1. Supplementary services
   A radar unit normally operates as an integral part of the parent ATS unit and provides radar service to aircraft to the maximum extent practicable, to meet the operational requirement. Many factors, such as radar coverage, controller workload and equipment capabilities, may affect these services, and the radar controller shall determine whether he is able to provide, or continue to provide radar services in each specific case.
   A pilot will know when radar services are provided by use of following phrases by a radar controller:

a. “... (call sign), radar contact ...”

b. “... (call sign), identified ...”

2. The application of radar control service
   Radar identification is achieved in accordance with the provisions specified by ICAO.
   A radar control service is provided in controlled airspaces to aircraft operating within the Riga TMA above 1500 FT MSL and along all AWYs above FL 095. This service may include:
3. 1. radar separation of arriving, departing and en-route traffic;
   2. radar monitoring of arriving, departing and en-route traffic to provide information on any significant deviation from the normal flight path;
   3. radar vectoring when required;
   4. assistance to aircraft in an emergency;
   5. assistance to aircraft crossing controlled airspace;
   6. warnings and position information on other aircraft considered to constitute a hazard;
   7. information to assist in the navigation of aircraft.

The minimum horizontal radar separations are:

1. 1. CTA and ATS routes: 5 NM between identified controlled aircraft in the same, opposite or crossing track, at the same level;
   2. TMA RIGA: 3 NM between identified controlled aircraft;
   3. 10 NM between identified and unidentified aircraft, in all cases.

Levels assigned by the radar controller to pilots will provide a minimum terrain clearance according to the phase of flight.

3. Radar and air-ground communication failure procedures
   Radar failure
   In the event of radar failure or loss of radar identification, the appropriate ATS unit shall establish: the longitudinal interval - 10 minutes and in the crossing airways - 10 minutes.
   Radio failure
   The radar controller will establish whether the aircraft radio receiver is working by instructing the pilot to carry out a turn or turns. If the turns are observed, the radar controller will continue to provide radar service to the aircraft.
   If the aircraft radio is completely unserviceable, the pilot should carry out the procedures for radio failure in accordance with ICAO provisions. If radar identification has already been established, the radar controller will vector other identified aircraft clear of its track until such time as the aircraft leaves radar coverage.
4. Voice and CPDLC position reporting requirements
   NIL
5. Graphic portrayal of area of radar coverage
   PSR station at Riga, position 565547.00N 0235705.41E, range 80 NM.
   For the area of radar coverage see Figure 1 - Area of Primary Radar Coverage.

General

When an aircraft carries a serviceable SSR transponder, the pilot shall operate the transponder at all times during flight, regardless of whether the aircraft is within or outside airspace where SSR is used for ATS purposes.

Pilots shall not operate the IDENT feature unless requested by ATS.

Except for flight in airspace for mandatory operation of transponder, aircraft without sufficient electrical power supply are exempted from the requirement to operate the transponder at all times.

When entering the Riga FIR, pilots who have already received specific instructions from ATS unit concerning the setting of the transponder, shall maintain that setting until otherwise instructed.

Except specific contingency situation, pilots shall:

• select codes as instructed by the ATS unit; or
• in the absence of ATS instructions related to code setting, select Mode A code 2000; or
• when not receiving air traffic services, select Mode A code 7000 in order to improve the detection of suitably equipped aircraft.

1. Emergency 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 Riga FIR, pilots who have already received specific instructions from ATC concerning the setting of the transponder, shall maintain that setting until otherwise instructed.
Pilots of aircraft about to enter the Riga FIR who have not received specific instructions from ATC concerning the setting of the transponder shall operate the transponder on mode A/3+C code 20 (or 2000) before entry and maintain that code setting until otherwise instructed.
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/3+C code 77 (or 7700).
Notwithstanding the procedure in paragraph 2.1.1 above, a pilot may select mode A/3+C code 77 (or 7700) whenever the nature of the emergency is such that this appears to him to be the most suitable course of action.
The pilot of an aircraft equipped with SSR shall select Mode A Code 7700 to indicate a state of emergency unless ATC has previously directed the pilot to operate the transponder on a specified code. In the latter case, a pilot may nevertheless select Mode A Code 7700 whenever there is a specific reason to believe that this would be the best course of action.

