(178 pages) 

COMMITTEE ON AVIATION ENVIRONMENTAL PROTECTION (CAEP)

EIGHTH MEETING

Montréal, 1 to 12 February 2010

AGENDA ITEM 2

The attached constitutes Appendices B, C and D to the report on Agenda 

Item 2 and should be inserted at the appropriate place in the yellow 

folder.

CAEP/8-WP/80

11/2/10

English only

CAEP/8-WP/80

Appendix B to the Report on Agenda Item 2 2 B-1

APPENDIX B

ICAO Emissions Environmental Technical Manual

Volume II

Guidelines on the use of procedures in the 

Emissions certification of aircraft engines
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2 B-2 Appendix B to the Report on Agenda Item 2

Environmental Technical Manual

Volume II

Guidelines on the Use of Procedures in the

Emissions Certification of Aircraft Engines
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Appendix B to the Report on Agenda Item 2 2 B-3

TABLE OF CONTENTS

Page No.

Nomenclature ........................................................................................................................................

Section 1. Introduction

1.1 Purpose

1.2 Framework .................................................................................................................................

1.3 Emissions compliance demonstration plans ...............................................................................

1.4 Emissions certification reports ...................................................................................................

Section 2. Guidance material

Part I. Definitions and Symbols ............................................................................................................

Part II. Vented Fuel [Reserved] ..............................................................................................................

Part III. Emissions Certification ..............................................................................................................

Chapter 1. Administration [Reserved] .........................................................................................

Chapter 2. Turbojet and turbofan engines intended for

propulsion only at subsonic speeds ............................................................................

2.1 General ..........................................................................................................................

2.1.1 Applicability ..................................................................................................................

2.1.2 Emissions involved [Reserved] .....................................................................................

2.1.3 Units of measurement ....................................................................................................

2.1.4 Reference conditions .....................................................................................................

2.1.4.1 Atmospheric conditions .................................................................................................

2.1.4.2 Thrust settings [Reserved] .............................................................................................

2.1.4.3 Reference emissions landing and take-off

(LTO) cycle ...................................................................................................................

2.1.4.4 Fuel specification ..........................................................................................................

2.1.5 Test conditions [Reserved] ............................................................................................

2.2 Smoke ............................................................................................................................

2.2.1 Applicability [Reserved] ...............................................................................................

2.2.2 Regulatory smoke number [Reserved] ..........................................................................

2.3 Gaseous emissions .........................................................................................................

2.3.1 Applicability [Reserved] ...............................................................................................

2.3.2 Regulatory levels ...........................................................................................................

2.4 Information required ......................................................................................................

2.4.1 General information [Reserved] ....................................................................................

2.4.2 Test information [Reserved] ..........................................................................................
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2 B-4 Appendix B to the Report on Agenda Item 2

2.4.3 Derived information ......................................................................................................

Chapter 3. Turbo-jet and turbofan engines intended for

propulsion at supersonic speeds [Reserved] ....................................................................

Appendix 1. Measurement of reference pressure ratio [Reserved] ..............................................

Appendix 2. Smoke emission evaluation .........................................................................................

1. Introduction and definitions [Reserved] ..............................................................................

2. Measurement of smoke emissions .......................................................................................

2.1 Sampling probe for smoke emissions ..................................................................................

2.2 Sampling line for smoke emissions .....................................................................................

2.3 Smoke analysis system ........................................................................................................

2.4 Fuel specifications ...............................................................................................................

2.5 Smoke measurement procedures ..........................................................................................

2.5.1 Engine operation ..................................................................................................................

2.5.2 Leakage and cleanliness checks ...........................................................................................

2.5.3 Smoke measurement ............................................................................................................

3. Calculation of smoke number from measured data .............................................................

4. Reporting of data to the certificating authority [Reserved] .................................................

Appendix 3. Instrumentation and measurement techniques

for gaseous emissions ...................................................................................................

1. Introduction ..........................................................................................................................

2. Definitions [Reserved] .........................................................................................................

3. Data required ........................................................................................................................

3.1 Gaseous emissions ...............................................................................................................

3.2 Other information [Reserved] ..............................................................................................

4. General arrangement of the system ......................................................................................

5. Description of component parts ...........................................................................................

5.1 Sampling system ..................................................................................................................

5.1.1 Sampling probe ....................................................................................................................

5.1.2 Sampling lines [Reserved] ...................................................................................................

5.2 HC analyser [Reserved] .......................................................................................................

5.3 CO and CO2 analysers [Reserved] .......................................................................................

5.4 NOX analysers [Reserved] ...................................................................................................

6. General test procedures ........................................................................................................

6.1 Engine operation [Reserved] ................................................................................................

6.2 Major instrument calibration [Reserved] .............................................................................
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6.3 Operation [Reserved] ...........................................................................................................

6.4 Carbon balance check [Reserved] ........................................................................................

7. Calculations .........................................................................................................................

7.1 Gaseous emissions [Reserved] .............................................................................................

7.1.1 General [Reserved] ..............................................................................................................

7.1.2 Basic parameters [Reserved] ................................................................................................

7.1.3 Correction of emissions indices to reference conditions [Reserved] ...................................

7.2 Control parameter functions [Reserved] ..............................................................................

7.3 Exceptions to the proposed procedures [Reserved] .............................................................

Attachment A to Appendix 3. Specification for HC analyser .....................................................

1. General .................................................................................................................................

2. Synergistic effects ................................................................................................................

3. Optimization of detector response and alignment ................................................................

Appendix 4. Specification for fuel to be used in

aircraft turbine engine emission testing ....................................................................

Appendix 5. Instrumentation and measurement techniques for gaseous

emissions from afterburning gas turbine engines [Reserved] .................................

Appendix 6. Compliance procedures for

Gaseous emissions and smoke [Reserved] .................................................................
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2 B-6 Appendix B to the Report on Agenda Item 2

NOMENCLATURE

Symbols and Units

Symbols and abbreviations employed in Volume II of this manual are consistent with those contained in 

Annex 16 – Environmental Protection, Volume II – Aircraft Engine Emissions (Third Edition, July 2008).
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Appendix B to the Report on Agenda Item 2 2 B-7

SECTION 1. INTRODUCTION

1.1 PURPOSE

1.1.1 The aim of Volume II of this manual is to promote uniformity in the implementation of 

ICAO Annex 16 — Environmental Protection, Volume II — Aircraft Engine Emissions, by providing 

guidance to certificating authorities and applicants regarding the intended meaning of the current 

Annex 16, Volume II emissions Standards and those specific procedures that are deemed acceptable in 

demonstrating compliance to these Standards.

1.1.2 This manual also provides guidance in the wider application of equivalent procedures that 

have been accepted as a technical means for demonstrating compliance with the emissions certification 

requirements of Annex 16, Volume II. Such equivalent procedures are referred to in Annex 16, 

Volume II, but are not dealt with in the same detail as in the Appendices which describe the emissions 

evaluation methods for compliance with the relevant Chapters of Annex 16, Volume II.

1.1.3 Annex 16, Volume II procedures must be used unless an equivalent procedure is 

approved by the certificating authority. Procedures presented in this manual should not be considered as 

limited only to those described herein as this manual will be expanded as new procedures are developed. 

Also, their presentation does not infer limitation of their application or commitment by certificating 

authorities to their further use.

1.1.4 References to Annex 16, Volume II relate to the Amendment 6 thereof.

1.2 FRAMEWORK

1.2.1 The basic framework of Volume II of this manual is a replication of the ICAO Annex 16, 

Volume II structure in order to ensure easy reference between the requirements and guidance. References 

in the Table of Contents are only made to a part of the requirements when there is an associated guidance 

material; otherwise the relevant paragraph has been ―Reserved‖ for future use. There is minimal repetition 

of the requirement text in order to simplify the ETM content, lower maintenance costs, and reduce the 

danger of inconsistencies between Volume II and the ETM following future revisions. The requirement 

text is enclosed between two horizontal lines.

1.2.2 This first section provides general information while the second Section contains 

guidance material to ICAO Annex 16, Volume II. The format of the guidance material includes three 

types of information described as explanatory information, equivalent procedures and technical 

procedures. The definitions of these three types of information are as follows:

Explanatory information

• Explains ICAO Annex 16 emissions Standards language.

• States current policies of regulatory authorities regarding compliance with ICAO 

Annex 16 emissions Standards.
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2 B-8 Appendix B to the Report on Agenda Item 2

• Provides awareness of critical issues for approval of applicants‘ compliance methodology 

proposals.

Equivalent procedures

• An equivalent procedure is a test or analysis procedure which, while differing from one 

specified in Annex 16, Volume II, in the technical judgement of the certificating 

authority, yields effectively the same emissions levels as the specified procedure.

• The use of equivalent procedures may be requested by applicants for many reasons, 

including: 

a) to make use of previously acquired certification test data for the engine type; and

b) to minimize the costs of demonstrating compliance with the requirements of ICAO 

Annex 16, Volume II by keeping engine test time, test bed usage, and equipment and 

personnel costs to a minimum.

Technical procedures

• A technical procedure is a test or analysis procedure not defined in detail in ICAO 

Annex 16 emissions Standards but which certificating authorities have approved as being 

acceptable for compliance with the general provisions the emissions Standards specify.

1.3 EMISSIONS COMPLIANCE DEMONSTRATION PLAN

1.3.1 Prior to undertaking an emissions certification demonstration, the applicant is normally 

required to submit to the certificating authority an emissions compliance demonstration plan. This plan 

contains the method by which the applicant proposes to show compliance with the emissions 

requirements. Approval of this plan and the proposed use of any equivalent procedure remain with the 

certificating authority. The determination of equivalency for any procedure or group of procedures must 

be based upon the consideration of all pertinent facts relating to the application.

1.3.2 Emissions compliance demonstration plans should include the following types of 

information:

a) Introduction: description of the engine emissions certification basis, i.e. the applicable 

Annex 16, Volume II Amendment and Chapter;

b) Engine description: type, model number and specific details of the basic configuration to 

be certified;

c) Engine emissions certification methodology: test concepts, equivalent procedures and 

technical procedures;

d) Test description: test methods to comply with the emissions Standards;
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Appendix B to the Report on Agenda Item 2 2 B-9

e) Measurement system: description of measurement and sampling system components and 

procedures, including calibration procedures, that are intended to be used to demonstrate 

compliance with the emissions Standards; and 

f) Data evaluation procedures: emissions evaluation and adjustment procedures (including 

equivalent and technical procedures such as those provided in this manual) to be used in 

compliance with the provisions of ICAO Annex 16, Volume II appropriate to the engine 

type being certificated.

1.4 EMISSIONS CERTIFICATION REPORTS

1.4.1 Following completion of an emissions certification demonstration test, an applicant is 

normally required to submit an emissions certification report. This report provides a complete description 

of the test process and the test results with respect to compliance with the provisions of Annex 16, 

Volume II.

1.4.2 These reports should include the following types of information:

a) Basis for test approval: the approved emissions certification compliance plan for the 

engine type and model being certificated;

b) Description of tests: actual configurations tested and non-conforming items (with 

justification that they are not significant to emissions, or if significant, can be dealt with 

by an approved method), test methodology (including equivalent procedures and 

technical procedures), tests conducted, test data validity, and data analysis and adjustment 

procedures used;

c) Test results: data to demonstrate compliance with the provisions of Annex 16, 

Volume II regarding maximum emissions levels for the engine type being certificated; 

and

d) References.
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2 B-10 Appendix B to the Report on Agenda Item 2

SECTION 2. GUIDANCE MATERIAL

PART I. DEFINITIONS AND SYMBOLS

CHAPTER 1. DEFINITIONS

Exhaust nozzle. In the exhaust emissions sampling of gas turbine engines where the jet effluxes are not 

mixed (as in some turbofan engines for example) the nozzle considered is that for the gas generator 

(core) flow only. Where, however, the jet efflux is mixed the nozzle considered is the total exit 

nozzle.

EQUIVALENT PROCEDURE:

Defining the exhaust nozzle in this manner, where the fan and core nozzles are not coplanar, is 

problematic. With imperfect knowledge of the fan flow characteristics when discharged upstream of the 

core exit nozzle, the effective nozzle size may be ambiguous. This affects the extreme downstream 

location of the sampling probe or rake and causes problems in terms of a detailed traverse of the total 

exhaust nozzle. In order to obtain equivalent, but more accurate gaseous emissions measurements and 

representative samples, it is considered best practise to arrange the engine configuration in such a way as 

to separate the fan and core flows, without affecting the engine performance, and sample just the core 

flow. The above is equally applicable to both gaseous and smoke emission measurements, however for 

smoke, the dilution and mixing of bypass air also needs to be taken into account and this is covered under 

Appendix 2, paragraph 2.1. 

CHAPTER 2. SYMBOLS [Reserved]

PART II. VENTED FUEL [Reserved]

PART III. EMISSIONS CERTIFICATION

CHAPTER 1. ADMINISTRATION [Reserved]
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Appendix B to the Report on Agenda Item 2 2 B-11

CHAPTER 2. TURBOJET AND TURBOFAN ENGINES INTENDED FOR

PROPULSION ONLY AT SUBSONIC SPEEDS

2.1 General

2.1.1 Applicability

EXPLANATORY INFORMATION:

Part I of Annex 16, Volume II defines a derivative version1in terms of emissions certification, but this 

definition is only referred to in the Annex in the context of granting exemptions and does not specify how 

the rule should be applied to modifications of already certificated engine types. Many changes to a 

certificated engine, which are considered to be major from an airworthiness perspective, require an 

amendment or supplement to the Type Certificate (TC). However, this same modification(s) may have no 

or very little effect on the emissions characteristics of that engine. If Annex 16 is interpreted literally, 

these small effects would require a full investigation of compliance against the emissions certification 

requirements. This may not be necessary in many cases. The following guidelines have been developed in 

order to help determine whether a modification could be classified as a ―no emission change‖ or if it 

would affect the emissions levels to such an extent that the engine type would need to be re-certificated 

against Annex 16, Volume II requirements. Of course manufacturers may elect to recertify to the latest 

requirements at any time.

