Technology Standards

​Certification Standards and Technology Goals

Aircraft are required to meet the environmental certification standards adopted by the Council of ICAO. These are contained in Annex 16 (Environmental Protection) to the Convention on International Civil Aviation. This Annex at present consists of two volumes, viz., Volume I: Aircraft Noise and Volume II: Aircraft Engine Emissions. These certification Standards have been designed and are kept up to date in order to respond to concerns regarding environmental impact of aviation on communities in the vicinity of airports as well as society at large.


More recently, ICAO, under the CAEP process, has undertaken an effort to establish medium and long-term environmental goals relating to three types of technologies, viz., noise, NOx, and fuel burn. In addition, assessments of environmental improvements expected from operational initiatives in the medium and long term are also underway. This process is being led by panels of independent experts to ensure transparency and involvement from all stakeholders. The purpose of this goal setting exercise is to provide stretch yet reasonable targets for industry R&D to aim at in cooperation with States.


In October 2010 the 37th Assembly (Resolution A37-19) requested the development of an ICAO CO2 Emissions Standard.On 11 July 2012, global aviation moved an important step closer to establishing the worldwide Aircraft CO2 Emissions Standard when the CAEP reached a unanimous agreement on a CO2 metric system to underpin the CO2 Standard. For more details see this ICAO fact sheet: "Aircraft CO2 Emissions Standard metric system​".


Aircraft and Engine Emissions

Aircraft are required to meet the engine certification standards adopted by the Council of ICAO. These are contained in Annex 16 – Environmental Protection, Volume II – Aircraft Engine Emissions to the Convention on International Civil Aviation. These were originally designed to respond to concerns regarding air quality in the vicinity of airports. As a consequence, they establish limits for emissions of oxides of nitrogen (NOx, carbon monoxide, unburned hydrocarbons, for a reference landing and take-off (LTO) cycle below 915 metres of altitude (3000 ft). There are also provisions regarding smoke and vented fuel.


While these standards are based on an aircraft's LTO cycle, they also help to limit emissions at altitude. Of particular relevance is the Standard for NOx, a precursor for ozone, which at altitude is a greenhouse gas. The standard for NOx was first adopted in 1981, then made more stringent in 1993, 1999, and 2005. Most recently, the eight meeting of CAEP (CAEP/8) in February 2010 agreed on a new NOx Standard, which improves on the current Standard by up to 15 per cent with an effective date of 31 December 2013, as well as a production cut-off of engines according to the current Standard with an effective date of 31 December 2012.The ICAO Engine Exhaust Emissions Data Bank (Doc 9646), issued in 1995, contains a comprehensive database of aircraft jet engine emissions certification data. Subsequent updates of the data bank are available through the ICAO website.


Regarding particulate matter (PM) emissions, CAEP/8 agreed to focus on non-volatile PM since the science is more advanced in this area, compared to volatile PM. Establishment of a certification requirement is targeted by 2013 and a certification Standard by 2016.


The independent expert review for NOx reduction technologies was completed in 2006 and subsequently updated for CAEP/8 in February 2010. The panel of independent experts decided to maintain the following goals established in 2006:

Medium Term Goal (2016): CAEP/6 levels – 45%, ±2.5% (of CAEP/6) at an overall pressure ratio of 30

Long Term Goal (2026): CAEP/6 levels – 60%, ±5% (of CAEP/6) at an overall pressure ratio of 30

Similarly, a workshop to consolidate the knowledge base for fuel burn improvements through weight reduction, aerodynamic improvement, engine fuel efficiency improvement, and aircraft system optimization was conducted in 2009 and a follow-on review was conducted in May 2010. A report of these reviews and workshop and the resultant medium and long term goals for fuel burn reduction technologies will be presented to the CAEP/9 meeting in 2013.

Aircraft Noise

Much of ICAO's effort to address aircraft noise over the past 40 years has been aimed at reducing noise at source. Aeroplanes and helicopters built today are required to meet the noise certification standards adopted by the Council of ICAO. These are contained in Annex 16 — Environmental Protection, Volume I — Aircraft Noise to the Convention on International Civil Aviation, while practical guidance to certificating authorities on implementation of the technical procedures of Annex 16 is contained in the Environmental Technical Manual on the use of Procedures in the Noise Certification of Aircraft (Doc 9501).


The first generation of jet-powered aeroplanes was not covered by Annex 16 and these are consequently referred to as non-noise certificated (NNC) aeroplanes (e.g. Boeing 707 and Douglas DC-8). The initial standards for jet-powered aircraft designed before 1977 were included in Chapter 2 of Annex 16. The Boeing 727 and the Douglas DC-9 are examples of aircraft covered by Chapter 2. Subsequently, newer aircraft were required to meet the stricter standards contained in Chapter 3 of the Annex. The Boeing 737-300/400, Boeing 767 and Airbus A319 are examples of "Chapter 3" aircraft types. In June 2001, on the basis of recommendations made by the fifth meeting of the Committee on Aviation Environmental Protection (CAEP/5), the Council adopted a new Chapter 4 noise standard, more stringent than that contained in Chapter 3. Starting 1 January 2006, the new standard became applicable to newly certificated aeroplanes and to Chapter 3 aeroplanes for which re-certification to Chapter 4 is requested. Most recently, CAEP/8 in February 2010 requested the noise technical group to review and analyze certification noise levels for subsonic jet and heavy propeller driven-driven aeroplanes and, based on the analysis, develop a range of increased stringency options. This analysis will be considered at the CAEP/9 meeting in 2013.


A Noise database NoisedB was developed in 2006 by the French DGCA under the aegis of the International Civil Aviation Organization (ICAO). The database is intended to be a general source of information to the public on certification noise levels for each aircraft type as provided by certification authorities.Based on the success of the independent expert process to set medium and long term NOx reduction goals, a similar process was launched for noise reduction technologies. This independent expert review was completed in 2008 and the panel presented its final report to CAEP/8 meeting in February 2010. The goals for four classes or categories of aircraft were as follows:


Aircraft Category
Margin to Chapter 4 (EPNdB)
Mid-Term (2018)
Long-Term (2028)
Regional Jet
Small-Med. Range Twin

Long-Range Twin
Long-Range Quad

When compared to a baseline of today’s aircraft, the goals show more promise of noise reduction for larger aircraft because of a broader scope of technologies that can be applied to such aircraft.

Read more (presentation Goals and Standards - The ICAO Perspective)

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