April 1, 2015

U.S. Department of Transportation

Docket Operations

West Building Ground Floor, Room W12-140

1200 New Jersey Avenue, SE

Washington, DC 20590

Subject: Petition for Exemption

Reference: 14 CFR 91.227 - Automatic Dependent Surveillance-Broadcast (ADS-B) Out 

equipment performance requirements.

Dear Sir or Madam:

In accordance with the provisions of Title 14, Code of Federal Regulations (14 CFR) §11.63 and 

§11.81, Airlines for America, on behalf of our passenger and cargo airline members and similarlysituated air carriers1

, petitions for a limited exemption from the Navigational Accuracy Category 

for Position (NACp) and Navigational Integrity Category (NIC) aspects of the ADS-B Out 

performance requirements in 14 CFR §91.227(c). Specifically, A4A requests a temporary 

exemption from these performance requirements in the event of a satellite disruption or 

occasional satellite geometry configuration of the Global Positioning System (GPS) constellation 

resulting in diminished accuracy or integrity, where an alternate means of traffic separation safely 

used today can be implemented by the FAA Air Traffic Organization (ATO). The exemption would 

have an effective date of January 1, 2020 and expire on January 1, 2025. We request the FAA 

process this exemption promptly.

Background 

ADS-B Out is an integral part of FAA’s overall plan for the next generation of air traffic control and 

surveillance (NextGen). Taking advantage of new and emerging technology, and when fully 

implemented, NextGen is designed and intended to create more efficiency in the National 

Airspace System (NAS), resulting in reduced fuel consumption, reduced emissions, enhanced air 

traffic capacity and greater safety for the flying public in all segments of aviation. Certain aspects 

of NextGen, most notably ADS-B Out, are scheduled to be implemented in the United States by 

January 1, 2020 (“the 2020 (regulatory) mandate”).2 The position accuracy and integrity 

performance requirements of ADS-B Out standards exceed the capabilities of GPS receivers 

currently available for use in transport category airplanes. However, the performance capabilities 

of existing GPS receivers provide a safe alternate means of surveillance and control to ADS-B 

Out standards when alternate means of surveillance, such as radar, are available. These are 

expected to remain available for the foreseeable future, and certainly beyond January 1, 2025.

 

1 A4A airline members are: Alaska Airlines, Inc.; American Airlines Group, Inc. (American and US Airways); Atlas Air, Inc.; Delta Air 

Lines, Inc.; Federal Express Corporation; Hawaiian Airlines; JetBlue Airways Corp.; Southwest Airlines Co.; United Air Lines, Inc.; 

and United Parcel Service Co. Air Canada is an associate member.

2 § 91.225 Automatic Dependent Surveillance-Broadcast (ADS-B) Out equipment and use, paragraph (b)
A4A Petition for Exemption, April 1, 2015

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ADS-B out compliance requires a two-step process; (1) Original Equipment Manufacturers 

(OEMs) and avionics manufacturers produce equipment necessary to meet ADS-B Out standards 

and issue service bulletins or, alternatively, airlines obtain a Supplemental Type Certificate for 

non-standard equipment; and (2) airlines will retrofit aircraft with the equipment and information 

produced from step one, a time consuming process for large airline fleets due to maintenance 

scheduling. The first step has been delayed due to the unavailability of certified equipment in spite 

of the fact that the final rule was issued in 2010. It is critical that we achieve NAS efficiencies while 

avoiding multiple aircraft retrofits during the transition to NextGen. Multiple retrofits would be an 

expensive, disruptive and wasteful outcome. All segments of the industry have been working on 

avionics solutions and look forward to enhanced GPS integrity and accuracy that will become 

available from navigation equipment still under development, and enhancements to Global 

Navigation Satellite System (GNSS) constellations. Industry groups including the RTCA Inc., 

SAE-ARINC Industry Activities (“ARINC”), MITRE, and others have monitored, reported, and 

published papers with standards aimed at realizing ADS-B Out position source capabilities on 

time. In January 2013, ARINC’s Aeronautical Electronics Engineering Committee (AEEC) 

concluded that enhanced GPS positional accuracy will not be available on air transport aircraft 

before the airline equipage 2020 mandate effective date3, leading to the following scenario:

1) Airplanes flying in the affected airspace will need to augment GPS accuracy to meet the 

requirements of 14 CFR §91.227(c), or

2) Alternate means of traffic separation will be available to augment GPS in the event of reduced 

accuracy or integrity during a GPS service disruption or unfavorable satellite geometry.