TECHNICAL PROCEDURE:

1. No emissions change

The principle of a ―no emissions change‖ criteria is that an engine would not need to be 

re-certified against the emissions requirements if the manufacturer could demonstrate that the 

modification(s) would result in a small cumulative change to the current certified engine emission levels. 

Cumulative change could be as a result of more than one change at a given time or multiple changes from 

more than one derivative version of the same engine being developed. 

The potential determination of a ―no emissions change‖ is limited to the following 

conditions:

i) If all of the characteristic levels prior to any modification are greater than or equal to 

95 per cent of the existing ICAO Standard, the manufacturer must provide new engine 

emissions test data to demonstrate that the resulting characteristic levels after the cumulative 

changes since original emission testing will not exceed the existing ICAO exhaust emission 

Standard.

 

ii) If all of the characteristic levels are less than 95 per cent of the existing ICAO exhaust 

emission Standards, then new or related emissions test data and good engineering judgment 

 

1 Derivative version. An aircraft gas turbine engine of the same generic family as an originally type certificated engine and 

having features which retain the basic core engine and combustor design of the original model and for which other factors as 

judged by the certificating authority, have not changed.
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2 B-12 Appendix B to the Report on Agenda Item 2

based on substantive analysis may be an acceptable means to demonstrate that the resulting 

emission levels after the cumulative changes since original emission testing will not exceed 

the existing ICAO exhaust emission Standard.2 Analyses should consider areas such as cycle 

changes, combustor and fuel nozzle design, or large changes in combustor inlet velocity 

profile or turbine cooling flows as discussed in paragraph 5 below.

iii) Any new emissions test data and/or engineering/technical analysis under subparagraphs (i) 

and (ii) must demonstrate that the cumulative changes in absolute emission levels, as 

compared to those of the original certification, are within:3

NOX ± 3 g/kN

HC ± 1 g/kN

CO ± 5 g/kN

Smoke ± 2 SN

With respect to the tracking of cumulative changes, an applicant should maintain formal 

documentation of the technical basis for all approved ―no emissions changes‖ for an engine 

model. The tracking list will be reproduced in each emissions certification dossier 

demonstration.

If a modification is classified as a ―no emissions change‖, the characteristic levels for the 

derivative version will be considered the same as the parent engine. 

2. Changes requiring new emissions levels

A change, or cumulative set of changes to the type design, which is/are not considered a 

―no emissions change‖ and thus affects the characteristic levels would require new characteristic levels to 

be determined during the certification program. This would normally be done through a new emissions 

certification test. 

3. Existing emissions certification basis retained

If a modified engine remains on the existing type certificate, it may retain the existing 

certification basis of the parent engine4if the modification(s):

i) meets the demonstration criteria of 1(i) or 1(ii);

ii) results in a decrease of the absolute emissions levels; 

iii) results in an increase of the absolute emissions levels below those prescribed in 1(iii);

iv) are necessary for improved safety and continued airworthiness (e.g. ADs).

 

2 Good engineering judgment means judgments made consistent with generally accepted scientific and engineering principles and 

all available relevant information.

3 Absolute emission level refers to the average of the measured emission levels corrected to reference conditions. This does not 

include application of the Appendix 6 statistical factors used to determine characteristic levels.

4

In terms of emissions certification, the parent engine must have demonstrated emissions compliance and is not considered to be 

a derivative of an even earlier Standard itself.
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Appendix B to the Report on Agenda Item 2 2 B-13

4. Latest emissions Standards applied

An engine type should demonstrate compliance with the latest emissions standards when:

i) The engine requires a new TC;

ii) The engine modification(s) involves significant technical modifications and where, in the 

judgment of the certificating authority, the engine would not meet the definition of a 

derivative engine as defined in Annex 16, Volume II;

iii) The engine modification(s) does not meet the demonstration criteria of 1(i) or 1(ii);

iv) The engine modification(s) results in an increase in any of the absolute emissions levels 

below those prescribed in 1(iii) but which results in an exceedance of the existing ICAO 

Standard;

v) The engine modification(s) results in an increase in any of the absolute emissions levels in 

excess of those prescribed in 1(iii); or

v) There are significant future environmental impacts.5 

5. Engineering analysis examples

The basic premise in assessing emissions effects of design changes from an engineering 

analysis perspective is that emissions are mainly affected by cycle changes, combustor and fuel nozzle 

design, or large changes in combustor inlet velocity profile or turbine cooling flows. A number of 

examples are provided below for illustration.

Cycle change

Annex 16, Volume II only requires the measurement of fuel mass flow by direct 

measurement to an accuracy of ±2 per cent (Attachment F to Appendix 3, d.) and thrust to an accuracy of 

±1 per cent at take-off power and ±5 per cent at the minimum thrust. It may be that no affect on emissions 

beyond those prescribed in paragraph 1(iii) would be expected unless changes in air fuel ratio (AFR) 

result in a specific fuel consumption (SFC) change of more than 1 per cent. 

Regarding combustor inlet temperature (T3), the Annex also states that the combustor 

inlet parameters shall preferably be measured but may be calculated from ambient conditions by 

appropriate formulas. Following a comparison on T3 detailed traverses versus typical certification test 

measurements, it was concluded that measurements are within ±6°F (ca. 3.5°C) of theoretical 

calculations. It may be that no affect on emissions beyond those prescribed in paragraph 1(iii) would be 

expected if the cycle T3 change is within ±6°F.

Combustor and fuel nozzle

Combustor and fuel nozzle changes include some key design characteristics that can 

significantly affect emissions (e.g. swirl cup flow, primary hole flow, front end cooling flow, injector 

 

5 The application of an old engine type to a new aircraft design could mean a life time of 30 years or more and thereby have a 

more serious impact on the environment than if the engine was produced for spare only.
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2 B-14 Appendix B to the Report on Agenda Item 2

atomization). Changes within or outside of production tolerances or part-to-part variation may indicate 

when a change would be important for emissions or else considered to be not measurable. No affect on 

emissions beyond those in prescribed paragraph 1(iii) might be expected if the changes are within current 

part-to-part variation or prescribed production tolerances. 

Boundary conditions

Similar limitations to that for key design characteristics can be applied to that resulting 

from changes in boundary conditions. For example, if turbine cooling changes by 2 per cent, one could 

look at the resulting change in combustor flow distribution, and if the change is of the same order as 

typical part-to-part variation, it may be acceptable to conclude that no affect on emissions beyond those 

prescribed in paragraph 1(iii) would be expected.

2.1.1.1 The provisions of this chapter shall apply to all turbojet and turbofan engines, as further 

specified in 2.2 and 2.3, intended for propulsion only at subsonic speeds, except when certificating 

authorities make exemptions for:

a) specific engine types and derivative versions of such engines for which the type certificate of the 

first basic type was issued or other equivalent prescribed procedure was carried out before 

1 January 1965; and

b) a limited number of engines beyond the dates of applicability specified in 2.2 and 2.3 for the 

manufacture of the individual engine.

2.1.1.2 In such cases, an exemption document shall be issued by the certificating authority, the 

identification plates on the engines shall be marked ―EXEMPT,‖ and the grant of exemption shall be 

noted in the permanent engine record. 

TECHNICAL PROCEDURE

1. Introduction

1.1 The current ICAO Annex 16, Volume II contains two different references to applicability 

dates:

• ―date of manufacture for the first individual production model‖ which refers to the engine 

type certification; and

• ―date of manufacture for the individual engine‖ which refers to the production date of a 

specific engine serial number. 

1.2 The second reference is used in the application of global engine NOX production cut-off 

Standards which specify a date after which all in-production engine models must meet a certain NOX

emission Standard. For example, all engines manufactured after 31 December 1999 must be compliant 

with the CAEP/2 NOX Standard. It should be noted that these requirements are applicable to complete 
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Appendix B to the Report on Agenda Item 2 2 B-15

new ―engine units‖ released into service as spares or for new aircraft installations, as discussed below, 

and not engine components required for maintenance aspects, overhaul, parts, etc. 

1.3 It is recognized that there may be certain circumstances where it is justified to permit 

manufacturers to continue to produce new non-compliant engine units after a production cut-off date. 

These take the form of exemptions against the relevant Annex 16, Volume II provisions. 

1.4 In order to promote a harmonized global approach to the granting, implementing and 

monitoring of these exemptions, this section provides guidelines on the process and criteria for issuing 

exemptions against a NOX production cut-off Standard. 

2. Exemption process

2.1 Application

2.1.1 The applicant should submit a formal application letter to the competent authority6for the 

manufacture of the exempted engines, signed by an appropriate manager, and copied to all other relevant 

organizations and involved competent authorities. The letter should include the following information in 

order for the competent authority to be in a position to review the application:

 a) Administration

 Name, address and contact details of the applicant.

 b) Scope of application for exemptions

 Engine type (model designation, type certificate (TC) number, TC date, emission TC 

basis, ICAO Engine Emissions Databank Unique Identification (UID) Number).

 Number of engine exemptions requested.

 Duration (end date) of continued production of exempted engines.

 Designate whether the proposed exempted engines are ―spares‖ or ―new‖7and to 

whom the engines will be originally delivered.

c) Justification for exemptions

In applying for an exemption, an applicant should, to the extent possible, address the 

following factors, with quantification, in order to support the merits of the exemption 

request:

 technical issues, from an environmental and airworthiness perspective, which may 

have delayed compliance with a production cut-off;

 economic impacts on the manufacturer, operator(s) and aviation industry at large;

 

6

In most cases this will be the Certificating Authority although it may vary depending on individual Member State processes.

7

In the case that engines are to be ―new‖ (installed on new aircraft), and would thus result in a larger negative environmental 

impact compared to spare engines, greater justification could be required to approve this application.
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2 B-16 Appendix B to the Report on Agenda Item 2

 environmental effects. This should consider the amount of additional NOX that will 

be emitted as a result of the exemption. This could include consideration of items 

such as:

- the amount that the engine model exceeds the standard, taking into account any 

other engine models in the engine family covered by the same type certificate 

and their relation to the Standard;

- the amount of NOX that would be emitted by an alternative engine for the same 

application;

- impact of changes to reduce NOX on other environmental factors, including 

community noise and CO2 emissions;

 impact of unforeseen circumstances and hardship due to business circumstances 

beyond the manufacturer‘s control (e.g. employee strike, supplier disruption or 

calamitous events);

 projected future production volumes and plans for producing a compliant version of 

the engine model seeking exemption;

 equity issues in administering the production cut-off among economically competing 

parties (e.g. provide rationale for granting this exemption when another manufacturer 

has a compliant engine and does not need an exemption, taking into account the 

implications for operator fleet composition, commonality and related issues in the 

absence of the engine for which exemptions are sought); and

 any other relevant factors.

2.2 Evaluation

2.2.1 The evaluation of an exemption application should be based on the justification provided and the 

following definitions and criteria:

a) Use of engines 

―Spare engines‖ are defined as complete new engine units which are to be installed on inservice aircraft for maintenance and replacement. It can be presumed that applications 

associated with engines for this purpose would be granted as long as the emissions were equal 

to or better than those engines they are replacing. The application should also include the 

other items described in paragraphs 2.1.1 (a) and (b), but it would not need to include the 

items specified in paragraph 2.1.1(c). For spare engines, the evaluation of the exemption

application would be conducted for recordkeeping and reporting purposes, but it would not be 

done for approval of an exemption. 

―New engines‖ are defined as complete new engine units which are to be installed on new 

aircraft. They can only be exempted from a NOX production cut-off requirement if they 

already meet the previous standard (e.g. exemption from a CAEP/6 NOX production cut-off is 
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Appendix B to the Report on Agenda Item 2 2 B-17

only possible if an engine type already meets the CAEP/4 NOX Standard). Also, in order to 

gain approval for this type of exemption the applicant must clearly demonstrate that they 

meet the criteria for an exemption by including items described in paragraphs 2.1.1(a), (b), 

and (c). The competent authority may require additional information regarding the 

appropriateness of the potential exemption.

b) Number of new engine exemptions

Exemptions should be based on a total number of engines and time period for delivery of 

these engines, which would be agreed at time the application is approved and based on the 

considerations explained in 2.1.1.c) above. The number of engines exempted would normally 

not exceed 75 per engine type certificate and the duration would not exceed four years from 

the effective date of the production cut-off. Exemptions would only apply to non-compliant 

engine models on an engine type certificate.

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 aviation, 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. 

As part of the review and approval process for exemptions from any production cut-off 

requirement associated with the CAEP/6 NOX Standard, competent authorities may in some 

cases require a form of NOX emissions offsetting, as appropriate within the context of 

aviation and considering an applicant's ability to utilize such measures. However, offsetting 

measures should be applied only when necessary in view of the number of engines for which 

exemptions are sought (e.g., greater than 30), duration and/or percent exceedance described 

in an application. 

c) Exceptions

Unlimited exemptions should be granted for spare engines having emissions equivalent to or 

better than the engines they replace. Engines for use on state aircraft (e.g., military, customs 

and police) are not covered by the Chicago Convention and therefore excluded from these 

civil aircraft NOX production cut-off requirements.

2.3 Review

The competent authority should review, in a timely manner, the application using the 

information provided in paragraph 2.1 and against the definitions/criteria in paragraph 2.2.

The analysis and the conclusions from the review should be communicated to the 

applicant in a formal response. If the application is approved, the response should clearly state the scope 

of the exemptions which have been granted. If the application is rejected, then the response should 

include a detailed justification.
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2 B-18 Appendix B to the Report on Agenda Item 2

3. Registration and communication

3.1 Oversight of the granted exemptions should include the following elements:

• The competent authority should publish details of the exempted engines in an official 

public register, including engine model, maximum number of permitted exemptions and 

use of engines. 

• The applicant should have a quality control process for maintaining oversight of and 

managing the production of engines which have been granted exemptions against a NOX

emissions production cut-off Standard. 

• Exempted engine plates should be marked with ―EXEMPT [SPARE] or [NEW]‖.

• An exemption should be recorded in the engine release to service document which states 

conformity with the Type Certificate (e.g., EASA Form 1, FAA Form 8130-3). Proposed 

standard text - ―[New] or [Spare] Engine exempted from NOX emissions production cutoff requirement‖.

