Appendix C – Background information on Mode S EHS

(a)     Introduction

This appendix provides background information on Enhanced Surveillance (EHS) useful to understand EHS airborne surveillance system defined in the CS ACNS.D.EHS and its associated AMCs.

(b)     Related material

(1)     EASA

ETSO-C112d, Minimum Operational Performance Specification for SSR Mode S Transponders. (Based on EUROCAE ED-73E).

(2)     EUROCONTROL

(i)      The Concept of Operations - Mode S in Europe, document SUR.ET2.ST02.1000-CNP-01-00, Edition 2, Nov 1996:

(ii)     Operational Hazard Assessment of Elementary and Enhanced Surveillance, Edition 1.1, EATMP Infocentre Reference: 04/04/07-01, 07.04.2004; and

(iii)     Preliminary System Safety Analysis for the Controller Access Parameter service delivered by Mode S Enhanced Surveillance, Edition 1.1, EATMP Infocentre Reference: 04/04/07-02, 07.04.2004

(3)     ICAO

(i)      ICAO Annex 10, Volume IV, Amd. 85, Aeronautical Communications (Surveillance Radar and Collision Avoidance Systems; )

(ii)     ICAO Document 9871 Edition 2;

(iii)     ICAO Document 8168-OPS/611 Volume I (Procedures for Air Navigation Services); and

(iv)     ICAO Document Doc 4444-RAC/501 Procedures for Air Navigation Service, Air Traffic Management.

(4)     EUROCAE

(i)      ED-73E Minimum Operational Performance Specification for Secondary Surveillance Radar Mode S Transponders;

(ii)     ED-26 Minimum Performance Specification for Airborne Altitude Measurement and Coding Systems; and

(iii)     ED-12C Software Considerations in Airborne Systems and Equipment Certification.

(5)     RTCA

DO-181E Minimum Operational Performance Specification for Air Traffic Control Radar Beacon System/ Mode Select (ATCRBS/Mode S) Airborne Equipment.

(c)      Background information

(1)     Airborne surveillance system description

         This section describes the EHS system including transponder, interfaces, and antenna.

         The following diagram represents the Mode S Transponder, and its main functional interfaces. It is to be noted that different interfaces coming from different parts of the avionics may need to be connected to the transponder to support EHS.

Figure 4: Mode S EHS transponder interfaces

(2)     Registers used to support EHS capability

(i)      Capability

In addition to the registers already used for ELS capability establishment, the EHS capability of the aircraft will be established using register 17₁₆ and 1D₁₆.

Register 17₁₆ will indicate which other registers (e.g. 40₁₆,50₁₆,60₁₆₎ are currently supported by the airborne surveillance system.

Ground systems could also use register 18₁₆ to 1C₁₆, if available, to determine which registers are installed if those register are not included in register 17₁₆.

Register 1D₁₆ is used to determine if Dataflash specific MSP is installed. Dataflash is an application allowing the transmission of registers to the ground only when they have changed, and, therefore, removing the need for periodic extraction of registers. Dataflash is not expected to be installed, however, some Mode S ground stations have been developed to take benefit of the dataflash application when available on aircraft.

Mode S ground stations can also use Mode S sub network version to filter old systems not correctly supporting EHS.

(ii)     Basic Data

Example of a basic list of registers and parameters to use to support the declaration of registers and parameters supported by an EHS installation is provided in Table 2 below.

Table 2 - Example of basic list of EHS registers and parameters

(3)     Other data

Mode S ground stations can extract other data when available. It is, therefore, important that all data provided are verified.

The Table 3 provides more data to facilitate the declaration of other registers and parameters which may be supported and which may need to be added to the basic list provided above.

Table 3 - Example of extended list of Transponder registers and supported parameters

Note 1: When different fields are defined with their own status, each field will be listed in the table. In this case, it is possible to indicate the provision of the associated parameter by checking the value of the associated status bit.

Note 2: For more information about the content of the registers see Doc 9871 Edition 2 or above.

Note 3: It is recommended to provide registers E316, E416, E516 and E616.

(d)     Existing installed transponders

A number of service bulletins have been issued to rectify some observed deficiencies and have already been addressed by the equipment manufacturers Therefore, the installed transponders should have all published corrective transponder equipment service bulletins (SB) relating to the correct operation of the elementary functionality embodied.

[Issue: CS-ACNS/4]