U.S. EPA Response to OMB EO12866 Interagency Review Comments on 

“interagency comments aircraft NOx rule 04142011.docx”

This responds to the interagency comments on the draft notice of proposed rulemaking for 

aircraft engine emission standards that were provided to us on April 14, 2011. We agree with 

many of the comments and have incorporated them either directly or with some modification as 

reflected in the attached redline/strikeout version of the revised draft preamble and regulations. 

However, there are a number of areas where we disagree with the substance of the comments. 

Specifically, there are five outstanding issues. For convenience, we have summarized the 

comments on each issue and provided our response in the remainder of this document.

Exemptions from the Proposed Tier 6 NOx Standard Production Cutoff

Comment: The FAA disagrees with the adoption of a limit that substantively differs from what 

the FAA agreed to at ICAO as guidance. The FAA believes that EPA’s argument that the more 

restrictive limit is somehow better is seriously undercut by EPA’s own admission that they do 

not expect the situation to occur and that there may be special circumstances that allow the limit 

to be exceeded. FAA states that a reference to ICAO guidance as a basis provides for our 

proposal is all of the flexibility needed in the United States without specifying meaningless 

regulatory limits that the agencies can ignore. Further, FAA states that if the ICAO guidance 

changes, we will not be locked into a comparison of provisions as needed. Finally, FAA further 

states that they would not be able to justify the proposed limit of 75 per type certificate holder so 

as to adopt it into their standards.

Response: We would like to respond to the concerns raised by FAA through the points below. 

EPA agreed to the draft ICAO ETM language in August 2009 knowing that time had run 

out for further debate on the exemption limits for the CAEP/6 (Tier 6) NOx production 

cut-off for engines used on new aircraft. Time was needed for the CAEP Certification 

Task Group (CTG) to draft its report and ETM guidance language for the meeting of the 

CAEP Steering Group in October 2009. At that time, we made it clear to the parties 

involved in the CTG, including the FAA, that we thought that the value of 75 per type 

certificate in the draft ETM guidance was inappropriate and that we would continue to 

work the issue post CAEP/8 as we prepared our proposed rulemaking to adopt the NOx 

standards and related provisions. As discussed below, we also did so knowing that the 

ETM is indeed guidance, and that we could propose to adopt a different value based on 

our additional efforts, if justified.

During subsequent deliberations as more information became available it became 

apparent to us that incomplete information to the CTG regarding the potential need for 

exemptions was leading to a focus on an unnecessarily large value. As summarized in 

the preamble, when discussions first began in the CTG there were reportedly up to twenty
models/sub-models that may have been affected by the CAEP/6 (Tier 6) NOx production 

cut-off. By the time we completed our consultations for this draft NPRM the number was 

down to only one or two models potentially needing exemptions each for a number much 

less than 75. Thus, in our judgment, the ETM limit of 75 per type certificate is an 

unnecessary loophole that potentially could be used to inappropriately exempt a large 

number of engines for new production aircraft. It is worth noting that FAA technical 

staff participated in the consultations with the manufacturers and were aware of the 

responses we received to our questions on the exemption level and the manufacturers’ 

perspectives on the need for 75 per type certificate. We also held separate conversations 

with FAA technical staff on this issue. 

Regarding the FAA’s comment about uniformity with the ETM, we do not believe we are 

compelled nor is it wise to be consistent with ICAO guidance just for the sake of 

consistency itself, especially when there are compelling reasons to propose a different 

approach. Even the Chicago Convention (the basis of ICAO) allows nations to adopt 

their own unique standards that differ from the language in Annex 16.

In addition WTO’s Technical Barriers to Trade Agreement, Annex 3: “Code of good 

practice for the preparation, adoption, and application of standards”, paragraph F. states:

“Where international standards exist or their completion is imminent, the 

standardizing body shall use them, or the relevant parts of them, as a basis for the 

standards it develops, except where such international standards or relevant parts 

would be ineffective or inappropriate, for instance, because of an insufficient level of 

protection or fundamental climatic or geographical factors or fundamental 

technological problems.”

