OFFICE OF THE SECRETARY OF DEFENSE 1480 DEFENSE PENTAGON WASHINGTON DC

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1 OFFICE OF THE SECRETARY OF DEFENSE 1480 DEFENSE PENTAGON WASHINGTON DC DOD POLICY BOARD ON FEDERAL AVIATION MEMORANDUM 'FOR: Docket Operations, M-30 U.S. Department of Transportation 1200 New Jersey Avenue, SE West Building Ground Floor, Room W Washington, DC February 2008 SUBJECT: DoD Comments to Docket No. FAA ; Notice No , Automatic Dependent Surveillance - Broadcast (ADS-B) Out Performance Requirements to Support ATC Service The Department of Defense (DoD) Policy Board on Federal Aviation is pleased to provide the attached comments in response to the Federal Aviation Administration (FAA) Notice of Proposed Rulemaking (NPRM) entitled "ADS-B Out Performance Requirements to Support ATC", docket number FAA As a user, DoD requires access to all elements of the NAS and requires Special Use Airspace (SUA) for conducting missions in support of the National Security Strategy and the National Military Strategy. Under various circumstances, e.g. age of aircraft fleet, funding requirements, etc., some DoD aircraft may not meet equipage requirements and will need accommodation from the FAA to operate in designated ADS-B Out airspace. The scope of the attached comments reflect DoD's focus upon fiscal, security, and operational considerations and the current timeline for ADS-B Out implementation. To ensure DoD-unique requirements for national defense and security are provided for, DoD will continue to collaborate with the FAA for it's integration into the Next Generation process. My POC for this effort is Mr. Allan Storm, (703 Lagr , allan.storm@pentagon.af.mil GERALD F. PEASE Executive Director DoD Policy Board on Federal Aviation Attachment: DoD Comments to NPRM

2 DoD Comments to Docket No. FAA ; Notice No , Automatic Dependent Surveillance Broadcast (ADS-B) Out Performance Requirements to Support ATC Service GENERAL COMMENTS 1) Comment: NPRM seems to omit impacts or operations for State and military aircraft. These proposals would affect all U.S. commercial air carrier operations, foreignflag carriers operating in the designated classes of U.S. airspace, air charter operations, air cargo operations, and a significant portion of the general aviation fleet operating in the NAS. These proposals would affect all U.S. commercial air carrier operations, foreignflag carriers, DoD and other State aircraft operating in the designated classes of U.S. airspace, air charter operations, air cargo operations, and a significant portion of the general aviation fleet operating in the NAS. Rationale: NPRM proposals would affect all U.S. DoD and other state aircraft. 2) Comment: The NPRM performance requirements are excessively stringent, applied too broadly, and the levels of performance are not justified. Recommend changes: Performance requirements should vary based on operations and airspaces. Rationale: In the NPRM all classes of airspace are identified as requiring the same performance standard. Certain applications and classes of airspaces should require different performance standards. For example, Class A airspace may require a lower performance standard than published in the NPRM when compared to Class B or C airspaces where closely spaced parallel approaches and other air-to-air applications may be conducted. Users should be able to decide which applications they want to equip for, and equip to those standards. For example, not all aircraft are CAT III, nor is it a requirement in at all airports. Therefore, if an operator chooses not to equip to that level, then they can t perform the required operation. Not all users will need nor want to equip for the highest level of operations. 3) Comment: The proposed rule seems inconsistent with regard to the major safety benefits of ADS-B. Significant safety and efficiency advantages such as pilot selfseparation and situational awareness are obtained with ADS-B In.