Two well-understood and tested equipage plans have been shown to satisfy FAA’s ADS-B Out 

requirements when adequate numbers of GPS satellites are visible (line-of-sight) to the aircraft 

antennae. These equipage plans differ only in their ability to interpret and report potential 

accuracy and integrity of navigational performance. Selective Availability (SA), a switchable 

security feature that deliberately reduces the reported accuracy and integrity of an aircraft 

position, was deactivated by Executive Order in 2000.4 “SA-On” avionics systems assume SA is 

still active, which it is not, while “SA-Aware” systems assume that SA is inactive. SA-Aware 

systems therefore can still determine an aircraft position and provide adequate navigational 

accuracy and integrity. SA-On and SA-Aware have been shown in actual operations with the 

current GPS constellation to meet ADS-B Out accuracy and integrity requirements operationally 

available in excess of 99% of the time, with SA-Aware capable of exceeding operational 

availability 99.9% of the time.

Significant uncertainty stems from the nature of the ADS-B Out performance-based rule. The FAA 

has stated that operators can use GPS SA-On or SA-Aware equipment to comply. However that 

equipment does not always satisfy the performance requirements of the rule due to changes in 

the number and spatial location of GPS satellites. While GPS augmentation systems are readily 

available in some segments of the user community, such solutions are far less available for the 

integrated avionics suite designs of modern transport aircraft. Implementation using existing 

augmented receiver technology on such aircraft, while possible, is not rational because the 

equipment would be used for a relatively short period of time before enhanced GPS systems 

appropriate for transport aircraft integration are expected to become available. Moreover, it is 

questionable there will be sufficient availability of integrated augmented GPS equipment for 

 

3 ARINC report 660B, “CNS/ATM Avionics Architectures Supporting NEXTGEN/SESAR Concepts”

4 Found at http://www.gpo.gov/fdsys/pkg/WCPD-2000-05-08/pdf/WCPD-2000-05-08-Pg959-2.pdf.
A4A Petition for Exemption, April 1, 2015

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transport category aircraft in the needed timeframe. Given these circumstances, including the 

operational disruptions that would occur with multiple equipment change events, the better 

solution is a temporary bridge to final equipage to meet ADS-B Out performance standards.

Beginning in October 2014, FAA convened the “Equip 2020” workgroup that included regulators, 

operators, vendors, and manufacturers to address this situation. This workgroup reached 

consensus in December 2014 on the temporary alternate approach, discussed above, regarding 

a transition period from 2020 to 2025. During this transition period, operators will acquire 

operational data with currently installed (SA-On and SA-Aware) GPS position source equipment 

to refine final ADS-B Out equipage implementation. Furthermore, innovative new equipment is 

expected to become available during that timeframe. A summary of the consensus is included as 

Attachment 1. This petition, if granted, should substantially reflect the details of the Equip 2020 

workgroup recommendations. Salient among the many agreed upon points, FAA Air Traffic 

Organization (ATO) will support “reduced availability” for SA-On GPS systems reported by the 

Service Availability Prediction Tool (SAPT) where an alternate means of traffic separation in the 

affected area can be implemented by the ATO. Further, SAPT will not need to be used in aircraft 

equipped with SA-Aware GPS receivers as a means to provide ADS-B position sources during 

the transition. 

Equipment ordering, pre-wiring, and installation all need to proceed immediately with confidence

that SA-On and SA-Aware GPS along with the potential use of available alternate traffic 

separation means by the FAA will facilitate uninterrupted operation even when the GPS satellite 

constellation is temporarily degraded. 

The Applicable Regulations and Relief Sought

We seek an exemption from 14 CFR §91.227(c), “ADS-B Out Performance Requirements” during 

the limited periods of GPS satellite disruption or adverse geometry that reduces navigation 

accuracy and integrity capability below ADS-B Out rule-compliant performance requirements for 

aircraft otherwise equipped with SA-On and SA-Aware.

Reasons for seeking the relief at this time include: 

1) Carriers need assurance that aircraft retrofit/equipage completed prior to the ADS-B Out 

deadline will ensure uninterrupted operation after the January 1, 2020 deadline, even during 

periods of GPS degradation. 

