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Vol. 77 Monday,

No. 117 June 18, 2012

Part II

Environmental Protection Agency

40 CFR Parts 87 and 1068Control of Air Pollution From Aircraft and Aircraft Engines; Emission

Standards and Test Procedures; Final Rule

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36342 Federal Register / Vol. 77, No. 117/ Monday, June 18, 2012 / Rules and Regulations

ENVIRONMENTAL PROTECTIONAGENCY

40 CFR Parts 87 and 1068

[EPA–HQ–OAR–2010–0687; FRL–9678–1]

RIN 2060–AO70

Control of Air Pollution From Aircraft

and Aircraft Engines; EmissionStandards and Test Procedures

AGENCY: Environmental ProtectionAgency (EPA).

ACTION: Final rule.

SUMMARY: EPA is adopting several newaircraft engine emission standards foroxides of nitrogen (NOX), complianceflexibilities, and other regulatoryrequirements for aircraft turbofan orturbojet engines with rated thrustsgreater than 26.7 kilonewtons (kN). Wealso are adopting certain otherrequirements for gas turbine engines

that are subject to exhaust emissionstandards as follows. First, we areclarifying when the emissioncharacteristics of a new turbofan orturbojet engine model have becomedifferent enough from its existing parentengine design that it must conform tothe most current emission standards.Second, we are establishing a newreporting requirement for manufacturers

of gas turbine engines that are subject toany exhaust emission standard toprovide us with timely and consistentemission-related information. Third,and finally, we are establishingamendments to aircraft engine test andemissions measurement procedures.EPA actively participated in the UnitedNations’ International Civil Aviation

Organization (ICAO) proceedings inwhich most of these requirements werefirst developed. These regulatoryrequirements have largely been adoptedor are actively under consideration byits member states. By adopting suchsimilar standards, therefore, the UnitedStates maintains consistency with theseinternational efforts.DATES: These final rules are effective on

July 18, 2012. The incorporation byreference of certain publications listedin this regulation is approved by theDirector of the Federal Register as of

July 18, 2012.

ADDRESSES: EPA has established adocket for this action under Docket IDNo. EPA–HQ–OAR–2010–0687. Alldocuments in the docket are listed onthe http://www.regulations.gov Website. Although listed in the index, someinformation is not publicly available,e.g., confidential business informationor other information whose disclosure isrestricted by statute. Certain other

material, such as copyrighted material,is not placed on the Internet and will bepublicly available only in hard copyform. Publicly available docketmaterials are available electronicallythrough http://www.regulations.gov orin hard copy at the EPA Docket Center,EPA/DC, EPA West, Room 3334, 1301Constitution Ave. NW., Washington,

DC. The Public Reading Room is openfrom 8:30 a.m. to 4:30 p.m., Mondaythrough Friday, excluding legalholidays. The telephone number for thePublic Reading Room is (202) 566–1744,and the telephone number for the AirDocket is 202–566–1742.

FOR FURTHER INFORMATION CONTACT:Richard Wilcox, Office ofTransportation and Air Quality, Officeof Air and Radiation, EnvironmentalProtection Agency, 2000 TraverwoodDrive, Ann Arbor, MI 48105; telephonenumber: (734) 214–4390; fax number:(734) 214–4816; email address:[email protected].

SUPPLEMENTARY INFORMATION:

Does this action apply to me?

Entities potentially regulated by thisaction are those that manufacture andsell aircraft engines and aircraft in theUnited States. Regulated categoriesinclude:

Category NAICS a Codes SIC b Codes Examples of potentially affected entities

Industry ................................................................... 336412 3724 Manufacturers of new aircraft engines.Industry ................................................................... 336411 3721 Manufacturers of new aircraft.

a

North American Industry Classification System (NAICS).bStandard Industrial Classification (SIC) system code.

This table lists the types of entitiesthat EPA is now aware could potentially

be regulated by this action. Other typesof entities not listed in the table couldalso be regulated. To determine whetheryour activities are regulated by thisaction, you should carefully examinethe applicability criteria in 40 CFR 87.1(part 87). If you have any questionsregarding the applicability of this actionto a particular entity, consult the personlisted in the preceding FOR FURTHER

INFORMATION CONTACT section.Table of Contents

I. Executive SummaryII. Overview and Background

A. Contents of the Final RuleB. EPA’s Authority and Responsibilities

Under the Clean Air ActC. Interaction With the International

CommunityD. Brief History of EPA’s Regulation of

Aircraft Engine EmissionsE. Brief History of ICAO Regulation of

Aircraft Engine EmissionsIII. Why is EPA taking this action?

A. Inventory ContributionB. Health, Environmental and Air Quality

Impacts1. Background on Ozone, PM and NOX a. What is ozone?

b. What is particulate matter?c. What is NOX?2. Health Effects Associated With Exposure

to Ozone, PM and NOX a. What are the health effects of ozone?

b. What are the health effects of PM?c. What are the health effects of NOX?3. Environmental Effects Associated With

Exposure to Ozone, PM and NOX

a. Deposition of Nitrogen b. Visibility Effectsc. Plant and Ecosystem Effects of Ozone4. Impacts on Ambient Air Quality

IV. Details of the Final RuleA. NOX Standards for Newly-Certified

Engines1. Tier 6 NOX Standards for Newly-

Certified Enginesa. Numerical Emission Limits for Higher

Thrust Engines b. Numerical Emission Limits for Lower

Thrust Engines

2. Tier 8 NOX Standards for Newly-Certified Engines

a. Numerical Emission Limits for HigherThrust Engines

b. Numerical Emission Limits for LowerThrust Engines

B. Application of NOX Standards forNewly-Manufactured Engines

1. Phase-In of the Tier 6 NOX Standards forNewly-Manufactured Engines

2. Carryover of Previously GeneratedEmission Data

3. Exemptions and Exceptions From the

Tier 6 Production Cutoffa. New Provisions for Spare Engines

b. New Provisions for Engines Installed inNew Aircraft

i. Time-Frame and Scopeii. Production Limitiii. Exemption Requestsiv. Coordination of Exemption Requestsv. Low-Volume, Time-Limited Transitional

Exception Programc. Voluntary Emission Offsets4. Potential Phase-In of New Tier 8 NOX

Standards for Newly-ManufacturedEngines


http://www.regulations.gov/http://www.regulations.gov/mailto:[email protected]:[email protected]://www.regulations.gov/http://www.regulations.gov/


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36343Federal Register / Vol. 77, No. 117/ Monday, June 18, 2012 / Rules and Regulations

C. Application of Standards for DerivativeEngines

D. Annual Reporting RequirementE. Standards for Supersonic Aircraft

Turbine EnginesF. Amendments to Test and Measurement

ProceduresG. Possible Future Revisions to Emission

Standards for New Technology TurbineEngines and Supersonic Aircraft Turbine

EnginesV. Description of Other Revisions to the

Regulatory TextA. Applicability Issues1. Military Engines2. Noncommercial EnginesB. Non-Substantive RevisionsC. Clarifying Language for Regulatory Text

VI. Technical Feasibility and Cost ImpactsVII. Consultation With FAAVIII. Public ParticipationIX. Statutory Provisions and Legal AuthorityX. Statutory and Executive Order Reviews

A. Executive Order 12866: RegulatoryPlanning and Review, and ExecutiveOrder 13563: Improving Regulation andRegulatory Review

B. Paperwork Reduction ActC. Regulatory Flexibility AnalysisD. Unfunded Mandates Reform ActE. Executive Order 13132: FederalismF. Executive Order 13175: Consultation

and Coordination With Indian TribalGovernments

G. Executive Order 13045: Protection ofChildren From Environmental Health &Safety Risks

H. Executive Order 13211: Actions ThatSignificantly Affect Energy Supply,Distribution, or Use

I. National Technology TransferAdvancement Act

J. Executive Order 12898: Federal ActionsTo Address Environmental Justice in

Minority Populations and Low IncomePopulations

K. Congressional Review ActL. Executive Order 13609: Promoting

International Regulatory Cooperation

I. Executive Summary

A. Purpose of the Regulatory Action

The primary purpose of this rule is toadopt new oxides of nitrogen (NOX)emission standards for aircraft engineswith rated thrusts greater than 26.7 kNthrust. These are mostly commercialpassenger and freighter aircraft incommon use at airports across the U.S.

It does not include engines used onmilitary aircraft. NOX is stronglycorrelated with NO2, for which EPA hasestablished National Ambient AirQuality Standards (NAAQS), i.e., acriteria pollutant, and it is an importantprecursor gas in the formation oftropospheric ozone and secondaryparticulate matter which are commonair pollutants in urban areas whereairports are located. Currently,approximately 154 million people livein areas designated nonattainment forone or more of the current NAAQS. This

rule will allow us to enforce in the U.S.the emission standards adopted byICAO, and will be useful to states inattaining or maintaining the ozone,PM2.5, and NO2 NAAQS standards. Thisrule also contains several provisions tofacilitate the implementation of EPA’saircraft engine emission regulations andrelated requirements. It is also

important to note that adoption of theprovisions in this rule meets U.S. treatyobligations under the ChicagoConvention of 1944 by aligning ourregulations with those in theInternational Civil AviationOrganization Annex 16, Volume II(adopted in 2010) that the U.S. helpedto develop and support as part of theinternational process. This rule is beingimplemented under the authorityprovided in section 231 of the Clean AirAct (42 U.S.C. 7571), which directs theAdministrator of EPA to, from time totime, propose aircraft engine emission

standards applicable to the emission ofany air pollutant from classes of aircraftengines which in her judgment causesor contributes to air pollution that mayreasonably be anticipated to endangerpublic health or welfare.