3 Rationale: The FAA is not proposing to mandate ADS-B In performance requirements even though ADS-B In is seen as the backbone of benefits gained by ADS-B. While ADS-B In provides substantial benefits to operators, it has not been identified as a requirement for maintaining the safety and efficiency of NAS operations or as an essential building block toward NextGen. Despite the everincreasing demands on airspace, full benefits of ADS-B cannot be fully realized until ADS-B In has been identified as a requirement. 4) Comment: Based upon the following comments: The FAA is uncertain if separation minima can be reduced; The FAA may examine the possible reduction in separation standards might be applied and The FAA may examine the possible reduction of separation standards once ADS-B has been certified to meet existing separation standards safe and consistently, DoD does not support the implementation of a rule where the primary benefits are not yet completely validated. Rationale: Throughout the NPRM, there are comments supporting the rule to help achieve a level of surveillance accuracy that would support reducing aircraft separation standards. However, reduced separation standards using ADS-B as described in the NPRM have not been approved. DoD will be looking for definitive and reasonable plans to define, validate, and implement airspace improvements based on ADS-B Out as well as In. Until reduced separation standards are approved, DoD does not support the publication of the final rule. 5) Comment: The FAA needs to continue to work with the DoD and DHS to ensure that concerns about ADS-B security are adequately addressed prior to the issuance of the final ADS-B rule. Rationale: ADS-B is a new standard adopted by many aviation authorities worldwide which offers a great leap forward in aircraft surveillance capabilities. More information is made available than before with conventional primary and secondary radar technologies. Because ADS-B does not require major conventional radar ground infrastructure, by its nature, it makes the position of aircraft in flight and intent generally available to everyone. In this regard, DoD believes there are some potential security vulnerabilities which need to addressed. There are several specific concerns noted in FAA planning documents, including unauthorized use of ADS-B information for introducing false targets/aircraft spoofing into the system. A thorough security assessment involving DoD and DHS is needed to determine ADS-B risks and appropriate countermeasures. Additionally, a technique for detecting ADS-B spoofing which is independent of ADS-B systems is required. 6) Comment: The FAA, DHS, DOJ, NSA and DoD will need to develop operational procedures for special USG flights (such as low observable surveillance aircraft, combat air patrol missions, counter-drug missions, counter-terrorism missions, VIP transport, law enforcement surveillance, etc), that are inconsistent with broadcasting their position over

4 a link that can be easily received and resolved. State aircraft, due to national security issues, will require special accommodations in ADS-B assigned airspace. Recommend addition to page 19, paragraph 1, end of paragraph: Due to special USG flights that are incompatible with the broadcasting of their position over an unencrypted ADS-B datalink, ATC will accommodate these flights in the NAS by means other than ADS-B. Criteria for these special flights will be approved by interagency coordination. Rationale: ADS-B uses information from a position service, e.g. GPS, to broadcast the aircraft s position, thereby making this information more timely and accurate than the information provided by the conventional radar system which has a latency factor since it is based on interrogation and reply. Currently, large, expensive, and transmitting primary or secondary radars are needed to resolve the position of aircraft performing these sensitive national security missions. These aircraft positions are currently stripped from data that is released to the public. With the advent of very low cost, non-transmitting, portable devices that can receive ADS-B data of these flights, stripping these aircraft from the publicly available data is no longer sufficient. These flights must be accommodated using conventional Mode 3 or Mode S transponders. These special missions must be accommodated whenever necessary and not restricted on workload availability of the servicing ATC facility. Specific procedures and approval criteria for these flights will need to be negotiated through interagency coordination. Additionally, ADS-B has the capability of transmitting Flight ID, 24-bit Aircraft Address and flight intent. Certain State aircraft, to include certain military aircraft and Low Observable Surveillance (LOS) aircraft are restricted from transmitting GPS present position in the clear. ICAO Codes are typically unique Aircraft Addresses (24-bit) that are assigned to an airframe. Similarly, the call sign or flight ID can uniquely identify an aircraft. This information can be used to identify the aircraft type and characteristics. By the unique nature of these codes and/or flight IDs, special flights could be identified and their mission could be compromised. Since more than one governmental department is impacted in this implementation plan, appropriate interagency discussions will need to address this concern. Additionally, international standardization is paramount. 7) Comment: DoD recommends that FAA coordinate with DOS for the treaty implications of mandating foreign equipage with WAAS prior to implementing ADS-B Out rule. Rationale: DoD has reservations regarding a mandate for WAAS equipage for foreign aircraft to access U.S. domestic airspace in light of the treaty signed with Europe which prohibits them from mandating Galileo for access to European airspace. On page 42 of the proposed rule; the sentence With specific and limited exceptions, the ADS-B Out performance requirements proposed here would apply to all aircraft operating in the U.S. designated airspace. These

