CLEEN IV Draft SIR Comment Matrix and FAA Responses_FINAL UPDATED 03.31.2026.xlsx
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- Continuous Lower Energy, Emissions and Noise (CLEEN) Phase IV Program: Q&A Responses and FINAL SIR Release
- Solicitation number
- 693KA9-26-R-00006
About this file
This file is a comment matrix tracking industry feedback on the CLEEN Phase IV Draft Statement of Intent to Research (SIR) and corresponding FAA responses. The matrix documents submitted questions, comments, and suggestions across multiple document sections, with FAA replies clarifying program intent and addressing respondent concerns.
Key program details include a total funding allocation of $25 million for all awards using FY25 appropriations, with a single period of performance of up to 24 months. The program establishes a 1:1 minimum cost-share requirement between the FAA and industry participants. Eligibility requires respondents to be U.S.-incorporated and primarily operate within the United States, though non-U.S. subcontractors may support U.S. prime contractors. The FAA has removed the stated preference for TRL 6 or 7 demonstrations and adjusted aircraft technology work elements to allow proposals addressing only a subset of design, build, and test activities. Performance objectives include fuel efficiency improvements relative to ICAO CAEP/10 standards, NOx reductions relative to CAEP/8, and particulate matter reductions relative to CAEP/11, with technology eligible across all aircraft types and TRL levels. The final SIR will provide clarification on deliverables templates, cost-share eligibility criteria, data rights negotiations, reporting frequency (adjusted to monthly rather than biweekly), and publication procedures for test data. Questions and concerns regarding the Final SIR must be submitted by 12:00 PM EDT on April 13, 2026, with proposals due by 12:00 PM EDT on May 18, 2026.
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Other files
| File | Type | Posted |
|---|---|---|
| CLEEN IV SIR Comment Matrix and FAA Responses 05.08.2026.xlsx | XLSX spreadsheet | |
| CLEEN IV SIR Comment Matrix and FAA Responses 04.28.2026.xlsx | XLSX spreadsheet | |
| FAA Order 1600.75 Safeguarding Sensitive Unclassified Information (SUI).pdf | ||
| 1 CLEEN IV SIR FINAL_.pdf | ||
| 3 CLEEN IV Technical Summary.xlsx | XLSX spreadsheet | |
| 4 Copy of CLEEN IV Draft SIR Comment Matrix and FAA Responses_FINAL.xlsx | XLSX spreadsheet | |
| 2 CLEEN IV SIR Attachment A - Cooperative Agreement Template_FINAL.pdf |
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Text version
Instructions Please use this matrix to provide comments, questions, and suggestions on any of the provided draft SIR documents. Please use the Comments tab to provide all responses to all documentation.
Column A - Document - Provide which document you are making a comment against.
Column B - Page/Tab - Provide the page number for the associated document or tab label for Excel documents Column C - Section/para/Cell - Provide the section/paragraph for pdf documents or cell for Excel documents Column D - Text - Provide the applicable text taken from the respective document Column E - Comments - Provide all comments, questions, and suggestions Column F - Rationale - Provide any rationale/reasoning for the comment or suggested change
Comments
| Document | Page/Tab | Section/Para/Cell | Text | Comment | Rationale | FAA Reponse |
| Draft SIR | Page 5 | Section 4: Eligibility | "Respondents must be located in the United States... incorporated in the United States..." | Please clarify if a U.S.-based Prime Respondent is permitted to utilize a non-U.S. based partner or subcontractor for specific technical tasks (e.g., specialized instrumentation, engineering analysis), provided the Prime remains the responsible party. | Certain specialized environmental measurement capabilities (e.g., for contrails) may require global partnerships. We recommend explicitly allowing non-U.S. sub-tier support if it enhances the U.S. Prime's data quality. | This will be addressed in the Final SIR. |
| Draft SIR | Page 5 | Section 6: Funding | "The CLEEN Phase IV program includes a 1:1 (one-to-one) minimum cost share requirement." | Can the value of contributions (cash or in-kind services) provided by a non-U.S. partner be counted towards the U.S. Prime Respondent's 50% cost share requirement? | This would allow U.S. Applicants (especially small businesses) to leverage significant external investment to meet the FAA's matching requirements without burdening U.S. taxpayer funds. | This will be addressed in the Final SIR. |
| Draft SIR | Page 7 | Section 7: Background | "...not less than 2 of the cooperative agreements involve the participation of an entity that is a small business concern..." | Are specialized U.S.-based flight operations companies (falling into the Small Business category) eligible to serve as the Prime Respondent, with a larger OEM serving as a supporting advisory partner/subcontractor? | This structure allows agile U.S. small businesses (e.g., flight test experts) to lead rapid experimentation while leveraging the deep technical expertise of major OEMs. | Yes, if the entity meets the eligibility requirements outlined in the SIR. |
| Draft SIR | Page 10 | Section 8.2: Performance Objectives | "...(e.g., contrail understanding and mitigation)." | Does a project focused on atmospheric measurement and model validation (via flight test) qualify as a "technology demonstration" under this objective, even if no physical aircraft component is modified? | Developing the capability to measure humidity is a critical "enabling technology" for navigational avoidance, distinct from hardware changes. | FAA cannot comment on specific project proposals. |
Recognizing the smaller size of the program relative to prior phases of CLEEN, for the final SIR, FAA will remove the stated preference for TRL 6 or 7 demonstration. The required aircraft technology work elements will also be adjusted to allow for proposals that complete only a subset of the design, build, and test elements. The evaluation factors will not change.