• The applicant should provide, on a regular basis and appropriate to the limitation of the 

approval, details to the competent authority on the actual exempted engines which have 

been produced (e.g., model, serial number, use of engine, aircraft type and serial number 

on which new engines are installed).

2.1.1.3 The provisions of this chapter shall also apply to engines designed for applications that otherwise 

would have been fulfilled by turbojet and turbofan engines.

EXPLANATORY INFORMATION

This sentence anticipates the introduction of future engine technologies. The emissions Standards in 

Chapter 2 would also be applicable to future engine types not categorized as a turbo-jet or turbofan but 

intended for use in international air transport services. The provision above is not directly applicable to 

turbo-prop engines for example.

2.1.2 Emissions involved [Reserved]

2.1.3 Units of measurement

EXPLANATORY INFORMATION

Smoke level is determined indirectly, by means of the loss of reflectance of a filter used to trap smoke 

particles from a prescribed mass of exhaust per unit area of filter. The result is a dimensionless smoke 

number ―SN‖ which acts as a surrogate for, or indicator of, plume opacity. These smoke sampling and 
CAEP/8-WP/80

Appendix B to the Report on Agenda Item 2 2 B-19

measurement procedures standardized in Annex 16, Appendix 2 are derived from SAE Aerospace 

Recommended Practice (ARP) 1179, Aircraft Gas Turbine Exhaust Smoke Measurement. 

The smoke measurement Standard was developed for engines that generated smoke at considerably 

higher levels than are seen today. This affects the relative accuracy of the method. The measurement is 

considered (by the SAE E-31 committee that developed the method) to be no more accurate than ±3 SN. 

At smoke levels of SN 50-60 this represents an accuracy of 6% - 5%. At regulatory standards of 30 and 

below, relative accuracy becomes 10% - 20% or more.

2.1.4 Reference conditions

2.1.4.1 Atmospheric conditions

EXPLANATORY INFORMATION

The reference atmospheric conditions to which the gaseous emissions (HC, CO and NOX) are to be 

corrected are the reference day conditions, as follows: Temperature = 15°C, Humidity = 0.00634 kg 

H2O/kg of dry air, Pressure = 101.325 kPa.

2.1.4.2 Thrust settings [Reserved]

2.1.4.3 Reference emissions landing and take-off (LTO) cycle

EXPLANATORY INFORMATION

The exhaust emissions test is designed to measure hydrocarbons, carbon monoxide, carbon dioxide and

oxides of nitrogen concentrations, and to determine mass emissions through calculations during a 

simulated aircraft landing-takeoff cycle (LTO). The LTO cycle is based on times in mode data during 

high activity periods at major airports for four modes of engine operation: taxi/idle, takeoff, climb-out, 

and approach. The mass emissions for these modes are combined to yield the reported emissions 

certification levels.

2.1.4.4 Fuel specifications

EXPLANATORY INFORMATION 

Aircraft gas turbine engines use a variety of fuels. The specific fuel type and composition can and often 

does have a significant effect on engine emissions. Hence, it is an important factor when comparing 

emissions levels from one engine with those from another. It is particularly important in evaluating engine 

emission levels relative to a regulation that was based, in part, on an assumed fuel specification. The 

ICAO fuel specification defined in Appendix 4 is typical, but tighter, than the general Jet A aviation fuel 
CAEP/8-WP/80

2 B-20 Appendix B to the Report on Agenda Item 2

specification. The requirement for emissions certification testing with a fuel that meets a particular 

specification provides a fixed point of reference for the engine. It provides for some degree of control 

over the effect of fuel composition on smoke formation and emission. It also helps in the assessment of 

the effects of changing technology.

2.1.5 Test Conditions [Reserved]

2.2 Smoke

2.2.1 Applicability [Reserved]

2.2.2 Regulatory Smoke Number [Reserved]

2.3 Gaseous Emissions

2.3.1 Applicability [Reserved]

2.3.2 Regulatory levels

EXPLANATORY INFORMATION

The date when a Standard in paragraph 2.2 and 2.3 becomes applicable within a certification project is 

related to the ―... date of manufacture of the first individual production model ...‖. As this date is not 

always clear, certificating authorities have used the date of issue of the engine type certificate (TC) as a 

surrogate. The date is transparent as it is recorded on the TC and has therefore proven a useful approach 

in defining the certification basis for an engine type or model. 

The Part 1, Chapter 1 definition of ―Date of manufacture‖ refers to the date of the document issued to an 

individual production engine which attests compliance with the type certificate.

2.4 Information Required

2.4.1 General information [Reserved]

2.4.2 Test information [Reserved]

2.4.3 Derived information

EXPLANATORY INFORMATION

The ―maximum Smoke Number‖ is formally defined as the greatest value of SN measured at any of the 

four thrust levels defined in 2.1.4.2. However, if a higher Smoke Number is measured at any other test 

condition between 7 per cent and 100 per cent of rated thrust during emissions certification tests, it is 

recommended that the higher value be reported as the ―Maximum Smoke Number‖.
CAEP/8-WP/80

Appendix B to the Report on Agenda Item 2 2 B-21

CHAPTER 3. TURBOJET AND TURBOFAN ENGINES INTENDED FOR

PROPULSION AT SUPERSONIC SPEEDS

EXPLANATORY INFORMATION

During the CAEP/7 work programme, Working Group 3 reviewed the historic background on the 

development of the emissions Standards for turbojet and turbofan engines intended for propulsion at 

supersonic speeds and discussed general technology aspects of supersonic engines in comparison to those 

for subsonic applications. The output of this work was reported in CAEP/7-WP/10 in February 2007.

While further work, taking into account aircraft and engine development, was considered to be necessary 

to give clear recommendations on future changes to Chapter 3, the following preliminary observations 

and conclusions were agreed:

a) The current supersonic Standard seems to be outdated.

b) The Standard should not be applied for new engine projects.

c) Part III, Chapter 3 of ICAO Annex 16, Volume II would need to be revised.

d) The timescale for updating should take into account the technological development of any new 

SST engine project and be in line with the work to be undertaken on development of revised 

noise Standards.

e) Any alleviation compared to the current subsonic Standard would require detailed technical 

investigation.

f) In order for these conclusions to become recommendations work needs to be completed on 

whether the current subsonic LTO regulatory approach can be applied to supersonic.

g) Effects from cruise emissions from a potential fleet of supersonic business jets require more 

scientific understanding.

WG3 continues to monitor developments within the aviation industry and scientific community on this 

issue. WG3 has also agreed not to update Chapter 3 until a new SST engine project reaches a sufficiently 

mature level such that it can inform discussions on potential future revisions.

APPENDIX 2. SMOKE EMISSION EVALUATION

EXPLANATORY INFORMATION

The procedure for evaluating smoke emissions is an indirect measure of smoke plume visibility which is 

obtained by using a filter to trap smoke particles contained in a predetermined mass of exhaust gas and 
CAEP/8-WP/80

2 B-22 Appendix B to the Report on Agenda Item 2

measuring the loss of reflectance, i.e., degree of staining, of this filter relative to the absolute reflectance 

of the filter when clean or free of stain. The uncertainty of the smoke emission evaluation is estimated to 

be within ±3 SN (smoke numbers). 

1. INTRODUCTION AND DEFINITIONS [Reserved]

2. MEASUREMENT OF SMOKE EMISSIONS 

2.1 Sampling probe for smoke emissions

a) The probe material with which the exhaust emission sample is in contact shall be stainless 

steel or any other non-reactive material.

b) If a probe with multiple sampling orifices is used, all sampling orifices shall be of equal 

diameter. ...

EQUIVALENT PROCEDURES

Stainless steel is the preferred probe material but other non-reacting materials may be more suitable under 

specific circumstances, e.g. engine exhaust temperatures which exceed the physical specification limits of 

stainless steel. Inconel 625 and Nimonic 75 alloys have previously been accepted as a non-reactive probe 

material in the context of the regulated species. Other materials may be suitable but need to be approved 

by the certificating authority.

b) ... The probe design shall be such that at least 80 per cent of the pressure drop through the 

probe assembly is taken at the orifices.

EXPLANATORY INFORMATION

Smoke particles are submicron in size which, for sampling from gas turbine engines, precludes the need 

for isokinetic sampling. Never-the-less good practice would suggest sampling as close to isokinetic as 

possible. Taking an 80 per cent pressure drop at the probe orifices is a reasonable compromise. Further 

information on probe design is provided within the section on Appendix 3, paragraph 5.1.1.
CAEP/8-WP/80

Appendix B to the Report on Agenda Item 2 2 B-23

c) The number of locations sampled shall not be less than 12. [Reserved]

d) The sampling plane shall be as close to the engine exhaust nozzle exit plane as permitted by 

considerations of engine performance but in any case shall be within 0.5 nozzle diameters of 

the exit plane.

EXPLANATORY INFORMATION

The definition of the engine exhaust nozzle is contained in Part 1, Chapter 1, Definitions.

EQUIVALENT PROCEDURE (for mixed flow engine configurations)

For accurate gaseous emissions measurements and representative samples, it is considered best practise to 

arrange the engine configuration in such a way as to separate the fan and core flows, without affecting the 

engine performance, and to sample just the core flow. This is equally applicable to smoke emission 

measurements, however for mixed flow engine designs, the dilution and mixing of bypass air also needs 

to be taken into account with respect to the exhaust nozzle location. This means that the measured core 

SN would need to be corrected analytically for dilution and mixing in order to compare against the 

original visibility criteria. 

Currently, Annex 16, Volume II does not contain any method or procedure for these corrections which 

has led to inconsistent application of the requirements. Where no specific engine data is available, 

Version 3 of the First Order Approximation (FOA) for estimating Particulate Matter emissions, which 

contains correlations between SN and non-volatile PM, is provided as a generic dilution correction in the 

technical procedure below. If it can be shown that an improved correlation is available for a given engine 

type, or the FOA is developed further, then the improved correlation shall be used with the approval of 

the certificating authority. No generic mixing correction procedure has yet been identified, and as such, 

certificating authorities need to address this issue on a project by project basis. Ideally the measured core 

SN would already meet the SN limit. Where this is not the case, further evidence may be required to 

inform a technically based engineering judgement as to whether the plume could still considered to be 

invisible. This could include a detailed traverse at the mixed exhaust nozzle plane in order to perform a 

contour analysis and determine the level of mixing.

TECHNICAL PROCEDURE

The following procedure is provided as guidance material on how to correct core Smoke Numbers for 

dilution at a mixed flow engine exhaust nozzle:
CAEP/8-WP/80

2 B-24 Appendix B to the Report on Agenda Item 2

Step 1: Convert measured core smoke number to equivalent carbon mass concentration

Figure 1: SN plotted against carbon concentration

Based on various research studies, the following FOA carbon correlation equation has been established:

CI = 0.0694(SN)1.23357 for SN < 30

Example: From an engine with a maximum measured core Smoke Number of 20, the FOA reference 

curve provides an equivalent carbon mass concentration of 2.8 mg/m3 at the core exit plane. 

Step 2: Adjust carbon mass concentration for mixed stream equivalent

The carbon concentration can now be corrected for the amount of bypass air using the following 

formulae:

Bypass Ratio

Core Carbon Mass Mixed Carbon Mass





1

Example: Assuming a bypass ratio of 5, the mixed carbon mass concentration is 2.8/(1+5) = 0.47 mg/m3

at the mixed nozzle exit plane. 

Step 3: Convert mixed stream carbon mass back to a smoke number

Using the FOA reference curve, the mixed flow carbon mass (calculated in the previous step) is converted 

to an equivalent smoke number. 

Example: The diluted smoke number, accounting for the fan air using the FOA reference curve, is 4.8 at 

the mixed nozzle exit plane.

0

0,5

1

1,5

2

2,5

3

3,5

4

4,5

5

0 5 10 15 20 25 30

SN

Carbon Conc. mg/m3

FOA 3 curve for SN < 30
CAEP/8-WP/80

Appendix B to the Report on Agenda Item 2 2 B-25

e) The applicant shall provide evidence to the certificating authority, by means of detailed 

traverses, that the proposed probe design and position does provide a representative sample 

for each prescribed thrust setting.

EXPLANATORY INFORMATION

Smoke measurements can be performed by means of a single point probe which is traversed through the 

sampling plane in sufficient detail to provide a representative sample. This measurement can also be made 

using a multi-orifice probe which has been demonstrated to provide a representative sample by 

comparison with those of the single point traverse. Work sponsored by the SAE E-31 Committee has 

shown that the best agreement between a detailed traverse, used to establish the mean value of smoke 

emissions in the sampling plane, and a multi-point sampling probe is achieved when this probe‘s 

sampling orifices are located on centres of equal area. The most common configuration is that of a 

cruciform with the individual orifices equally distributed and located on centres of equal area.

2.2 Sampling line for smoke emissions

2.2.2 Note.— Stainless steel or carbon loaded grounded polytetrafluoroethylene (PTFE) meet these 

requirements.

EXPLANATORY INFORMATION

If carbon-loaded grounded polytetrafluoroethylene (PTFE) is used special care must be taken to allow 

sufficient cooling of the exhaust sample from the probe to the PTFE line to prevent damaging the PTFE 

line and possibly compromising the sample. 

2.3 Smoke analysis system

a) sample size measurement [Reserved]

b) sample flow rate measurement [Reserved]

c) filter and holder [Reserved]

d) valves [Reserved]

e) vacuum pump [Reserved]

f) temperature control [Reserved]

g) If it is desired to draw a higher sample flow rate through the probe than through the filter 

holder, an optional flow splitter may be located between the probe and valve A (Figure 2-1), 

to dump excess flow. The dump line shall be as close as possible to probe off-take and shall 
CAEP/8-WP/80

2 B-26 Appendix B to the Report on Agenda Item 2

not affect the ability of the sampling system to maintain the required 80 per cent pressure 

drop across the probe assembly. The dump flow may also be sent to the CO2 analyser or 

complete emissions analysis system.

EXPLANATORY INFORMATION

Achieving an 80 per cent pressure drop across the probe assembly can result in an unacceptably high 

sample flow rate through the filter holder due to the pressure drop taken across the filter. In these 

instances, a flow splitter may be required.

h) If a flow splitter is used, a test shall be conducted to demonstrate that the flow splitter does 

not change the smoke level passing to the filter holder. This may be accomplished by 

reversing the outlet lines from the flow splitter and showing that, within the accuracy of the 

method, the smoke level does not change.