5 requirements would be applicable to operations conducted by domestic and foreign operators in U.S. territorial airspace. may unwittingly give the Europeans cause to nullify the treaty and require all U.S. aircraft to equip with Galileo in order to access European airspace. 8) Comment: DoD intends to use PPS GPS to meet performance requirements in various aircraft. Rationale: The FAA ADS-B NPRM has identified the requirement for WAAS quality GPS positioning and position integrity to support ADS-B Out. DoD intends to use the upgraded PPS signal on L-1 and L-2 with M Code to meet the required performance. It is anticipated that the PPS performance using M-code will be equal to or better than the present PPS signal. 9) Comment: In the NPRM, there is no discussion concerning the derived benefits of GPS modernization to include GPS L-5. Has the FAA taken into consideration the upgrade of GPS receivers for GPS L-5, WAAS or Galileo in their cost benefit analysis? Rationale: Part of the GPS program involves the addition of a third civil signal at L5 ( MHz). The L5 signal will make GPS a more robust navigation service by further mitigating RF interference and reducing errors due to the ionosphere. Because the L5 constellation will not be fully operational for some time, current GPS receivers will need to be modified to reap derived benefits. For DoD commercial derivative aircraft that use a Pre-WAAS TSO C-129 SPS GPS receiver today, a future GPS receiver upgrade will probably be required prior to the ADS-B Out implementation. The timing of this GPS upgrade will be important since several GPS vendors are starting to offer L-5, WAAS, and Galileo receivers already. The decision to upgrade the GPS receiver for the ADS-B Out performance for these commercial derivative aircraft should be determined by the sunset date of the airframe. 10) Comment: DoD/DHS and FAA need to negotiate provisions for GPS electronic testing on a recurring basis. Recommendation: DoD will provide the FAA a single point of contact to coordinate GPS electronic testing. Rationale: As identified on page 48 of the proposed rule, There are times when GPS may be unreliable in certain areas and during certain times due to planned testing or solar flare activity. GPS electronic interference testing is essential to national security.

6 11) Comment: While the NPRM specifically addresses aircraft installations of ADS- B Out, there are implications to military deployable ATC surveillance (ground based) equipment in regards to ADS-B ground surveillance data formats. Rationale: There are various ground surveillance formats/protocols such as ASTERIX Category 11, Category 21, etc. DoD deems it imperative that a close technical relationship be established between FAA and DoD, with Services representation, to plan for a workable ground infrastructure transition that will enable both the military's Homeland Security and National Defense missions to be met as exists today. 12) Comment: Need to reinforce through the final rule that ADS-B is a surveillance system and not a navigation system. Rationale: Throughout the draft rule, there are multiple uses of navigation system terminology. In some areas this has caused confusion in determining surveillance functionality requirements. Final rule must ensure ADS-B is a surveillance functionality and is providing current aircraft position and not navigation information. 13) Comment: Recommend making Page 21, paragraph 2, more technically complete. Rationale: Since many commercial or general aviation aircraft are equipped with Mode S transponders to meet TCAS requirements, this information as discussed in this paragraph is available to ATC via Mode S. Mode S provides more accurate positional information and minimizes interference. This is accomplished by discrete interrogation of each Mode S transponder-equipped aircraft and improved processing of aircraft replies. In addition, Mode S provides the medium for a digital data link which can be used to exchange information between aircraft and various air traffic control functions and weather databases. Many FAA sites are currently being replaced by Mode S capable interrogators which essentially mirror or could emulate the Mode S transponders requirements in Europe and allow for international interoperability. With Mode S, ATC radar data can be linked to aircraft that had compatible transponders to receive the data and at no cost to the users. Mode S transponder equipped aircraft can be tracked and identified using Mode S interrogation without assignment of a secondary surveillance radar (SSR or squawk ) code. 14) Comment: On Page 26, paragraph 2, recommend separating required elements necessary for surveillance, and advanced applications. Rationale: The list of required elements is extensive. On integrating ADS-B on old legacy aircraft, it may be significantly less expensive to leave out some of these elements. Similar to the two levels of Mode S functionality in Europe, Elementary Surveillance (ELS) and Enhanced Surveillance (EHS), there needs to