| Draft SIR | Page 10 | Section 8.2: Performance Objectives | "TRL 7 demonstration is achieved through flight test demonstrations." | On contrail research, how would a flight campaign using a "chase plane" to evaluate wake characteristics of a target aircraft qualify as a TRL 7 demonstration of the measurement technology? | Answer will help to establish whether "flight test" encompasses atmospheric science campaignsnecessary for non-CO2 roadmap validation. | Recognizing the smaller size of the program relative to prior phases of CLEEN, for the final SIR, FAA will remove the stated preference for TRL 6 or 7 demonstration. The required aircraft technology work elements will also be adjusted to allow for proposals that complete only a subset of the design, build, and test elements. The evaluation factors will not change. | |
| Attachment A - Cooperative Agreement | Page 29 | Article X.G: Preference for United States Industry | "...manufactured substantially in the United States." | Please clarify how this clause applies to "Subject Inventions" developed solely by a non-U.S. sub-recipient (e.g., a European partner) using their own funding. Does the requirement for U.S. manufacturing apply to these specific sub-components? | Critical for international supply chains. If a European partner develops a specific sensor or subsystem at their own cost, requiring U.S. manufacturing for that specific piece may be unfeasible or contradict their local funding rules. | The Patent Rights clause applies to all inventions developed in performance of work under the Agreement. This applies to subcontractor developments as well. | |
| Attachment A - Cooperative Agreement | Page 42 | Appendix A: Reimbursement... | "Unacceptable contributions include... work performed using U.S. Government funding..." | Please confirm that funding provided by non-U.S. government entities (e.g., EU research grants or national funds) is considered an acceptable source of Participant Cost Share, as it does not constitute "U.S. Government funding." | Clarifies that European public funding (if used) is a valid match, ensuring the U.S. Prime can leverage the full value of the international partnership to meet the 1:1 requirement. | This will be addressed in the Final SIR. | |
| Draft SIR | 5 | 4 | Respondents must be located in the United States. In accordance with Executive Order 14005, Ensuring the Future is Made in All of America by All of America's Workers, and consistent with the “America First” initiative, the federal government is directed to maximize the procurement of good sand services from domestic sources to support American manufacturing, innovation, and job creation. | Suggest the FAA provide more specific information on which Made in America laws will be required to be followed as part of the CLEEN IV effort (Buy America, Build America Buy America, etc.). | The details defined by the legal requirements will help drive project planning and shape work scope and resource discussions. | FAA notes the comment. | |
| Draft SIR | 5 | 5 | The period of performance for each Agreement is expected to be a base period of twelve (12) months with one (1) twelve (12) month option period, subject to the sole discretion of the FAA. | We note the significantly reduced period of performance compared to prior phases of the CLEEN program. As demonstrated by the successful development of technologies during previous CLEEN programs and projects, recommend the FAA increase the period of performance to the full five years, recognizing that prior CLEEN program phases have always noted option years were subject to the required funding becoming available. | A 2-year period of performance is insufficient to develop the types of technologies that have been the hallmark of prior CLEEN program phases, where fleet transition has been the ultimate goal. The design, build, and test cycle for these new technologies is well established and understood, especially when the certifiability, manufacturability, maintainability, affordability, and/or repairability are paramount to implementation. New technology projects that fit within a 2-year period of performance comprise either fully mature prototypes pending demonstration to TRL 6/7 or lower TRL technologies that achieve only marginal TRL advancement, significantly delaying fleet implementation. | ||
| It is also noted that there are currently three years of appropriations for the CLEEN Program (FY24, FY25, and FY26) | CLEEN Phase IV will have a two-year period of performance ceiling. CLEEN Phase IV will be fully funded using existing appropriations. FY26 appropriations will not be used for CLEEN Phase IV. Any obligations involving future fiscal years are subject to the availability of appropriations and applicable law. |
Recognizing the smaller size of the program relative to prior phases of CLEEN, for the final SIR, FAA will remove the stated preference for TRL 6 or 7 demonstration. The required aircraft technology work elements will also be adjusted to allow for proposals that complete only a subset of the design, build, and test elements. The evaluation factors will not change.