While ICAO’s ETM is only guidance and does not constitute a technical regulation or 

standard by the World Trade Organization’s definitions (See WTO’s Technical Barriers 

to Trade Agreement, Annex 1: Terms and their definitions for the purpose of this 

Agreement), we still assert that the ETM in this case is ineffective because of its 

insufficient level of protection against the potential for excessive exemptions. For 

example, if one calculates the hypothetical maximum for exemptions under ICAO’s ETM

provision of 75 exemptions per type certificate, one sees that this maximum exceeds 

industry’s projected production of all engines by nearly a factor of two. While such a 

situation may not fully occur, clearly, this provision offers an insufficient level of 

protection relative to the proposed Tier 6 production cutoff. Furthermore, even though 

we believe we have shown that a difference is justifiable, the WTO’s TBT agreement 

states that the burden of proof is upon the complainant regarding any claim that a 

difference from an international technical regulation or standard is inconsistent with the 

TBT provisions. (See WTO Website on Interpretation of Article 2.4). 
Based on this, there can be no doubt that a difference from ETM guidance is within the 

accepted boundaries of the Convention and the WTO’s TBT Agreement. As described 

above we think we have a good policy reason to be different. Furthermore, unlike the 

ETM limit, a different approach could respond directly to the potential needs of the 

engine manufacturers. The numerical value we identified is based on discussions with 

the engine manufacturers affected by the proposed Tier 6 standards, and they agreed that 

it was reasonable for Tier 6. In fact, this approach was suggested by one of the 

manufacturers. In other EPA mobile source rules we have provisions for hardship 

exemptions for unusual circumstances. These exemptions are crafted carefully to meet a 

justified need but not to be unnecessarily generous. We are concerned that specifically 

identifying an exemption provision that is too generous could create an expectation that 

potential future exemption provisions will be equally generous even if not warranted by 

data or policy considerations. 

FAA asserts that our provision including a regulatory flexibility that would allow for 

additional exemptions in unusual circumstances undercuts our position with regard to the 

appropriateness of 75 per type certificate holder. However, we strongly disagree. It has 

been our experience that such regulatory flexibility is invaluable in providing EPA 

provisions to address unexpected circumstances and developments. This was also 

suggested by the engine manufacturers. 

We must disagree with the FAA concern that an inconsistency now would lock us into a 

comparison of provisions if ICAO guidance changes in the future. Even if the exemption 

provisions were consistent now as suggested by FAA, good public policy would 

necessitate a critical review any time ICAO provisions changed in the future. Thus we 

see no real basis for a concern here. 

We also note that in general the exemption provision has no cost associated with it for the 

government or industry and there is no cost savings under either approach. It is designed 

to provide manufacturers with an opportunity to reduce costs or adverse economic effects 

should the need for exemptions arise.

Finally, the assertion by FAA that they could not adopt a regulatory provision that differs 

from the ETM in their regulations is troubling. That would be an interagency review and 

notice/comment issue for their later rule proposing changes to 14 CFR 34. While we 

would hope that FAA would propose and adopt this limit, we do not believe that they 

need a separate justification to develop implementing regulations under section 232 of the 

Clean Air Act to enforce emission standards EPA adopts under section 231 of the Clean 

Air Act.
EPA does not feel bound to follow ETM guidance in these circumstances. We are continuing to 

deliberate on an improved approach for an appropriate regulatory provision that is responsive to 

the identified need but does not include the potential for excessive exemptions contained in the 

current ETM exemption provision.

Comment: Replace “exemption” with “exception” in the context of exemptions for spare 

engines.

Response: We do not understand the FAA’s insistence to substitute “exception” for 

“exemption” with regard to spare engines. First, doing so is inconsistent with language in the 

ICAO guidance and is therefore potentially confusing to the regulated community. Second, 

FAA’s distinction between spare and new engines seems to be based on a process difference (no 

need for a pre-approval for spare engines) not on a program difference (the fact that the 

regulations would allow spares exemption from proposed Tier 6 requirements as needed). 

However, even for spares there is an implied approval in our regulatory process consistent with 

the ICAO guidance and the need for recordkeeping and reporting to EPA. In our view such a 

wording change is not needed or helpful.

