FROM Philippe de Gouttes DATE 04 Mar 2008 PHONE +33(0)5 61 93 27 91 FAX +33(0)5 61 93 31 55 E-MAIL philippe.de-gouttes@airbus.com OUR REFERENCE M08004177 YOUR REFERENCE Docket Management Facility U.S. Department of Transportation 1200 New Jersey Avenue, SE. West Building Ground Floor Room W12-140 Washington, DC 20590-0001 U.S.A. DOCKET No. FAA-2007-29305 AIRBUS COMMENTS TO NOTICE No. 07-15, ADS-B OUT PERFORMANCE REQUIREMENTS Dear Sir, Airbus thanks the FAA for offering an opportunity to comment on NPRM 07-15. Airbus supports the development and deployment of ADS-B applications as key elements of the future air traffic management systems in the United States of America and in other regions in the world, such as Europe, Canada, or Australia. We commend the FAA for its commitment to establish a long-term vision and an implementation plan for ADS-B applications, for its international co-operation efforts, and for setting up the ADS-B Aviation Rulemaking Committee. We believe, however, that NPRM 07-15 does not fully deliver the outputs that could be expected, and we would like to express our concerns in the attached pages. Yours sincerely, Philippe de Gouttes Head of Regulations Product Integrity Division AN EADS COMPANY AIRBUS S.A.S SOCIÉTÉ PAR ACTIONS SIMPLIFIÉE AU CAPITAL DE 2.704.375 EUROS 383 474 814 R.C.S. TOULOUSE SIÈGE SOCIAL : 1, ROND-POINT MAURICE BELLONTE 31707 BLAGNAC CEDEX, FRANCE PHONE +33 (0)5 61 93 33 33
NPRM 07-15 ADS-B OUT AIRBUS COMMENTS A. GENERAL COMMENTS 1. AVIATION INDUSTRY NEEDS A PHASED, INTERNATIONALLY HARMONIZED AND PRAGMATIC IMPLEMENTATION OF ADS-B The scope of the document is unclear. The title, the summary (paragraph III page 56951) and the considerations on the Paperwork Reduction Act (paragraph IX page 56963) imply that the scope is limited to ADS-B Out equipage requirement. However the NPRM contains multiple references to future ADS-B In applications deemed to be the real NextGen project requisite, without setting a clear and phased implementation schedule for each possible application. This NPRM is supposed to propose requirements for ADS-B Out airborne applications in RAD (Radar) and NRA (non-radar) environments. Those requirements are being developed in a joint RTCA-EUROCAE-FAA-EUROCONTROL Requirement Focus Group (RFG). For example, ED-126/DO-303 defines interoperability, safety and performance requirements for airborne and ground components of ADS-B Out application in NRA. In Europe, draft AMC 20-24 (ref NPA 2007-05) recognizes this standard. The definition of ASAS packages 1 (horizon 2013) and 2 (horizon 2020), which is common to the FAA and EUROCONTROL through the RFG, is not used in the NPRM, which generates much confusion, as the NPRM definition is not in line with international standards, including ICAO SARPs Convergence between NextGen and Europe s SESAR project should be ensured for similar applications. Consistent and phased packages of ADS-B applications have been defined in cooperation with FAA representatives, and that work should be used to allow adequate specification and industrial development of future transponders. FAA NPRM relies on performance capabilities that are not necessary for the ADS-B Out equipage. The discussion in paragraph IV.B should make it clear that each intended use of ADS-B results in specific requirements for avionics, which may be more or less severe. Consequently, a given airborne installation may be compliant or eligible for some applications only, and early authorization for those applications, consistent with the ASAS packages 1 and 2, should be accommodated. At the moment, the ADS-B Out application for NRA environment is the only one for which the RFG has defined requirements allocated to each contributor. The scope of the proposed EASA AMC 20-24 (ref NPA 2007-05) is limited to this application. No aircraft has been certified to the proposed standards. There is a need identified for a unique concurrent program of system demonstrations, in-service evaluations and compliance, and R&D to develop advanced standards and build confidence and benefits for further development. It is important to recognize this need for demonstration projects, and take advantage now of the time REFERENCE M08004177 PAGE 2
available to carry out those projects in a collaborative government-industry effort. If the projects are not planned and initiated soon, this time will be lost. The aeronautical community needs to learn operationally and technologically from easy applications. Early use of existing ADS-B helps in training of controllers and pilots, and developing lessons learnt with this new tool. It is very important to have controllers and pilots closely involved in the development of ADS-B applications, as it is they who will, in the end, be implementing these new tools. An early learning phase from existing avionics and applications will help mature better standards and benefit from technology improvements between now and mid-term (say 2013) to satisfy 2020 requirements. FAA should collaborate with industry to determine by 2010 which non-ads-b avionics can be replaced by ADS-B equipage. 