7 be discrimination on what is absolutely necessary for surveillance, and what is just nice to have and for future application. Some of the message elements may be necessary only for advanced applications that will not be utilized by all users. 15) Comment: Due to special requirements, age, and military avionics, it is not reasonably feasible to equip some DoD aircraft with ADS-B Out. Recommend addition to page 19, paragraph 1, end of paragraph: Due to special requirements, age, and military specific avionics, it is not reasonably feasible to equip some State aircraft with ADS-B Out. Special accommodations will be provided to these aircraft to utilize the NAS. Rationale: It may be unreasonably expensive to equip some State aircraft with ADS-B Out. Accommodations must be given to ensure DoD needs to access airspace to fulfill military, training, and test and evaluation requirements for peacetime, contingency, and wartime operations.

8 ADMINISTRATIVE COMMENTS 1) Page 7, paragraph 3, line 4 such as the constraints ground-based radar places on the distance aircraft must be separated and the limits caused by Recommend restating to: such as the constraints that ground-based radars place on aircraft separation standards or requirements, and the limits caused by 2) Page 8, paragraph 2, line 5 traditional procedures.. Recommend delete 2 nd period at end of sentence traditional procedures. 3) Page 8, paragraph 3, line 6 Attaining the goal of performance-based communications will depend on technology, such as datalink, which would transmit key instructions directly to aircraft flight managements systems, which would speed receipt of critical information and prevent errors that can come from manual data entry. Recommend restating to: Attaining the goal of performance-based communications will depend on technology, such as aircraft data links, which transmit key instructions directly to aircraft flight management systems to accelerate the delivery of critical information, limit voice frequency congestion, and prevent errors that can come from manual data entry. 4) Page 9, paragraph 1, line 3 When displayed in the cockpit, information obtained through ADS-B greatly improves situational awareness in the en route segment, in the terminal area during approaches, and on the airport surface.

9 Recommend restating to: When ADS-B In technology becomes available, derived information will greatly improve situational awareness in the cockpit during the en route segment, in the terminal area during approaches, and on the airport surface. Rationale: Technical accuracy ADS-B Out, which this NPRM applies to, will not directly provide aircrews the benefit of improved situational awareness in the cockpit. 5) Page 11, Footnote #3 It addition, many airports Correct typographical error In addition, many airports 6) Page 14, paragraph 2, line 1: To accommodate the projected level of traffic without increasing delay, more comprehensive surveillance in the NAS, including more radar sites in certain areas, would be necessary. To accommodate the projected level of traffic without increasing delays, more comprehensive surveillance in the NAS would be necessary, including more radar sites in certain areas. 7) Page 15, paragraph 2, line 1 The ADS-B system is an advanced surveillance technology that combines a satellite positioning service, aircraft avionics, and ground infrastructure to enable more accurate transmission of information between aircraft and ATC. The ADS-B system is an advanced surveillance technology that combines a positioning capability, aircraft avionics, and ground infrastructure to enable more accurate transmission of information between aircraft and ATC. Rationale: ADS-B is not necessarily based on a satellite positioning service. Even though today GPS is the generally accepted method to achieve the required performance it is not necessarily the required method. Other positioning systems that meet the required performance may be used. Stating satellite positioning

10 service in the Final Rule limits future growth potential in a performance based environment and may lead to the belief that only GNSS positioning services meet the required performance. Other types of positioning systems that meet the requisite performance requirements may be developed in the future, and may include satellite constellations similar to the Galileo system, or tightly coupled IRU to existing GPS. At this point, however, the DoD is still studying the ability of these other navigation position systems to meet the performance standards articulated in this proposal. 8) Page 15, paragraph 2, line 9 ADS-B also can provide the platform for aircraft to receive various types of information, including ADS-B transmissions from other equipped aircraft or vehicles. ADS-B also can provide the means for aircraft to receive various types of information, including ADS-B transmissions from other equipped aircraft or vehicles. 9) Page 16, paragraph 3, line 1 ADS-B Out refers to an appropriately equipped aircraft s broadcasting of various aircraft information. ADS-B Out refers to an appropriately equipped aircraft s broadcasting of various information of the aircraft. 10) Page 15, paragraph 1, line 1 ADS-B has been identified as the technology to facilitate that goal. ADS-B In has been identified as the technology to facilitate that goal. Rationale: In order to be technically correct and to avoid creating an expectation that ADS-B Out provides traffic, weather or airport ground vehicle information to the crew, clarifying is necessary.