2) The scope of this exemption is limited because GPS disruption or inability to meet the ADS-B 

Out performance requirements for aircraft equipped with SA-Aware and SA-On equipment will 

be rare and infrequent. Use of secondary surveillance radar as backup will eliminate any 

adverse operational effects of SA-Aware and SA-On receivers not meeting ADS-B Out 

performance for NIC and NACp. 

3) Alternate means of surveillance during such occurrences exist and are used safely today.

4) GPS receivers capable of meeting the 14 CFR §91.227(c) accuracy and integrity requirements 

even in the presence of anticipated (though infrequent) GPS disruptions are not available for 

purchase or installation in many transport category airplanes and may not be available in 

quantity until after January 1, 2020. 

In accordance with the Equip 2020 consensus, we request that FAA stipulate that each affected 

operator will submit its own letter that requests use of this proposed exemption5. Exemption 

 

5 Ref Regulatory Docket FAA-2012-0429 as an example of FAA Exemptions granted to OEM and Associations that require 

individual requests to use the petition
A4A Petition for Exemption, April 1, 2015

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grantees would be required to create, maintain and update a GPS equipage plan that will commit 

to complete 14 CFR §91.227(c) compliance prior to the end of the transition period (1/1/2025). 

This carrier plan need not be approved by the Administrator but must be available for the 

Administrator’s review. We propose that FAA require initial, rudimentary operator-specific plans 

to be available by August 2018, with annual updates (or more frequent if necessary) thereafter 

reflecting increased technical and schedule confidence and details. Before the January 1, 2020 

mandate deadline, the plan details should be mature and include a “high confidence” of execution. 

Plans may reasonably be expected to include the following elements:

1) Manufacturer and Part Number, applicable service bulletin, or STC, of GPS receiver to be 

implemented

2) Upgrade schedule, preferably tail-number specific 

3) Interim fleet milestones, e.g. initial installation, 30%, 80%, 100% completion

4) If a specific set of aircraft will not be upgraded but are desired to be covered by the Exemption, 

the operator’s plan for fully rule-complaint operation beyond the expiration of the Exemption 

must be included (e.g. use of SAPT even for SA-Aware equipage and possible operational 

impacts).

In consideration of these matters, we request relief from the NACp and NIC requirements of 14 

CFR §91.227(c), “ADS-B Out Performance Requirements” until January 1, 2025, a period of five 

years from the date specified by 14 CFR §91.225. 

Granting the Exemption Would be in the Public Interest

FAA has invested significant public funds and time readying their systems for this important step 

forward in the NextGen effort. Granting this Exemption assures that FAA’s investment is usable 

by operators and allows FAA to maintain its NextGen schedule. The limited time frame of this 

exemption assures FAA can proceed with a modified retirement schedule for selected aging 

terminal area radar systems. 

By acting now to resolve the market uncertainty described above, operators will be able to plan 

for ADS-B Out compliant transponder solutions by the mandated deadline of January 2020. The 

ability of operators to commit to upgrade plans should move vendors to improve product 

availability. Airspace system efficiency will increase in a coordinated fashion during the proposed 

exemption period.

On a technical level, by waiting for receivers to be available in about 2018 or shortly beyond (too 

late for January 1, 2020 full installation), a more workable upgrade path to satellite-based 

augmentation systems (SBAS) and multi-frequency/multi-constellation global navigation satellite 

system (GNSS) GPS will emerge that will benefit the public by adding more robust performance 

and inherent improved operational reliability.

Finally, absent this relief, airlines will be forced to adopt a two-step position source upgrade 

process with the first step providing a means of compliance necessary/useful for a short period of 

time and the second step providing full compliance with the FAA rule or face the possibility of 

service interruptions if a satellite service disruption occurs. Either case adversely affects the public 

interest with respect to passenger travel and air cargo services. This will result in increased 

delays in the NAS, adversely affecting the public and producing the opposite outcome of what 

NextGen is designed to accomplish. Granting this exemption would help to ensure that air service 

continues uninterrupted and in this respect would serve the public interest. 
A4A Petition for Exemption, April 1, 2015

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Granting the Exemption Would Not Adversely Affect Safety

Safety will not be adversely impacted if the FAA grants this petition because FAA would utilize 

airplane traffic separation methods used safely today. In addition, the ADS-B position accuracy 

and integrity performance required by ADS-B Out far exceeds that which the FAA can currently 

utilize, while adequate alternate means of safe traffic separation will continue to exist beyond the 

2020 mandate effective date and for the foreseeable future.