| Draft SIR | 5 | 5 | The period of performance for each Agreement is expected to be a base period of twelve (12) months with one (1) twelve (12) month option period, subject to the sole discretion of the FAA. | If FAA chooses to keep the timeframe as listed in the draft SIR, recommed the FAA allow flexibility in responses, such that technology advancement would occur in phases that may extend beyond the total two (2) year timeframe. The initial phase would be proposed under CLEEN phase IV and then subsequent effort required to mature TRL level of the proposed technology would either be part of an industry planned effort or could be a separate project proposed as part of a subsequent CLEEN program phase. | As previously mentioned, our experience is that technology development exceeds a two (2) year timeframe. We could envision structuring a future CLEEN phase IV proposal as a piece of a broader effort. For example, we are in the process of developing a technology roadmap for an evolving research issue that is not currently regulated in ICAO Annex 16. This project (and perhaps others) could benefit from joint partnership with other CLEEN Consortium participants, but due to the period of performance, a CLEEN phase IV proposal might be limited to planning and/or early TRL modeling and large scale lab testing. The full TRL development, including a flight demonstration, will likely require future investments past the two (2) year period of performance. | CLEEN Phase IV will have a two-year period of performance ceiling. CLEEN Phase IV does not include specific requirements for starting and ending TRL. There is no required TRL in SIR. The required aircraft technology work elements will be adjusted to allow for proposals that complete only a subset of the design, build, and test elements. | |
| Draft SIR | 7 | 7 / 2 | The FAA intends to establish on a cost share, 1:1 minimum basis, agreements for activities to mature Continuous Lower Energy, Emissions and Noise (CLEEN) technologies for civil airplanes and inform the development of FAA airframe and engine environmental standards and environmental review of rulemaking and other actions. This program will enable and expedite the introduction of innovative airframe and engine technologies with improved performance and safety and enhance the technological and economic competitiveness of American civil aircraft. | We note that unlike prior phases of CLEEN, the draft SIR places considerable emphasis on the development of FAA airframe and engine environmental standards and environmental review of rulemaking and other actions. It appears this emphasis is intended to solicit projects that may differ in ultimate focus and scope than the types of projects conducted under prior phases of the CLEEN Program. | We recognize that the data generated by CLEEN program technical projects in phases I, II, and III, has been used by the FAA as a source of information for environmental standards and environmental review. We support strong collaboration between industry and the FAA on certification and standards development. However, we encourage the FAA to continue to focus the CLEEN program on the maturing of new technologies to advance the environmental performance, safety, and economic competitiveness of American civil aircraft. The CLEEN program has effectively leveraged industry investment to advance technologies that may not have been matured without it and this focus would reinforce and build on that successful partnership. | FAA notes the comment. | |
| Draft SIR | 7 | 7 / 2 | The FAA intends to establish on a cost share, 1:1 minimum basis, agreements for activities to mature Continuous Lower Energy, Emissions and Noise (CLEEN) technologies for civil airplanes and inform the development of FAA airframe and engine environmental standards and environmental review of rulemaking and other actions. This program will enable and expedite the introduction of innovative airframe and engine technologies with improved performance and safety and enhance the technological and economic competitiveness of American civil aircraft. | We note that development of promising environmental technologies is a substantially different task than establishing standards and rulemaking activities. Additionally, as technology is developed and matured, product implementation can result in changes to address certifiability, manufacturability, maintainability, affordability, and repairability. How does the FAA envision the use of promising environmental technologies, developed under CLEEN phase IV, to establish standards and rulemaking activities given the risk that further maturation may diminish the expected environmental benefits? Further, how does the FAA plan to assess an applicant's ability to determine potential environmental benefits given the significant additional effort and expertise required to take a promising technology to product implementation? | One of the challenges, as technologies are matured from lower TRLs through to higher TRLs, is the subsequent efforts required to further mature high TRL technologies for product implementation. Sections 8.4.2 and 8.4.5 of the CLEEN IV draft SIR acknowledges the importance of addressing manufacturability, maintainability, affordability, and repairability to ensure a promising technology can transition to an aircraft. Aircraft manufacturers do what they can to assess these potential challenges early in the development phase of new technologies. However, until a new technology has been matured sufficiently, it is possible that additional unexpected roadblocks to implementation can occur. Further, these potentially unforeseen roadblocks can impact the ultimately realized environmental performance levels. | Respondents can communicate potential knockdown effects to benefits given current technology maturity and potential roadblocks/risks. | |
| Draft SIR | 8 | 7 / 5 | The total funding available for all projects is 25 million dollars for the duration of the program based on Congressional appropriation levels for FY25. | Why is the total funding available for all projects limited to $25M when congress has appropriated FY24, FY25, and FY26 funds that exceed this amount? Prior CLEEN programs have included option years that anticipate future congressional funding. | Congress has appropriated funds for the CLEEN Program in the FY24, FY25, and FY26 budgets. It seems reasonable that the CLEEN program funding be commensurate with the appropriation levels of at least $25M per year. Further, the FAA could extend the period of performance with additional option years such that the FAA could obligate all of the currently appropriated funds. This is especially important as the impact that commercial aviation has on the environment requires new technologies that industry might not otherwise be motivated to pursue without adequate funding. Further, funding of $25M precludes the ability to conduct large scale demonstrations, like engine ground test or flight test, of technologies designed and fabricated as part of CLEEN phase IV. Developing new technologies to much lower TRL levels, via lab testing or modeling, significantly hampers development timelines. | CLEEN Phase IV will be fully funded using existing appropriations. FY26 appropriations will not be used for CLEEN Phase IV. Any obligations involving future fiscal years are subject to the availability of appropriations and applicable law. | |
