4460 - 4464Codes assigned by Luxembourg APP
VFR Flights
4465 - 4467Codes assigned by Luxembourg APP/TWR
4470 - 4477Codes assigned by Luxembourg APP/TWR

2   MILITARY

2.1   General

ATS units and Air Defence Stations use SSR for identification and automatic tracking of aircraft.

The carriage of a serviceable transponder capable of replying to Mode A and C is compulsory for all aircraft operating in all military controlled airspace. An exemption to this rule may be granted, provided that the request is made before the flight to the authority having jurisdiction over the airspace concerned. Aircraft flying OAT within the Brussels FIR/UIR must have a serviceable SSR transponder.

The carriage of a serviceable Mode S (ELS or EHS) SSR transponder is highly recommended but not yet compulsory for State aircraft flying OAT within the Brussels FIR/UIR including low level VFR flights. State aircraft flying GAT within the Brussels FIR/UIR shall comply with the regulation for the carriage and operation of SSR mode S airborne equipment published in the AIP and/or related AIC.

Flights with a wrong Mode S ACID will be instructed by ATC to correct this. Flight limitations may be imposed until the ACID is correct (e.g. not leaving the CTR or TMA).

2.2   SSR Mode

Aircraft flying OAT within the Brussels FIR/UIR shall squawk:

Mode 1as instructed by the appropriate NATO authority
Mode 2always activated unless instructed otherwise
Mode 3/Aas instructed by the controlling agency
Mode Calways activated unless instructed otherwise
Mode SOnly mandatory for declared Mode S capable Belgian military aircraft. Mode S ACID must exactly match the ACID as entered in item 7 of the FPL (See ENR 1.10, § 2.3.1.1)

Note: In a formation flight, only one aircraft shall squawk as mentioned above, the other aircraft shall squawk “stand-by”.

Note: Mode 4 is forbidden.

2.3   SSR Mode 3 Code Allocation

Domestic Flights
1401 - 1477Semmerzake ATCC
2601 - 2627Cross-border to EH/ED
5401 - 5417Koksijde/HELI
5420 - 5427UAV
5430 - 5477SF260M
6001 - 6077Glons CRC
6401 - 6477Semmerzake ATCC
Local Flights
4201 - 4207Chièvres
4210 - 4227Beauvechain
4230 - 4247Kleine-Brogel
4250 - 4267Florennes
4270 - 4277Koksijde
Special Codes
A1000conspicuity code applicable to civil city pair aircraft, forbidden for OAT fligths.
A7000 + Cuncontrolled flights, which have not received an instruction concerning the setting of their transponder
A7500unlawful interference
A7600radio communication failure
A7700emergency (unless instructed otherwise by the controlling agency)
2.4   Radio Communication Failure
2.4.1   Receiver Failure

The pilot shall transmit reports at the scheduled times or positions, preceded by “transmitting in the blind due to receiver failure”. These reports should include his intentions and the time of his next intended transmission.

2.4.2   Receiver and Transmitter Failure
2.4.2.1   VFR
  • Squawk A7600, and
  • Maintain VMC, and
  • Land at the nearest suitable aerodrome, and
  • Report his arrival by the most expeditious means to the appropriate ATC unit.
2.4.2.2   IFR
  • Squawk A7600, and
  • Proceed according to flight plan and hold over the last navaid, and
  • Commence a descent from this navaid as close as possible to the last acknowledged EAT or the flight plan EAT, and
  • Complete the normal instrument approach procedure and land, if possible within 30 MIN of EAT (last acknowledged or flight plan).

If the pilot is established on a published ATS route, he shall maintain the last assigned speed and level for a period of 7 MIN. After this period, he shall adjust to the level in accordance with the flight plan. If the pilot is established on a published ATS route but he was receiving radar vectors or he was proceeding offset, the pilot shall proceed in the most direct manner possible to rejoin the current flight plan route.

If the pilot has been given level clearances for only a part of the route, he shall fly this level to the point specified in the clearance and then the cruising level of the flight plan. Departing aircraft shall fly the level they are cleared to for 3 MIN and then fly the cruising level of their flight plan.

2.4.3   Transmitter (and Receiver) Failure and SSR inoperative

The pilot may or, if transponder is inoperative, shall fly triangles of 1 MIN legs (TAS higher than 300 KT) or 2 MIN legs (TAS equal or less than 300 KT) clockwise if his receiver still works, anti-clockwise if the radio receiver and transmitter are both out of service. He can expect to be intercepted by a shepherd aircraft.