Operating on the Radio Frequency of 1090 Megahertz (MHz)

Transcription

1 Deviation Request #107 for an ETSO approval for CS ETSO applicable to Extended Squitter Automatic Dependent Surveillance Broadcast (ADS B) and Traffic Information Service Broadcast (TIS B) Equipment Operating on the Radio Frequency of 1090 Megahertz (MHz) (ETSO C166b) and to Air Traffic Control Radar Beacon System/Mode Select (ATCRBS/Mode S) Airborne Equipment (ETSO C112d) Consultation Paper 1 Introductory Note The hereby presented deviation requests shall be subject to public consultation, in accordance with EASA Management Board Decision No as amended by EASA Management Board Decision No products certification procedure dated 11th September 2007, Article 3 (2.) of which states: 2. Deviations from the applicable airworthiness codes, environmental protection certification specifications and/or acceptable means of compliance with Part 21, as well as important special conditions and equivalent safety findings, shall be submitted to the panel of experts and be subject to a public consultation of at least 3 weeks, except if they have been previously agreed and published in the Official Publication of the Agency. The final decision shall be published in the Official Publication of the Agency. 2 Deviation Requests 2.1 ETSO C166b#7 Extended Squitter Automatic Dependent Surveillance Broadcast (ADS B) and Traffic Information Services (TIS B) Equipment Operating on the Radio Frequency of 1090 Megahertz (MHz) Summary of Deviation Deviates from EUROCAE ED 102A , , , , , , , , , , A by applying a timeout of 2.8 seconds instead of 2 seconds Original Requirement EUROCAE ED 102A: ADS B Message Timeout b. The ADS B Transmitting Subsystem shall clear all but the altitude and surveillance status subfields of the Airborne Position Message, if no new position data is received within two (2) seconds of the previous input data update. Page 1 of 7

2 Verification of ADS B Airborne Position Message Broadcast Rate ( ) Step 3: Data Ceases to be Updated ( a) Establish the broadcast of the ADS B Airborne Position Message as in Step 1 above. Then stop the input of data (No position and no altitude) for the ADS B Airborne Position Message). Verify that the ADS B Airborne Position Message is broadcast with all data bits being set to ZER, 2.0 seconds after stopping the data input Airborne Latitude Position Data Retention In the event that the latitude position data is no longer available, the extrapolation or estimation of, and update of latitude data and fields specified in through shall be limited to no more than two seconds. At the end of two seconds, the latitude data registers and the encoded latitude field shall be set to ALL ZEROs Airborne Longitude Position Data Retention The extrapolation or estimation, and update of longitude data and fields specified in through shall be limited to no more than two seconds, in the event that the longitude position data is no longer available. At the end of two seconds, the longitude data registers and the encoded longitude field shall be set to ALL ZEROs Surface Latitude Position Data Retention The extrapolation and update of latitude data and fields specified in through shall be limited to no more than two seconds, in the event that the latitude position data is no longer available. At the end of two seconds, the latitude data registers and the encoded latitude field shall be set to ALL ZEROs Surface Longitude Position Data Retention The extrapolation and update of longitude data and fields specified in through shall be limited to no more than two seconds, in the event that the longitude position data is no longer available. At the end of two seconds, the longitude data registers and the encoded longitude field shall be set to ALL ZEROs Verification of Airborne Latitude Position Data Retention ( ) Purpose/Introduction: The extrapolation or estimation, and update of latitude data fields specified in through and will be limited to no more than two seconds, in the event that the latitude position data is no longer available. At the end of two seconds, the latitude data registers and the encoded latitude field will be set to ALL ZEROs. Page 2 of 7