| Draft SIR | 8 | 7 / 6 | FAA anticipates that the development of technology concepts would begin during the base period and extend to the option period until the project is concluded, preferably with TRL 6 or 7 demonstration. | The FAA eliminated the starting and ending TRL requirements while expressing a preference for a TRL 6 or 7 demonstration. How does the FAA plan to evaluate technology projects based on a TRL preference? Furthermore, how will starting and ending TRL levels be prioritized or weighted during proposal evaluations? Greater clarity on evaluation criteria, relative to project TRL and the FAA assessment of project benefits, would be helpful for industry to appropriately focus proposed technologies for the CLEEN IV program. | The draft SIR does not explicitly cite a starting TRL or ending TRL requirement. However, this paragraph states "that the development of technology concepts would begin during the base period", implying relatively low starting TRL. The paragraph further expresses a preference for a TRL 6 or 7 demonstration during the option year. It is unlikely, given the limited amount of available funding, combined with the 2-year period of performance, that a new technology could be advanced beyond TRL 4 or 5, therefore industry would need to propose technologies already at TRL 4 or 5+ with prior development history and investments. | Recognizing the smaller size of the program relative to prior phases of CLEEN, for the final SIR, FAA will remove the stated preference for TRL 6 or 7 demonstration. The required aircraft technology work elements will also be adjusted to allow for proposals that complete only a subset of the design, build, and test elements. The evaluation factors will not change. | |
| Draft SIR | 9 | 8.1 | Phase IV of the CLEEN Program is focused on activities that will inform the development of FAA airframe and engine environmental standards and environmental review of rulemaking and other actions in order to enable and expedite the safe introduction of new airframe and engine technologies with improved performance and safety | As stated in this paragraph, we note that unlike prior phases of CLEEN, the draft SIR places considerable emphasis on the development of FAA airframe and engine environmental standards and environmental review of rulemaking and other actions. It appears this emphasis is intended to solicit projects that may differ in ultimate focus and scope than the types of projects conducted under prior phases of the CLEEN Program. | As noted in our comments to page 7, section 7, paragraph 1, the draft SIR places considerable emphasis on activities that will inform the development of FAA airframe and engine environmental standards and environmental review of rulemaking and other actions. In fact, this paragraph (section 8, paragraph 1) explicitly cites these activities as the exclusive focus of phase IV of the CLEEN program. It is well understood that the data generated by CLEEN program technical projects in phases I, II, and III, has been used by the FAA as a source of information for environmental standards and environmental review. We also support strong collaboration between industry and the FAA on certification and standards development. | FAA notes the comment. | |
| Draft SIR | 9 | 8.2 | For CLEEN Phase IV, an additional objective is to collect | ||||
| information that can assist the FAA in developing more effective and timely environmental standards and conducting environmental reviews, thereby supporting a pathway to type certification for proposed CLEEN technologies. | We encourage FAA include a wider focus of certification challenges that could inhibit technology development as industry looks to transition technologies to production. For example, both fire protection and icing protection certification requirements on the structure surrounding the engine may make an environmentally beneficial design nonviable for commercial transport aircraft. | The FAA notes in section 7 that a "challenge to novel aircraft technology research and development is ensuring that technologies are certifiable." This paragraph (page 9, 8.2) also mentions an additional objective that supports a ..."pathway to type certification for CLEEN technologies" There are non-environmental airworthiness certification requirements that also pose a challenge to the certification of new technologies. These other certification challenges, such as icing, can be an impediment to transition of new technologies, including environmental technologies. Please consider encouraging a wider focus of certification challenges that could inhibit technology development transition to better support future certification efforts. | FAA notes the comment. | ||||
| Draft SIR | 9 | 8.2 / 1 | For CLEEN Phase IV, an additional objective is to collect information that can assist the FAA in developing more effective and timely environmental standards and conducting environmental reviews, thereby supporting a pathway to type certification for proposed CLEEN technologies. Three types of information may be provided in support of this objective: 1) information that can assist the FAA in setting appropriate levels for environmental standards, 2) information that can assist the FAA in improving certification procedures from an environmental perspective where the existing regulations and policy do not address or are not adequate for a given technology, and/or 3) information that can assist the FAA in conducting environmental reviews of rulemaking and other actions. | Industry understands that the FAA collects information from the CLEEN program to assist the FAA in developing more effective and timely environment standards and conducting environmental reviews. Further, we agree with the FAA adding a performance objective to CLEEN phase IV to overtly collect this information. However, the predominant shift in emphasis, in terms of both focus and objectives, dilutes the CLEEN program from what has made it so successful. We encourage the FAA to continue to focus the CLEEN program objectives on the maturing of new technologies to advance the environmental performance, safety, and economic competitiveness