B. Summary of Major Provisions of theRegulatory Action

The rule contains six majorprovisions. The first two provisions arenew NOX emission standards for newlycertified-engine models. The firststandards, Tier 6, take effect when thisrule becomes effective. These representapproximately a 12 percent reduction

from current Tier 4 levels. They wereactually adopted by ICAO in 2005 withan implementation date in 2008. Thesecond standards, Tier 8, were adopted

by ICAO in 2008 and take effect in 2014.These represent approximately a 15percent reduction from Tier 6 levels. Asnoted above, both tiers of emissionstandards are needed to address local airquality concerns (NAAQS) and to meetU.S. treaty obligations under theChicago Convention. The third majorprovision is a production cut-off fornewly-manufactured engines (asopposed to newly-certified engines)

which basically requires that afterDecember 31, 2012 all newly-manufactured engines must meet atleast Tier 6 NOX emission standards.This is also needed to meet ourobligations under the ChicagoConvention. The production cut-off isneeded to ensure that the emissionreductions envisioned by the emissionstandards are achieved on newproduction engines. The fourth majorprovision is related to potentialexemptions or exceptions to theproduction cut-off requirement. These

include revised provisions allowingmanufacturers to request that FAA inconsultation with EPA grant exemptionsfrom the production cut-off for adesignated number of engines within aprescribed time frame. These alsoinclude a low-volume, time-limitedexception provision that will excludeseveral engines from the production

cutoff. Both of these provisions help toassure an orderly transition to the newstandards for engines needing more timeto comply or for a few engines at theend of their production life. Finally, therule includes a set of provisions whichmay be considered as minor if viewedseparately, but collectively areimportant in upgrading EPA’sregulations by incorporating somerelated agreements from our ICAOprocess and clarifying and improvingexisting provisions. Examples of thisinclude special provisions for spareengines, provisions related to derivative

engine models, test procedurespecifications and reportingrequirements. These changes areimportant for an effectiveimplementation of the newrequirements, and in many cases arealso needed to meet our obligationsunder the Chicago Convention.

C. Costs and Benefits

This is not an economicallysignificant regulatory action. Aircraftengines are international commoditiesused on aircraft manufactured and soldaround the world. When developingnew engine models manufacturers not

only consider current emissionrequirements but also try to anticipatethe stringency of future standards andrespond appropriately. Enginemanufacturers participated in thedeliberations leading up to ICAOdecisions on the aircraft engine NOX emission standards and after the ICAOdecisions they incorporated enginetechnology changes as needed to meetthe new ICAO requirements. This helpsto ensure the world wide acceptabilityof their products. Essentially all of thesechanges are now complete. Thus, whilethere is some cost to a manufacturer for

responding to the new ICAO provisions,there is no significant further direct costto the manufacturers created by EPA’sadopting the requirements into U.Sregulations. In fact, it is likely that ouradopting these requirements facilitatesthe acceptance of U.S. type certificates

by aircraft manufacturers and airlinesaround the world.

II. Overview and Background

This section summarizes the majorprovisions of the final rule for aircraftgas turbine engines. It also contains



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1Turbofan and turbojet engines will becollectively referred to as turbofan engines hereafterfor convenience.

2As previously mentioned, these new NOX standards are identical to requirements established by ICAO. The stringency of any new emission

standard is selected based on an assessment of thetechnical feasibility, cost, and environmental benefit of potential requirements. The NOX standards we are promulgating today will not affectfuel economy or have any practical effect on CO2 emissions. (See International Civil AviationOrganization (ICAO), ‘‘Committee on AviationEnvironmental Protection (CAEP), Eighth Meeting,Montreal, 1 to 12 February 2010, CAEP/8 NOX Stringency Cost–Benefit Analysis DemonstrationUsing APMT–IMPACTS,’’ CAEP/8–IP/30, December1, 2010. A copy of this document is in docketnumber EPA–HQ–OAR–2010–0687.)

3These exemption or exception provisions areconceptually the same as the ICAO exemptionprovisions and provide the same regulatoryflexibilities to all engine manufacturers.

4The term gas turbine engine includes turbofan,turbojet, and turboprop engines designs. The ratedoutput for turbofan and turbojet engines is normallyexpressed as kilonewtons (kN) thrust. The ratedoutput for turboprop engines is normally expressedas shaft horsepower (hp) or shaft kilowatt (kW).

5This includes turbofan and turbojet engines lessthan 26.7 kN thrust and all turboprop engines thatare subject to any emission standard, e.g., smoke.

6As discussed further in section III.D., thevoluntary emission data report to ICAO does notinclude turbofans at or below 26.7 kN or turbopropssubject to any emission standard.

7The functions of the Secretary of Transportationunder part B of title II of the Clean Air Act (§§231–234, 42 U.S.C. 7571–7574) have been delegated tothe Administrator of the FAA. 49 CFR 1.47(g).

background on the EPA’s standardsetting authority and responsibilitiesunder the Clean Air Act, the connection

between our emission standards andthose of the international community,and a brief regulatory history for thissource of emissions.

A. Contents of the Final Rule

We are adopting several new emissionstandards and other regulatoryrequirements for aircraft turbofan andturbojet engines 1 with rated thrustsgreater than 26.7 kilonewtons (kN).First, we are establishing two new tiersof more stringent emission standards foroxides of nitrogen (NOX).2 Thestandards apply differently to twoclasses of these engines, i.e., ‘‘newly-certified engines’’ and ‘‘newly-manufactured engines.’’ The newly-certified engine standards apply toaircraft engines that have received anew type certificate and have never

been manufactured prior to the effectivedate of the new emission standards.Requirements for newly-manufacturedengines apply to aircraft engines thatwere previously certified andmanufactured in compliance withpreexisting standards, and they requiremanufacturers to either comply with thenewer standards by a specified futuredate or cease production of the affectedengine models. Newly-manufacturedengine standards are also sometimesreferred to as ‘‘production cutoff’’standards. Second, we are adoptingcertain time-limited flexibilities, i.e., the

potential for exemptions or exceptionsas defined in the regulations for newly-manufactured engines that may not beable to comply with the first tier of theNOX standards because of specifictechnical or economic reasons.3

We are also making a number ofadditional changes that would apply toa wider range of aircraft gas turbine

engines 4 than those that would besubject to the new emission standards.5 First, we are defining the meaning of aderivative engine for emissionscertification purposes. The intent of thisdefinition is to distinguish when theemission characteristics of a newturbofan engine model vary sufficientlyfrom its existing parent engine design,

and must show compliance with theemission standard for a newly-certificated engine. Second, we areestablishing new reporting requirementsfor manufacturers that produce gasturbine engines subject to any exhaustemission standard. This will provide uswith timely and consistent emissiondata and other information that isnecessary to conduct emissioninventory and air quality analyses anddevelop appropriate public policy forthe aviation sector. Specifically, reportsare required for turbofan engines withrated thrusts greater than 26.7 kN,

which are subject to gaseous emissionand smoke standards, in addition toturbofans less than or equal to 26.7 kN,and all turboprop engines, that are onlysubject to smoke standards.6 Third, weare adopting minor amendments to thetest and measurement procedures foraircraft engines. Finally, as described insection IV, we are making minoramendments to regulator provisionsaddressing definitions, acronyms andabbreviations, general applicability andrequirements, exemptions, andincorporation by reference.

Most of these new regulatoryrequirements have already been adopted

by the United Nation’s InternationalCivil Aviation Organization (ICAO). Therequirements contained in this final rule

bring the United States into alignmentwith the international standards andrecommended practices.

B. EPA’s Authority and ResponsibilitiesUnder the Clean Air Act

Section 231(a)(2)(A) of the Clean AirAct (CAA) directs the Administrator ofEPA to, from time to time, proposeaircraft engine emission standardsapplicable to the emission of any airpollutant from classes of aircraft engines

which in her judgment causes orcontributes to air pollution that may

reasonably be anticipated to endangerpublic health or welfare. (See 42 U.S.C.7571(a)(2)(A).) Section 231(a)(2)(B)directs EPA to consult with theAdministrator of the Federal AviationAdministration (FAA) on suchstandards, and prohibits EPA fromchanging aircraft emission standards ifsuch a change would significantly

increase noise and adversely affectsafety. 42 U.S.C. 7571(a)(2)(B)(i)–(ii).Section 231(a)(3) provides that after wepropose standards, the Administratorshall issue such standards ‘‘with suchmodifications as he deems appropriate.’’42 U.S.C. 7571(a)(3). The U.S. Court ofAppeals for the D.C. Circuit has heldthat this provision confers an unusually

broad degree of discretion on EPA toadopt aircraft engine emission standardsas the Agency determines arereasonable. NACAA v. EPA, 489 F.3d1221 (D.C. Cir. 2007).

