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NOTE: It is expected that the Safety Assurance activities will consider procedures for the safe accommodation of existing levels of traffic using the remaining surveillance systems (or procedural control where none remain) and whether Flow Control to lower traffic levels will be required.
Annex A to SUR 01 Surveillance Systems Overview
1 Introduction
1.1 Limitations of traditional surveillance systems (primary and secondary radar) such as in range, cost and accuracy can lead to consideration of other systems. These other systems have particular characteristics that need careful safety assessment consideration against the particular operational requirement, service and traffic. Systems such as Automatic Dependant Surveillance (ADS) have extended range due to the use of datalink services to transmit information between aircraft and ground stations. The application of such systems is limited by the type of datalink used. VHF datalink is only useful for line of sight ranges. HF datalink is limited by the speed of data transmission. HF and Satellite links also route via third party providers, such as ARINC and SITA, introducing further system delays and potential for the introduction of errors. Multi-lateration or MLAT systems can offer cost savings over traditional systems and provide good accuracy at the same time but are generally dependant on co-operative traffic as for SSR. It is of course the independent nature of primary radar that continues to make it a prime system for certain types of airspace and traffic for which detection of non-transponder equipped traffic is considered essential.
2 FANS (Future Air Navigation System)
2.1 As a strategy to counter global increases in air traffic and an aging worldwide infrastructure, the ICAO Council established the Special Committee on Future Air Navigation Systems (FANS).
2.2 CPDLC (Controller Pilot DataLink Communications) and ADS data link applications were designed for transportation of data across the Aeronautical Telecommunications Network (ATN). Until the ATN became available, Boeing built a FANS application to run on the existing ACARS system. This avionics package became known as FANS-1. The Airbus Industrie equivalent system is known FANS-A, and these systems are known collectively as FANS-1/A. To gain benefit from these systems in the terms of reduced separation there must be mandated equipage and associated procedures. It is proposed that mandate is made for FANS1/A ADS-C capabilities for aircraft using the organised track system in the North Atlantic by 2013 with a further mandate in 2015 for all Minimum Navigation Performance Specification (MNPS) regions.
3 SESAR (Single European Sky ATM Research)
3.1 Prompted by the Air France Airbus loss over the Atlantic, the SESAR Joint Undertaking (SJU) has called for tenders on a program titled OPTIMI (Oceanic Position Tracking and Monitoring) to enable the rapid intervention of Search and Rescue resources in areas outside standard surveillance regions. The project aims to recognise current technology usage such as ADS-C and CPDLC.
3.2 Both the SJU and the US Nextgen program (which aims to restructure the US airspace system based on ADS and datalink technologies) have recognised that the industry is reluctant to commit to re-equipping with expensive hardware without any perceived benefit in terms of cost savings for them.
4 Automatic Dependant Surveillance (ADS)
4.1 ADS uses data gained from the aircraft systems, derived from sensors such as GPS and transmits information to interested parties using datalink technology. ADS may be used across a range of applications from local airfield monitoring (ADS works down to low level) to long range airspace coverage. For line of sight distances the datalink medium may be VHF, Mode-S extended squitter or a dedicated Universal Access Transceiver (UAT), for longer ranges HF datalink or Satellite datalink may be used.
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CAP 670 Air Traffic Services Safety Requirements 2(78)