EXPLANATORY INFORMATION

Smoke from gas turbine engines, although consisting of sub-micron particles, can be particularly sensitive 

to flow splitter design or other flow elements in the sampling stream due to inertial separation at very high 

flow velocities. This test addresses these concerns and ensures that the splitter design does not adversely 

impact the smoke emissions evaluation. 

i) leak performance [Reserved]

j) reflectometer

EQUIVALENT PROCEDURE

ARP 1179 Rev. C requires the use of a green tristimulus filter to adjust for the effect of various light 

sources from different reflectometer manufacturers. While this is not a requirement in Annex 16,

Volume II, it is considered best practice to follow this approach.

2.4 Fuel specifications [Reserved]

2.5 Smoke measurement procedures

2.5.1 Engine operation [Reserved]

2.5.2 Leakage and cleanliness checks
CAEP/8-WP/80

Appendix B to the Report on Agenda Item 2 2 B-27

EXPLANATORY INFORMATION

Leakage checks are to ensure clean air does not leak into the system thereby diluting the sample and 

lowering the smoke number. Cleanliness checks ensure that the sampling system is acceptably clean and 

the collecting filter will not be contaminated. If the probe cannot be removed from the sampling stream 

during engine start-up, the probe and lines should be back pressured with a suitably clean gas, such as dry 

nitrogen, to minimize contamination problems.

2.5.3 Smoke measurement

EXPLANATORY INFORMATION

It is common practice, while sampling for smoke, to also measure levels of CO2 as an operational check 

of the sampling system. The engine fuel-air ratio is calculated from the measured CO2 and compared to 

the fuel-air ratio obtained from engine performance data. These should be in agreement within ±10 per 

cent at engine power above idle and within ±15 per cent at idle.

Paragraphs a) through d) provides for adjusting and setting the sample flow rate through the filter holder. 

To duplicate the pressure drop through the filter holder during actual sampling conditions a clean filter is 

clamped into the holder. This filter should be removed and discarded before clamping a clean filter into 

the holder as described in d).

3. CALCULATION OF SMOKE NUMBER FROM MEASURED DATA

EXPLANATORY INFORMATION

The absolute reflectance of each clean filter should be determined as well as that of the stained filter. 

Work performed by Dieck, et al, ―Aircraft Gas Turbine Smoke Measurement Uncertainty Using the 

SAE/EPA Method‖, Journal of Aircraft, Vol. 15, No. 4, April 1978, concluded that ―The major 

instrument-related source of error in SAE/EPA smoke measurement is clean-filter reflectance precision. It 

is a direct result of the variability in filter reflectance about the average value used‖. 

The backing material should be flat and provide equal pressure across the surface of the filter. 

4. REPORTING OF DATA TO THE CERTIFICATING AUTHORITY [Reserved]
CAEP/8-WP/80

2 B-28 Appendix B to the Report on Agenda Item 2

APPENDIX 3. INSTRUMENTATION AND

MEASUREMENT TECHNIQUES FOR GASEOUS EMISSIONS

1. INTRODUCTION

EXPLANATORY INFORMATION

The sampling and analysis procedures prescribed in ICAO Annex 16, Volume II, Second Edition, 1993 

were adopted from SAE Aerospace Recommended Practice ARP 1256, "Procedure for the Continuous 

Sampling and Measurement of Gaseous Emissions from Aircraft Turbine Engines". The calculation 

procedures were derived from ARP 1533  ̳Procedure for the Analysis and Evaluation of Gaseous 

Emissions from Aircraft Engines‖. ARP 1256 and ARP 1533 were developed and are maintained by SAE 

committee E-31, Aircraft Exhaust Emission Measurement.

2. DEFINITIONS [Reserved]

3. DATA REQUIRED 

3.1 Gaseous Emissions

a) Hydrocarbons (HC): a combined estimate of all hydrocarbon compounds present in the 

exhaust gas.

EXPLANATORY INFORMATION

Gas turbine engine exhaust gases typically contain a variety of hydrocarbon compounds. The specific 

compounds present and their relative concentrations are usually unknown. Flame Ionization Detectors, 

used to measure hydrocarbons, do not respond equally to all hydrocarbon compounds. Although this 

differential hydrocarbon response is to be held within specific bounds, the resulting measurement is an 

estimate of the hydrocarbon compounds present in the exhaust gas.

3.2 Other information [Reserved]

4. GENERAL ARRANGEMENT OF THE SYSTEM

EXPLANATORY INFORMATION

Water is a major product of combustion. Its removal upstream of the measuring instruments is attractive. 

Removal would minimize possible interference effects where the instrument responds to the water present 

as well as to the gas or vapour being measured. It would also prevent or minimize water condensing in the 

instruments which could cause erratic flow and/or contamination. In the worst case, the instrument would 

be rendered inoperable until thoroughly cleaned. However, devices which remove water are known to 
CAEP/8-WP/80

Appendix B to the Report on Agenda Item 2 2 B-29

remove hydrocarbons and oxides of nitrogen, and are therefore only permitted for CO and CO2

measurements. If the sample is dried, an appropriate dry/semi-dry to wet correction must be made.

For most aircraft gas turbine engines, and most engine running modes, supplemental pumps will be 

needed to meet the probe system pressure drop requirement (80 per cent at the probe entrance orifices), 

the sample line residence time and pressure drop, and the need to remove excess flow from the sampling 

system. Any pump used for the purpose of sample transfer must be heated. Usually, because of the sample 

gas physical properties and the need to maintain temperature and flow control within the Flame Ionization 

Detector used for hydrocarbon analysis, these instruments utilize internal heated, inert sample transfer 

pumps. The use of an upstream flow splitter to dump a portion of the sample is also an acceptable 

procedure to assist in controlling flow to the analytical sampling train.

If loss of hydrocarbons in the sampling system is a concern, the FID can be, when configured with a 

heated transfer pump, located upstream of the system hot pump as close as physical constraints will allow 

(e.g. temperature, noise, vibration). The necessity for a dump and/or a hot-sample pump will depend on 

the ability to meet the sample transfer time and analysis sub-system sample flow rate requirements. This 

in turn depends on the exhaust sample driving pressure and line losses. Therefore, in general, the size and 

location of the pumps, and the associated flow control devices, are determined from the particular 

sampling system configuration.

5. DESCRIPTION OF COMPONENT PARTS

5.1 Sampling system

5.1.1 Sampling probe

a) The probe material with which the exhaust emission sample is in contact shall be stainless 

steel or any other non-reactive material.

b) If a probe with multiple sample orifices is used, all sampling orifices shall be of equal 

diameter. ...

EQUIVALENT PROCEDURES

Stainless steel is the preferred probe material but other non-reacting materials may be more suitable under 

specific circumstances, e.g. engine exhaust temperatures which exceed the physical specification limits of 

stainless steel. Inconel 625 and Nimonic 75 alloys have previously been accepted as a non-reactive probe 

material in the context of the regulated species. Other materials may be suitable but need to be approved 

by the certificating authority.

EXPLANATORY INFORMATION

A probe design with multiple orifices (mixing probe) could include either several sampling orifices 

leading into a single plenum, or several sampling orifices leading into individual sample lines which are 

mixed external to the probe, as shown in Figure App.3-1. The sampling orifices should be equal in size 

and located on centres of equal area for all mixing probes. If a multi-armed probe is used, then there 

should be an equal number of orifices on each arm. Considerations for probe design leading to these 
CAEP/8-WP/80

2 B-30 Appendix B to the Report on Agenda Item 2

criteria can be found in ―Gas/Turbine Emission Probe Factors‖, SAE Aerospace Information Report 

AIR4068A, 1996.The most common configuration is that of cruciform with individual orifices located on 

centres of equal area.

b) ... The probe design shall be such that at least 80 per cent of the pressure drop through the 

probe assembly is taken at the orifices.

EXPLANATORY INFORMATION

The pressure drop is needed to isokinetically sample flows at the different orifices. The orifice is 

supposed to be the minimum area right at the probe entrance. To achieve the pressure drop criterion, there 

must be a rapid expansion into the sampling tube. 

The pressure drop refers to the dynamic head, not the total pressure, and is needed to ensure that each 

orifice takes a flow rate that is proportional to the dynamic head present at the sampling orifice. Thus, 

when the samples taken by the individual sampling orifices are mixed together within the probe, the total 

sample is representative of the mass flux of emissions through the engine exhaust sampling plane.

0.8

0

0 ( )







t sout

s n i

t

P p

P p o

t sout s n i

Pt  p o  P0  p 0 ( )0.8

Figure App.3-1. Sampling probe designs

c) The number of locations sampled shall not be less than 12.

5mm

Pt0

Ps(n°i)

Psout

Averaging

of individual samplings

Multi-hole non mixing probe Mixing at the probe exit (before entering the line) Multi-hole mixing probe

(Mixing in the probe)

Pt0

Ps(n°i)

Psout

5mm

Pt0

Ps(n°i)

Psout

Averaging

of individual samplings

Multi-hole non mixing probe Mixing at the probe exit (before entering the line) Multi-hole mixing probe

(Mixing in the probe)

Pt0

Ps(n°i)

Psout
CAEP/8-WP/80

Appendix B to the Report on Agenda Item 2 2 B-31

EXPLANATORY INFORMATION

While 12 orifices is the minimum number for a sampling rake in Annex 16, Volume II, a more 

appropriate number would be 20 when validated by means of a detailed traverse. 

d) The sampling plane shall be as close to the engine exhaust nozzle exit plane as permitted by 

considerations of engine performance but in any case shall be within 0.5 nozzle diameter of 

the exit plane.

EXPLANATORY INFORMATION

Further guidance on the issue of ―Exhaust Nozzle‖ is available under the Definitions in Part 1, Chapter 1.

e) The applicant shall provide evidence to the certificating authority, by means of detailed 

traverses, that the proposed probe design and position does provide a representative sample 

for each prescribed thrust setting.

EXPLANATORY INFORMATION

Detailed traverse measurements, although expensive, could be performed with a single hole probe which 

measures stabilized concentrations at various positions. These individual measurements will then be used 

to derive average values and demonstrate representative sampling. The carbon balance check is also 

derived in the same way. The ―80 per cent pressure drop‖ condition which has been introduced in the past 

to guarantee the sample is representative, is no more justified for the purpose of a single hole probe.

TECHNICAL PROCEDURE

There is no standard definition of a ―representative sample‖ for emissions from aircraft gas turbine 

engines, nor is there a specification for ―detailed traverse‖. ―Representative‖ and ―detailed‖ are, in this 

instance, matters of opinion to be negotiated between the manufacturer and the certificating authority. 

The issue is to do with how much the measured averaged sample can deviate from the true sample mean 

before it is no longer considered to be representative. The most commonly used definition, arrived at from 

decades of testing and collaborative analytical exercises by user groups, is 10 per cent for engine modes 

above idle (i.e., approach, decent, climb and take-off), and ±15 per cent for idle, as per the carbon balance 

check in section 6.4 of Appendix 3. There is a significant difference however. For the carbon balance 

check a comparison is made between sets of independently related measured values. With knowledge 

about the combustion process and the hydrogen to carbon ratio of the fuel used, an estimate can be made 

from the measured carbon containing species, most of which is CO2, of the engine average fuel to air 

ratio. The actual engine fuel to air ratio can be independently arrived at from measured fuel and airflow. 

These two values can be compared to provide an estimate of how well the exhaust stream was sampled 

for carbon containing compounds. However, as CO2 far outweighs the influence of any other carbon 

bearing species in the calculation of fuel to air ratios, the spatial variability of CO2 will determine how 

many sampling points are required and how these sampling points should be distributed. CO2 has been 

found to consistently exhibit the least variability of all the species of interest, which include CO, HC, 
CAEP/8-WP/80

2 B-32 Appendix B to the Report on Agenda Item 2

NOX and smoke. This suggests that it would be possible to meet the 10 and 15 per cent criteria for carbon 

balance without having obtained a representative sample, using the same 10 and 15 per cent criteria, of 

the other species. In other words, obtaining a carbon balance, while a necessary pre-condition for a 

representative sample, could not be considered to be a sufficient demonstration of representative sampling 

on its own. 

Historically engine manufacturers, or testing agencies, have addressed this problem in different ways. 

Recognizing that gas turbine engines are predominately axi-symmetric, one acceptable method (for fixed 

rake designs) has been to sample the exhaust plume, point by point, with a sufficient number of points to 

be able to estimate, by statistical means, the true engine average species concentration for each of the 

species of interest. Engine exhaust species seem almost normally (Gaussian) distributed, thus making 

simple statistical tools acceptable. Using these sampling points, and the measured concentration values 

for each of the species of interest, contour plots of constant concentration (isopleths) have been 

analytically generated at each power setting tested. There are a number of computer programs available 

for workstations or desktop computers to do this. A probe or rake design is then overlaid on the contour 

plots in order to estimate the average probe/rake values and compare to the estimated true average arrived 

at from the detailed traverse. If the comparisons match the carbon balance criteria, within 10 per cent for 

engine powers above idle and ±15 per cent at idle, the probe/rake can be considered to provide 

representative sampling. This process may have to be repeated several times before an acceptable design 

is found.

EQUIVALENT PROCEDURE

When applying this analytical technique, for core flow only, multi-orifice rake designs which have proven 

most robust seem to have four sampling arms spaced 90 degrees apart with sampling orifices located on 

centres of equal area. The sampling orifices are equally distributed across the sampling arms and the 

contour analysis will determine the minimum number of sampling ports necessary to yield a 

representative sample. 

A detailed traverse was not required for rotating rake designs as they provide, in normal use, as many or 

more sampling points than the typical single point traverse thus ensuring a representative sample. 