In addition, under CAA section 231(b)

EPA is required to ensure, inconsultation with the U.S. Departmentof Transportation (DOT), that theeffective date of any standard providesthe necessary time to permit thedevelopment and application of therequisite technology, giving appropriateconsideration to the cost of compliance.42 U.S.C. 7571(b). Section 232 thendirects the FAA to prescribe regulationsto ensure compliance with EPA’sstandards. 42 U.S.C. 7572. Finally,section 233 of the CAA vests theauthority to promulgate emissionstandards for aircraft or aircraft engines

only in EPA. States are preempted fromadopting or enforcing any standardrespecting aircraft engine emissionsunless such standard is identical toEPA’s standards. 42 U.S.C. § 7573.Section VI of today’s final rule furtherdiscusses our coordination with DOTthrough the FAA.7 It also describesDOT’s responsibility under the CAA toenforce the aircraft emission standardsestablished by EPA.

C. Interaction With the InternationalCommunity

We began regulating the air pollutionemissions from aircraft engines in 1973.

Since that time, we have worked withthe FAA and later with the InternationalCivil Aviation Organization (ICAO) todevelop international standards andother recommended practices pertainingto aircraft engine emissions. ICAO wasestablished in 1944 by the UnitedNations (by the Convention onInternational Civil Aviation, the



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8 ICAO, ‘‘Convention on International CivilAviation,’’ Ninth Edition, Document 7300/9, 2006.Copies of this document can be obtained from theICAO Web site located at www.icao.int.

9Members of ICAO’s Assembly are generallytermed member States or contracting States. These

terms are used interchangeably throughout thispreamble.

10There are currently 191 Contracting Statesaccording to ICAO Web site located at www.icao.int.

11 ICAO, ‘‘Convention on International CivilAviation,’’ Article 87, Ninth Edition, Document7300/9, 2006. Copies of this document can beobtained from the ICAO Web site located atwww.icao.int/icaonet/arch/doc/7300/7300 _9ed.pdf.

12 ICAO, ‘‘Convention on International CivilAviation,’’ Article 33, Ninth Edition, Document7300/9, 2006. Copies of this document can beobtained from the ICAO Web site located atwww.icao.int/icaonet/arch/doc/7300/7300 _9ed.pdf.

13 ICAO, ‘‘Convention on International CivilAviation,’’ Articles 38, Ninth Edition, Document

7300/9, 2006. Copies of this document can beobtained from the ICAO Web site located atwww.icao.int/icaonet/arch/doc/7300/7300 _9ed.pdf.

14Pursuant to the President’s memorandum ofAugust 11, 1960 (and related Executive Order No.10883 from 1960), the Interagency Group onInternational Aviation (IGIA) was established tofacilitate coordinated recommendations to theSecretary of State on issues pertaining tointernational aviation. The DOT/FAA is the chair ofIGIA, and as such, the FAA represents the U.S. onenvironmental matters at CAEP.

15 ICAO, ‘‘Aircraft Engine Emissions,’’International Standards and RecommendedPractices, Environmental Protection, Annex 16,Volume II, Second Edition, July 2008. A copy ofthis document is in docket number EPA–HQ–OAR–2010–0687.

16CAEP develops new emission standards basedon an assessment of the technical feasibility, cost,and environmental benefit of potentialrequirements.

17U.S. EPA, ‘‘Emission Standards and TestProcedures for Aircraft;’’ Final Rule, 38 FR 19088, July 17, 1973.

18U.S. EPA, ‘‘Control of Air Pollution fromAircraft and Aircraft Engines; Emission Standardsand Test Procedures;’’ Final Rule, 62 FR 25356,May 8, 1997. While ICAO’s standards were notlimited to ‘‘commercial’’ aircraft engines, our 1997standards were explicitly limited to commercialengines, as our finding that NOX and CO emissionsfrom aircraft engines cause or contribute to airpollution which may reasonably be anticipated toendanger public health or welfare was so limited,See 62 FR 25358. As explained later in sectionIV.A.2. of today’s notice, we are expanding thescope of that finding and of our standards pursuantto section 231(a)(2)(A) of the Clean Air Act toinclude such emissions from both commercial andnon-commercial aircraft engines based on thephysical and operational similarities betweencommercial and noncommercial civilian aircraftand to bring our standards into full alignment withICAO’s.

19This does not mean that in 2005 wepromulgated requirements for the re-certification orretrofit of existing in-use engines.

20U.S. EPA, ‘‘Control of Air Pollution fromAircraft and Aircraft Engines; Emission Standardsand Test Procedures;’’ Final Rule, 70 FR 2521,November 17, 2005.

‘‘Chicago Convention’’) ‘‘* * * in orderthat international civil aviation may bedeveloped in a safe and orderly mannerand that international air transportservices may be established on the basisof equality of opportunity and operatedsoundly and economically.’’ 8 ICAO’sresponsibilities include developingaircraft technical and operating

standards, recommending practices, andgenerally fostering the growth ofinternational civil aviation. The UnitedStates is currently one of 191participating member States of ICAO.9 10

In the interests of globalharmonization and international aircommerce, the Chicago Conventionurges a high degree of uniformity by itsmember States. Nonetheless, theConvention also recognizes that memberStates may adopt their own uniqueairworthiness standards and that somemay adopt standards that are morestringent than those agreed upon by

ICAO.The Convention has a number of otherfeatures that govern internationalcommerce. First, States that wish to useaircraft in international transportationmust adopt emission standards andother recommended practices that are atleast as stringent as ICAO’s standards.States may ban the use of any aircraftwithin their airspace that does not meetICAO standards.11 Second, States arerequired to recognize the airworthinesscertificates of any State whose standardsare at least as stringent as ICAO’sstandards, thereby assuring that aircraft

of any member State will be permittedto operate in any other member State.12 Third, and finally, to ensure thatinternational commerce is notunreasonably constrained, aparticipating nation which elects toadopt more stringent standards isobligated to notify ICAO of thedifferences between its standards andICAO standards.13 However, if a nation

sets tighter standards than ICAO, aircarriers not based in that nation wouldonly be required to comply with ICAOstandards or more stringent standardsimposed by their own nations, ifapplicable.

ICAO’s Committee on AviationEnvironmental Protection (CAEP)undertakes ICAO’s technical work in the

environmental field. The Committee isresponsible for evaluating, researching,and recommending measures to theICAO Council that address theenvironmental impact of internationalcivil aviation. CAEP is composed ofvarious task groups, work groups, andother committees whose contributingmembers include atmospheric,economic, aviation, environmental, andother professionals interested inaviation and environmental protection.At CAEP meetings, the United States isrepresented by the FAA, which plays anactive role at these meetings.14 EPA has

historically been a principal participantin the development of U.S. policy invarious ICAO/CAEP working groupsand other international venues, assistingand advising FAA on aviationemissions, technology, and policymatters. If ICAO adopts a CAEPproposal for a new environmentalstandard, it then becomes part of ICAOstandards and recommended practices(Annex 16 to the ChicagoConvention).15 16

D. Brief History of EPA’s Regulation ofAircraft Engine Emissions

As mentioned above, we initially

regulated gaseous exhaust emissions,smoke, and fuel venting from aircraftengines in 1973.17 Since that time, wehave occasionally revised thoseregulations. Two of these revisions aremost pertinent to today’s final rule.First, in a 1997 rulemaking, we made

our emission standards and testprocedures more consistent with thoseof ICAO for turbofan engines used incommercial aviation with rated thrustsgreater than 26.7kN.18 These ICAOrequirements are generally referred to asCAEP/2 standards. (The numberingnomenclature for CAEP requirements isdiscussed in the next section.) That

action included new NOX emissionstandards for newly-manufacturedcommercial turbofan engines (thoseengines built after the effective date ofthe regulations that were alreadycertified to pre-existing standards) 19 and for newly-certified commercialturbofan engines (those engine modelsthat received their initial type certificateafter the effective date of theregulations). It also included a COemission standard for newly-manufactured commercial turbofanengines. Second, in our most recentrulemaking in 2005, we promulgated

more stringent NOX emission standardsfor newly-certified commercial turbofanengines.20 That final rule brought theU.S. standards closer to alignment withICAO CAEP/4 requirements that wereeffective in 2004. In ruling on a petitionfor judicial review of the 2005 rule filed

by the National Association of Clean AirAgencies (NACAA), the U.S. Court ofAppeals held that EPA’s approach oftracking the ICAO standards wasreasonable and permissible under theCAA. NACAA v. EPA, 489 F.3d 1221,1230–32 (D.C. Cir. 2007).

E. Brief History of ICAO Regulation of

Aircraft Engine EmissionsThe first international standards and

recommended practices for aircraftengine emissions was recommended byCAEP’s predecessor, the Committee onAircraft Engine Emissions (CAEE), and


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21 ICAO, Foreword of ‘‘Aircraft EngineEmissions,’’ International Standards andRecommended Practices, Environmental Protection,Annex 16, Volume II, Third Edition, July 2008.Copies of this document can be obtained from theICAO Web site at www.icao.int.

