Carriage and Use of Notice of Final Rule Making ADS-B Avionics
1.7 The source of ADS-B transmitted positional data is essentially GNSS although the ADS-B standards allow for equivalent performance systems. Current IFR certified GNSS receivers suitable for ADS-B position data output a value termed Horizontal Protection Limit (HPL) which ensures with extremely high probability (10E-7) that the reported position is within the HPL. The HPL value is calculated by the GNSS receiver based on the ability of the receiver to detect a “bad” ranging signal from the satellites in view. GNSS receivers also output a value termed HFOM, which is the expected accuracy of the positional data assuming that all satellites in view are operating correctly.
1.8 DO-260 stipulates that the transmitted NUC value is to be based on HPL if HPL is available as an output from the aircraft’s GNSS receiver. However, DO-260 allows the transmitted NUC to be based on HFOM if HPL is not provided. The weakness with HFOM is that it does not protect from satellite ranging errors. DO-260A requires that the NIC value is derived from HPL and does not allow that exception. If NUC is based on HPL, then DO-260 and DO-260A standard avionics are essentially similar regarding positional integrity.
1.9 Airservices Australia is currently installing ADS-B ground stations for operational use with a 5 NM air traffic separation standard. Its ground stations can receive and process both DO-260 and DO-260A transmissions. DO-260 aircraft avionics are only considered adequate if the transponder is provided with HPL and that is used to compute the NUC value. The guidance material (AC 21-45) that supports the final rule in this NFRM provides that ADS-B transmissions are to be to DO-260 with HPL, or to DO-260A standard.
2. Purpose
2.1 The purpose of this NFRM is to provide a consolidation of all comments received on the NPRM, with CASA’s evaluation and response to each of the comments. The final disposition of the regulatory and supporting material in respect to each comment is given.
2.2 This NFRM also notifies the form of the intended final rules (CAOs) and final guidance material (AC 21-45).
3. Analysis of Comments
3.1 CASA received a total of eighteen (18) responses to the NPRM. All responses received have been considered. See Annex A to this NFRM for the consolidated Summary of Comments, with CASA’s responses to these comments and the final disposition of those comments in the final rule CAOs.
Page 8 of 12 Document NFRM 0601AS
Notice of Final Rule Making
3.2 The respondents who consented to the publishing of their name are shown below:
Organisations
Terry Wesley-Smith representing RAAA
Stephen Lansell representing RFDS WA
Michael Vaughan representing AFAP
Lewis Benham representing QANTAS
Jim Davis representing REX
Elizabeth Pasztor representing Boeing Commercial Airplanes Seattle
David Holt representing AIPA
Melinda Evans representing Airservices Australia
Individuals
Mick Muller James Cieplak
Kevin Haase Gareth Davey
Scotty Fairbairn Ed Hawthorn
Peter Marosszeky Andrew Andersen
Oliver Brock Nick Strange
3.3 The disposition of responses against the three key issues follows and the percentages are shown for these in figures 1 to 3 below.
Key Issue 1 – Use of ADS-B equipment (operational requirements)
Not acceptable unless changed
Disposition of Responses No. of Responses 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：Notice of Final Rule Making(3)