Foreign Aircraft and Exemptions

Comment: The FAA recommends removing most of the discussion on exemptions for foreign 

aircraft because they deem it to be confusing and in their judgment contains presumed 

conclusions about U.S. decisions based on the decisions of foreign certificating authorities. They 

also stated that it is not feasible or likely that approvals will be processed among all authorities 

worldwide.

Response: The purpose of this text is to lay out how the U.S. government would coordinate with 

other certificating authorities with regard to exemption requests and our view on how we would 

handle requests from airlines for U.S. airworthiness certificates when the original exemption was 

granted by an authority which did not coordinate with us.

The number of exemptions covered in any one request is intended to apply toward a world-wide 

total limit of 75. We believe it provides a helpful explanation of the U.S.’ intent with respect to 

international coordination and is consistent with our understanding of the manner in which this 

provision of the ETM is to be implemented. We believe this language is helpful to engine 

manufacturers and even necessary because concerns have been expressed that different treatment 

by the four certificating authorities (without coordination) could create competitive imbalances 

for manufacturers. This text also explains how the proposed regulations would address 

exemptions for foreign aircraft (aircraft certificated by another authority). It is consistent with 

our understanding of FAA certification practice and the intent of the ETM. While the preamble 
text can be clarified, we disagree that these discussions should be removed. The revised 

preamble text is provided below: 

iv. Coordination of Exemption Requests

The limit on the number of potentially exempt engines as described in the ETM is 

intended to apply to overall worldwide production. Toward that end, the ETM envisions 

collaboration and consultation among certificating authorities and member states whenever any 

authority receives an exemption request. Specifically, the ETM states:

“Exemptions for new engines should be processed and approved by the competent 

authorities for both the manufacture of the exempted engines and the initial operator of 

the aircraft to which they are to be fitted. Given the international nature of the aviation 

enterprise, civil aviation authorities of member states should attempt to collaborate and 

consult on the details of exemptions. In the case where engine type certification is done 

through a reciprocity agreement between or among member states, the states involved 

should coordinate on the processing of exemptions and concur before approval is 

granted.” 1

Working with the FAA, we would fully expect to conduct such collaboration and 

consultation among the competent authorities whenever we receive an exemption request. This 

would include consultation with other certificating authorities as well as coordination with the 

competent civil aviation authority of any country where the aircraft with the exempted engines 

will be registered. 

To facilitate this consultation and coordination we are proposing that manufacturers also 

include in their requests a list of countries in which the aircraft are expected to be registered. 

While not specifically listed in the ETM, we believe that this information is consistent with the 

ETM as it would be necessary to ensure proper coordination. The ETM appears to presume that 

each member country will recognize exemptions granted by other countries. This presumption 

seems reasonable assuming that the exemption being granted is consistent with the guidelines of 

the ETM and that the collaboration, consultation and coordination called for in the ETM was 

conducted in good faith. However, there should be no presumption that EPA would agree to an 

exemption for an engine model if the aforementioned collaboration, consultation, and 

coordination were not conducted. The Clean Air Act (which provides EPA with its authority to 

establish emission standards) includes no provisions that would allow any foreign country to 

exempt subject aircraft engines, over the objection of FAA and EPA, from the applicable 

standards EPA promulgates. Nevertheless, since our proposed exemptions provisions are 

 

1

ICAO, “Committee on Aviation Environmental Protection (CAEP), Eighth Meeting, Montreal, 1 to 12 February 

2010,” CAEP/8-WP/80, Agenda Item 2: Review of Technical Proposals Relating to Aircraft Emissions, April 2, 

2010. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.
consistent with the procedures called for in the ETM, assuming appropriate consultation and 

coordination in accordance with the ETM, we would not expect FAA and EPA to object to 

exemptions for engines properly exempted by other countries under those procedures. The FAA 

would still need to take the certification action as called out in 14CFR 91.203 and 14 CFR 

21.183. 

This, however, raises the question as to how we would respond to an exemption request 

when another certificating authority did not consult or coordinate on a previous request for the 

same engine model. For example, it could well be problematic if a manufacturer was seeking 75 

exemptions from more than one certificating authority. A related concern arises if a type 

certificate is sought under a reciprocity agreement and the original exemption was not 

coordinated with the United States. Such requests would likely be viewed as new exemption 

requests if the anticipated collaboration, consultation, and coordination had not occurred. 