of American civil aircraft. | Data generated by CLEEN program technical projects in phases I, II, and III, has been used by the FAA as a source of information for environmental standards and environmental review. Further, we agree with the FAA adding a performance objective to CLEEN phase IV to collect information that can assist the FAA in developing more effective and timely environment standards and conducting environmental reviews. However, we encourage the FAA to continue to focus the CLEEN program on the maturing of new technologies to advance the environmental performance, safety, and economic competitiveness of American civil aircraft. This will continue to provide an on-going source of information to help the FAA on the development of airframe and engine environmental standards and on the environmental review of rulemaking. The CLEEN program has effectively leveraged industry investment to advance technologies that may not have been matured without it and this focus would reinforce and build on that successful partnership. | FAA notes the comment. | |
| Draft SIR | 9 | 8.2 / 1 | reduce fuel burn, engine emissions, and noise | The document does not explicitly state that the FAA has a priority when it comes to projects that address fuel burn, noise, and/or emissions. Does the FAA have a priority for these environmental goals? | References to performance goals in the draft SIR cite fuel burn, emissions, and noise in various order. While this may not be intentional, would like to confirm the FAA does not have a priority order or preference during the evaluation of submitted projects. | FAA is not giving a priority order to these performance goals. | |
| Draft SIR | 9 | 8.2 / 1 | For CLEEN Phase IV, an additional objective is to collect information that can assist the FAA in developing more effective and timely environmental standards and conducting environmental reviews, | Recommend FAA provide additional context or specifics with respect to the "environmental reviews" to better understand the FAA's intent in the draft SIR. | “Environmental reviews” is a very broad term and it would be helpful to understand the specific context being used for CLEEN phase IV. We note that it could refer to Part 150 and similar reviews under NEPA, but it is unclear if there are other reviews the FAA has in mind. | Reviews under NEPA are an example of the "environmental reviews" cited in the SIR. | |
| Draft SIR | 10 | 8.3 | CLEEN Phase IV is not limited to specific technologies or aircraft types. | While this sentence provides a disclaimer that all technologies are of interest, the majority of this section is focused on new entrants to the National Airspace System. If so, we recommend there be a more explicit statement encouraging technology development for commercial aviation. | While this sentence provides a disclaimer that all technologies are of interest, the majority of section 8.3 is focused on potential new entrants to the National Airspace System. The vast majority of both the current fleet, as well as what is anticipated to be flying for the next 20 to 40 years, is dominated by traditional single-aisle and twin-aisle subsonic aircraft. As such, CLEEN projects addressing these aircraft comprise the strongest influence on improving the environmental impact of aviation in this time frame. While it is noted that the FAA "is also interested in information that can assist the FAA in setting appropriate levels for environmental standards, including information for technologies for which the certification requirements and procedures are more well-established", the entire section, when read in its entirety, encourages technology projects for these new emerging platforms, potentially at the cost of more broad-based environmental improvement across the commercial flying fleet. | FAA notes the comment. | |
| Draft SIR | 10 | 8.3 | Project proposals must support the performance objectives detailed in Section 8.2. However, there are emerging technology areas where there are potential gaps in knowledge or procedures related to environmental standards and environmental review | Recommend the FAA discuss its preference, or the relative ranking, for CLEEN IV proposal projects to address potential gaps for emerging technologies, as listed in 8.3, versus projects at a higher TRL with a much higher likelihood of fleet transition. | FAA notes the comment. | ||
| Draft SIR | 15 | 8.6 / 4 | |||||
| 8.7.1 | Every two weeks, technical, financial and schedule progress must be reviewed orally via teleconference | We recommend changing the frequency of telecons from bi-weekly to monthly. | To balance expected progress and project management overhead, monthly telecons should provide sufficient insight into project status. | Subject to negotiation at agreement stage. | |||
| Draft SIR | 16 | 8.7.1 | Informal Test Reports | We suggest eliminating informal test reports and keeping the FAA informed on post-test activities via monthly telecons prior to submission of final test reports. | Providing informal test reports as a program deliverable creates significant additional overhead for a relatively short-duration program. Test data and analysis can change dramatically prior to final report submission and isn't likely meaningful prior to completing data integrity assessments and analyses. | Subject to negotiation at agreement stage. | |
| Draft SIR | 19 | 9.1 | Proposal Due Date - Month DD, 2026 | We respectfully request the FAA consider a 90 day proposal response period. However, given the familiarity we have with the CLEEN program and the amount of time since release of the Market Survey, we could be prepared to respond in 60 days. Note that a significant challenge to a 60 day proposal response period are the unexpected number of changes, along with the reduced scope of the program. | We have a long history of working with the FAA on prior phases of CLEEN. It has also been 2 years since the FAA released the CLEEN phase IV Market Survey. These combine to provide some lead time toward preparing a strong offering to the FAA. However, we have also seen an unexpected number of changes in the draft SIR, combined with a significant shift in funding and duration. Given these factors, we respectfully request 90 days to respond. This time allows for proposal development, adequate alignment of technology projects with business unit priorities, project cost estimating, internal reviews, and final approvals prior to submission. Note that, if required, we could respond in 60 days. | FAA notes the comment. | |
| Draft SIR | 22 | 9.10 | The Executive Summary must provide an overview of the Offeror’s CLEEN IV Technology proposal(s) to include a completed summary Excel file attachment | Please clarify what the "excel summary file" contains and provide a detailed description or template. | summary Excel file not described or defined | Will release with Final SIR. | |