A Summary of this Petition that FAA Could Publish in the Federal Register

Petitioner: Airlines for America

Affected Regulations: 14 CFR 91.227(c), ADS-B Out Performance Requirements for 

NACp, NACv, NIC, SDA, and SIL.

Summary of Relief Sought: During periods of GPS constellation disruption/degradation 

rendering otherwise compliant ADS-B Out systems non-compliant 

with the regulation, operation may be permitted when FAA has 

alternate means of providing safe traffic separation.

Granting this Exemption is in the public interest as it maintains an equivalent level of safety, 

utilizing airplane traffic separation methods used today and avoids potential, unpredictable 

disruptions in scheduled and unscheduled air transport service and/or elevated travel and 

shipping costs.

Conclusion

For the foregoing reasons, we respectfully request an Exemption from the requirements of 14 

CFR 91.227(c) pertaining to the ADS-B Out performance requirements..

Sincerely,

Paul J. McGraw

Vice President

Operations and Safety

 

Enclosures/
A4A Petition for Exemption, April 1, 2015

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Attachment 1, “Equip 2020” Draft Consensus, 17 December 2014

ADSB CTA 11/18/2014: TRANSITION 

PERIOD FOR NIC AND NAC REQUIREMENTS

1. FAA General Counsel has explored regulatory options to provide relief, during a defined transition 

period beginning on January 1, 2020, from 91.227 performance requirements for Navigation 

Integrity Category (NIC) and Navigation Accuracy Category (NAC). This should be accomplished by 

Exemptions rather than by amendment to the regulation.

2. FAA and industry agree, based upon currently available information, that the earliest that multiconstellation, multi-frequency GNSS receivers will be available in quantity is 2022. FAA and 

industry agree that third-generation SBAS-augmented ADS-B position sources can be available on 

newly-produced air transport aircraft from manufacturers earlier perhaps by 2018 (refer to 

attached Boeing and Airbus schedules). SBAS-augmented navigation/ADS-B position sources are 

available for some air transport aircraft types from manufacturers via STCs. Additionally, SBAS 

receivers for ADS-B that are independent from navigation position sources are currently available, 

also via STCs. Consequently, the Equip 2020 Group believes that a five-year transition period from 

1/1/2020 is sufficient. As a condition of seeking an Exemption, operators agree to provide the 

FAA, by January 1, 2020, a plan for ADS-B position source equipage. 

3. FAA stipulated that some terminal area SSR radars would be decommissioned starting in 2018. 

The Equip 2020 Group agrees that there will be transparency and collaboration in this process. 

4. During the transition period, in the event of “reduced availability” by operators to meet the 

91.227 ADSB NIC and NAC performance requirements in terminal airspace with operational SSR 

terminal radar there would be no impact to ATC operations and no reduction in services to 

affected airplanes so long as those operations do not take credit for a level of ADS-B performance 

that is not achieved during the period of “reduced availability”. 

5. During the transition period, in the event of “reduced availability” by operators to meet the 

91.227 ADSB NIC and NAC performance requirements in enroute airspace with SSR radar or WAM 

backup, there will be no ATC impact in that airspace when 5 nm separations are being used, so 

long as those operations do not take credit for a level of ADS-B performance that is not achieved 

during the period of “reduced availability”; if reduced ADS-B separations are being used, ATC will 

apply 5 nm separation standards.

6. During the transition period, in the event of “reduced availability” by operators to meet the 

91.227 ADSB NIC and NAC performance requirements in airspace without operational SSR radar, 

ATC will provide 5 nm separation (if an operator’s ADS-B performance supports such separations) 

or procedural separation as necessary.

7. During the transition period, operators with SA-Aware (TSO-C196 or its equivalent) ADS-B position 

sources will not be required to use SAPT or an equivalent. 

8. During the transition period, operators with SA-On position sources will be required to use SAPT 

or an equivalent and may be required to change their flight plans if a “RAIM hole” overlaps with 

an SSR outage or the predicted ADS-B performance during the “RAIM hole” does not support an 

operation based upon ADS-B alone.