22CAEP conducts its work over a period of years.Each work cycle is numbered sequentially and thatidentifier is used to differentiate the results fromone CAEP to another by convention. The firsttechnical meeting on aircraft emission standardswas CAEP’s successor, i.e., CAEE. The first meetingof CAEP, therefore, is referred to as CAEP/2.

23CAEP/5 did not address new aircraft engineemission standards.

24

ICAO, ‘‘Aircraft Engine Emissions,’’ Annex 16,Volume II, Third Edition, July 2008, Amendment 4effective on July 20, 2008. Copies of this documentcan be obtained from the ICAO Web site atwww.icao.int.

25CAEP/7 did not address new aircraft engineemission standards.

26 ICAO, ‘‘Committee on Aviation EnvironmentalProtection (CAEP), Report of the Eighth Meeting,Montreal, February 1–12, 2010,’’ CAEP/8–WP/80. Acopy of this document is in docket number EPA–HQ–OAR–2010–0687.

27 ICAO, ‘‘Aircraft Engine Emissions,’’ Annex 16,Volume II, Third Edition, July 2008, Amendment 7effective on July 18, 2011. Copies of this documentcan be obtained from the ICAO Web site atwww.icao.int.

28Ground-level ozone, the main ingredient insmog, is formed by complex chemical reactions ofvolatile organic compounds (VOC) and NOX in thepresence of heat and sunlight. Standards thatreduce NOX emissions will help address ambientozone levels. They can also help reduce particulatematter (PM) levels as NOX emissions can also bepart of the secondary formation of PM. See SectionII.B below.

29According to Airport Council International—North America and similar FAA databases, mostcommercial operations occur at airports that are inor near large cities or urbanized areas. There areabout 130 commercial airports in 78 ozone and fineparticulate nonattainment areas (based on thenonattainment areas status of 2008). There are about325 commercial airports in the U.S.

30For a current list of nonattainment areas see:http://www.epa.gov/oar/oaqps/greenbk/index.html.

31 ‘‘Historical Assessment of Aircraft Landing andTake-off Emissions (1986–2008),’’ Eastern ResearchGroup, May 2011. A copy of this document can be

found in public docket EPA–HQ–OAR–2010–0687.32The cumulative LTO NOX reduction associated

with the new NOX standards is projected to beabout 100,000 tons from 2014 to 2030 (2014 is theimplementation date of the CAEP/8 NOX standards). See ‘‘Historical Assessment of AircraftLanding and Take-off Emissions (1986–2008),’’Eastern Research Group, May 2011. A copy of thisdocument can be found in public docket EPA–HQ–OAR–2010–0687.

33U.S. EPA, ‘‘Comparison of Aircraft LTO andFull Flight NOX Emissions to Total Mobile SourceNOX Emissions,’’ memorandum from John Mueller,Assessment and Standards Division, Office ofTransportation and Air Quality, to docket EPA–HQ–OAR–2010–0687, May 10, 2011.

adopted by ICAO in 1981.21 Thesestandards limited aircraft engineemissions of HC, CO, and NOX. In 1994,ICAO adopted a CAEP/2 proposal totighten the original NOX standard by 20percent and amend the testprocedures.22 At the next CAEP meeting(CAEP/3) in 1995, the Committeerecommended a further tightening of 16

percent and additional test procedureamendments, but in 1997 the ICAOCouncil rejected this stringencyproposal and approved only the testprocedure amendments. At the CAEP/4meeting in 1998, the Committee adopteda similar 16 percent NOX reductionproposal, which ICAO approved on1998. The CAEP/4 standards appliedonly to new engine designs certifiedafter December 31, 2003 (i.e., therequirements did not also apply topreviously certified, newly-manufactured engines unlike the CAEP/2 standards). In 2004, CAEP/6

recommended a 12 percent NOX

reduction, which ICAO approved in2005.23 24 The CAEP/6 standards appliedto new engine designs (newly-certifiedmodels) certified after December 31,2007. At the most recent meeting,CAEP/8 recommended a furthertightening of the NOX standards by 15percent for newly-certified engines.25 26

The Committee also recommended thatthe CAEP/6 standards be applied tonewly-manufactured engines. ICAOapproved these recommendations in2011.27

III. Why is EPA taking this action?

As mentioned above, section231(a)(2)(A) of the CAA authorizes the

EPA Administrator to ‘‘from time totime, issue proposed emission standardsapplicable to the emission of any airpollution from any class or classes ofaircraft or aircraft engines which in hisjudgment causes, or contributes to airpollution which may reasonably beanticipated to endanger public health orwelfare.’’ 42 U.S.C. 7571(a)(2)(A).

One of the principal components ofaircraft exhaust emissions is NOX, aprecursor to the formation oftropospheric ozone and secondaryPM.28 Most commercial airports arelocated in urbanized areas 29 and manyurbanized areas have ambient pollutantlevels above the National Ambient AirQuality Standards (NAAQS) for ozoneand fine particulate matter (PM2.5) (i.e.,they are in nonattainment for ozone andPM2.5).30 This section discusses thecontribution of aircraft engines used incommercial service with rated thrustsgreater than 26.7kN to the national NOX

emissions inventory and to NOX

emission inventories in selected ozoneand PM2.5 nonattainment areas, thepotential effect of NOX emissions in theupper atmosphere on ground level PM2.5 in addition to the health and welfareimpacts of NOX and PM emissions.

A. Inventory Contribution

In contrast to all other mobile sources,whose emissions occur completely atground level, the emissions from aircraftand aircraft engines can be divided intotwo flight regimes. The first regimeincludes the emissions that are releasedin the lower layer of the atmosphere and

directly affect local and regionalambient air quality. These emissionsgenerally occur at or below 3,000 feetabove ground level, i.e., during thelanding and takeoff (LTO) cycle. Theaircraft operations that comprise an LTOcycle are: engine idle at the terminalgate (and sometimes during grounddelays while holding for the activerunway); taxiing between the terminaland the runway; take-off; climb-out; andapproach to the airport. The second

regime includes emissions that occurabove 3,000 feet above ground level,known as non-LTO emissions.Collectively, the emissions associatedwith all ground and flight operations aregenerally referred to as full flightemissions.

In this section, we will discuss NOX

emission inventories for commercialturbine-engine aircraft, both nationallyand for selected ozone and PM2.5 nonattainment areas (NAAs). Theseinventories reflect emissions during thelanding and takeoff cycle only. Themost recent comprehensive analysis ofhistorical and current LTO emissionsfrom aircraft engines comes from astudy undertaken for us by EasternResearch Group (ERG).31 The studyanalyzed the national emissions ofcommercial aircraft operations in theUnited States, and showed that in themost recent year studied (2008), such

aircraft LTO operations contributedabout 97 thousand tons to the nationalNOX inventory.32 A summary of thenational inventory of LTO NOX emissions is shown in Table 1.

When these nationwide LTOemissions are compared to the total U.S.mobile source inventory for 2009, theyaccount for less than one percent of thetotal. However, such a comparison may

be a bit misleading, as it only includesthose aircraft emissions that occur

below 3,000 feet altitude, whilecomparing them to the entirety of other

mobile source emissions. In the U.S.,LTO emissions account for only aboutten percent of full flight NOX emissions.When considering full flight aircraftemissions (i.e., including both LTO andnon-LTO emissions), the contribution ofaircraft to the total mobile source NOX inventory is approximately 7.7percent.33 It is also worth noting thatthese LTO emissions are more localizedin that they occur near airports, whichare mostly within urban areas.


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34Although 41 NAAs were studied, the non-aircraft emissions data source that the aircraftemissions were compared to for this analysis didnot distinguish between the Boston NAA inMassachusetts and the greater Boston NAA in NewHampshire. Thus, aircraft emissions from those twoNAAs were combined into a single NAA for thepurpose of this analysis, yielding 40 NAAs forstudy.

35For a current list of nonattainment areas see:http://www.epa.gov/oar/oaqps/greenbk/index.html.

36U.S. EPA, ‘‘Relative Contribution of Aircraft toTotal Mobile Source NOX Emissions in SelectedOzone Nonattainment Areas,’’ memorandum from John Mueller, Assessment and Standards Division,Office of Transportation and Air Quality, to docketEPA–HQ–OAR–2010–0687, May 10, 2011.

37U.S. EPA, ‘‘Addendum to ‘RelativeContribution of Aircraft to Total Mobile SourceNOX Emissions in Selected Ozone NonattainmentAreas,’ ’’ memorandum from John Mueller,Assessment and Standards Division, Office of

Transportation and Air Quality, to docket EPA–

HQ–OAR–2010–0687, May 17, 2011.38U.S. EPA, ‘‘Update to ‘Relative Contribution of

Aircraft to Total Mobile Source NOX Emissions in

Selected Ozone Nonattainment Areas,’’’

memorandum from John Mueller, Assessment and

Standards Division, Office of Transportation and

Air Quality, to docket EPA–HQ–OAR–2010–0687,

April 30, 2012.