11 11) Page 18, Note 11 & 12 Flight Information Services-Broadcast (FIS-B) is a ground-based uplink of flight information services and weather data. Other flight information provided by the FIS-B service includes Notices to Airmen and Temporary Flight Restrictions. Recommend Changing to Flight Information Services-Broadcast (FIS-B) is a ADS-B In ground-based uplink (UAT only) of flight information services and weather data. Other flight information provided by the FIS-B service includes Notices to Airmen and Temporary Flight Restrictions. Rationale: The uplink phraseology is relevant/meaningful to knowledgeable individuals but isn t intuitively connected to In or Out terminology used throughout the document. Recommend change to reflect accuracies and standardization. 12) Page 18, paragraph 2, line 2 and Class E airspace areas at or above 10,000 feet Mean Sea Level (MSL) over and Class E airspace areas at or above 10,000 feet Mean Sea Level (MSL) or 2000 feet Above Ground Level (AGL) in mountainous terrain, whichever is higher, over Rationale: There are large areas of the Western United States where mountainous regions cannot be safely transited below 10,000 MSL. As the NPRM is presently written, non-ads-b equipped aircraft will not be able to transit mountainous terrain. 13) Page 19, paragraph 2, line 1 The implementation of ADS-B requires two datalinks to support the full set of applications. UAT is intended to support applications for the general aviation user community that are not needed by air carriers because air carriers have weather radar, fly at high altitudes, and have other aeronautical links. The implementation of ADS-B In requires two datalinks to support the full set of applications. UAT is intended to support applications for the general aviation user community.

12 Rationale: The information provided in the paragraph is out of scope for this section of the proposal. Recommend rewording first sentence to accurately reflect ADS-B In since the paragraph is discussing the In portion of ADS-B. As written now, this paragraph concentrates on ADS-B In capabilities. Also, extra verbiage is not entirely correct. The data would be useful to commercial carriers; however, as stated later in the paragraph, it is a bandwidth issue over 1090, not a lack of need by the 1090 user. 14) Page 22, paragraph 2, line 5. Finally, we explain the necessary requirements for antenna diversity on the aircraft and the required latency of the data in the ADS-B transmission from the aircraft. Finally, we explain the necessary requirements for antenna diversity on the aircraft and the latency allowed for the data in the ADS-B transmission from the aircraft. Rationale: This sentence implies that latency is a requirement 15) Page 35, paragraph 3, line 7 If the aircraft broadcast message element for position has an NACp of less than 9, ATC would be notified and it could choose to revert to a backup system or apply procedural mitigation. If the aircraft broadcast message element for position has an NACp of less than 9, ATC would be notified and ATC will ensure adequate separation is maintained. Rationale: Is a bit confusing and implies that either ATC or the aircraft will revert to a backup system. Depending on the cause of the degraded performance and the operations being conducted by the aircraft, various options are available to the controller to ensure adequate separation. If no other traffic is nearby, no action may be required. If the aircraft is also being detected via secondary or primary radar, fusion may allow normal ATC operations, depending on geometry and distance from other radars, etc.

