Notice of Final Rule Making
CASA’s response
It is definitely not CASA’s intention to have rules that necessitate expensive modifications or re-equipment of current aircraft systems for the stated purpose of ADS-B activation and deactivation.
The requirement that ADS-B equipment must be designed to allow the pilot to activate or deactivate it during flight will be met by the pilot having a cockpit control to select the ADS-B ES transponder(s) or ADS-B OUT equipment to on, and to standby or off, or to disable the navigation source data.
There may be situations where this is necessary as a result of GNSS position source equipment or ADS-B equipment malfunction causing the transmission of information that is hazardous to other aircraft. Although it is possible for the ground ATS system to quarantine or discard such faulty ADS-B transmissions if detected, air-to-air transmission of erroneous ADS-B data remains a safety issue. In the event of such occurrences, where detected ATC would advise the pilot to deactivate the transmission, as is the present case when ATC detects invalid SSR Mode C transponder replies.
Disposition
A note has been included in the final rule CAO 20.18 after paragraph 4 of Appendix XI as follows:
“Note: The requirement at 4(a) is satisfied if there is a cockpit control to enable the pilot to turn the ADS-B transmission equipment on and off.”
A similar entry will be included in the ADS-B guidance material – Advisory Circular AC 21-45.
COMMENT 3: THE PROPOSED TECHNICAL STANDARDS FOR ADS-B AVIONICS – The year 2012 requirement for TSO-C145a/146a compliance
Most respondents did not negatively comment on the 28 June 2012 date for compliance with TSO-C145a/146a. However, several respondents raised specific questions or concerns.
An airline commented that it understood that the accuracy and reliability of position reports was provided by GPS receivers meeting TSO-C145a or TSO-C146a, but the date of 28 June 2012 for compliance with those TSOs would place an excessive burden on operators for expensive equipment upgrades of existing aircraft having receivers that do not meet those TSOs. Upgrading existing airline aircraft that are equipped with three non-TSO-C145a/146a receivers would cost in excess of $100,000 per aircraft. The effect of the compliance date in the NPRM will be counter-productive to the up-take of ADS-B in Australia; it will drive operators to deactivate the Extended Squitter function rather than face such expensive upgrades. An acceptable rule would be to make the TSO-C145a/146a requirement for forward fit only for aircraft newly delivered after a certain date.
Carriage and Use of Notice of Final Rule Making ADS-B Avionics
An airline aircraft manufacturer stated that the specification for the use of GPS equipment certified to TSO-C145a/146a standards by the year 2012 should be replaced with performance based requirements for the ADS-B navigation source equipment. For example, technical requirements for availability and continuity of the navigation source should be specified. In that context, TSO-C145a/146a equipment should be listed as only one possible means of compliance. Performance based requirements are necessary since there are several alternative means feasible for achieving equivalent or better availability in the next-generation ADS-B systems. The designs can accomplish the requirements without reference to GPS WAAS capability as sited in the TSOs. For example, one means of achieving equivalent availability in Australian airspace is to use RAIM algorithms that account for the current status of SA. Equipment without WAAS capability can, and in some cases does, use those algorithms and would achieve essentially equivalent performance to TSO-C145a/146a equipment in Australian airspace. It is anticipated that US policy with respect to maintenance of the GPS constellation will change, such that the nominal constellation will include 30 or 32 satellites. In this case, existing equipment certified under TSO-C129a could potentially provide the functional availability needed for non-radar airspace. Another means of meeting NAV source availability requirements is to use a backup NAV source, such as FMS position data compliant with the STP MOPS (DO-302) as a backup to GPS in the event of RAIM based service interruptions. The respondent recommended that the proposed requirement should be revised to state or reference the performance requirements for NAV source equipment, and that Appendix XI to CAO 20.18 should list the means of meeting those requirements, including but not limited to, the cited TSOs.
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