Thus to avoid these issues, in most cases, manufacturers should be working with all 

relevant certificating authorities at the same time as well as the civil aviation authority of 

nation(s) where the aircraft will be initially registered or operated if that nation requires a type 

certificate issued under its own regulations to operate in its air space consistent with international 

agreements.

Emission Inventories

Comment: FAA commented that the previous version of the preamble included other source 

data for comparative purposes. FAA supported that data being included, and requested more 

detail to properly characterize aviation’s contribution to the total NOx emissions inventory. The 

percent contribution of aviation should be included here to disclose to the public the extent of 

aviation emissions impact. This is important context for the public to be able to adequately 

address EPA’s question later on about additional control measures that might be necessary. 

Specifically, FAA added a sentence that according to the EPA National Emissions Inventory for 

2008, the contribution of commercial aviation NOx emissions is less than 1% of the total 

inventory for the United States. 

Response: In response to FAA’s desire for more emission inventory information, we accept their 

addition regarding aviation’s contribution to the total U.S. NOx inventory from landing and 

takeoff operations. However, that statistic by itself presents a misleading picture of aviation’s 

contribution in ozone non-attainment areas, which allows a better characterization of potential 

health and welfare effects. Therefore, we will correct that imbalance by adding comparisons for 

those areas. Additionally for completeness, we are adding information on the contribution of full 

flight emissions to the total U.S. NOx inventory. 

The revised preamble text is provided below:

A. Inventory Contribution
In contrast to all other mobile sources, whose emissions occur completely at ground 

level, the emissions from aircraft and aircraft engines can be divided into two flight regimes. 

The first regime includes the emissions that are released in the lower layer of the atmosphere and 

directly affect local and regional ambient air quality. These emissions generally occur at or 

below 3,000 feet above ground level, i.e., during the landing and takeoff (LTO) cycle. The 

aircraft operations that comprise an LTO cycle are: engine idle at the terminal gate (and 

sometimes during ground delays while holding for the active runway); taxiing between the 

terminal and the runway; take-off; climb-out; and approach to the airport. The second regime 

includes emissions that occur above 3,000 feet above ground level, known as non-LTO 

emissions. Collectively, the emissions associated with all ground and flight operations are 

generally referred to as full flight emissions.

The aircraft engine NOx emission inventories for the LTO and non-LTO flight regimes 

described above are discussed separately in the following sections.

1. Landing and Takeoff Emissions

In this section, we will discuss NOX emission inventories for commercial turbine-engine 

aircraft, both nationally and for selected ozone nonattainment areas (NAAs). These inventories

reflect emissions during the landing and takeoff cycle only. The most recent comprehensive 

analysis of historical and current LTO emissions from aircraft engines comes from a study 

undertaken for us by Eastern Research Group (ERG).2 The study analyzed the national 

emissions of commercial aircraft operations in the United States, and showed that in the most 

recent year studied (2008), such aircraft operations contributed about 97 thousand tons to the 

national NOX inventory. A summary of the national inventory of LTO NOX emissions is shown 

in Table 1. When these nationwide LTO emissions are compared to the total U.S. mobile source 

inventory for 2009, they account for less than one percent of the total. However, such a 

comparison may be a bit misleading, as it only includes those aircraft emissions that occur below 

3000 feet altitude, while comparing them to the entirety of other mobile source emissions. In the 

U.S., LTO emissions account for only about ten percent of full flight NOX emissions. When 

considering full flight aircraft emissions (i.e., including both LTO and non-LTO emissions), the 

contribution of aircraft to the total mobile source NOX inventory is approximately 7.7 percent.3

Table 1: Current National NOX Emissions from Commercial Aircraft

Aircraft Category 2008 Total NOX (thousand tons)

Air Carrier 86

Commuter/Air Taxi 11

Total Commercial 97

 

2

 “Historical Assessment of Aircraft Landing and Take-off Emissions (1986-2008),” Eastern Research Group, May 

XX, 2011. A copy of this document can be found in public docket EPA-HQ-OAR-2010-0687.