2. NAVIGATION SYSTEMS AND INTERNATIONAL INTEROPERABILITY FAA relies on very demanding level requirements, e.g. performance equivalent to Wide Area Augmentation System (WAAS) not currently in the commercial air transport aircraft roadmap worldwide. These specific resolutions including dual-link concept, presumed by FAA, need to be assessed in terms of technical compatibility. The FAA considers that in order to obtain the high integrity requirements specified for in the NPRM for ADS-B OUT, the only system available that can do this today is one that employs WAAS. We believe this is a flawed solution, since WAAS is not a globally available system, and is not planned to be globally available. FAA should not rely on a partial solution if such high integrity values are required. In addition, we believe that technology evolution in the coming years may make other solutions attractive, such as tightly coupled inertial system architectures. 3. INCENTIVE POLICY Financial incentives should be developed for airspace users to support the proposed program and in-service demonstrations and evaluations. Although today s requirements might be obsolete in 2020,early benefits could be provided with currently available avionics standards, especially in non-dense areas. 4. CONSIDERATIONS ON ADS-B IN As the purpose of the NPRM is limited to ADS-B Out requirements, considerations and discussion of ADS-B In should be limited to the extent necessary to understand the ADS-B Out proposals. In the current document, too many references to ADS-B In application are detrimental to its focus and its clarity. The NPRM defines 2 services and 5 applications to be available to operators voluntarily equipping with ADS-B In. To what extent are airline operators interested in Flight Information Service Broadcast (FIS-B), and of what benefit is it to them? We also ask why the NPRM applications are at REFERENCE M08004177 PAGE 3
variance with RFG s requirements that were developed and agreed with full FAA participation. These are redundant with the existing systems (Conflict Detection and TCAS). A focus on improved surface movement safety appears to be appropriate. 5. LINK WITH ADVISORY CIRCULAR 120-86 AC 120-86, Aircraft Surveillance Systems and Applications, should be updated in conjunction with the development of this new rule. B. SPECIFIC COMMENTS Paragraph IV.B.1 (pages 56952-56953) In Europe, early implementation possibilities are open for avionic architectures complying with RTCA/DO-260. The same approach should be encouraged in the United States, in order to draw a short-term operational benefit (within 5 years) and help in defining the final requirements for the targeted implementations. While it is yet unknown if the next change to DO-260A will be sufficient for NextGen (2025), it is important to authorize and encourage early implementation using DO-260. (Note: where reference is made to DO-260A Change 2, it should be understood as a minimum ). Discussion on NIC/NAC/SIL performance capabilities: NIC of 7 seems achievable, although it would require a wiring change in most aircraft. NACp of 9 is not justified by applications foreseen in the 2015 time frame. It is believed that we should wait for the establishment of requirements (NRA, RAD, ATSAW, APT, ATSA-SURF, ASPA-S&M) 1 before mandating performance values. For example, for ATC use, the ADS-B precision needed is different in en-route non-radar airspace, in en-route radar airspace, in approach, on airport surface. As a result, a different NACp is allocated for each application in a given environment. The applications that would conceivably require NACp 9 have not been demonstrated yet, and are not to be implemented for perhaps a decade or more. Such a specification at this early stage is premature and perhaps unneeded, depending on the results of yet-to-be conducted (and as yet unplanned) research and demonstration. 1 NRA: Non-Radar Area RAD: Radar Area ATSAW: Air Traffic Situational Awareness APT: Airport ATSA-SURF: enhanced traffic situational awareness on the airport surface ASPA-S&M: Airborne Spacing Application enhanced sequencing and merging operations REFERENCE M08004177 PAGE 4
Paragraph IV.B.3 (pages 56953-56955) This paragraph lists the interoperability requirements (message elements to be supported by the aircraft), independent of the targeted application. The required elements should be specified for each application. (a) The length and width of the aircraft This element would be required only for airport surface applications (APT). It is out of the scope of RAD and NRA ADS-B Out applications It is not part of the interoperability requirements in DO-260A, which only deals with airborne applications and is referred to in paragraph IV.B.1. The standards for APT applications are not defined today. Indeed there is no choice made today on the APT supporting technology: possible use of multilateration is considered, which would not require element (a). If element (a) is kept, there should be in addition a requirement for the transmission of the point of reference used to determine the aircraft position. (b) An indication of the aircraft s lateral and longitudinal position The integrity requirements for this element, which may vary depending on the particular application, are missing (see for example draft AMC 20-24 in EASA NPA 2007-5, for NRA). (d) An