TABLE 1—CURRENT NATIONAL NOX EMISSIONS FROM COMMERCIAL AIR-CRAFT

Aircraft category2008 Total NOX (thousand tons)

Air Carrier ....................... 86Commuter/Air Taxi .......... 11

Total Commercial .... 97

In addition, it is important to assessthe contribution of commercial aircraftLTO NOX emissions on a local level,especially in areas containing oradjacent to airports. The historicalanalysis conducted by ERG alsoincluded an assessment of selected

ozone nonattainment areas (NAAs). TheNAAs selected for study were chosen asfollows. First, the 25 NAAs withairports which had high commercialtraffic volumes were identified. Second,the 25 NAAs with the largest populationwere identified. These lists werecombined. However, there was someoverlap, and this led to a total of 40NAAs being identified for the study.34 These NAAs collectively include 200airports, accounting for about 70 percentof commercial air traffic operations.

Of the 40 NAAs originally studied byERG as previously described, weidentified the 30 areas that were innonattainment for ozone or PM2.5 as ofMarch 30, 2012.35 Current (2008) and

projected (2020) NOX emissions forthese 30 ozone and PM2.5 NAAs, as wellas the percent contribution of aircraft tototal mobile source inventories (ascompared to 2005 and 2020 mobilesource inventories), are shown in Table2.36 37 38 The relative contribution ofaircraft in any given NAA varies basedon activity in other transportation andindustrial sectors. As can be seen fromthis table, expected growth in aircraftoperations in many of these areascombined with anticipated reductionsin NOX emissions from other mobilesource categories results in the growthof the relative contribution of aircraftLTO emissions to mobile source NOX emissions in NAAs.

TABLE 2—NOX EMISSIONS IN SELECTED OZONE AND PM2.5 NONATTAINMENT AREAS

Nonattainment area2008 Total NOX

(tons)

2008 Aircraftpercent of

mobile

source NOX

2020 Aircraftpercent of

mobile

source NOX

Atlanta, GA ................................................................................................................ 5,808 2.6 8.2Baltimore, MD ............................................................................................................ 1,148 1.3 4.4Boston—including MA and NH NAAs ....................................................................... 2,032 1.0 2.7Charlotte-Gastonia-Rock Hill, NC-SC ........................................................................ 1,917 2.6 10.0Chicago-Gary-Lake County, IL-IN ............................................................................. 6,007 1.8 5.0Cleveland-Akron-Lorain, OH ...................................................................................... 680 0.5 1.3Dallas-Fort Worth, TX ................................................................................................ 3,880 1.7 6.9Denver-Boulder-Greeley-Fort Collins-Loveland, CO ................................................. 2,649 2.5 7.1Detroit-Ann Arbor, MI ................................................................................................. 2,312 1.1 3.0Greater Connecticut, CT ............................................................................................ 405 0.8 2.4Houston-Galveston-Brazoria, TX ............................................................................... 3,045 1.3 3.4Indianapolis, IN .......................................................................................................... 1,089 1.4 3.0Las Vegas, NV ........................................................................................................... 2,308 6.0 15.8Los Angeles South Coast Air Basin, CA ................................................................... 6,479 1.5 4.5Louisville, KY-IN ........................................................................................................ 1,211 1.9 6.2

Milwaukee-Racine, WI ............................................................................................... 557 0.9 3.2New York-N. New Jersey-Long Island, NY-NJ-CT ................................................... 10,093 2.3 6.3Philadelphia-Wilmington-Atlantic City, PA-NY-MD-DE .............................................. 2,308 1.0 2.8Phoenix-Mesa, AZ ..................................................................................................... 2,298 1.4 3.3Pittsburgh-Beaver Valley, PA .................................................................................... 480 0.5 1.1Providence (entire State), RI ..................................................................................... 232 1.0 2.3Riverside County (Coachella Valley), CA .................................................................. 70 0.2 0.5Sacramento Metro, CA .............................................................................................. 603 1.0 2.0Salt Lake City, UT ..................................................................................................... 1,235 4.4 14.1San Diego, CA ........................................................................................................... 1,035 1.4 3.4San Francisco Bay Area, CA .................................................................................... 4,405 2.7 6.7San Joaquin Valley, CA ............................................................................................. 74 0.0 0.1Seattle-Tacoma, WA .................................................................................................. 1,958 1.4 3.9St. Louis, MO-IL ......................................................................................................... 810 0.6 1.6Washington, DC-MD-VA ............................................................................................ 2,983 2.0 6.2

Table 3 shows how commercialaircraft operations are projected to rise

in the future on a nationwide basis. Asoperations increase, the inventory

impact of these aircraft on national andlocal NOX inventories will also increase.


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43National Research Council (NRC), 2008.Estimating Mortality Risk Reduction and EconomicBenefits From Controlling Ozone Air Pollution. TheNational Academies Press: Washington, DC A copyof this document is in docket number EPA–HQ–OAR–2010–0687.

44U.S. EPA (2009) Integrated Science Assessmentfor Particulate Matter, EPA 600/R–08/139F. A copyof this document is in docket number EPA–HQ–OAR–2010–0687.

45U.S. EPA (2009). Integrated ScienceAssessment for Particulate Matter (Final Report).U.S. Environmental Protection Agency,Washington, DC, EPA/600/R–08/139F, 2009.Section 2.3.1.1.

46U.S. EPA (2009). Integrated ScienceAssessment for Particulate Matter (Final Report).U.S. Environmental Protection Agency,Washington, DC, EPA/600/R–08/139F, 2009. page2–12, Sections 7.3.1.1 and 7.3.2.1.

47U.S. EPA (2009). Integrated ScienceAssessment for Particulate Matter (Final Report).U.S. Environmental Protection Agency,Washington, DC, EPA/600/R–08/139F, 2009.Section 2.3.2.

48U.S. EPA (2008). Integrated ScienceAssessment for Oxides of Nitrogen—Health Criteria(Final Report). EPA/600/R–08/071. Washington,DC: U.S. EPA. A copy of this document is in docketnumber EPA–HQ–OAR–2010–0687.

the elderly, and individuals withrespiratory disease such as asthma.Those with greater exposures to ozone,for instance due to time spent outdoors(e.g., children and outdoor workers), areof particular concern. Ozone can irritatethe respiratory system, causingcoughing, throat irritation, and

breathing discomfort. Ozone can reduce

lung function and cause pulmonaryinflammation in healthy individuals.Ozone can also aggravate asthma,leading to more asthma attacks thatrequire medical attention and/or the useof additional medication. Thus, ambientozone may cause both healthy andasthmatic individuals to limit theiroutdoor activities. In addition, there issuggestive evidence of a contribution ofozone to cardiovascular-relatedmorbidity and highly suggestiveevidence that short-term ozone exposuredirectly or indirectly contributes to non-accidental and cardiopulmonary-related

mortality, but additional research isneeded to clarify the underlyingmechanisms causing these effects. In areport on the estimation of ozone-related premature mortality published

by the National Research Council (NRC),a panel of experts and reviewersconcluded that short-term exposure toambient ozone is likely to contribute topremature deaths and that ozone-relatedmortality should be included inestimates of the health benefits ofreducing ozone exposure.43 Animaltoxicological evidence indicates thatwith repeated exposure, ozone caninflame and damage the lining of the

lungs, which may lead to permanentchanges in lung tissue and irreversiblereductions in lung function. Therespiratory effects observed incontrolled human exposure studies andanimal studies are coherent with theevidence from epidemiologic studiessupporting a causal relationship

between acute ambient ozone exposuresand increased respiratory-relatedemergency room visits andhospitalizations in the warm season. Inaddition, there is suggestive evidence ofa contribution of ozone tocardiovascular-related morbidity and

non-accidental and cardiopulmonarymortality.

b. What are the health effects of PM?

Scientific studies show ambient PM isassociated with a series of adversehealth effects. These health effects arediscussed in detail in EPA’s Integrated

Science Assessment for ParticulateMatter (ISA).44 The ISA summarizeshealth effects evidence associated with

both short-term and long-termexposures to PM2.5, PM10–2.5, andultrafine particles.

The ISA concludes that health effectsassociated with short-term exposures(hours to days) to ambient PM2.5 include

mortality, cardiovascular effects, such asaltered vasomotor function andmyocardial ischemia, and hospitaladmissions and emergency departmentvisits for ischemic heart disease andcongestive heart failure, and respiratoryeffects, such as exacerbation of asthmasymptoms in children and hospitaladmissions and emergency departmentvisits for chronic obstructive pulmonarydisease and respiratory infections.45 TheISA notes that long-term exposure(months to years) to PM2.5 is associatedwith the development/progression ofcardiovascular disease, premature

mortality, and respiratory effects,including reduced lung function growthin children, increased respiratorysymptoms, and asthma development.46 The ISA concludes that the currentlyavailable scientific evidence fromepidemiologic, controlled humanexposure, and toxicological studiessupports a causal association betweenshort- and long-term exposures to PM2.5 and cardiovascular effects andpremature mortality. Furthermore, theISA concludes that the collectiveevidence supports likely causalassociations between short- and long-term PM2.5 exposures and respiratory

effects. The ISA also concludes that thescientific evidence is suggestive of acausal association for reproductive anddevelopmental effects includingrespiratory-related infant mortality andcancer, mutagenicity, and genotoxicityand long-term exposure to PM2.5.47

For PM10-2.5, the ISA concludes thatthe current evidence is suggestive of acausal relationship between short-termexposures and premature mortality,cardiovascular effects, and respiratory

effects. Data are inadequate to drawconclusions regarding the health effectsassociated with long-term exposure toPM10-2.5.