3

 “Comparison of Aircraft LTO and Full Flight NOX Emissions to Total Mobile Source NOX Emissions,” 

memorandum from John Mueller, U.S. EPA, to docket EPA-HQ-OAR-2010-0687, May XX, 2011.
In addition, it is important to assess the contribution of commercial aircraft LTO NOX

emissions on a local level, especially in areas containing or adjacent to airports. The historical 

analysis conducted by ERG also included an assessment of selected ozone nonattainment areas 

(NAAs). The top 25 ozone NAAs were identified based first in terms of NAAs with airports 

which had high commercial traffic volumes and then those with the largest population. There 

was some overlap, and this led to a total of 41 NAAs for the study. These 41 NAAs collectively 

include 200 airports, accounting for about 70 percent of commercial air traffic operations. 

Current (2008) and projected (2020) NOX emissions for these 41 NAAs, as well as the percent 

contribution of aircraft to total mobile source inventories (as compared to 2005 and 2020 mobile 

source inventories), are shown in Table 2.4 The relative contribution of aircraft in any given 

NAA varies based on activity in other transportation and industrial sectors. As can be seen from 

this table, expected growth in aircraft operations in many of these areas combined with 

anticipated reductions in NOX emissions from other mobile source categories results in the 

growth of the relative contribution of aircraft LTO emissions to mobile source NOX emissions in 

NAAs.

Table 2: Current NOX Emissions in Selected Ozone Nonattainment Areas

Nonattainment Area 2008 Total NOX (tons)

2008 Aircraft Percent of 

Mobile Source NOX

2020 Aircraft Percent of 

Mobile Source NOX

Albuquerque, NM 380 1.6 4.3

Anchorage, AK 2,538 23.4 49.3

Aspen 16 2.0 6.6

Atlanta, GA 5,808 2.6 8.2

Baltimore, MD 1,148 1.3 4.4

Boston including MA and NH 

NAAs 2,131 1.0 2.7

Charlotte-Gastonia-Rock Hill, 

NC-SC 1,917 2.6 10.0

Chicago-Gary-Lake County, 

IL-IN 6,007 1.8 5.0

Cincinnati-Hamilton, OH-KYIN 1,287 1.5 3.3

Cleveland-Akron-Lorain, OH 680 0.5 1.3

Dallas-Fort Worth, TX 3,880 1.7 6.9

Denver-Boulder-Greeley-Fort 

Collins-Loveland, CO 2,649 2.5 7.1

Detroit-Ann Arbor, MI 2,312 1.1 3.0

El Paso, TX 223 0.9 1.1

Greater Connecticut, CT 405 0.8 2.4

Houston-Galveston-Brazoria, 

TX 3,045 1.3 3.4

Indianapolis, IN 1,089 1.4 3.0

Las Vegas, NV 2,308 6.0 15.8

Los Angeles South Coast Air 

Basin, CA 6,479 1.5 4.5

Louisville, KY-IN 1211 1.9 6.2

Memphis, TN-AR 2,988 6.3 16.8

Milwaukee-Racine, WI 557 0.9 3.2

Minneapolis-St Paul, MN 2,154 1.0 5.1

New York-N. New Jersey- 10,093 2.3 6.3

 

4

 “Relative Contribution of Aircraft to Total Mobile Source NOX Emissions in Selected Ozone Nonattainment 

Areas,” memorandum from John Mueller, U.S. EPA, to docket EOA-HQ-OAR-2010-0687, MayXX, 2011.
Long Island, NY-NJ-CT