However, in order to demonstrate that a fixed rake design is orientated in the right position to collect a 

representative sample, traverse measurements were necessary. The detail (single point, number of rake 

orientations, number of different power settings) of traverse measurements may depend on the number of 

sampling orifices on the rake and existing experience of similar engines or derivatives. These rake design 

requirements were recognized as being complemented by the system check performed in the carbon 

balance criteria. Where a sample has low EIs and relatively large ―per cent‖ variations between the 

detailed traverse and the fixed rake measurements, it could be accepted as representative without having 

demonstrated NOX, CO and HC to be within 10 per cent (15 per cent for idle) as long as there is a 

sufficient large number of orifices and an AFR match within 10 per cent (15 per cent at idle).

All data used in arriving at a probe/rake design should be made available to the certificating authority.

5.1.2 Sampling lines [Reserved]

5.2 HC Analyser [Reserved]
CAEP/8-WP/80

Appendix B to the Report on Agenda Item 2 2 B-33

5.3 CO and CO2 analysers [Reserved]

5.4 NOX analysers [Reserved]

6. GENERAL TEST PROCEDURES

6.1 Engine operation [Reserved]

6.2 Major instrument calibration [Reserved]

6.3 Operation [Reserved]

6.4 Carbon balance check [Reserved]

7. CALCULATIONS

TECHNICAL PROCEDURE

This technical procedure provides guidance on the processing of measured data from an emissions 

certification test in the form of a simplified worked example.

Definitions:

Reference engine – For this example, the emissions certification values are calculated based on 

combustor inlet conditions (T3, P3, and fuel flow) from a validated engine performance model. 

Test engine(s) – Recommended practice is to use an engine which conforms to the production build 

standard. If differences exist, these differences must be documented for approval by the 

certificating authorities. If any of these non-conformances are predicted to impact engine 

performance, gaseous emissions or smoke levels, then an explanation and quantification of the 

impacts will be provided to the certificating authorities for approval. Generally manufacturers 

will keep deviations from the production standard to a minimum. Measured emissions levels will 

be corrected to reference engine (production build standard) and standard day conditions. 

Detailed traverse – For a new engine type, the next step prior to the actual emission certification test 

is to conduct a detailed traverse of the engine exhaust to show that a representative sample is 

being obtained (further guidance in the ETM on detailed traverse see ETM Appendix 3, 5.1.1).

Emissions tests – Emissions are typically measured at more than the four required thrust levels 

(typically 8-16 conditions) between ground idle and maximum rated thrust.

Instrument calibration curves for the different analyzers may need to be established in order to translate 

instrument readings to calibrated concentration values. These gas concentrations will be recorded and 

emission indices will be calculated from that using the equations in 7.1.2 of the Annex 16 Vol. II. The 

following simple example shows how to derive EI(CO). Assuming the measured values all on a wet basis:

n/m = H/C = 2; 

CO = 500 ppm(v)wet = 0,0005; 
CAEP/8-WP/80

2 B-34 Appendix B to the Report on Agenda Item 2

HC = 800 ppm(v)wet = 0,0008; 

CO2 = 2,25% = 0,0225; 

NO2 = 20 ppm(v)wet = 0,00002;

hamb = 0,0025 volwater/voldryair

CxHy = CH4  x=1, y=4

The equation in 7.1.2 for EI(CO) would then read:

EI(CO) = (CO/(CO + CO2 + HC)) * (103* 28,011g / ( 12,011g + n/m* 1,008g) * (1 + (0,0003 * (P0/m)))

Where:

(P0/m) = (2*Z - n/m) = 2*Z – 2

Z = {2 – CO – (2/1 – 4/2*1) * HC + NO2}/ {CO + CO2 + HC}

 = 2 – 0,0005 – 0 * HC + 0,00002 = 1,99952

(P0/m) = 1,99904

Hence, from the equation above:

EI(CO) = (0,0005/0,0225+0,0005+0,0008) * (28011/(12,011 + 2,016)) * (1 + (0,0003*1,99904)) 

= 0,021008 * 1996,934483 * 1,000056

= 41,98 g/kgfuel

EI(HC) and EI(NOX) are calculated in a similar manner using the other two equations in 7.1.2. For 

EI(NOX) the NO2/NO converter efficiency must also be taken into account. EIs are calculated for each 

measurement point (thrust condition) and engine run. 

Attachment E of Appendix 3 contains a comprehensive and precise numerical method which is often used 

by engine manufacturers software programs. Further information is contained in SAE ARP 1533 

Procedure for the Analysis and Evaluation of Gaseous Emissions from Aircraft Engines which contains 

two fully worked examples of the Matrix method solving the combustion chemical equation. 

To correct these EIs from measured to reference engine and ambient conditions, a curve fitting technique 

is recommended. One acceptable alternative method of plotting measured test data is to plot the 

following:

EI(CO) * P3 v. T3

EI(HC) * P3 v. T3

EI(NOx) * P3 ^-0.5 * exp (19 [ hmass – 0.006 34 ] ) v. T3

A best fit of each of the data curves can then be obtained, typically using a polynomial function. In some 

cases, two curve fit equations are needed, one for low power data and one for high power data. When 

more than one engine test has been conducted on an engine, data may be plotted for each test run or a 

single correlation may be used for the multiple runs. However, if multiple engines are tested, a separate 

set of plots should be made for each test engine. 

The procedure for calculating the corrected EI(CO) at values of Fn corresponding to the four LTO 

operating modes includes the following steps (as shown in Figure A3.1) [Reserved]:
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Appendix B to the Report on Agenda Item 2 2 B-35

1. Use validated engine performance model to determine T3ref, P3ref and reference fuel flow 

2. Starting with T3ref, determine EI(CO) * P3 from the EI(CO) * P3 v. T3 curve

3. Divide by the corresponding P3ref to get: Corrected EI(CO) = EI(CO) * P3 / P3ref

Calculation of corrected EI(HC) follows exactly the same process as EI (CO), as does the calculation of 

corrected EI(NOx) except step 3 involves multiplying by P3ref ^ 0.5 rather than dividing by P3ref.

Once the Corrected EI(CO), EI(HC) and EI(NOx) have been calculated for each operating mode, Dp is 

calculated using the standard LTO times in mode and corresponding values of reference fuel flow from 

the validated engine performance model.

EI (CO) * P3 EI (HC) * P3

EI (NOx) * P3-0.5 * exp(19(hmass

-0.00634))

T3

T3

T3ref

P3ref

F00ref F00ref

100% Foo 

100% Foo

Example:

EI (CO)korr = EI (CO) * P3 / P3ref

Step 1

Step 2

Step 3

Step 4

From measured data From performance model

EI (CO) * P3 EI (HC) * P3

EI (NOx) * P3-0.5 * exp(19(hmass

-0.00634))

T3

T3

T3ref

P3ref

F00ref F00ref

100% Foo 

100% Foo

Example:

EI (CO)korr = EI (CO) * P3 / P3ref

Step 1

Step 2

Step 3

Step 4

From measured data From performance model

Figure A3.1 – Gaseous Emissions Calculation Procedure

7.1 Gaseous emissions [Reserved]

7.1.1 General [Reserved]

7.1.2 Basic Parameters [Reserved]
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2 B-36 Appendix B to the Report on Agenda Item 2

7.1.3 Correction of emissions indices to reference conditions [Reserved]

7.2 Control parameter functions [Reserved]

7.3 Exceptions to the proposed procedures [Reserved]

ATTACHMENT A TO APPENDIX 3. SPECIFICATION FOR HC ANALYSER

1. GENERAL

Precautions: The performance specifications indicated are generally for analyser full scale. Errors at part 

scale may be a significantly greater percentage of reading. The relevance and importance of such 

increases shall be considered when preparing to make measurements. If better performance is necessary, 

then appropriate precautions shall be taken.

EXPLANATORY INFORMATION

The performance specifications for these analyzers, given in terms of full scale response, can have a 

significant and adverse impact on part scale measurements. In extreme instances, concentrations of HC at 

high power, such as take-off, can differ from concentrations at idle by orders of magnitude. In general it is 

always good practice to use a multi-range instrument and to adjust ranges such as to keep the 

measurement in the upper 30 per cent of the instrument response range. Calibrations should be performed 

on each range used as required.

The instrument to be used shall be such as to maintain the temperature of the detector and samplehandling components at a set point temperature within the range 155°C to 165°C to a stability of ±2°C.

EXPLANATORY INFORMATION

ICAO Annex 16, Volume II previously (Amendment 6 and before) had a set point temperature within the 

range of 155oC to 165oC to a stability of +/- 2°C. This was adopted from SAE ARP1256, ―Procedure for 

the Continuous Sampling and Measurement of Gaseous Emissions From Aircraft Turbine Engines - 1971. 

ARP1256 specified this range to meet the need for minimising the condensation of hydrocarbons in the 

instrument and in recognition of the operating characteristics of then commercially available total 

hydrocarbon analysers (THAs). Since then the ARP has been revised, and now requires a single 

temperature set point of not less than 160oC but with no temperature stability requirement. Commercially 

available THAs have evolved and the more common detector housing temperatures approach 200oC. This 

increase in temperature does not effect the emissions certification measurements but does place an 

unnecessary constraint on the test procedure.

a) Total range: 0 to 5 000 ppmC in appropriate ranges.
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Appendix B to the Report on Agenda Item 2 2 B-37

EXPLANATORY INFORMATION

A total range of 0 to 5,000 ppmC, while appropriate for the engines in use when Annex 16, Volume II 

was published in 1981, is broader than needed for today's engines where concentrations are much lower. 

Appropriate instruments should be used to ensure best practice measurements in the upper 30 per cent of 

the range. Thus an instrument with a range upper limit of 5000ppmC may not be necessary and may, in 

fact, negatively affect the ability to ensure suitable range span due to instrument design limitations.

b) Resolution: better than 0.5 per cent of full scale of range used or 0.5 ppmC, whichever is 

greater. [Reserved]

c) Repeatability: better than ±1 per cent of full scale of range used. or ±0.5 ppmC, whichever is 

greater. [Reserved]

d) Stability: better than ±2 per cent of full scale of range used or ±l.0 ppmC, whichever is 

greater, in a period of 1 hour.

EXPLANATORY INFORMATION

Stability, taken to be span stability and sometimes referred to as repeatability or reproducibility, is the 

maximum variation in instrument output over a specified time period and within specified environmental 

conditions when identical concentration samples, near FSD, are passed through the instrument and after 

zero corrections have been made. Stability is the sum of time dependent drift, i.e. the change in output 

under invariant laboratory conditions, and changes in output due to other factors such as environmental 

temperature and/or variations in FID enclosure temperature. Stability is highly dependent on how, and 

under what environmental conditions the analyzer is used. As such it is out of their control and they 

choose to specify a value for time dependent drift along with a range of environmental temperatures, i.e., 

basically under laboratory conditions. Due to improvement of instruments using solid state electronics the 

drift specifications from modern THC Analysers quote better drift performance (<1 per cent FS over 

eight hours in laboratory conditions) than the stability requirements of the standard. Errors associated 

with this factor are small to negligible. As measurements are not taken under laboratory condition and as 

changes in environmental conditions are the norm rather than the exception operational procedures, as 

described in 6.3.2 d) of Appendix 3 are required.
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2 B-38 Appendix B to the Report on Agenda Item 2

e) Zero drift: less than ±1 per cent of full scale of range used or ±0.5 ppmC, whichever is greater, 

in a period of 1 hour. [Reserved]

f) Noise: 0.5 Hz and greater, less than ±1 per cent of full scale of range used or ±0.5 ppmC, 

whichever is greater, in a period of 1 hour.

EXPLANATORY INFORMATION

The FID requires fuel and oxidant gases for operation. The fuel gas is typically either a mixture of 

hydrogen/nitrogen, or hydrogen/helium. If the noise specification cannot be met, and a hydrogen/nitrogen 

mixture is being used as the fuel gas, it can be helpful to change to a hydrogen/helium mixture.

g) Response time: shall not exceed 10 seconds from inlet of the sample to the analysis system, to 

the achievement of 90 per cent of the final reading. [Reserved]

h) Linearity: response with propane in air shall be linear for each range within ±2 per cent of 

full scale, otherwise calibration corrections shall be used.[Reserved]

2. SYNERGISTIC EFFECTS

Oxygen response: measure the response with two blends of propane, at approximately 500 ppmC 

concentration known to a relative accuracy of ±1 per cent, as follows:

1) propane in 10 ±1 per cent O2, balance N2

2) propane in 21 ±1 per cent O2, balance N2

If R1 and R2 are the respective normalized responses then (R1 - R2) shall be less than 3 per cent of R1.

EXPLANATORY INFORMATION

The typical range of O2 concentrations in the core exhaust gas is 18 per cent at idle to 15 per cent at 

take-off. The specification for a response of <3 per cent between samples of 10 per cent and 21 per cent is 

conservative and effectively limits the differential response to <1 per cent over the range of interest. If 

needed the O2 response can be minimized by adjusting the FID burner fuel/air ratio.
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Appendix B to the Report on Agenda Item 2 2 B-39

Differential hydrocarbon response: measure the response with four blends of different hydrocarbons in 

air, at concentrations of approximately 500 ppmC, known to a relative accuracy of ±1 per cent, as 

follows:

a) propane in zero air

b) propylene in zero air

c) toluene in zero air

d) n-hexane in zero air.

If Ra, Rb, Rc and Rd are, respectively, the normalized responses (with respect to propane), then (Ra – Rb), 

(Ra – Rc) and (Ra – Rd) shall each be less than 5 per cent of Ra.

EXPLANATORY INFORMATION

While the FID response is assumed to respond in a manner proportional to carbon number, it does vary 

somewhat with the particular hydrocarbon or class of hydrocarbons being measured. For example, three 

molecules of methane (CH4) will not necessarily result in the same instrument response as one molecule 

of propane (C3H8). Due to this differential response, it is useful to think of the FID as responding to an 

―effective‖ carbon number. It is important that the instrument responses are acceptable for all of the 

hydrocarbons in the engine exhaust. The group of hydrocarbons (propylene, toluene, and n-hexane), with 

propane as a reference, was chosen to represent, in terms of differential response, the range of 

hydrocarbons expected in the engine exhaust.