For ultrafine particles, the ISAconcludes that there is suggestiveevidence of a causal relationship

between short-term exposures andcardiovascular effects, such as changes

in heart rhythm and blood vesselfunction. It also concludes that there issuggestive evidence of association

between short-term exposure toultrafine particles and respiratoryeffects. Data are inadequate to drawconclusions regarding the health effectsassociated with long-term exposure toultrafine particles.

c. What are the health effects of NOX?

Information on the health effects ofNO2 can be found in the EPA IntegratedScience Assessment (ISA) for NitrogenOxides.48 The EPA has concluded thatthe findings of epidemiologic,controlled human exposure, and animaltoxicological studies provide evidencethat is sufficient to infer a likely causalrelationship between respiratory effectsand short-term NO2 exposure. The ISAconcludes that the strongest evidencefor such a relationship comes fromepidemiologic studies of respiratoryeffects including symptoms, emergencydepartment visits, and hospitaladmissions. The ISA also draws two

broad conclusions regarding airwayresponsiveness following NO2 exposure.First, the ISA concludes that NO2 exposure may enhance the sensitivity to

allergen-induced decrements in lungfunction and increase the allergen-induced airway inflammatory responsefollowing 30-minute exposures ofasthmatics to NO2 concentrations as lowas 0.26 ppm. Second, exposure to NO2 has been found to enhance the inherentresponsiveness of the airway tosubsequent nonspecific challenges incontrolled human exposure studies ofasthmatic subjects. Small but significantincreases in non-specific airwayhyperresponsiveness were reportedfollowing 1-hour exposures ofasthmatics to 0.1 ppm NO2. Enhanced

airway responsiveness could haveimportant clinical implications forasthmatics since transient increases inairway responsiveness following NO2 exposure have the potential to increasesymptoms and worsen asthma control.Together, the epidemiologic andexperimental data sets form a plausible,consistent, and coherent description of



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49U.S. EPA. (2005). Review of the NationalAmbient Air Quality Standards for ParticulateMatter: Policy Assessment of Scientific andTechnical Information, OAQPS Staff Paper.Retrieved on April 9, 2009 from http:// www.epa.gov/ttn/naaqs/standards/pm/data/ pmstaffpaper _20051221.pdf .

50U.S. EPA. (2004). Air Quality Criteria forParticulate Matter (AQCD). Volume I Document No.EPA600/P–99/002aF and Volume II Document No.EPA600/P–99/002bF. Washington, DC: U.S.Environmental Protection Agency. Retrieved onMarch 18, 2009 from http://cfpub.epa.gov/ncea/ cfm/recordisplay.cfm?deid=87903.

51U.S. EPA (2009). Integrated ScienceAssessment for Particulate Matter (Final Report).U.S. Environmental Protection Agency,Washington, DC, EPA/600/R–08/139F, 2009. Acopy of this document is in docket number EPA–HQ–OAR–2010–0687.

52U. S. EPA (2010) Our Nation’s Air: Status andTrends through 2008. Office of Air Quality Planningand Standards, Research Triangle Park, NC.Publication No. EPA 454/R–09–002. This documentcan be accessed electronically at: http://www.epa.gov/airtrends/2010/ .

53U.S. EPA, 2012. http://www.epa.gov/oar/oaqps/greenbk/index.html

a relationship between NO2 exposuresand an array of adverse health effectsthat range from the onset of respiratorysymptoms to hospital admission.

Although the weight of evidencesupporting a causal relationship issomewhat less certain than thatassociated with respiratory morbidity,NO2 has also been linked to other health

endpoints. These include all-cause(non-accidental) mortality, hospitaladmissions or emergency departmentvisits for cardiovascular disease, anddecrements in lung function growthassociated with chronic exposure.

3. Environmental Effects AssociatedWith Exposure to Ozone, PM and NOX

a. Deposition of Nitrogen

Emissions of NOX from aircraftengines contribute to atmosphericdeposition of nitrogen in the U.S.Atmospheric deposition of nitrogencontributes to acidification, altering

biogeochemistry and affecting animaland plant life in terrestrial and aquaticecosystems across the United States.The sensitivity of terrestrial and aquaticecosystems to acidification fromnitrogen deposition is predominantlygoverned by geology. Prolongedexposure to excess nitrogen depositionin sensitive areas acidifies lakes, riversand soils. Increased acidity in surfacewaters creates inhospitable conditionsfor biota and affects the abundance andnutritional value of preferred preyspecies, threatening biodiversity andecosystem function. Over time,

acidifying deposition also removesessential nutrients from forest soils,depleting the capacity of soils toneutralize future acid loadings andnegatively affecting forest sustainability.Major effects include a decline insensitive forest tree species, such as redspruce (Picea rubens) and sugar maple(Acer saccharum); and a loss of

biodiversity of fishes, zooplankton, andmacro invertebrates.

In addition to the role nitrogendeposition plays in acidification,nitrogen deposition also leads tonutrient enrichment and altered

biogeochemical cycling. In aquaticsystems increased nitrogen can alterspecies assemblages and causeeutrophication. In terrestrial systemsnitrogen loading can lead to loss ofnitrogen sensitive lichen species,decreased biodiversity of grasslands,meadows and other sensitive habitats,and increased potential for invasivespecies.

Adverse impacts on soil chemistryand plant life have been observed forareas heavily influenced by atmosphericdeposition of nutrients, metals and acid

species, resulting in species shifts, lossof biodiversity, forest decline damage toforest productivity and reductions inecosystem services. Potential impactsalso include adverse effects to humanhealth through ingestion ofcontaminated vegetation or livestock (asin the case for dioxin deposition),reduction in crop yield, and limited use

of land due to contamination.Atmospheric deposition of pollutants

can reduce the aesthetic appeal of buildings and culturally importantarticles through soiling, and cancontribute directly (or in conjunctionwith other pollutants) to structuraldamage by means of corrosion orerosion.49 Atmospheric deposition mayaffect materials principally bypromoting and accelerating thecorrosion of metals, by degrading paints,and by deteriorating building materialssuch as concrete and limestone.Particles contribute to these effects

because of their electrolytic,hygroscopic, and acidic properties, andtheir ability to adsorb corrosive gases(principally sulfur dioxide).

b. Visibility Effects

NOX emissions contribute to visibilityimpairment in the U.S. through theformation of secondary PM2.5.50 Visibility impairment is caused by lightscattering and absorption by suspendedparticles and gases. Visibility isimportant because it has directsignificance to people’s enjoyment ofdaily activities in all parts of thecountry. Individuals value goodvisibility for the well-being it providesthem directly, where they live andwork, and in places where they enjoyrecreational opportunities. Visibility isalso highly valued in significant naturalareas, such as national parks andwilderness areas, and special emphasisis given to protecting visibility in theseareas. For more information on visibilitysee the final 2009 PM ISA.51

c. Plant and Ecosystem Effects of Ozone

Elevated ozone levels contribute toenvironmental effects, with impacts toplants and ecosystems being of mostconcern. Ozone can produce both acuteand chronic injury in sensitive speciesdepending on the concentration leveland the duration of the exposure. Ozoneeffects also tend to accumulate over thegrowing season of the plant, so that evenlow concentrations experienced for alonger duration have the potential tocreate chronic stress on vegetation.Ozone damage to plants includes visibleinjury to leaves and impairedphotosynthesis, both of which can leadto reduced plant growth andreproduction, resulting in reduced cropyields, forestry production, and use ofsensitive ornamentals in landscaping. Inaddition, the impairment ofphotosynthesis, the process by whichthe plant makes carbohydrates (itssource of energy and food), can lead to

a subsequent reduction in root growthand carbohydrate storage below ground,resulting in other, more subtle plant andecosystems impacts. These latterimpacts include increased susceptibilityof plants to insect attack, disease, harshweather, interspecies competition andoverall decreased plant vigor. Theadverse effects of ozone on forest andother natural vegetation can potentiallylead to species shifts and loss from theaffected ecosystems, resulting in a lossor reduction in associated ecosystemgoods and services. Lastly, visible ozoneinjury to leaves can result in a loss of

aesthetic value in areas of special scenicsignificance like national parks andwilderness areas. The final 2006 OzoneAir Quality Criteria Document presentsmore detailed information on ozoneeffects on vegetation and ecosystems.

4. Impacts on Ambient Air Quality

The aircraft NOX emission standardswe are promulgating would affectambient concentrations of air pollutants.Nationally, levels of PM2.5, ozone, andNOX are declining.52 However as ofMarch 30, 2012, over 15 million peoplelive in areas designated nonattainmentfor one or more of the current NAAQS.53

These numbers do not include thepeople living in areas where there is afuture risk of failing to maintain orattain the NAAQS.

States with ozone nonattainmentareas are required to take action to bring


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54The Los Angeles South Coast Air Basin 8-hourozone nonattainment area and the San JoaquinValley Air Basin 8-hour ozone nonattainment areaare designated as extreme and will have to attain before June 15, 2024. The Sacramento, CoachellaValley and Houston 8-hour ozone nonattainmentareas are designated as severe and will have toattain by June 15, 2019. In addition, the WesternMojave 8-hour ozone nonattainment area hasrequested to be reclassified as severe. This requesthas not yet been acted on.