Philadelphia-WilmingtonAtlantic City, PA-NY-MD-DE 2,308 1.0 2.8

Phoenix-Mesa, AZ 2,298 1.4 3.3

Pittsburgh-Beaver Valley, PA 480 0.5 1.1

Providence (entire State), RI 232 1.0 2.3

Raleigh-Durham-Chapel Hill, 

NC 565 1.0 3.2

Reno, NV 246 1.9 4.4

Riverside County (Coachella 

Valley), CA 70 0.2 0.5

Sacramento Metro, CA 603 1.0 2.0

Salt Lake City, UT 1,235 4.4 14.1

San Diego, CA 1,035 1.4 3.4

San Francisco Bay Area, CA 4,405 2.7 6.7

San Joaquin Valley, CA 74 0.0 0.1

Seattle-Tacoma, WA 1,958 1.4 3.9

St. Louis, MO-IL 810 0.6 1.6

Syracuse, NY 139 0.8 1.9

Washington, DC-MD-VA 2,983 2.0 6.2

Table 3 shows how commercial aircraft operations are projected to rise in the future on a 

nationwide basis. As operations increase, the inventory impact of these aircraft on national and 

local NOX inventories will also increase, as was seen in Table 2.

Table 3: Current and Projected Commercial Aircraft Operations

Year Air Carrier 

Operations

(millions)

Commuter/

Air Taxi Operations

(millions)

Total Commercial 

Operations

(millions)

Total increase in 

commercial operations 

over 2008 (percent)

2008 14.1 13.8 27.9 --

2020 16.5 14.1 30.5 9

2030 20.6 16.0 36.6 31

Source: December 2010 FAA TAF, which is located at http://aspm.faa.gov/main/taf.asp .

Derivative Engines

Comment: The FAA commented that it does not have a description of the certification process 

for distinguishing derivatives, and suggested a revised definition and related edits to resolve their 

concerns. The FAA also struck text allowing it to approve derivatives on the basis of safety 

alone, and suggested other editorial revisions.

Response: We agree with FAA’s suggestion that the regulations should use a new term 

“derivative engine for emission certification purposes”. 

We believe FAA’s request to strike the text related to safety was based on a misreading of the 

provision as a necessary condition for derivatives. However, the provision actually treats safety 

concerns as a sufficient rationale for modifying engine models, without regard to whether the 

modified engines meet the emission criteria.
We made some of the editorial suggestions. However, we did not make those that were incorrect 

or incompatible with keeping the safety-related provision. For example, we did not incorporate 

the following changes:

(a) General. A type certificate holder may request from the FAA a determination that an 

engine model is considered a derivative engine for emissions certification purposes. This 

would mean that the engine model is determined to be similar in design for the purposes 

of smoke and exhaust emissions evaluations. In order to be considered a derivative 

engine for emissions purposes under this part, it must have been: [Note: Should be 

gaseous and smoke rather than smoke and exhaust since smoke is an exhaust emission]

(a)(1) Derived from an engine certificated to the requirements of 14 CFR part 33 and this 

part; and [Note: This incorrectly replaces safety language]

(a)(2) Demonstrate that it meets the emissions criteria specified in paragraph (b) of this 

section. The criteria specified in paragraph (b) of this section may be adjusted by the 

FAA based on unusual circumstances when the type certificate holder has made 

determinations consistent with good engineering judgment. [Note: FAA makes the 

determinations rather than the type certificate holder]

(b) (2) If the characteristic level of the originally certificated engine before modification 

is at or above 95% of the applicable standard for any pollutant, the type certificate holder 

must measure the proposed derivative for all pollutants to demonstrate that the derivative 

engine’s resulting characteristic levels will not exceed the applicable emission standards. 

If the characteristic level of the originally certificated engine before modification is 

below 95% of the applicable standard for any pollutant, then consistent with good 

engineering judgment, the type certificate holder may use engineering analysis to 

demonstrate that the derivative engine will not exceed the applicable emission standards. 

[Note: Emissions must be below 95% of the applicable standard for ALL pollutants]

Paragraphs (a) and (b) now read as follows:

(a) General. A type certificate holder may request from the FAA a determination that an engine 

model is considered a derivative engine for emissions certification purposes .This would mean 

that the engine model is determined to be similar in design to a previously certificated 

engine(the “original” or “parent” engine) for purposes of compliance with exhaust emission 

standards (gaseous and smoke). In order for the engine model to be considered a derivative 

engine for emission purposes under this part, it must have been derived from an original engine 

that was certificated to the requirements of 14 CFR part 33, and one of the following conditions 

must be met:
(1) The modifications to the engine were necessary for both improved safety and continued 

airworthiness, as determined by FAA.

