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Continuous Lower Energy, Emissions, and Noise (CLEEN) Program

The Continuous Lower Energy, Emissions and Noise (CLEEN) Program is the FAA's principal environmental effort to accelerate the development of new aircraft and engine technologies and advance sustainable alternative jet fuels. Through the CLEEN Program, the FAA is a cost-sharing partner with industry. CLEEN projects develop technologies that will reduce noise, emissions, and fuel burn and enable the aviation industry to expedite integration of these technologies into current and future aircraft. CLEEN is a key element of the NextGen strategy to achieve environmental protection that allows for sustained aviation growth.

In 2010 the FAA initiated the first CLEEN Program, entering into five-year agreements with Boeing, General Electric (GE), Honeywell, Pratt & Whitney (P&W), and Rolls-Royce. These companies matched or exceeded the FAA funding in this cost-sharing program. Over the five-year period, the FAA invested a total of $125 million. With the funding match from the five companies, the total investment value exceeded $250 million.

Building upon the success of the initial CLEEN Program, in 2015 the FAA initiated a follow-on program, CLEEN II, which continues efforts to achieve the CLEEN goals and develop and demonstrate aircraft technology and alternative jet fuels.

Under the CLEEN II program, FAA has awarded five-year agreements to Aurora Flight Sciences, Boeing, Delta Tech Ops/MDS Coating Technologies, General Electric, Honeywell, Pratt & Whitney, Rolls-Royce, and Rohr, Inc./UTC Aerospace Systems. These companies will match or exceed the awards in this cost-sharing program. The total federal investment is expected to be $100 million over five years.

Program goals

The CLEEN Program goals include developing and demonstrating:

  • Certifiable aircraft technology that reduces aircraft fuel burn, and/or supports the FAA's goal to achieve a net reduction in climate impact from aviation;
  • Certifiable engine technology that reduces landing and takeoff cycle (LTO) nitrogen oxide (NOx) emissions below International Civil Aviation Organization (ICAO) Committee for Aviation Environmental Protection (CAEP) standards, and/or reduces absolute NOx production over the aircraft's mission;
  • Certifiable aircraft technology that reduces noise levels, relative to the Stage 4 standard and/or reduces the noise contour area in absolute terms;
  • "Drop-in" sustainable alternative jet fuels, including quantification of benefits — drop in alternative fuels will require no modifications to aircraft or fuel supply infrastructure.
Quantitative goals for the fuel burn, emissions, and noise metrics under CLEEN I and CLEEN II
Goal Area CLEEN I Goals CLEEN II Goals
(cum below Stage 4)
-32 dB -32 dB
LTO NOx Emissions
(Below CAEP/6)
-60% -75% (-70% re: CAEP/8)
Aircraft Fuel Burn -33% -40%

For more information on the CLEEN Program, its benefits, and accomplishments to date, please see the CLEEN Program Fact Sheet.

Consortium meeting

The CLEEN program holds biannual consortium meetings occurring in May and November of each year. During the meeting companies provide detail description of the progress of their technology development projects. While the majority of the meeting consists of government only review sessions, the meeting also includes one open day where companies share highlights of their work with the general public. Please contact for more information.

Alternative fuels activities

A complementary piece of the CLEEN Program to the technology and fuel development activities is an independent technology modeling and assessment. This was initially done through the now complete PARTNER Center of Excellence Project 36 with Georgia Tech. A new project has been established under the Aviation Sustainability Center of Excellence (ASCENT) to model and assess aircraft technology for CLEEN, as well as other emerging technologies and their impacts on aircraft environmental metrics.

See more information on the full scope of FAA's alternative fuels activities.

CLEEN Reports & Meetings

CLEEN II Meetings

The next Consortium meeting will be held November 6 through November 8, 2018 in Washington, DC. The public plenary session will be on November 7, 2018.

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