55U.S. EPA, 2012. Proposed Rule—Implementation of the 2008 National Ambient AirQuality Standards for Ozone: Nonattainment AreaClassifications Approach, Attainment Deadlinesand Revocation of the 1997 Ozone Standards forTransportation Conformity Purposes. (77 FR 8107,February 14, 2012).

56U.S. EPA (2010). Regulatory Impact Analysis:Final Rulemaking To Establish Greenhouse GasEmission Standards and Fuel Efficiency Standardsfor Medium- and Heavy-Duty Engines and Vehicles.Chapter 8: Health and Environmental Impacts. EPA420–R–11–901.

57U.S. EPA (2010). Regulatory Impact Analysis:Final Rulemaking To Establish Greenhouse Gas

Emission Standards and Fuel Efficiency Standardsfor Medium- and Heavy-Duty Engines and Vehicles.Chapter 8: Health and Environmental Impacts. EPA420–R–11–901.

58These figures are based on the results of EPAcomputer modeling, which is not affected by theupcoming 2008 ozone NAAQS nonattainmentdesignations.

59U.S. Environmental Protection Agency,‘‘Summary and Analysis of Comments: Control ofAir Pollution From Aircraft and Aircraft Engines,’’Office of Transportation and Air Quality, EPA–420–R–12–011, May 2012. A copy of this document isin docket number EPA–HQ–OAR–2010–0687.

60The standards will apply to engines used in

commercial and noncommercial aviation for whichthe FAA issues airworthiness certificates, e.g., non-revenue, general aviation service. The vast majorityof these engines are used in commercialapplications.

61 ICAO standards describe newly-certifiedengines as ‘‘* * * engines of a type or model forwhich the date of manufacture of the firstindividual production model was after. * * *’’ theeffective date of the emission standards. See ICAO,‘‘Aircraft Engine Emissions,’’ Annex 16, Volume II,Third Edition, July 2008, Amendment 4 effective on July 20, 2008. Copies of this document can beobtained from the ICAO Web site at www.icao.int. The term ‘‘first individual production model’’means the first engine ever produced of a uniquemodel or type.

62The standards for newly-manufactured enginesare described in general regulatory terms as the datethat the type or model was first certified andproduced in conformance with specific emissionstandards, and the date beyond which an

individual engine meeting those same requirementscannot be made. So ICAO standards describenewly-manufactured engines as ‘‘* * * engines ofa type or model for which the date of manufactureof the first individual production model was after.* * *’’ the effective date of the applicablestandards, and ‘‘* * * for which the date ofmanufacture of the individual engine was on or before. * * *’’ a specific date that is later than thefirst effective date of the standards. See ICAO,‘‘Aircraft Engine Emissions,’’ Annex 16, Volume II,Third Edition, July 2008, Amendment 4 effective on July 20, 2008. Copies of this document can beobtained from the ICAO Web site at www.icao.int.

63These apply only to the first tier of NOX standards. We are not adopting a production cutofffor the second tier of standards.

those areas into attainment. Theattainment date assigned to an ozonenonattainment area is based on thearea’s classification. Most ozonenonattainment areas are required toattain the 1997 8-hour ozone NAAQS inthe 2007 to 2013 time frame and then tomaintain it thereafter.54 We anticipatedesignating areas for the 2008 ozone

standards in late spring 2012; thus, theattainment dates for areas designatednonattainment for the 2008 8-hourozone NAAQS would likely be in the2015 to 2032 timeframe, depending onthe severity of the problem in eacharea.55

Areas designated as not attaining the1997 PM2.5 NAAQS will need to attainthe 1997 standards in the 2010 to 2015time frame, and then maintaincompliance with them thereafter. The2006 24-hour PM2.5 nonattainment areaswill be required to attain the 2006 24-hour PM2.5 NAAQS in the 2014 to 2019

time frame and then be required tomaintain the 2006 24-hour PM2.5 NAAQS thereafter.

EPA has already adopted manyemission control programs that areexpected to reduce ambient ozone andPM2.5 levels and which will assist inreducing the number of areas that fail toachieve the NAAQS. Even so, our airquality modeling projects that in 2030as many as 10 counties with apopulation of over 30 million may notattain the 2008 ozone standard of 0.075ppm (75 ppb) without additionalcontrols.56 In addition, our air quality

modeling projects that in 2030 at leastfour counties with a population ofnearly 7 million may not attain the 1997annual PM2.5 standard of 15 mg/m3 and22 counties with a population of over 33million may not attain the 2006 24-hourPM2.5 standard of 35 mg/m3 without

additional controls.57 58 These numbersdo not account for those areas that areclose to (e.g., within 10 percent of) thestandards. These areas, although notviolating the standards, would also

benefit from any reductions in NOX ensuring long-term maintenance of theNAAQS.

In summary, the aircraft NOX

reductions resulting from these newaircraft engine emission standards will

be useful to states in attaining ormaintaining the ozone, PM2.5, and NO2 NAAQS standards.

IV. Details of the Final Rule

The following is a description of theregulations being adopted in this finalrule, with any changes from theproposal also noted. The descriptionsalso include our response to the mostsignificant comments received on theproposal. A full summary of thecomments and our responses are

contained in the response to commentsdocument for the rule that is availablein the public docket for this action.59

We are establishing two differentlevels or ‘‘tiers’’ of increasingly morestringent NOX emission standards forgas turbofan engines with maximumrated thrusts greater than 26.7kilonewtons (kN).60 Each of the tiersapply to newly-certified engines.Newly-certified aircraft engines arethose that would receive a new typecertificate after the effective date of theapplicable standards. Such engine typesor models would not have begunproduction prior to the effective date ofthe new requirement.61

We are also requiring newly-manufactured engines to comply withthe first tier of the two tiers ofstandards. Newly-manufactured aircraftengines are those that have beenpreviously certified and manufacturedin compliance with preexistingstandards, and will continue to beproduced after the effective date of a

new applicable standard. Normally,these newly-manufactured engines mustcomply with the same NOX limits asnewly-certified engines, but at a laterdate or cease production.62 The end ofthis ‘‘phase-in’’ period for the newly-manufactured engine standards issometimes referred to as a ‘‘productioncutoff.’’. Again, we are adopting onlythe first of the two new tiers of NOX standards for newly-manufacturedengines. These provisions are describedin detail below.

Five other regulatory features are being established in this final rule. First,

we are revising provisions for certaintime-limited flexibilities, i.e., potentialexemptions, for newly-manufacturedengines that may not be able to complywith the first tier of the new NOX standards because of specific technicalor economic reasons.63 Second, we aredefining ‘‘derivative engine’’ foremissions certification purposes. Theintent of this definition is to distinguishwhen the emission characteristics of anew turbofan engine model varysubstantially from its existing parentengine design, and must showcompliance with the emission standardsfor a newly-certificated engine. Third,

we are establishing new CO and NOX

standards for turbofan engines that areused to propel supersonic aircraft.These standards were adopted by ICAOin the 1980s, but were not previouslyadded to our HC emission standard forthese engines. Promulgating thesestandards meets our treaty obligationunder the Convention on InternationalCivil Aviation as previously described


http://www.icao.int/http://www.icao.int/http://www.icao.int/http://www.icao.int/


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64There are no gaseous emission standards, e.g.,NOX, for gas turbine engines with maximum ratedthrusts equal to or less than 26.7 kN. These enginesare, however, subject to smoke and fuel ventingstandards.

65The combustor is a chamber where a mixtureof fuel and air is burned to form very hot,expanding gases. As these gases move through thecombustion chamber, the walls of the combustor arecooled with dilution air to prevent thermal damage.Dilution air is also used to tailor the gas’temperature profile as it exits the combustor so thatthe final temperatures will not exceed the allowablelimit at the turbine inlet.

in section I.C. Fourth, we are makingseveral changes to the emission testingand measurement procedures in ourregulations that are intended toimplement ICAO’s Annex 16 and toincorporate the entire annex in ourregulations by reference. Finally, asdescribed in section IV, we areamending the current regulatory

provisions that address definitions,acronyms and abbreviations, generalapplicability and requirements,exemptions, and incorporation byreference. These amendments areintended to clarify requirements, makethem more consistent with other parts ofthe program, update the text to beconsistent with current standardlanguage conventions, or removeobsolete provisions.

As discussed further below, with theexception of the annual reportingrequirement described in section III.D,the amendments reflect those changes

that were previously adopted by ICAO.This final rule also is consistent withour authority and obligations under theCAA as described in section I.B. Morespecifically, the technical feasibility andcost of the emission standards were welldocumented by our own analyses andCAEP as described later in this sectionand in section V, Technical Feasibility,Costs, and Emission Benefits. We thinkthat the final rule provides adequatelead time for the development andapplication of the requisite technologywith appropriate consideration to thecost of compliance. We have consultedwith the Department of Transportation

through the FAA regarding lead time,noise, safety, and the technicalfeasibility of the new standards. Today’sfinal rule is also consistent with U.S.treaty obligations under the ChicagoConvention as described in section I.C.,

because the requirements are consistentwith current ICAO standards.