3. OPTIMIZATION OF DETECTOR RESPONSE AND ALIGNMENT

3.1 The manufacturer‘s instructions for initial setting up procedures and ancillary services and supplies 

required shall be implemented, and the instrument allowed to stabilize. All setting adjustments shall 

involve iterative zero checking, and correction as necessary. Using as sample a mixture of approximately 

500 ppmC of propane in air, the response characteristics for variations first in fuel flow and then, near an 

optimum fuel flow, for variations in dilution air flow to select its optimum shall be determined. The 

oxygen and differential hydrocarbon responses shall then be determined as indicated above.

EXPLANATORY INFORMATION

The FID detector response and alignment can be optimized by adjusting the FID burner fuel and air flow 

while sampling a mixture containing approximately 500 ppmC propane. Care should be taken when 

changing fuel flow that the instrument zero does not shift. If it does, the instrument zero should be reset. 

Response curves illustrating this process are shown in Figures A3-3 and A3-4, and were taken from SAE 

ARP1256, "Procedure for the Continuous Sampling and Measurement of Gaseous Emissions from 

Aircraft Turbine Engines".
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2 B-40 Appendix B to the Report on Agenda Item 2

Figure A3-3 Typical Fuel Flow Response Curve

Figure A3-4 Typical Airflow Response Curve

The objective of this procedure is to select operating flow rates which will give near maximum 

response with least variation for minor fuel flow variations. It may be necessary to repeat this 

operation in an iterative fashion:

• Adjust the fuel flow to maximize output;

• Adjust zero if necessary;

• Adjust the air flow to maximize output;

• Readjust the fuel flow, if necessary; and
CAEP/8-WP/80

Appendix B to the Report on Agenda Item 2 2 B-41

• Repeat until the burner output is optimized.

APPENDIX 4. SPECIFICATION FOR FUEL

TO BE USED IN AIRCRAFT TURBINE ENGINE EMISSION TESTING

The fuel used during tests shall meet the specifications of this Appendix 4, unless a deviation and any 

necessary corrections have been agreed by the certificating authority. 

Additives used for the purpose of smoke suppression (such as organo-metallic compounds) shall not 

be present.

EQUIVALENT PROCEDURE 

Appropriate evidence should be provided to the certificating authority to substantiate any deviation from 

the fuel specification of Appendix 4 as early as possible. 

A deviation may be accepted when it can be shown that the locally available fuel does not meet the 

specification. In such a case, use of the available fuel may be acceptable, subject to the substantiation of 

corrections to compensate for the effect of the deviation on the measured emissions levels. The measured 

data should then be corrected to reflect the limiting values of the fuel specification of Appendix 4. 

Corrections will normally be accepted when the magnitude of the correction to the measured data is small 

in relation to the margin to the certification limits. 

The corrections to the declared emission levels resulting from the deviation in test fuel properties should 

be based upon engine or rig test data which can be related to the specific combustor type, supported by 

validated analysis where necessary. The corrections would need to be conservative, particularly when test 

data is not available for the specific combustor type being certificated. Manufacturers should avoid use of 

fuels that have been heavily hydro-treated, or produced using synthetic processes. 

The deviations from the fuel specification, and the associated corrections, require the agreement of the 

certificating authority.

APPENDIX 5. INSTRUMENTATION AND MEASUREMENT TECHNIQUES

FOR GASEOUS EMISSIONS FROM AFTERBURNING GAS TURBINE ENGINES

[Reserved]

APPENDIX 6. COMPLIANCE PROCEDURES

FOR GASEOUS EMISSIONS AND SMOKE

[Reserved]

— — — — — — — —

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Appendix C to the Report on Agenda Item 2 2 C-1

APPENDIX C

Amendment to Doc 9889 

New Chapters on Dispersion Modeling and Ambient Measurements, 

and Revised Aircraft and Road Vehicle Emissions Inventory Chapters for the 

Airport Air Quality Guidance Manual
2 C-2

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Appendix C to the Report on Agenda Item 2

Appendix 1

Airport Air Quality – Chapter 2 Emissions Inventory

Chapter 2

EMISSIONS INVENTORY

Annex 1

AIRCRAFT EMISSIONS

Table of Contents

A1.1 Introduction

A1.2 Aircraft Engine Emission Certification

A1.3 Aircraft Operational Flight Cycle

A1.4 Aircraft Emission Calculation Approaches

A1.5 Aircraft Fleet and Movements

A1.6 Aircraft Main Engine Emission Calculations

A1.7 Auxiliary Power Units Emissions

Appendix A Example ICAO Engine Emissions Datasheet

Appendix B Simplified Aircraft Emission Indices

Appendix C Definition of Publicly Available Databases for Use in the Matching Aircraft Type 

with Engine Type

Appendix D First Order Approximation v3.0 Method for Estimating PM Emissions from 

Aircraft Engines
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Appendix C to the Report on Agenda Item 2 2 C-3

A1.1 Introduction

A1.1.1 Aircraft main engines may, at times, receive the most amount of attention from those 

parties concerned with aviation emissions as they can be the dominant airport-related source. This 

chapter recommends methodologies for the estimation of aircraft engine emissions. Main engines 

are those used to propel the aircraft forward. Other on-board engines include APU that provide 

electrical power and pneumatic bleed air when the aircraft is taxiing or parked at the gate and no 

alternative is available. Fuel venting from aircraft fuel tanks is not allowed and therefore is not 

addressed as an emission source.

A1.1.2 Main engines are generally classified as either gas turbine turbofan (sometimes 

referred to as turbojet) and turboprop engines fuelled with aviation kerosene (also referred to as 

jet fuel) and internal combustion piston engines fuelled with aviation gasoline.

A1.1.4 Main Engine Emissions in the Vicinity of Airports

A1.1.5 Emissions from an individual aircraft main engine combination are primarily a 

function of three parameters: Time-in-mode (TIM), main engine emission indices (EI), and main 

engine fuel flows. Aggregate emissions from a fleet serving an airport also include two additional 

parameters; fleet size/type and number of operations. In the calculation of aircraft emissions at a 

given airport, the desired accuracy of the emissions inventory will dictate the values and 

methodology (e.g., Simple, Advanced, or Sophisticated approach) used for determining each of 

these parameters. While this document tries to simplify the inventory analysis into three

approaches, it is generally agreed that the user may at times use a hybrid approach, combining 

elements from the simple, advanced and sophisticated approaches. However, care should be 

taken not to use a hybrid approach where all aspects are over-estimated thereby inadvertently 

assigning a higher burden to aircraft emissions when assessing airport inventories. Consequently, 

it is recommended that the analyst fully document the analysis methodology including how the 

guidance document is used. This is discussed further in the ―Emissions Calculation Approaches‖ 

Section A1.4. The following information provides basic descriptions of each of these parameters:

A1.1.6 Time-in-mode (TIM) is the time period, usually measured in minutes, that the aircraft 

engines actually spends at an identified power setting; typically pertaining to one of the LTO 

operating modes of the operational flight cycle.

A1.1.7 Emission Index (EI) and Fuel Flow: An emission index is defined as the mass of 

pollutant emitted per unit mass of fuel burned for a specified engine. The ICAO Engine 

Emissions Databank provides the EI for certified engines in units of grams of pollutant per 

kilogram of fuel (g/kg) for NOx, CO, and HC, as well as the mode-specific fuel flow in units of 

kilogram per second (kg/s), for the four power settings of the engine emissions certification 

scheme. Multiplying the mode-specific EI by the TIM-specific fuel flow yields a mode-specific 

emission rate in units of grams per LTO. For more accurate inventories, adjustments are 

necessary to these values to take account of, for instance, different power settings, installation 

effects, etc.

A1.2 Emissions Certification LTO Cycle

A1.2.1 For emissions certification purposes, ICAO has defined a specific reference LTO 

cycle below a height of 915 meters (3,000 feet) AGL1, in conjunction with its internationally 

 

1 AGL: In an emissions inventory study 3000ft Above Ground Level would be referred to the elevation of chosen 

reference point used in the study. E.g. Elevation AMSL of the ARP. 
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Appendix C to the Report on Agenda Item 2

agreed certification test, measurement procedures and limits (see ICAO Annex 16 Volume II for 

additional information).

A1.2.2 This cycle consists of four modal phases chosen to represent approach, taxi/idle, takeoff and climb and is a much simplified version of the operational flight cycle. An example of its 

simplification is that it assumes that operation at take-off power abruptly changes to climb power 

at the end of the take-off roll and that this is maintained unchanged up to 3,000 feet. Whilst not 

capturing the detail and variations that occur in actual operations, the emissions certification LTO 

cycle was designed as a reference cycle for the purpose of technology comparison and repeatedly 

has been reaffirmed as adequate and appropriate for this purpose.

Operating phase Time-in-mode

(minutes)

Thrust setting

(percentage of

rated thrust)

Approach 4.0 30

Taxi and ground idle (in) 7.0 7

Taxi and ground idle (out) 19.0 7

Take-off 0.7 100

Climb 2.2 85

A1.2.3 This reference emissions LTO cycle is intended to address aircraft operations below 

the atmospheric mixing height or inversion layer. Whilst the actual mixing height can vary from 

location to location, on average it extends to a height of approximately 915 meters (3,000 feet), 

the height used in deriving airborne times-in-mode. Pollutants emitted below the mixing height 

can potentially have an effect on local air quality concentrations, with those emitted closer to the 

ground having possibly greater effects on ground level concentrations.2

A1.2.4 The certification LTO cycle characteristics selected were derived from surveys in the 

1970s. They reflected peak traffic operations (i.e. typical adverse conditions), rather than average 

LTO operations. The justification for using these for aircraft emission standards was largely 

based on protecting air quality in and around large metropolitan air terminals during high 

operational or adverse meteorological conditions. 

A1.2.5 It was recognized that even for aircraft of the same type there were large variations in 

actual operating times and power settings between different international airports, and even at a 

single airport there could be significant variations day-to-day or throughout a single day. 

However the use of a fixed LTO cycle provided a constant frame of reference from which 

differences in engine emissions performance could be compared.

A1.2.6 Thus, the reference emissions LTO cycle is of necessity an artificial model that is 

subject to many discrepancies when compared to real world conditions at different airports. It was 

 

2

ICAO recognizes that different States may have different standards or thresholds for designating whether a pollutant 

as emitted has a local effect. In many cases, this is expressed in terms of a maximum altitude up to which a particular 

pollutant is emitted. Some States may specify a specific altitude for such purposes. Others may direct that modeling 

be undertaken to identify the altitude at which pollutants may have local effect in a particular area. This is often 

referred to as the ―mixing height‖ within the atmospheric ―boundary layer.‖ In basic terms, the ―mixing height‖ is the 

height of the vertical mixing of the lower troposphere. Also in basic terms, the ―boundary layer‖ is that part of the 

troposphere that is directly influenced by the presence of the earth's surface. States that specify a mixing height is 

determined for purposes of local air quality assessment typically have accepted models for such analyses and/or 

specify a default height for the mixing height, such as 3,000 feet.
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Appendix C to the Report on Agenda Item 2 2 C-5

designed as a reference cycle for the purpose of certifying and demonstrating compliance to the 

emissions standards in effect.

A1.2.7 This LTO cycle, developed for certification purposes, may also be adequate for 

simple emissions inventory calculations. However, in light of its generic assumptions, use of this 

cycle typically would not reflect actual emissions. If more precise operations data are available, 

these data should be used instead to achieve a more accurate inventory.

A1.2.8 As stated elsewhere in the guidance, ICAO aircraft engine emissions standards cover 

emissions of CO, HC, NOx and smoke. They apply only to subsonic and supersonic aircraft 

turbojet and turbofan engines of thrust rating greater than or equal to 26.7 kN [Annex 16 Volume 

II – Aircraft Engine Emissions]. ICAO excluded small turbofan and turbojet engines (thrust rating 

less than 26.7 kN), turboprop, piston and turboshaft engines, APU and general aviation aircraft 

engines are omitted from ICAO standards on the grounds of the very large number of models, the 

uneconomic cost of compliance and small fuel usage compared to commercial jet aircraft.

A1.2.9 Emissions Certification Data

A1.2.10 Emissions certification testing is carried out on uninstalled engines in an instrumented 

and calibrated static test facility. Engine emissions and performance measurements are made at a 

large number of power settings (typically greater than ten) covering the whole range from idle to 

full power and not just at the prescribed four ICAO LTO modes. The measured data are corrected 

to reference engine performance conditions and reference atmospheric conditions of ISA at sea 

level and humidity of 0.00634 kg water/kg of air, using well established procedures (See ICAO 

Annex 16, Volume II for additional information).

A1.2.11 The ICAO engine emissions certification data for CO, HC, and NOx, together with 

associated fuel flow rates, are reported at a set of four reference power settings defined as ―takeoff‖, ―climb‖, ―approach‖, and ―taxi/ground idle‖, respectively and for prescribed times at each of 

these power settings (i.e., ―times-in-mode‖). However, smoke emissions are only required to be 

reported as a maximum value of smoke density, reported as smoke number (SN) for each engine, 

irrespective of the power setting (although for some certified engines, mode-specific smoke 

numbers have been reported). 

A1.2.12 The emissions certification values previously described are provided in the ICAO 

Engine Emissions Databank, both as individual engine datasheets and also as a spreadsheet 

containing the data for all certified engines for which manufacturers have made data available. 

This databank is publicly available on the worldwide web at www.caa.co.uk/srg/environmental 

and is periodically updated. An example of an Engine Emissions Datasheet is presented in 

Appendix A.

A1.3 Operational Flight Cycle Description

A1.3.1 The departure and arrival phases of an actual operational flight cycle for a commercial 

aircraft are more complex than the four modal phases (i.e., approach, taxi/idle, takeoff, and climb) 

used for ICAO certification purposes. Actual cycles employ various aircraft engine thrust 

settings, and the times at those settings are affected by factors such as aircraft type, airport and 

runway layout characteristics, and local meteorological conditions. However, there are a number 

of segments that are common to virtually all operational flight cycles. These are depicted in the 

following diagram (Figure A1-1) and described in the subsequent sections:
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Appendix C to the Report on Agenda Item 2

Figure A1-1 Operational Flight Cycle

A1.3.2 Departure

A. Engine start – It is normal to start the main engines prior to, or during, pushback from the 

aircraft gate/stand. Where aircraft do not require pushback, the main engines are started 

immediately prior to taxi.