3 Measurement Procedures: Step 1: Termination of Latitude Data Input Part 1 Provide normal Airborne Position data to the ADS B Transmitting Subsystem at the nominal rate. First, filter the data so that the ADS B Transmitting Subsystem does not receive any latitude data for at least 2 seconds. After 2 seconds, verify that the latitude data registers are set to ALL ZEROs Verification of Airborne Longitude Position Data Retention ( ) Measurement Procedure: Step 1: Longitude Data Termination Part 1 Provide normal Airborne Position data to the ADS B Transmitting Subsystem at the nominal rate. First, filter the data so that the ADS B Transmitting Subsystem does not receive any longitude data for at least 2 seconds. After 2 seconds, verify that the longitude data registers are set to ALL ZEROs Verification of Surface Latitude Position Data Retention ( , ) Purpose/Introduction: The extrapolation or estimation, and update of latitude data and fields specified in through is limited to no more than two seconds, in the event that the latitude position data is no longer available. At the end of two seconds, the latitude data registers and the encoded latitude field will be set to ALL ZEROs. Measurement Procedures: Step 1: Termination of Latitude Data Input Part 1 Provide normal Surface Position data to the ADS B Transmitting Subsystem at the nominal rate. First, filter the data so that the ADS B Transmitting Subsystem does not receive any latitude data for at least 2 seconds. After 2 seconds, verify that the latitude data registers are set to ALL ZEROs. Note: In order to terminate latitude data, it may also be necessary to terminate longitude information since a position fix normally includes both latitude and longitude Verification of Surface Longitude Position Data Retention ( , ) Purpose/Introduction: The extrapolation or estimation, and update of longitude data and fields specified in through is limited to no more than two seconds, in the event that the longitude position data is no longer available. At the end of two seconds, the longitude data registers and the encoded longitude field will be set to ALL ZEROs. Measurement Procedure: Step 1: Longitude Data Termination Part 1 Provide normal Surface Position data to the ADS B Transmitting Subsystem at Page 3 of 7

4 the nominal rate. First, filter the data so that the ADS B Transmitting Subsystem does not receive any longitude data for at least 2 seconds. After 2 seconds, verify that the longitude data registers are set to ALL ZEROs. A Time Out When New Position Data is Unavailable In the event that the navigation input ceases, the extrapolation described in A and A will be limited to no more than two seconds. At the end of this timeout of two seconds, all fields of the Airborne Position register, except the altitude field, will be cleared (set to zero) Industry The applicant clears the airborne and surface position registers after a worst case of 2.8 seconds. The input rate from an ARINC 743A 5 GPS position source is 0.8 to 1.2 seconds with actual data from older GPS systems observed to be as high as 1.4 seconds. The applicant s interpretation of the intent of the requirement is that that transponder must be able to miss 2 receptions from the GPS before the registers are cleared. If the GPS updates are received at the worst case of 1.4 seconds, the transponder would be required to clear the register after missing only one update, which is a common occurrence, and will lead to numerous field nuisance failures. Previous implementations which contained the capability to flag a failure with only a single missed GPS message have led to operational issues with various operator customers. This interpretation of the system to support 2 missed GPS inputs is supported by the FAA AIR 130 office and the implementation is approved by the FAA without requiring a deviation approval Equivalent Level of Safety An equivalent level of safety is provided by the certification requirements of the EASA Certification Specification and Acceptable Means of Compliance for Airborne Communications and Navigation and Surveillance (CS ACNS) and FAA Advisory Circular AC20 165A requiring the installer to assess the overall system latency for the position data as compliant to the airspace requirements. The installation manual associated with this article specifically notes this deviation and instructs the installer to account for the 2.8 second implementation versus 2.0 in their system latency analysis regarding position data to ensure acceptable operation EASA position The introduction of this deviation also makes the article non compliant to the following requirements of ICAO Annex 10, Volume IV: Register time out. The transponder shall clear all 56 bits of the airborne position, surface position, squitter status and airborne velocity information transponder registers 05, 06, 07 and 09 {HEX} if these registers are not updated within two seconds of the previous update. This time out shall be determined separately for each of these registers. Note 2. These registers are cleared to prevent the reporting of outdated position, velocity and squitter rate information. Page 4 of 7