Except to the extent needed to makeour standards conform to ICAO’sstandards by making them applicable to

both commercial and non-commercialengines, we are not revising exhaustemission standards for HC, CO, orsmoke. All engines subject to the new

NOX

standards would also continue to be subject to the existing HC, CO, andsmoke standards. It is worthemphasizing that although we areincluding these existing HC, CO, andsmoke standards in a new section 87.23,which would also contain the new Tier6 and Tier 8 NOX standards, we are notactually adopting new standards forthese three pollutants, since under thecurrent form of part 87 these HC, COand smoke standards would alreadycontinue to apply to new engine typessubject to future revised NOX standards.

As discussed above, we are adoptinga new naming convention in thispreamble and the regulatory text tomore easily distinguish between thetiers of increasingly more stringent NOX emission standards. This convention isalso consistent with the numericidentifier that CAEP uses to differentiatethe CAEP work cycle that produces new

NOX standards. (The CAEP namingconvention is described in section I.E.)As a result, the first tier of NOX standards, which correspond to CAEP/6, are referred to as Tier 6 in theremainder of today’s notice. The secondtier of standards is referred to as Tier 8,which correspond to CAEP/8. We arealso incorporating the new namingconvention in the regulations for theexisting NOX emission standards, i.e.,Tier 0, Tier 2, and Tier 4. There is nomaterial change to the existing NOX standards themselves, except to theextent that when today’s final rule

becomes effective, the existing NOX

standards would be superseded by Tier6 standards.

We acknowledge that this newnaming convention is a change from thepast practice of not describing aircraftengine emission standards as tiers.However, we believe the new namingscheme is a valuable tool that makesreferring to individual NOX standardsmuch easier. It is also similar to theterminology we use for other mobilesource sectors that are subject toenvironmental regulation and for whichstandards have become more stringent

or have otherwise been amended overtime.

A. NO X Standards for Newly-CertifiedEngines

We are adopting two different tiers ofincreasingly stringent NOX standards.These standards would apply for all fornewly-certified turbofan aircraft engineswith maximum rated thrusts greaterthan 26.7 kN.64 (See section III.B for adiscussion of how these standards applyfor newly-manufactured engines that arenot considered to be newly certified.)The numerical value of the applicable

standard for an individual engine modelis defined by the engine’s thrust leveland pressure ratio. Simply stated, thepressure ratio is the numerical ratio ofthe air pressure entering the engine tothe air pressure at the entrance to thecombustor, i.e., after the air has passedthrough the compressor section of the

engine.65 The new tiers are describedseparately below.

1. Tier 6 NOX Standards for Newly-Certified Engines

This first tier of new standards isequivalent to the CAEP/6 NOX limitsthat were adopted by ICAO and becameinternationally applicable after

December 31, 2007. Given that aircraftturbofan engines are internationalcommodities, engine manufacturersintroduced engine models after that datethat demonstrate compliance with theseinternational standards, or are alreadyplanning to do so for upcoming enginedesigns. Based on this, our evaluation ofthe necessary lead time, and the lack ofany comments on this aspect of theproposal, this tier of standards takeseffect immediately upon the effectivedate of this final rule.

The basic form of the NOX standardsfor turbofan engines is different for

higher- and lower-rated thrust engines.Higher output engines are defined ashaving rated thrusts equal to or greaterthan 89 kN, while lower output enginesare defined as having rated thrusts lessthan 89 kN but greater than 26.7 kN.The new Tier 6 NOX standards for eachof these power groupings are describedseparately below.

a. Numerical Emission Limits for HigherThrust Engines

The Tier 6 NOX standards for newly-certified gas turbine engines with ratedthrusts more than 89 kN are

differentiated by pressure ratio asshown below.• For engines with a pressure ratio of

30 or less:

g/kN rated output = 16.72 + (1.4080 *engine pressure ratio)

• For engines with a pressure ratio ofmore than 30 but less than 82.6:

g/kN rated output =¥1.04 + (2.0 *engine pressure ratio)

• For engines with a pressure ratio of82.6 or more:

g/kN rated output = 32 + (1.6 * enginepressure ratio)

The new Tier 6 NOX standards forthese higher thrust engines arepresented in Figure 1 along with theprevious EPA NOX standards, whichwere based on CAEP/4, for comparison.



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66 ICAO/CAEP, ‘‘Report of Third Meeting,Montreal, Quebec, December 5–15, 1995,’’Document 9675, CAEP/3. A copy of this paper can be found in Docket EPA–HQ–OAR–2010–0687.

67 ICAO, ‘‘Combined Report of the Certificationand Technology Subgroups,’’ section 2.3.6.1, CAEPWorking Group 3 (Emissions). Presented by theChairman of the Technology Subgroup, ThirdMeeting, Bonn, Germany, June 1995. A copy of thispaper can be found in Docket EPA–HQ–OAR–2010–0687.

As a matter of convention, the relativestringency from one CAEP standard toanother is expressed relative to apressure ratio of 30, because thepercentage reduction is usuallyinconsistent across all of the possiblepressure ratios, which otherwise makesa simple comparison difficult. Usingthat convention, the Tier 6 standards(CAEP/6) are referred to as being 12percent more stringent than the existingEPA NOX Tier 4 standards (CAEP/4).

The relative stringency can also beillustrated at other pressure ratios. Atpressure ratios less than 30 thereductions are also 12 percent. Atpressure ratios above 30, however, thepercent reduction decreases as thepressure ratio is increased. Based on thefigure, the percent reduction for currenttechnology engines ranges from about 8to 12 percent.

b. Numerical Emission Limits for LowerThrust Engines

The new Tier 6 NOX standards fornewly-certified gas turbine engines with

rated thrusts between 26.7 and equal toor less than 89.0 kN are differentiated by both pressure ratio and rated thrust asshown below.

• For engines with a pressure ratio of30 or less:

g/kN rated output = 38.5486 + (1.6823* engine pressure ratio)¥ (0.2453* kN rated thrust)¥ (0.00308 *engine pressure ratio * kN ratedthrust)

• For engines with a pressure ratio ofmore than 30 but less than 82.6:

g/kN rated output = 46.1600 + (1.4286* engine pressure ratio)¥ (0.5303* kN rated thrust) + (0.00642 *engine pressure ratio * kN ratedthrust)

In developing the corresponding NOX standards for lower thrust engines,CAEP recognized the technicalchallenges that physically smaller-sizedengines sometimes present relative toincorporating some of the lowest NOX technology approaches, which areotherwise available to their largercounterparts. These technicaldifficulties are well documented andincrease progressively as size is reduced(from around 89 kN).66 For example, therelatively small combustor space andsection height of these engines createsconstraints on the use of low NOX fuel-staged combustor concepts whichinherently require the availability ofgreater flow path cross-sectional areathan conventional combustors. Also,fuel-staged combustors need more fuelinjectors, and this need is notcompatible with the relatively smaller

total fuel flows of lower thrust engines.(Reductions in fuel flow per nozzle aredifficult to attain without havingclogging problems due to the small sizesof the fuel metering ports.) In addition,lower thrust engine combustors have aninherently greater liner surface-to-combustion volume ratio, and thisrequires increased wall cooling air flow.

Thus, less air will be available to obtainacceptable turbine inlet temperaturedistribution and for emissions control.67 With these technological constraints inmind, CAEP fashioned the CAEP/6 NOX standards across the range of thrustsrepresented by low-thrust engines to

become comparatively less stringent,i.e., CAEP/6 relative to CAEP/4, as therated output and physical size of theengines decrease. We agree with thisapproach.

As mentioned, the new Tier 6standards depend on an individualengine’s rated thrust and pressure ratio.With two variables in the calculation,the standards cannot be represented ina simple figure, i.e., no single line graphshowing the standards for all engineswithin the thrust range is possible as itwas for higher thrust engines.Regardless of this complexity, however,some general observations are useful tocharacterize the Tier 6 NOX standardsfor lower thrust engines based on theengine size versus technologicalchallenge described in the previous

paragraph.Comparing the new lower and higherthrust standards at 89 kN, which is thedemarcation point between the two setsof standards, shows that the standardsfor lower thrust engines are numericallyequivalent to the limit for higher thrust



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engines at each pressure ratio. This is asexpected because the engine sizes andability to incorporate low-NOX technologies are the same at 89.0 kNdelineation point.

Again focusing only on 89 kNengines, the new Tier 6 standardsrepresent a 12 percent reduction fromthe existing EPA Tier 4 (CAEP/4 basedstandards) for pressure ratios of 30 orless as shown below in Figure 2. This

includes the region represented byalmost all current engine designs. Athigher pressure ratios, the relativenumerical reduction is progressivelyless because the slope of the twostandards is essentially the same.

At other thrust ratings the percentreduction between the new Tier 6 andexisting EPA NOX standards at any

pressure ratio becomes progressivelysmaller as thrust decreases. This isillustrated in Figure 3 for a pressureratio of 30. This pressure ratio waschosen for the example because, as

before, the relative stringency of CAEPNOX standards is generally compared at

this point as a matter of convention. Asshown in the figure for current engines,the reduction ranges from 12 percent at

the upper end of the thrust range to 0percent at the lower end of the range.The pattern is similar for the otherpressure ratios. On

control of air pollution from aircraft-2012-13828

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