13 16) Page 37, paragraph 1, line 9 This value would provide integrity assurance that meets a failure rate probability of per flight hour. This value would provide integrity assurance that meets a maximum allowed failure rate probability of per flight hour. Rationale: As stated, integrity would not be assured for % of each flight hour. 17) Page 38, paragraph 1, line 3: This proposal specifies performance standards for aircraft avionics equipment for operation to enable ADS-B Out. These performance standards would accommodate and facilitate the use of new technology. Presently, GPS augmented by the Wide Area Augmentation System (WAAS) is the only navigation position service that provides the level of accuracy and integrity (NIC, NACp, and NACv) to enable ADS-B Out to be used for NAS-based surveillance operations with sufficient availability. The FAA is considering whether other navigation position systems such as the Global Navigation Satellite System (GNSS) combined with tightly coupled inertial navigation systems are also capable of meeting the proposed performance standards. Other types of positioning systems that meet the requisite performance requirements may be developed in the future, and may include satellite constellations similar to the Galileo system, or tightly coupled IRU to existing GPS. At this point, however, the agency is still studying the ability of these other navigation position systems to meet the performance standards articulated in this proposal. In order to meet the proposed performance requirements using the GPS/WAAS system, aircraft would be required to have equipment installed onboard the aircraft that meets one of the following: (1) TSO-C145b, Airborne Navigation Sensors using the GPS augmented by WAAS; or (2) TSO-C146b Stand-Alone Airborne Navigation Equipment using the GPS augmented by WAAS. This proposal specifies performance standards for aircraft avionics equipment to enable ADS-B Out. Since no specified navigation position data source is required, and only a performance standard that needs to be achieved, these required performance standards will accommodate current and future technologies.

14 Rationale: As currently written the paragraphs do not support Performance Based Navigation. For DoD, military GPS PPS receivers incorporate RAIM with FDE and barometric and inertial aiding and will support ADS-B based on MITRE s study on GPS Constellations and Support. Nor does this sentence take into consideration future GPS constellations, to include Galileo, to meet future availability requirements. Attempting to specify a navigation source requirement will lead to confusion, runs afoul of international agreements, and jeopardizes the implementation of ADS-B. 18) Page 39, paragraph 3, line 3 For ADS-B In, however, additional 1090 MHz receive antennas may be necessary depending on the additional avionics equipment installed on the aircraft. Recommend deleting sentence. Rationale: Sentence is relevant to antenna arrays; however, the overall section should concentrate on ADS-B Out only. As written, the sentence strays from the scope of the section. 19) Page 47, paragraph 3, line 1 In accordance with proper preflight actions, each operator would have to verify ADS-B Out availability for the flight planned route through the appropriate flight planning information sources. If the aircraft cannot meet the proposed performance requirements using a given position service, the operator would have to use either a different, available position service, re-route, or reschedule the flight. Under this proposal, pilot procedures are expected to be minimal. Pilots would have to: (1) check that the ADS-B avionics equipment is turned on and operating properly; (2) ensure that message elements (g)-(k) of part 91, appendix H, section 4 are entered during the appropriate phase of flight; (3) turn off the ADS-B equipment if directed by ATC; and (4) if notified by ATC that the aircraft s ADS-B information is not being transmitted, request special handling that may include accommodation (on a case-by-case basis), or direction to exit the present airspace. Recommend restating to: In accordance with proper flight actions, each operator would have to verify ADS-B avionics equipment is installed, turned on and operating properly. Rationale: There is too much written in the original paragraph that can be interpreted differently and cause confusion. Aircraft will need to be equipped and operating as required by the operations. Operational information will need to be clear and concise.

15 20) Page 50, paragraph 1, line 3 When deciding to issue NOTAMs to allow operations by aircraft with inoperable ADS B Out equipment, the FAA will weigh the impact of denying airspace access to those aircraft that do not comply with the performance requirements against the reduction in operational capability due to the limitations of the backup surveillance system. The FAA will weigh the impact of constraining airspace access against the reduction in operational capability due to the limitations of the backup surveillance system when deciding to issue NOTAMs. Rationale: The final sentence is confusing, and the intent of the statement is unclear. For example, when a NOTAM is issued regarding the use of the backup surveillance system, would the FAA then attempt to accommodate aircraft not originally ADS-B Out capable into airspace that is usually reserved for ADS-B Out operations? Or, is the statement of inoperable ADS-B Out equipment referring solely to those aircraft originally ADS-B Out capable impacted by the degradation in the GPS constellation? Or, is the statement only aimed at what the FAA will take into consideration in issuing a NOTAM or the severity of the NOTAM? 21) Page 51, paragraph 1, line 4 However, this NPRM includes a discussion of ADS-B In because ADS-B Out transmissions provide the aircraft information viewed by the flight crew in aircraft equipped for ADS-B In. Recommend change to: However, this NPRM includes a discussion of ADS-B In because ADS-B Out transmissions would provide the aircraft with information that may be viewed by the flight crew in aircraft equipped for ADS-B In. Rationale: Clarity 22) Page 52, paragraph 2, line 1 B. Application and Services Recommend change to: B. Potential Applications and Services of ADS-B In