B. Taxi to runway – Aircraft typically taxi out on all engines to the runway or holding area 

prior to entering the runway; though aircraft may taxi on fewer than all engines under 

some circumstances. Taxi-out is normally carried out at the idle/taxi power setting apart 

from brief bursts of power to overcome the initial inertia at the start of taxiing; or if 

necessary, to negotiate sharp turns.

C. Holding on ground – Where necessary, aircraft may be required to hold in a queue whilst 

awaiting clearance to enter the runway and taxi to the take-off position. Main engines are 

normally set to idle thrust with brief bursts of power to move into position.

D. Take-off roll to lift-off – The aircraft is accelerated along the runway to the 

predetermined rotation speed and the end of the take-off run, with the main engines set to 

take-off power. Operators rarely use full power for takeoff; rather, a pre-determined 

thrust setting is set at the beginning of the take-off roll. Operators use either de-rated 

take-off thrusts or, more often, reduced (e.g., flexible) thrust settings, which are 

determined by the aircraft actual take-off weight, runway length and prevailing 

meteorological factors. Throttle handling during the take-off run is sometimes staged in 

the early part, whereby the throttles are initially set to an intermediate position then a few 

seconds later are advanced to the predetermined take-off power setting.

E. Initial climb to power cutback – After leaving the ground, the undercarriage (i.e., wheels) 

of the aircraft is raised and the aircraft climbs at constant speed with the initial take-off 

power setting until the aircraft reaches the power cutback height (i.e., between 800 and 

1,500 feet agl) where the throttles are retarded.

F. Acceleration, clean-up and en-route climb – After the throttle cutback, the aircraft 

continues to climb at a thrust setting less than that used for take-off with flap/slat 

retraction following as the aircraft accelerates and reaches cruising altitude.

A1.3.3 Arrival
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Appendix C to the Report on Agenda Item 2 2 C-7

G. Final approach and flap extension – The stabilized final approach from the Final 

Approach Fix (FAF) follows a relatively predictable glide slope at low engine thrusts. 

Thrust settings are increased to counteract the additional drag as flaps and the 

undercarriage are lowered, whilst speed decreases towards the flare.

H. Flare, touchdown and landing roll – Throttles are normally retarded to idle during the 

flare and landing roll. This is followed by application of wheel brakes and (where 

appropriate) reverse thrust to slow down the aircraft on the runway.

I. Taxi from runway to parking stand/gate – Taxi-in from the runway is a similar process to 

taxi-out to the runway described above; however, operators may shut down one or more 

engines, as appropriate, during the taxi if the opportunity arises.

J. Engine shutdown – Remaining engines are shut down after the aircraft has stopped 

taxiing and power is available for onboard aircraft services.

A1.3.4 APU operation, for aircraft equipped with this equipment, is usually confined to 

periods when the aircraft is taxiing or stationary at the terminal. The APU is typically shut down 

just after main engine start-up and after landing, the APU is generally started when the aircraft is 

approaching the terminal area parking position. If one or more main engines are shut down during 

the taxi, it may also be necessary to start the APU during the taxi-in. A number of airports specify 

maximum APU running times, principally to limit noise in the terminal area.

A1.3.5 As contained within the following discussion, aircraft activity at an airport is 

quantified in terms of either LTO cycles or operations. An operation represents either a landing or 

a takeoff, and two operations can equal one LTO cycle (e.g., taxi out, take-off, a landing and taxi 

in).

A1.4 Emissions Calculation Approaches

A1.4.1 There are various approaches, or methodologies, to quantify aircraft emissions – each 

with a degree of accuracy and an inverse degree of uncertainty. 

A.1.4.2 This section covers three general approaches to quantifying aircraft engine emissions, 

with each still having several levels of complexity incorporated. Each approach may incorporate 

various options for certain parameters and contributing factors, depending in the availability of 

the data and information.

 Simple Approach is the least complicated approach, requires the minimum amount of 

data, and provides the highest level of uncertainty often resulting in an over estimate of 

aircraft emissions. It uses public information and data tables that are very easily available 

and requires a minimum amount of airport specific information.

This is the most basic approach for estimating aircraft engine emissions provided in the 

guidance. The only airport-specific data required are the number of aircraft movements 

(over a certain period such as a year) and the type of each aircraft involved in each 

movement (Option A) or some additional basic information on the engine used for each 

aircraft type (Option B).

This Simplified Approach should only be used as means of conducting an initial 

assessment of the aircraft engine emissions at an airport. For most pollutant species, the 

approach is generally conservative, meaning that the outcome will often overestimate the 

total level of aircraft engine emissions. However, for some emission species and less 

common aircraft, the resultant emissions may be underestimated. As such, it is unclear 
2 C-8

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Appendix C to the Report on Agenda Item 2

how accurately the Simple Approach accounts for actual aircraft engine emissions at a 

given airport. 

 Advanced Approach reflects an increased level of refinement regarding aircraft types, 

engine types, EI calculations and TIM. This approach requires specific airport related 

information or qualified assumptions which are still publicly available but may be more 

difficult to obtain. It reflects local conditions in incorporating some sort of performance 

calculation of the aircraft. These improvements result in a more accurate reflection of 

main engine emissions over the Simple Approach, yet the total emissions are still 

considered conservative. 

 Sophisticated Approach best reflects actual aircraft emissions. It is the most 

comprehensive approach, requires the maximum amount of data and provides the highest 

level of certainty. This Sophisticated Approach goes beyond LTO certification data and 

TIM and utilizes actual engine/aircraft operational performance data. Use of this 

approach requires a greater knowledge of aircraft and engine operations and in certain 

instances will require the use of proprietary data or data or models that are normally not 

available in the public domain and in most instances require the users to perform higher 

levels of analysis.

A1.4.3 The alternate methodologies afford a progressively higher degree of accuracy and an 

inverse degree of uncertainty. The purpose and need for quantifying aircraft emissions drive the 

level of accuracy needed in an inventory, which in turn, determines the appropriate methodology. 

A secondary factor is data availability. Although an analysis may warrant a high degree of 

accuracy, it may not be possible for certain elements of the analysis due to lack of available data. 

ICAO urges that if an emissions inventory involves policies that will affect aircraft operations at a 

particular airport, then the calculations should be based on the best data available, and the simple 

approach should not normally be used. Where further information on the aircraft operations at an 

airport is available, then a more advanced approach is more appropriate.

A1.4.4 It is also important to note that, although at its simplest level it may be possible for 

individuals to construct an emissions inventory, the advanced and sophisticated methods likely 

necessitate some form of collaboration with other aviation resources. For example, the identity of 

actual aircraft and engine types, realistic and accurate times in mode, and actual engine power 

settings used in the analysis requires data that is often difficult to obtain. In general, the more 

sophisticated the method, the greater the level of collaboration will be required.

A1.4.5 ICAO stresses the importance for airports and States to use the best data available when 

assembling an aircraft engine emissions inventory. The ICAO emission inventory methodologies 

increase in accuracy moving from the Simple to the Advanced and eventually to the Sophisticated 

Approach. ICAO recommends selecting an approach, or portions thereof, to reflect the desired, or 

required, fidelity of the results. The air quality practitioner can reference these approaches as 

ICAO Simple Approach, Advanced Approach, or Sophisticated Approach. It should also be noted 

that the methods can be combined and that just because a Simple Approach is used for one part of 

an inventory, does not preclude the use of more precise approaches from being employed for the 

remaining parts of the emissions inventory.

A1.4.6 The following table provides an overview of the calculation approaches. It lists each 

of the four primary parameters (e.g., fleet mix, movements, TIM and EI) along with other 

contributing factors. Also included are explanations of how each of these parameters are 

determined using the three approaches (e.g., Simple, Advanced, and Sophisticated).
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Appendix C to the Report on Agenda Item 2 2 C-9

Key 

Parameters

Simple Approach Advanced Approach Sophisticated 

Approach

Fleet

(aircraft/engine 

combinations) 

Identification of aircraft group 

types (e.g. all B737 or all 

A319/320/321)

Identification of aircraft and 

representative engine types (e.g. 

all A320 with 50% V2525 and 

50% CFM56-5B5P)

Actual aircraft 

type/subtype and 

engine 

combinations 

(by tail number 

and engine UID 

or similar) 

Movements Number of aircraft movements 

by aircraft type (according to 

look-up table), as defined in 

"Fleet" 

Number of aircraft movements by 

aircraft-engine combinations as 

defined in "Fleet"

Number of 

aircraft 

movements by 

aircraft tail 

number 

Emissions 

Calculation

Option A 

UNFCC Lookup table (no 

calculation)

Option B

Spreadsheet 

calculation

Performance based calculation, 

potentially reflecting additional 

parameters like forward speed, 

altitude, ambient conditions 

(model dependent).

Performance 

based with actual 

engine data 

(P3/T3) and 

including 

ambient 

conditions

Thrust Levels Option A

N/A

Option B

rated thrust 

Option A 

Average airport 

and/or aircraft 

group specific 

reduced thrust 

rate 

Option B

Performance 

model 

calculated 

rated reduced 

thrust 

Actual air carrier 

provided thrust

Time in Mode Option B 

ICAO 

Certification 

LTO 

Option A 

Modified times 

in mode (airport 

specific average 

or actual for one 

or several 

modes) 

Option B 

Performance 

model 

calculated time 

in mode. 

Movement based 

actual values for 

all modes

Fuel Flow Option B 

ICAO 

Certification 

Databank 

Values 

Option A

Derived from 

ICAO EEDB 

with thrust to 

fuel flow 

conversion 

model 

Option B

Derived from 

ICAO EEDB 

with 

performance 

model 

Refined values 

using actual 

performance and 

operational data 

derived from air 

carrier

Emission 

Indices

Option A 

UNFCC LTO 

Emission Mass 

by Aircraft 

Type 

Option B

ICAO 

Certification 

Databank 

Values 

Option A

Derived from 

ICAO EEDB 

and thrust level 

through BFFM2 

curve fitting 

method

Option B

Derived from 

ICAO EEDB 

through 

BFFM2 curve 

fitting method 

Refined values 

using actual 

performance and 

operational data 

derived from air 

carrier.

Start-up Not Considered Consider including - See Consider 
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Appendix C to the Report on Agenda Item 2

Emissions Sections A1.6.66 – A1.6.75 including - See 

Sections A1.6.66 

– A1.6.75

Engine 

deterioration

Do Not Consider - See Sections 

A1.6.56 – A1.6.65

Do Not Consider – See Sections 

A1.6.56 – A1.6.65

Do Not Consider 

– See Sections 

A1.6.56 –

A1.6.65 

TABLE 1

A1.4.7 When choosing an approach for creating an aircraft emission inventory, a mix of the 

various approaches and options can be selected. The choice is based upon the availability of data 

and information, as well as the required accuracy of the inventory. The various elements as listed 

and described in Annex 1.4.6 are to some degree independent of each other, i.e. not all "Option 

B" elements necessarily have to go together. 

A1.4.8 For logical and consistency reasons, the "Fleet" and "Movements" elements for each 

approach go together. The Simple Approach Option A as well cannot be mixed with other options 

or approaches; the same holds true for the Sophisticated Approach. The other elements (Simple 

Approach Option B and Advanced Options A and B) can be mixed.

A1.4.9 As a prelude to the details involved in each approach, ICAO wishes to establish the 

general concept within each method. In summary, the inventory starts with an individual 

aircraft/engine combination(s), and generally applies the operational and emission parameters in a 

two-step process, as follows:

Step One: Calculate emissions from a single aircraft/engine combination by summing the

emissions from all the operating modes which constitutes an LTO cycle, where emissions 

from a single mode could be expressed as:

Modal emissions for an aircraft/engine combination = TIM x fuel used (at the appropriate 

power) x EI (at the appropriate power) x number of engines

The emissions for the single LTO operational flight cycle are then a summation of the 

individual parts of the cycle. In more sophisticated methods, EI and fuel flows may not be 

constant throughout the time in mode.

Step Two: Calculate total emissions by summing over the entire range of aircraft/engine 

combinations and number of LTO cycles for the period required.

A1.5 Aircraft Fleet and Movements

A1.5.1 Aircraft fleet is a generic description to describe the various aircraft and engine 

combinations that serve an airport. In its simplest form, the aircraft fleet can be generally 

characterised according to descriptors such as, for example, heavy, large, small, turboprop, and 

piston. For aircraft emissions inventory purposes, however, it is typically necessary to identify 

fleets more accurately (for example, by aircraft type).

A1.5.2 Aircraft can be generically labelled according to manufacturer and model. For 

example, ―A320‖ is an Airbus model 320 or a ―B737‖ represents the Boeing 737, though it 

should be noted that a generic aircraft type may contain significant variations in engine 

technology and widely differing emissions characteristics between different types and their 

engine fits.

A1.5.3 A more descriptive labelling for an aircraft type would also include the series number 

for each model, such as B747-400 for a 400 series Boeing 747 aircraft. This helps to establish the 
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Appendix C to the Report on Agenda Item 2 2 C-11

size and technology used in the aircraft engine and is necessary for a more accurate emissions 

inventory.

A1.5.4 Finally, the most accurate representation of aircraft is to identify the aircraft model, 

and series along with the actual engines fitted on the aircraft and modifications that affect its 

emissions performance (e.g., B777-200IGW with GE90-85B engines with DAC II combustors). 

As the aircraft itself does not produce emissions, having detailed information on engines installed 

on the aircraft fleet is an essential component of an accurate emissions inventory.

A1.5.6 Simple Aircraft Fleet

A1.5.7 For the Simple Approach, the two primary elements of the aircraft fleet (e.g., aircraft 

and engine types) have been simplified in a list of the types of aircraft for which pre-calculated 

emission data is provided. For each aircraft, the engine type has been assumed to be the most 

common type of engine in operation internationally for that aircraft type3, and emissions from 

that engine type are reflected in the associated emission factors. Appendix B contains Table B-1 

which lists 52 aircraft and provides emission data for each of their engine types.4

A1.5.8 If the fleet servicing an airport includes aircraft that are not contained in Table B-1, 

then Table B-3 should be used to determine an appropriate generic aircraft. (Refer to the column 

headed ―IATA aircraft in group‖ to locate the aircraft type shown in the column headed ―Generic 

Aircraft Type‖.)

