4.1 Where suitable radar systems and communication systems are available, radar-derived information, including safety-related alerts and warnings such as conflict alert and minimum safe altitude warning, should be used to the extent possible in the provision of air traffic control service in order to improve capacity and efficiency as well as to enhance safety.
4.2 The number of aircraft simultaneously provided with radar services shall not exceed that which can safely be handled under the prevailing circumstances, taking into account:
a) the structural complexity of the control area or sector concerned;
b) the radar functions to be performed within the control area or sector concerned;
c) assessments of controller workloads and sector capacity;
VI. Radar Services
d) the degree of technical reliability and availability of the main radar and communication systems;
e) the possibility of a radar equipment failure or other emergency that would eventually require reverting to back-up facilities and/or non-radar separation; and
f) the degree of technical reliability and availability of the back-up radar and communication systems.
4.3 Where traffic density varies significantly on a daily or periodic basis, facilities and procedures should be implemented to vary the number of operational radar positions and/or sectors in order to meet the prevailing and anticipated traffic demand.
5. Use of SSR transponders
5.1 To ensure the safe and efficient use of SSR, pilots and controllers shall strictly adhere to published operating procedures. Standard radiotelephony phraseology shall be used and the correct setting of transponder codes shall be ensured at all times.
5.2 SSR Code management
5.2.1 Codes 7700, 7600 and 7500 shall be reserved internationally for use by pilots encountering a state of emergency, radiocommunication failure or unlawful interference respectively.
5.2.2 SSR Codes are to be allocated and assigned in accordance with the following principles.
5.2.2.1 Codes should be allocated to States or areas in accordance with regional air navigation agreements, taking into account overlapping radar coverage over adjacent airspaces.
5.2.2.2 The appropriate ATS authority shall establish a plan and procedures for the allocation of codes to ATS units.
5.2.2.3 The plan and procedures should be compatible with those practised in adjacent States.
5.2.2.4 The allocation of a code should preclude the use of this code for any other function within the area of coverage of the same SSR for a prescribed time period.
5.2.2.5 To reduce pilot and controller workload and the need for controller/pilot communications, the number of code changes required of the pilot should be kept to the minimum.
5.2.2.6 Codes shall be assigned to aircraft in accordance with the plan and procedures laid down by the appropriate ATS authority.
5.2.2.7 Where there is a need for individual aircraft identification, each aircraft shall be assigned a discrete code which should, whenever possible, be retained throughout the flight.
5.2.3 SSR Codes shall be reserved, as necessary, for exclusive use by medical aircraft operating in areas of international armed conflict. SSR Codes shall be allocated by ICAO through its Regional Offices in co-ordination with States concerned, and should be assigned to aircraft for use within the area of conflict.
Note.— The term “medical aircraft” refers to aircraft protected under the Geneva Conventions of 1949 and under the Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the protection of victims of international armed conflicts (Protocol I).
5.3 Operation of SSR transponders
Note.— SSR transponder operating procedures are contained in Procedures for Air Navigation Services — Aircraft Operations (PANS-OPS, Doc 8168), Volume I, Part VIII. 中國航空網(wǎng) m.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：Rules of the Air and Air Traffic Services(70)