(2) Emissions from the derivative engines are determined to be similar. In general, this 

means the emissions must meet the criteria specified in paragraph (b) of this section. FAA 

may adjust these criteria in unusual circumstances, consistent with good engineering 

judgment.

(b) Emissions similarity. The type certificate holder must demonstrate that the proposed 

derivative engine model’s emissions meet the applicable standards and differ from the original 

model’s emission rates only within the following ranges: 

(1) The difference between emission rates of a derivative engine and the original engine 

should be within the following allowable ranges:

(i) ± 3.0 g/kN for NOx.

(ii) ± 1.0 g/kN for HC.

(iii) ± 5.0 g/kN for CO.

(iv) ± 2.0 SN for smoke. 

(2) If the characteristic level of the original certificated engine model (or any other sub-models 

within the emission type certificate family tested for certification) before modification is at or 

above 95% of the applicable standard for any pollutant, you must measure the proposed 

derivative engine model’s emissions for all pollutants to demonstrate that the derivative engine’s 

resulting characteristic levels will not exceed the applicable emission standards. If the 

characteristic levels of the originally certificated engine model (and all other sub-models within 

the emission type certificate family tested for certification) are below 95% of the applicable 

standard for each pollutant, then consistent with good engineering judgment, you may use 

engineering analysis to demonstrate that the derivative engine will not exceed the applicable 

emission standards. The engineering analysis must address all modifications from the original 

engine, including those approved for previous derivative engines.

Incorporation the ICAO Annex 16 by Reference

Comment: The FAA does not believe that it is legally permissible to incorporate basic standards 

by reference to a foreign document. Such an attempt fails as legal notice of the proposed 

standard and does not give regulated entities access to the standards with which they must 

comply without resort to purchasing a document from a foreign entity (in this case ICAO). We 

confirmed this position of the Federal Register with their counsel in March 2011.
If the FAA were adopting parts of the ICAO Appendices, we would do so by repeating those 

provisions into our regulations as we would be required to do. We have not rewritten the 

standards into EPA’s regulatory text as U.S. regulations. 

Response: We believe that the FAA is wrong about the legality and permissibility of 

incorporating the ICAO Annex 16 by reference into the applicable regulations, and may have 

misunderstood the Federal Register counsel’s response to their inquiry. In the attached email 

record (see Appendix), the Director of Legal Affairs and Policy at the Office of the Federal 

Register (OFR) is in full agreement with incorporating the copyrighted annex appendices by 

reference. In fact, it is the only approach that conforms to OFR’s requirements. 

We recommend that the FAA seek guidance on repeating parts of the copyrighted ICAO annex 

in its regulations. Our understanding is that such an approach would conflict with OFR’s 

requirements and is therefore impermissible.

Regarding FAA’s comment on public availability, OFR requires that a copy of the IBR reference 

be maintained and publically available by the incorporator (in this case EPA). We will do this by 

placing the annex appendices in the public docket for the rulemaking. Our webpage that 

announces the publication of the proposed rule will clearly explain that we have incorporated the 

annex material by reference in the regulations, and that a copy of the appendices are publically 

available in the rulemaking docket. Finally, OFR also retains a copy of the material. 
APPENDIX

Documentation Approving Use of IBR for the Aircraft Engine Emission Standards NPRM from 

the Office of the Federal Register

From: "Bunk, Amy" <abunk@gpo.gov>

To: Alan Stout/AA/USEPA/US@EPA

Cc: "Vincent, Miriam" <mvincent@gpo.gov>

Date: 04/20/2011 04:13 PM

Subject: RE: Aircraft IBR

Alan,

Thank you for providing the draft proposed rule and the standards EPA wishes to incorporate by 

reference when this proposal becomes a final rule. The International Civil Aviation Organization (ICAO) 

Annex 16 and appendices provided qualify for incorporation by reference under our regulations at 1 CFR 

part 51. Please let us know if you have any further questions or want us to pre-review a draft of the final 

rule. You can find drafting guidance in our Document Drafting Handbook Chapter 6.

Amy Bunk

Director of Legal Affairs and Policy

Office of the Federal Register

work: 202-741-6025

Blackberry: 202-271-8041