Note: Continuous monitoring of responses on mode A/3+C code 77 is provided.Mode A Code 7700 is permanently monitored in the Riga FIR.

2. Air-ground communication failure and unlawful interference procedures

2.1 Radio communication failure procedure

In the event of an aircraft radio receiver failure, a pilot shall select mode A/3+C code 76 (or 7600) and follow established procedures; subsequent control of the aircraft will be based on those procedures.
In the event of a radio communication failure, Mode A code 7600 shall be selected. Applicable radio communication failure procedures are to be followed.

Note: Mode A Code 7600 is permanently monitored in the Riga FIR.

2.2 Unlawful interference procedure

Pilots of aircraft in flight subject to unlawful interference shall endeavor to set the transponder to Mode A Code 7500 to provide an indication of the situation, unless circumstances warrant the use of A/B Code 77 (or 7700).
The pilot of an aircraft which is subjected to unlawful interference shall attempt to select Mode A Code 7500 to provide an indication of a state of unlawful interference. If circumstances so warrant, Mode A Code 7700 should be used instead.

Note: Mode A Code 7500 is permanently monitored in the Riga FIR.

3. System of SSR code assignment

The functional codes 4300-4377 (international flights), 0060-0077 and 3360-3377 (domestic flights) are assigned by Riga ATC for departing, arriving and overflying traffic.
SSR codes used for IFR flights in Riga FIR are assigned and managed by European Centralised SSR Code Assignment and Management System (CCAMS).

SSR codes used for VFR flights in Riga FIR are assigned and managed by ATS unit according to the SSR Code Allocation List.

4. Voice and CPDLC position reporting requirements

NIL

5. Graphic portrayal of area of SSR coverage (see Figure 2)

• MSS-W RIX Wide Area Multilateration (WAM) Surveillance System at Riga, position 565821.27N 0235854.41E, range 80 NM (see Figure 3);
• Mode S MSSR station at Riga, position 565547.00N 0235705.41E, range 240 NM, Mode S IC allocation (II=05) (see Figure 4);
• Mode S MSSR station at Ergli, position 565704.21N 0254503.33E, range 240 NM, Mode S IC allocation (II=09) (see Figure 5);
• Mode S MSSR station at Cirava, position 564412.07N 0212158.49E, range 240 NM, Mode S IC allocation (II =04) (see Figure 6);
• Mode A/C MSSR station at Martna, Estonia*, position 585105.043N 0234850.196E, range 256 NM (see Figure 7);
• Mode S MSSR station at Palanga, Lithuania**, position 555904.12N 0210636.35E, Mode S MSSR range 200 NM (see Figure 8 and Figure 9);
• Mode S MSSR station at Vilnius, Lithuania**, position 543822.14N 0251748.93E, Mode S MSSR range 200 NM (see Figure 9);
• CWAM West cluster of Complete Wide Area Multilateration (CWAM) Surveillance System for Riga FIR + 30NM buffer area, position 572610.51N 0213708.70E (see Figure 10);
• CWAM Center cluster of Complete Wide Area Multilateration (CWAM) Surveillance System for Riga FIR + 30NM buffer area, position 565821.27N 0235854.42E (see Figure 11);
• CWAM East cluster of Complete Wide Area Multilateration (CWAM) Surveillance System for Riga FIR + 30NM buffer area, position 572643.24N 0265539.21E (see Figure 12).

* Initial publishing and distribution of NOTAMs, regarding the operational status of the Martna Mode A/C MSSR, will remain on own responsibility of “Lennuliiklusteeninduse Aktsiaselts” (Estonian Air Navigation Service Provider).

** Initial publishing and distribution of NOTAMs, regarding the operational status of the Palanga Mode S MSSR and Vilnius Mode S MSSR, will remain on own responsibility of SE “Oro Navigacija” (Lithuanian Air Navigation Service Provider).

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