16 Rationale: This section describes applications and services that ADS-B Out doesn t provide. 23) Page 53, paragraph 1, line 2 At night and in poor visual conditions, pilots could also see where they are in relation to the ground using onboard avionics and terrain maps associated with a multi-function display. Recommend to delete sentence: Rationale: This is not a benefit that is unique to ADS-B In and it should not be characterized as such since existing technology already enables aircrews to see where they are in relation to the ground. 24) Page 54, paragraph 1, line 1 TIS-B would be available during the transition period and until all affected aircraft are equipped for ADS-B Out. Once all aircraft are equipped to meet ADS- B Out performance requirements, TIS-B would be decommissioned as it would no longer be necessary since aircraft would receive traffic information through ADS- B. Recommend restating to: Since there are many areas of ADS-B coverage, where ADS-B Out is not required, all aircraft in ADS coverage area will not be required to equip. For aircraft to be equipped with ADS-B In applications to detect these aircraft, as well as temporary failures of individual aircraft ADS-B equipment, TIS-B will need to be continuously available in coverage areas. Rationale: Not all aircraft will be required to equip in ADS coverage; therefore, if there is a need for TIS-B prior to full equipage, there will be a need even after the mandate, since the mandate does not cover all areas (example Class E airspace below 10,000 feet). 25) Page 56, paragraph 4, line 1 Recommend change to: Add paragraph on air to air operations. Rationale: Explain the technical ability of ADS-B In to deliver air-to-air capability. NextGen anticipates that air-to-air functionality will facilitate some level of pilot self-separation capabilities. Shared separation management between aircraft will be key to expanding airspace capacity. And, as the system matures,

17 the possibility exists to exchange much more information--including 4D flight paths--between aircraft, as well as with a ground-based ATC infrastructure, enabling air-to-air strategic conflict avoidance and ground-to-air profile management to optimize runway capacity. 26) Page 58, paragraph 3, line 4 ADS-B information in the flight deck did provide increase pilot awareness of surrounding traffic ADS-B information in the flight deck did provide increased pilot awareness of surrounding traffic Rationale: Correct typographical error. 27) Page 60, paragraph 3, line 3 whether to place GBTs in these areas Recommend change to: whether to place ground-based terminals (GBT) in these areas Rationale: Spell out what GBTs are prior to using it as an acronym the first time. 28) Page 64, paragraph 1, line 3. The proposed rule would facilitate the use of ADS-B for aircraft surveillance by FAA air traffic controllers to accommodate the expected increase in demand for air transportation. The proposed rule would facilitate the use of ADS-B for aircraft surveillance by FAA and DoD air traffic controllers to accommodate the expected increase in demand for air transportation. Rationale: The summary fails to include DoD as an air traffic control provider within the NAS. 29) Page 66, paragraph 2, line 3 Considering that the long-term global capabilities of ADS-B are not yet fully defined, ICAO SARPS are still evolving and are not yet fully developed.

18 The long-term global capabilities of ADS-B are not fully defined and ICAO SARPS are still in development. Rationale: It is unclear what the proposed rule is trying to convey here. The entire paragraph is awkward and should be rewritten. 30) Page 88, paragraph 2, line 7 Multilateration would provide the same benefits as radar, but at a higher cost. Recommend providing data which supports this comment Rationale: Multilateration is less costly than equipping for ADS-B since it requires no addition or modification to the aircraft avionics and much less costly than a traditional radar. Several international civil aviation authorities are already replacing secondary radar with multilateration in both wide and terminal surveillance areas. DoD would like to see justification for statements used to support this analysis.