| Draft SIR | page 4 | Section 4 | To comply, respondents to this SIR must be incorporated in the United States, primarily operate within the United States. | California’s aircraft activity is projected to increase by approximately two-thirds between 2024 and 2050. Without technology-forcing emission standards, this surge in aircraft activity is expected to push NOx emissions up by almost 30%, from 55 to 71 tons per day, while emissions from all other mobile source sectors are projected to decline. This trajectory underscores the importance of achieving substantial reductions in aircraft-related emissions to support attainment of federal air quality standards, especially in regions with significant aviation activity. | Like many regions across the United States (U.S.) with major airport hubs and high air traffic, California is grappling with severe air pollution from aircraft. These pollutants, including Nitrogen Oxides (NOx) and Particulate Matter, create smog and tiny particles that trigger asthma, harm the heart and lungs, and even shorten lives over time. More than half of Californians, over 21 million out of nearly 40 million, live in areas that exceed the federal ozone standard and suffer from the adverse health effects of ozone. | FAA notes the comment. | |
| Draft SIR | page 9 | 8.2 | CLEEN Phase IV does not have explicit goals for noise, fuel burn (in terms of energy use) and emission reductions. | Strongly urge the FAA to set explicit energy efficiency, nitrogen oxides (NOx), particulate matter (PM), and carbon dioxide (CO2) targets for the CLEEN Phase IV Program. | Despite decades of engine certification improvements (1971–2020), ICAO Aircraft Engine Emissions Databank certification data show NOx emissions have remained largely flat, with limited improvement over time. Upcoming CLEEN Phase III technologies are expected to become commercially available starting in 2026; however, they are unlikely to deliver immediate emission reductions due to the time required for market adoption. To accelerate the deployment of these technologies and achieve tangible NOx reductions, stronger and more explicit NOx reduction targets are needed. | FAA notes the comment. | |
| Draft SIR | page 9 | 8.2 | Fuel efficiency: Aircraft technology that improves aircraft fuel efficiency relative to the International Civil Aviation Organization (ICAO) new type fuel efficiency standard for civil subsonic airplanes adopted in 2016 (Committee on Aviation Environmental Protection, CAEP/10); • NOx emissions: Engine technology that reduces landing and takeoff cycle (LTO) nitrogen oxide emissions relative to the ICAO standard for civil subsonic airplanes adopted in 2010 (CAEP/8) and/or reduces absolute NOx production over the aircraft’s mission. This must be achieved while limiting or reducing other gaseous or particulate matter emissions; and • Particulate matter: Engine technologies that reduce LTO particulate matter number and mass emissions relative to the ICAO new type standard for civil subsonic airplanes adopted in 2019 (CAEP/11) and/or reduces absolute nvPM production over the aircraft’s mission. This must be achieved while limiting or reducing other gaseous or particulate matter emissions. | Advise that FAA retains the 70% NOx target as a baseline as implemented in the CLEEN Phase III, and institute a target of 80% NOx reduction (relative to CAEP/8). Establishing this advanced NOx target is critical for the successful implementation of measures in California’s 2022 State Strategy for the State Implementation Plan, which is designed to achieve the 2015 8-hour ozone standard as required under the federal Clean Air Act . Additionally, we urge FAA to set CO2 reduction goals beyond the current aircraft CO2 standard, and to align with ICAO’s CORSIA program aimed at capping aviation CO2 emissions at 85% of the 2019 level. | In December 2022, CLEEN IV market survey, FAA proposed targets of a 35% improvement in aircraft energy efficiency relative to CAEP/10, a 70% reduction in landing-and-takeoff-cycle (LTO) nitrogen oxide (NOx) emissions relative to CAEP/8, and a 50% reduction in particulate matter (PM) relative to CAEP/11, while limiting other emissions. These recommendations prioritize public health benefits from reducing NOx and PM, and co-benefits from fuel efficiency improvements that reduce CO2 emissions. | FAA notes the comment. | |
| Draft SIR | page 8 | section 7 | The next phase of the CLEEN Program, referred to as Phase IV, is a follow-on program from the first three five-year phases of CLEEN. Phase IV of the CLEEN Program will continue the Program through calendar year 2028. The fourth phase of CLEEN, like the first three phases of CLEEN, is a public-private partnership in which projects are cost-shared between the FAA and industry. The FAA anticipates multiple awards from this solicitation. The total funding available for all projects is 25 million dollars for the duration of the program based on Congressional appropriation levels for FY25. The awards will include a base period of 12 months and one 12-month option period. The $25M total funding covers the base, and if exercised, the option period for the multiple awards. | Strongly urge the FAA to significantly increase funding for the CLEEN Phase IV Program to ensure its success. Sufficient funding and clear, measurable aircraft engine NOx targets are instrumental to the program’s ability to accelerate development and adoption of lower-NOx engine technologies. | Since its inception, the CLEEN Program has received substantial FAA investment, approximately $225 million across Phase I and II, and $125 million in Phase III , matched 1:1 by industry cost-sharing. In contrast, Phase IV is only allocated $25 million. | FAA notes the comment. | |
| Draft SIR | page 10-11 | 8.3 | The U.S. participates in the International Civil Aviation Organization (ICAO) Committee on Aviation Environmental Protection (CAEP) to develop and harmonize aircraft and engine environmental 693KA9-26-R-00006 January 16, 2026 Page 11 of 54 standards. As part of the standards setting process, CAEP conducts analyses of costs and benefits of different options for potential regulatory limits to ensure that standards are technically feasible, economically reasonable, and environmentally beneficial. Projects that can provide information that would assist the FAA in this standards setting process (e.g., noise/emissions data, technology responses to different stringency options, etc.) may be supported under CLEEN Phase IV | NOx reductions on the order of 80% are critical to ozone attainment in areas like South Coast. We urge our FAA partners to advocate within ICAO’s Committee on Aviation Environmental Protection (CAEP) for more stringent, technology-forcing emission standards—not only to help the Unites States meet its air quality and climate goals, but also to advance global technology development and accelerate NOx reductions worldwide. | We appreciate the opportunity to provide feedback to the FAA. Efforts like the CLEEN program, combined with national measures and coordination among states, local districts, airports, and industry, will strengthen both domestic and international progress toward cleaner air objectives. | FAA notes the comment. | |