indication of the aircraft s velocity The related text indicates it would provide ATC with the aircraft s airspeed. It should be the GPS ground velocity. (e) An indication if TCAS II or ACAS is installed and operating in a mode that may generate resolution advisory alerts This requirement does not exist for RAD and NRA applications. The reason for its addition should be explained. In RAD application, radar is the only backup. (f) For aircraft with an operable TCAS II or ACAS, an indication if a resolution advisory is in progress. ACAS resolutions advisory status can be achieved by going to DO-260A (g) An indication if ATC services are requested What is the justification of this element if element (h) is required? The meaning of ATC services and the details of this element should be clarified. We understand that this indication is useful only for aircraft flying in VFR. Anyway it is redundant with element (h). (h) An indication of the Mode 3/A transponder code specified by ATC Remark: Mode A code must be transmitted. (i) An indication of the aircraft s call sign that is submitted on the flight plan, or the aircraft s registration number The term call sign is usually related to voice communication. For the flight plan, ICAO terminology should be used instead: Flight Id = Flight Number (see draft AMC 20-24 in EASA NPA 2007-5). REFERENCE M08004177 PAGE 5
(j) An indication if the flight crew has identified an emergency and, if so, the emergency status being transmitted The applicable standards for the definition of emergency status should be clarified. (k) An indication of the aircraft s IDENT to ATC The sentence The pilot manually inputs the aircraft s identity is misleading. In fact the pilot manually activates the aircraft s identification function (a simple on/off action). (n) An indication whether a cockpit display of traffic information (CDTI) is installed and operable In the first sentence, alert should be replaced by inform, as the term alert is usually related to abnormal situations. The remainder of this paragraph (n) gives rise to some questions: o This element would require a modification to the transponder, not yet defined: the transponder is not aware if an ADS-B In equipment is installed. o It is unclear what ADS-B In means here: CDTI only? For which usage (and required integrity)? To which degree of qualification? o This element is out of the scope of this NPRM, which is supposed to be limited to ADS-B Out applications. o This element is not mentioned in RTCA/DO-260A. (o) An indication of the aircraft s geometric altitude Clarification: if the barometric altitude is lost, the geometric altitude is not transmitted in the current DO-260 installations. Paragraph IV.B.4 (pages 56955-56956) We suggest clarification of the second sentence in the second block as follows: The required accuracy and integrity of the transmitted aircraft position and velocity are critical must be appropriate for use in surveillance and various airborne and surface applications. It is unjustified to require NACp = 9 for most of the airborne applications, for which NACp = 7 has already been shown as sufficient. The possible need for NACp = 9, in relation with some applications, has to be justified. All in all, NACp > 7 is sufficient for the ADS-B Out applications that are the subject of this NPRM. Including a requirement for NACp = 9 at this time unjustifiably drives costs up considerably without any agreed need to do so. Footnote 19, page 56956, is misleading and should be removed. The criticality of applications and their consequences on the required design assurance level must be the result of an end-to-end safety study, as established by the RFG, in which FAA participates. Considerations on self-separation, and on future ADS-B In applications, should be removed from this paragraph, as they are out of the scope of this NPRM. Including them is misleading as it implies that ADS-B out somehow provides this capability, which it does not. As explained in our general comment # 2, there is no evidence that WAAS is today the only acceptable solution. The RFG has not reached this conclusion. We expect that other approaches will evolve in the coming years that will provide an alternative to this solution if, indeed, NACp 9 is re- REFERENCE M08004177 PAGE 6
quired. In addition, the lack of global applicability of WAAS makes it an unacceptable sole means of achieving NACp 9. There is no requirement for the integrity and the continuity of the onboard ADS-B system. There should be such requirements, to be adjusted depending on the application, as established by the RFG, in which FAA fully participates. Paragraph IV.B.6 (page 56957) Why is there a separation between the allowable latency for information processing and the one for information transmission? 0.5 second for information processing is not achievable for GPS architecture. This separation into two latency allowances for the avionics chain does not match what is required and standardized for NRA applications (see draft AMC 20-24 in EASA NPA 2007-05). The latency that is authorized in this paragraph is not compatible with NAC > 7 (see RTCA/DO- 302), which makes it inconsistent with paragraph IV.B.4. = END = REFERENCE M08004177 PAGE 7