5 It also makes non compliant to ICAO Doc 9871 which states that C Time Out When New Position Data is Unavailable In the event that the navigation input ceases, the extrapolation described in C and C shall be limited to no more than 2 seconds. At the end of this timeout of 2 seconds, all fields of the Airborne Position register, except the altitude field, shall be cleared (set to ZERO). European Commission Implementing Regulation (EU) No 1207/2011, Article 4. (a) and Article 5. (a) requires that flights within certain time and airspace are compliant with its Part A of Annex II. Part A of Annex II requires in turn compliance to ICAO annex 10 vol IV and to ICAO Doc 9871, which is quoted above. ICAO annex 10 vol IV requires compliance to and calls for , which contains which is also quoted above. This deviation therefore makes the article non compliant to EU regulation 1207/2011. In addition, the applicant proposes as an Equivalent Of Safety that the installer verifies compliance of the overall system with CS ACNS. However, CS ACNS requires that CS ACNS.D.ADSB.070 Horizontal Position and Velocity Data Sources (b) The GNSS receiver based horizontal position is approved. (...) CS ACNS.D.ADSB.110 Horizontal Position and Velocity Data Refresh Rate A horizontal position and velocity source calculates position and velocity data with a rate of at least 1 Hertz. AMC1 ACNS.D.ADSB.070 Horizontal Position and Velocity Data Sources (a) GNSS Standards (1) Basic GNSS System Approval To be approved, the horizontal position and velocity data source should hold an EASA equipment authorisation in accordance with either ETSO C129a, or ETSO C196, or ETSO C145/ETSO C146, including the additional qualification requirements as specified in paragraph (2) below. CS ACNS.D.ADSB.120 Horizontal Position Uncompensated Latency (See AMC1 ACNS.D.ADSB.115 and 120) The uncompensated latency of the horizontal position data introduced by the ADS B Out System does not exceed 0.6 second. Therefore, CS ACNS.D.ADSB.110 is requiring that the horizontal position is refreshed by the GNSS receiver at least once per second. This is consistent with CS ACNS.D.ADSB.070 that the GNSS is approved, as ETSO Page 5 of 7

6 C129a, ETSO C196a, ETSO C145c and ETSO C146c are all requiring the horizontal position to be updated at least once per second. It is recognized that some variation may happen on a particular frame output from GNSS sensors. However, these variations should be minimal and not repeated for the Horizontal Position source to be approved. As the deviation intends to cover for Horizontal Position source with a refresh rate larger than one second, and that these ones are not compatible with CS ACNS, the Equivalent Level Of Safety is not pertinent. As the deviation is not compliant to ICAO and EU regulation requirements and as the deviation intends to accommodate interfacing equipment not compatible of the Certification Specification used as an equivalent of safety, EASA rejects the deviation. 2.2 ETSO C166b#8 Extended Squitter Automatic Dependent Surveillance Broadcast (ADS B) and Traffic Information Services (TIS B) Equipment Operating on the Radio Frequency of 1090 Megahertz (MHz) Summary of Deviation Deviates from subpart A ED 14G section 21.5 Category M for Radio Frequency radiated emission limit in the following frequency bands: 2180MHz± 78MHz exceeds. Cat M limits by 27dB 4360MHz ± 78MHz exceeds Cat M limits by 5dB 5450MHz ± 78MHz exceeds Cat M limits by 10dB Original Requirement CS ETSO subpart A 2.1 Environmental standards Unless otherwise stated in the paragraph of the specific ETSO, the applicable environmental standards are contained in EUROCAE/RTCA document ED 14D change 3/DO 160D Environmental Conditions and Test Procedures for Airborne Equipment, change 3 dated December 2002, or ED 14E/DO 160E dated March 2005 or ED 14F/DO 160F dated March 2008 or ED 14G/RTCA 160G dated December Industry See equivalent Level Of Safety Equivalent Level of Safety An Equivalent Level of Safety (ELOS) is provided by The equipment meeting ED 73E and ED 102A transmitter reply spectrum bounds The absence of aeronautical safety related operations utilizing these frequencies. The article Installation Manual directing the installer to specifically verify non interference with other avionics systems for these frequencies. Page 6 of 7

7 2.2.5 EASA position It is noted that although the article exceeds ED 14G section 21 category M in three frequency bands, only the band in 2180 MHz ±78MHz exceeds the less stringent category (B) by 7 db. However, the transmitter meets the emission requirements specific to the transponders regarding frequency spectrum. Considering that no aeronautical safety operation use this frequency band and considering the requirement set in the article installation manual for the installer to assess the electromagnetic compatibility and interferences, we accept this deviation. 2.3 ETSO C112d#2 Air Traffic Control Radar Beacon System/Mode Select (ATCRBS/Mode S) Airborne Equipment See 2.2 Page 7 of 7