| Draft SIR | page 9 | 8.2 | How should we think about the likely magnitude and pace of NOx reductions that Phase IV can realistically drive under this structure (benefit-based eligibility rather than program-wide targets)? | Project-level “benefits” do not automatically translate into fleet-level NOx reductions; outcomes depend on certification timing and fleet integration rates. | Potential fleet-wide benefits and potential for technology transition into the fleet are evaluation factors. | ||
| Draft SIR | Page 7 and 8 | 7 | How does the FAA’s Phase IV approach compare to CLEEN III’s use of specific performance targets in terms of expected outcomes for aircraft engine NOx reductions? | Phase IV is described as a follow-on to earlier CLEEN phases, but it shifts from specific performance targets to benefit-based eligibility. Clarifying how FAA expects this change to affect accountability, project selection, and overall aircraft engine NOx outcomes helps stakeholders interpret whether Phase IV will drive comparable or stronger NOx progress than Phase III. | CLEEN Phase III included a goal of 70% LTO NOx reduction relative to CAEP/8. NOx emissions reductions continue to be a goal of CLEEN Phase IV. | ||
| Draft SIR | page 8 | The total funding available for all projects is 25 million dollars for the duration of the program based on Congressional appropriation levels for FY25. The awards will include a base period of 12 months and one 12-month option period. The $25M total funding covers the base, and if exercised, the option period for the multiple awards. | Given the Phase IV funding level of $25 million for the 1:1 government and industry partnership, how does the FAA expect the program to maintain or increase the pace of aircraft engine NOx reductions compared to earlier phases that provided more than $100 million? | It is not an explicit goal of CLEEN Phase IV to "maintain or increase the pace of aircraft engine NOx reductions compared to earlier phases". | |||
| Draft SIR | Page 7 and 9 | Section 7 and 8.1, respectively | The FAA intends to establish on a cost share, 1:1 minimum basis, agreementsfor activities to mature Continuous Lower Energy, Emissions and Noise (CLEEN) technologies for civil airplanes and inform the development of FAA airframe and engine environmental standards and environmental review of rulemaking and other actions. This program will enable and expedite the introduction of innovative airframe and engine technologies with improved performance and safety and enhance the technological and economic competitiveness of American civil aircraft. | How does the FAA view the role of CLEEN Phase IV in advancing technologies that could inform future ICAO CAEP standards? | This is discussed in Sections 7 and 8 of the SIR. | ||
| Draft SIR | Page 27 | 10 | How will the FAA consider community air quality and public-health relevance, particularly for airports in regions with persistent ozone challenges, when prioritizing Phase IV investments? | Because the Draft SIR prioritizes “benefit to the public” and evaluates fleet-wide and lifecycle impacts, it is unclear whether, and how, localized air-quality and public-health relevance near airports will influence investment priorities, especially since the same technology can deliver very different real-world benefits depending on where it is deployed and how it operates. | These are not explicit goals for CLEEN Phase IV. | ||
| Draft SIR | 22 | Para 1 | The Executive Summary must provide an overview of the Offeror’s CLEEN IV Technology proposal(s) to include a completed summary Excel file attachment. | Is this Excel file the same as the "Attachment B – CLEEN IV Technical Summary Spreadsheet (xlsx file)" referenced on p. 54 of the SIR? | Draft of the file was not included in this request, nor were the expected contents explained | Yes. This file will be provided with the final SIR. | |
| Draft SIR | 8 | Para 1 | The $25M total funding covers the base, and if exercised, the option period for the multiple awards. | What is the allocation of $25M between the initial phase and option period of the award? Should our proposals assume an option period? | Suggest a breakdown of funding for year of work + optional additional year | The final SIR will reflect a single period of performance of up to 24 months, removing the base and option period language. | |
| Draft SIR | 8 | Section 7 / Paragraph 5 | " The total funding available for all projects is $25M for the duration of the program" | Based on the FY2026 THUD Congretional Appropriations Bill, passed in January 2026, there is a provision for $38.5M for CLEEN in 2026, the total budget in the draft SIR seems quite off, specifically for one year the offset is $12.5M vs $38.5M | Clarification on the planned budget and magnitude of projects. Currently, a budget of $12.5M for "all the projects" does not seem a realistic target to conduct a demonstration of any kind in a industry research environment. Does the $38.5M for CLEEN invlude both CLEEN III and CLEEN IV budgets? | CLEEN Phase IV will be fully funded using existing appropriations. FY26 appropriations will not be used for CLEEN Phase IV. Any obligations involving future fiscal years are subject to the availability of appropriations and applicable law. | |
| Draft SIR | 10 | Section 8.2 / Para 3 | " CLEEN IV does not include specific requirements for starting and ending TRL" | Normal industry timeframes for TRL advancement is One incremental level per year or year and half. If preference is TRL6/7, seems that the preference is to have a technology with starting TRL midway into TRL 6. | The timeframe of 2 years does not support a proper TRL development, may only serve for completing a certain element of a demonstration. The budget and timeframe limits the amount of manufacturing. | CLEEN Phase IV will have a two-year period of performance ceiling. |
Recognizing the smaller size of the program relative to prior phases of CLEEN, for the final SIR, FAA will remove the stated preference for TRL 6 or 7 demonstration. The required aircraft technology work elements will also be adjusted to allow for proposals that complete only a subset of the design, build, and test elements. The evaluation factors will not change.
Draft SIR 9 Section 8.2 / Para 1 "an additional objective is to collect information that can assist the FAA in developing more effective and timely environmental
| standards and conducting environmental reviews" | This is a very generic statement. Research projects are not necessarily tied to standard and regulation settings. Project can provide the technology worth for certain metrics, but do not directly affect the commitment of the entire industry to provide a guaranteed regulation target. | FAA proposed target metrics are abstract, not clear, do not help the industry in selecting competitive technologies. | FAA notes the comment. | ||
| Attachment A - Cooperative Agreement | N/A | N/A | N/A | The terms and conditions within the SIR (especially concerning intellectual property and data rights) deviate significantly from the terms and conditions of CLEEN II and CLEEN III. | |
| Our participation in CLEEN IV is subject to negotiating and agreeing on terms and conditions substantially similar to those we have worked under during CLEEN II and CLEEN III. | N/A | FAA notes the comment. Per Section 10.2.3, FAA will consider whether any significant proposed changes to the sample agreement by the Respondent would reduce the value of the proposal to the government. | |||
| Draft SIR | N/A | N/A | N/A | The terms and conditions within the SIR (especially concerning intellectual property and data rights) deviate significantly from the terms and conditions of CLEEN II and CLEEN III. | |
| Our participation in CLEEN IV is subject to negotiating and agreeing on terms and conditions substantially similar to those we have worked under during CLEEN II and CLEEN III. | N/A | FAA notes the comment. Per Section 10.2.3, FAA will consider whether any significant proposed changes to the sample agreement by the Respondent would reduce the value of the proposal to the government. | |||
| Draft SIR | 9 | 8.2 | Any technologies targeted at civil supersonic airplanes should demonstrate quantifiable benefits for |
fuel efficiency, noise, NOx, and/or particulate matter emissions relative to current state of the art
| technology and design concepts. | Improved prognositic health monitoring (PHM) of key components and systems can result in an indirect emissions and cost benefit over the lifecycle of the aircraft by reducing maintenance cycles. Would PHM enabling technology be considered in this program? | Consider overall environmental footprint of the aircraft operation (lifecycle) | FAA cannot comment on specific project proposals. Refer to Section 8.2 for performance objectives. | |
| Draft SIR | 9 | 8.2 | Particulate matter: Engine technologies that reduce LTO particulate matter number and |
mass emissions relative to the ICAO new type standard for civil subsonic airplanes adopted in 2019 (CAEP/11) and/or reduces absolute nvPM production over the aircraft’s mission.
This must be achieved while limiting or reducing other gaseous or particulate matter
| emissions. | Current CAEP emissions utilize LTO, will consideration be given to components that might not improve LTO though would improve cruise pollutants? | N/A | Technology that reduces emissions over the aircraft's mission is also a stated goal of CLEEN Phase IV |
| Attachment A - Cooperative Agreement | 13 | ||
| 33 | VI.A.2 | ||
| X.Z.(c).(2) | "The parties acknowledge that the Government must have limited rights, as defined in Article X, Subparagraph Z, in all deliverables marked as such in Article V of this agreement." |
| "The Participant must not, without prior written permission of the Contracting Officer, incorporate any data delivered under this agreement any data not first produced in the performance of this agreement unless the Participant... Grants to the Government, or acquires on its behalf, a license of the same scope as set forth in subparagraph (c)(1) of this clause..." | We understand the combination of these two terms to mean that the Participant may assert data rights (presumably in a CFR equivalent format to DFARS 252.227-7017) for data produced with private expense that may relate to the technology proposed, and this data remains limited rights without licensing requirements if it is not utilized in Agreement deliverables. Can you confirm? | Protection of Participant IP | This is correct. | ||||
| Attachment A - Cooperative Agreement | 20 | X.T | "The Government may require continued performance within the limits and at the rates specified in the Agreement ... The option provision may be exercised more than once, but the total extension of performance hereunder must not exceed 6 months." | This term appears to conflict with earlier language in the agreement indicating that the term of the agreement is either one year (base period) or two years (if FAA exercises one year option period). With term T, is it possible to have an agreement term of 13 months to 18 months at the FAA's discretion? | Proposal planning | The final SIR will reflect a single period of performance of up to 24 months, removing the base and option period language. | |
| Attachment A - Cooperative Agreement | 43 | Appendix A | "Cost share may include the value of labor, facilities, equipment and utilities provided by the Participant that directly facilitates the efforts required under the Agreement and may be billed as direct or indirect costs (2 CFR 200.412, 413, and 415)." | We noted that 2 CFR 200.414 was not referenced here. We have a negotiated indirect cost rate agreement with another federal agency (DCMA); however, the rates in this agreement are utilized for work supporting defense objectives. Are we obligated to use the negotiated rates, or can we elect to use the de minimis rate for indirect costs? | Financial planning | Contributions may be cash, non-cash (in-kind) or both in accordance with 2 CFR Part 200, Uniform Administrative Requirements, Cost Principles, and Audit Requirements for Federal Awards, including 2 CFR § 200.306, Cost sharing, and 2 CFR Part 200, Subpart E, Cost Principles. 2 CFR Part 200.414 is applicable to the SIR. | |
| Attachment A - Cooperative Agreement | 14 | Appendix A | [Company name] hereby grants to the Government, in advance, a limited license in Intellectual Property, including any inventions or works, made or otherwise developed by the [Company name] or its employees and funded by the Government under this Agreement | Can FAA confirm that the limited license applies only to IP developed with USG funding under the Coop Agreement and does not extend to Background IP? | Protection of Participant IP | This is correct. | |
| Attachment A - Cooperative Agreement | 19 | Appendix A | The FAA intends to publish normalized test data and associated analyses results first produced |
in the course of this agreement relating to performance, emissions, noise, aerodynamics, and aeroacoustics. Publication of this data is necessary to achieve the goals of the CLEEN IV
| Program | Will we be able to review and approve materials prior to publication? What process will FAA use to redact proprietary and/or limited rights prior to publication? | Proposal Planning | Refer to sample agreement Article X, Subparagraph Q, Protection of Information. | ||||
| Attachment A - Cooperative Agreement | NA | Appendix A | Changes Clause - Not included | Can the FAA clarify who has the authority to direct changes to scope, deliverables, etc. and in such case, what mechanism exists to adjust funding or performance timelines? | Proposal Planning | Refer to sample agreement Article X, Subparagraph J, Amendments. |
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