A1.5.9 If an aircraft is not contained in either Table B-1 or B-3, then it is recommended to 

use supplementary information such as weight, number of engines, size category, range, etc. to 

identify a suitable equivalent aircraft that is in Table B-1 or B-3, recognising that this will 

introduce additional assumptions that may affect the accuracy of any result. In the case of an 

airport primarily served by regional jets, business jets and/or turboprops, it is unlikely that the 

range of aircraft will yield a reliable result. In these cases, a more advanced method is 

recommended.

A1.5.10 Simple Aircraft Movements

A1.5.11 For the Simple Approach, it is necessary to know (or to have an estimate of) the 

number of aircraft movements or operations (e.g., LTO) and type of aircraft at an airport over a 

specified period (e.g. hour, day, month, or year).

A1.5.12 Most airports levy user charges for provision of facilities and services typically 

collected as a landing fee. In these cases airport operators have accurate records of landing 

 

3 As of 30 July 2004 emissions data for the B747-300 is based on proportioned emissions for the two most common 

engine types.

4 CAEP developed this data at the request of the UNFCCC in connection with UNFCCC guidelines for national 

greenhouse gas inventories, which are used for global emissions issues rather than local air quality. It therefore 

includes data for greenhouse gas emissions that are not relevant to local air quality. These may be disregarded for 

purposes of inventories assembled for local air quality assessments (though some locations may wish to inventory 

CO2 emissions for other purposes). The data included in this document was current at the time of writing. The 

UNFCCC will provide updates to this table on an on-going basis and the most current table should be used whenever 

possible [www.ipcc-nggip.igs.or.jp]. If using new data from the UNFCCC website, CH4 and NMVOC data will 

require summing in order to obtain a value for HC. Since the UNFCCC‘s main focus was on greenhouse gas 

emissions over the entire course of flight, the data for LTO emissions is based on ICAO certification standards, and 

therefore will not accurately reflect actual emissions in an operating setting. In most cases, use of the refinements 

discussed in the Advanced and Sophisticated Approaches will help to achieve a more accurate inventory for the 

relevant pollutants.
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movements; including the number of landings and the type of aircraft. Some airports also record 

the number of take-offs, although the landing records usually provide more reliable data. For this 

reason, at larger airports, published data on the annual aircraft movements is often available.

A1.5.13 An LTO cycle contains one landing and one take-off, and so the number of landings 

and takeoffs at an airport should be equal. The total number of either landings or takeoffs may be 

treated as the number of LTO. Any difference in the number of landings and the number of takeoffs will usually indicate an error in the records; if there is no explanation for this discrepancy, 

then the greater number should be used.

A1.5.14 If no data is available, it will be necessary to conduct a survey of the number of 

aircraft movements and the types of aircraft over a short- or medium-term period (e.g. one to six 

months), noting that there are normally seasonal differences in the number of movements at most 

airports.

A1.5.15 Advanced Aircraft Fleet

A1.5.16 Like the Simple Approach, the first step of the Advanced Approach is to quantify the 

aircraft operations or LTO by aircraft type and specific to the airport. Typically, this information 

can be obtained directly from airport records, thereby reflecting the most accurate form of this 

information. However, because no database is entirely accurate and changes due to aircraft engine 

fits, temporary intermixes, and other considerations over time can introduce inaccuracy, it is 

important to gather as much information as close to the source of the operation as is possible. If 

access to this information is not possible, then national traffic statistics can be accessed if 

available. Additional sources of data include air navigation service providers such as 

EUROCONTROL and the U.S. FAA, the internet and the other sources described in the 

paragraphs below. .

A1.5.17 The Advanced Approach then tries to match the various aircraft types operating at the 

study airport with the engines that are fitted to them. Airports typically have lists with aircraft 

type/engine combinations obtained from the carriers that service the airport. However, if this 

information is unavailable, States have access to several publicly available databases that enable 

the matching of aircraft types with specific engines. Annex 1 Appendix C describes these 

important databases that can assist practitioners in identifying the aircraft/engine combinations 

that characterize fleet mix at a particular airport.

A1.5.18 Other sources of information include the International Official Airline Guide (IOAG) 

Database which contains data that identifies the type of aircraft, carrier, and frequency of

scheduled flights. In addition, the IOAG lists scheduled passenger flights by participating airlines, 

which are updated on a monthly basis. IOAG provides the main components in determining the 

fleet mix at a specific airport such as airport, aircraft type, carrier, and frequency of aircraft 

arrivals and departures. However, the IOAG does not include unscheduled and charter flights, or 

general aviation flights including business jets. The IOAG covers the flights of all U.S. scheduled 

airlines and the majority of scheduled worldwide airlines. Specifically, Appendix C provides a 

description of the useful fields contained in the IOAG database. The most important IOAG 

airport-specific parameters are the flight number, aircraft type, carrier, and schedule when 

determining the number of operations at a specific airport.

A1.5.19 BACK‘s World Fleet Registration Database (BACK) contains additional airline fleet 

information such as all worldwide commercial aircraft currently in use and other various aircraft 

parameters (see Appendix C for a list of useful fields). For emissions inventory purposes, the 
CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2 2 C-13

most important parameters from the BACK database (or other similar databases) are the aircraft 

identifiers, tail number, engine model, number of engines, and aircraft type.

A1.5.20 Bucher & Company‘s JP Airline-Fleets International Database (JPFleets) is another 

publicly available database that provides aircraft type/engine combinations for major commercial 

airlines worldwide (see Appendix C for a list of useful data fields).

A1.5.21 Airline Service Quality Performance (ASQP) Database is available from the U.S. 

Department of Transportation‘s (U.S. DOT) Bureau of Transportation Statistics (BTS). This 

database consists of performance and flight data for approximately 20 of the largest U.S. carriers. 

Appendix C lists the useful fields in the ASQP database. The practitioner should note the ASQP 

database provides good coverage for the fleet flying in the U.S. and their associated markets 

abroad.

A1.5.22 Depending upon the reasons for assembling an emissions inventory, a different 

method of assigning engines to aircraft can be used. One approach is to identify the specific 

engines used for the aircraft operations. This is achieved by collecting aircraft type information, 

scheduled flight numbers, and arrival/departure data for a specific airport (e.g., using IOAG), then 

finding the specific engine types assigned to the identified aircraft using the available databases 

described above. If this degree of accuracy is not necessary, then an alternative approach can be 

used to estimate the engine.

A1.5.23 This alternative is based upon the popularity of engines within the worldwide fleet. If 

the data available does not allow the identification of specific aircraft-engine combinations at a 

particular airport, these might be estimated. One way of doing this is to extrapolate the 

information on aircraft-engine combinations from a larger fleet database, such as a worldwide 

fleet database. For example, if the reference database shows that X percent of the B777 in the 

worldwide fleet have Y engines, and then it might be assumed for purposes of an airport 

inventory that X percent of the B777 that operate into that airport have Y engines. States should 

be aware that a single aircraft type may be fitted with more than one type or subtype of engine, 

which in turn can have differing emissions characteristics, in an airline‘s worldwide inventory. 

For these cases, databases such as BACK, JPFleets, and others can be used to develop 

distributions of engines based on reported airline and aircraft categories.

A1.5.24 It should be remembered that no database is entirely accurate, and changes due to 

aircraft engine fits, temporary intermixes, cross-referencing between databases, and other 

considerations over time can introduce even greater levels of inaccuracy. It is therefore important 

to gather as much information as close to the source of the operation as is possible in order to 

minimise uncertainties.

A1.5.25 Advanced Aircraft Movements

A1.5.26 The requirements for aircraft movements needed for the Advanced Approach is nearly 

identical to the Simple Approach: it is necessary to know the number of aircraft movements or 

operations by type of aircraft and engine for the advanced approach. When the emissions for the 

single LTO are calculated for each aircraft/engine combination using the above inputs and 

equations, the total emissions are calculated by multiplying the single LTO emissions for each 

aircraft/engine by the corresponding number of movements and summing over the entire range of 

aircraft/engine combinations and movements for the period required.

A1.5.27 Sophisticated Aircraft Fleet and Movements
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A.1.5.28 In the sophisticated approach it is assumed that the modeller has the actual and 

accurate information on aircraft type and subtype, number and correct engine name and 

designation for every single movement available. The match between aircraft and engine is 

through the aircraft registration number in connection with the ICAO or similar engine UID 

(unique identification number). 

A.1.5.29 The total of the movements is derived from the actual movement information for each 

single aircraft serving the particular airport. Every movement (landing or take-off) is logged by 

the aircraft's registration number in order to provide the detailed engine information. So the 

number of movements for a specific aircraft type might include various numbers of this type but 

by varying aircraft registrations numbers.

A1.6 Aircraft Main Engine Emission Calculations 

A1.6.1 Fuel Flow and Emissions Indices

A1.6.2 Aircraft engines with rated power greater than 26.7 kN are emissions-certified by ICAO 

for emissions of NOx, CO, and HC and maximum SN, based upon the standardised LTO cycle as 

set out in ICAO Annex 16, Volume II and published originally in Document 9646-AN/943 

(1995) and website amendments. ICAO provides the emissions certification data on the 

worldwide web at www.caa.co.uk. Updates to the Aircraft Engine Emissions Databank are made 

as new engines are certified. An example of the ICAO Engine Emissions Databank can be found 

in Appendix A.

A1.6.3 When ICAO engine data are used to calculate aircraft emissions, it is important to 

select the pollutant measured average value and not the pollutant characteristic level, which also 

is reported in the ICAO databank. The characteristic level of a gaseous pollutant or smoke is 

derived for certification purposes and contains statistical coefficients corresponding to the 

number of engines tested.

A1.6.4 For the vast majority of commercial aircraft engines operated at major airports, fuel 

flow and EI values are reported in the ICAO Aircraft Engine Emissions Databank, at the four 

certification thrust settings. Aircraft engine EI are reported in grams of pollutant per kilogram of 

fuel consumed (g/kg) and the fuel flow rates for each mode are reported in kilograms per second 

(kg/s). The reported EI and fuel flow values are recommended by ICAO to be used to calculate 

emissions from main aircraft engines.

A1.6.5 There are other databases available that address EI and fuel flow information for 

aircraft engines that are not certified nor regulated by ICAO. The following are two of the 

primary non-ICAO databases.

A1.6.6 The Swedish Defence Research Agency (FOI) is the keeper of a database of EI for 

turboprop engines supplied by the manufacturers for the purposes of developing emissions 

inventories. Although the database is publicly available only through FOI, International 

Coordinating Council of Aerospace Industries Associations (ICCAIA) closely monitors who 

requests the use of the database to ensure the data is not misused. The FOI database is not 

endorsed by ICAO because the data are not certified and may have inaccuracies resulting 

primarily from the unregulated test methodologies. There is also a significant issue of an 

appropriate idle setting for turboprops. Therefore, whilst this data is not ICAO-certified aircraft 

engine emission data, this information is included in this guidance document recognizing that the 

FOI turboprop database may assist airports in conducting emission inventories. Currently, 

documentation of how the EI were derived and the types of turboprop engines is unavailable. 
CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2 2 C-15

Information about turboprop engines, suggested TIM and how to obtain the data from FOI can be 

found at http://www.foi.se/FOI/templates/Page____7070.aspx

A1.6.7 Switzerland‘s Federal Office of Civil Aviation (FOCA) has developed a 

methodology and a measurement system to obtain emissions data from piston-powered aircraft 

and helicopters. For these engine types, there is no requirement for emissions certification; hence 

the FOCA data is one of the few sources of data available for conducting emission inventories 

with respect to aircraft with these engines. However, the FOCA data has not been corroborated by 

ICAO, and is not endorsed by ICAO. Therefore, whilst this data is not ICAO-certified aircraft 

engine emission data, this information is included in this guidance document recognizing that 

FOCA data may assist airports in conducting emission inventories for certain aircraft for which 

they otherwise might not have any data sources. The reader is referred to FOCA website to obtain 

documentation of the emissions measurement system, the consistent measurement methodology, 

recommendations for the use of their data to conduct simple emission inventories using suggested 

TIM. All material is openly available for download at www.bazl.admin.ch  for specialists 

environment  aircraft engine emissions.

A1.6.8 Emission Calculations Simple Approach (A)

A1.6.9 Emissions Indices

A1.6.10 In the Simple Approach (Option A), the EI is replaced with an emissions factor (EF)5

and Table B-1 in Appendix B provides these emissions factors for five pollutant species for each 

of the listed aircraft. 

A1.6.11 The emissions factor is provided in terms of kg of each emission species per LTO 

cycle per aircraft. These have been calculated based on the representative engine type for each 

generic aircraft type and using ICAO TIM, thrust settings and other basic assumptions. Other 

assumptions are described in the notes in Table B-1 in Appendix B.

A1.6.12 Emissions Calculation

A1.6.13 For NOx, HC, CO, SO2 and CO2 there is a standard method for calculating aircraft 

engine emissions using the Simple Approach (Option A). For each aircraft type, multiply the 

number of LTO cycles of that aircraft (over the assessment period) by the emissions factor in 

Table B-1 for each of the pollutant species and then add up the values for all the aircraft to get the 

amount of total emissions (in kg) for each pollutant. See the following generic equation:

Emission of Species X =  ([Number of LTO cycles) x (Emissions Factor) Eq. 

A1-1

(in kg) All Aircraft of Aircraft Y for Species X

A1.6.14 Notably, this equation does not account for specific engine types, operational modes 

or TIM as it assumes that the conditions under study are the same or similar to the default data 

being used.

 

5 EI = Emission Index, expressed as g pollutant per kg fuel;

EF = Emission Factor, expressed as mass of pollutant per specified unit (e.g. aircraft)
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A1.6.15 If required for the inventory, a similar process is used for fuel consumption over the 

period under consideration using fuel consumption data in Table B-1:

Fuel consumption =  [Number of LTO cycles] x [Fuel Consumption] Eq. 

A1-2

(in kg) All Aircraft of Aircraft Y

A1.6.16 There is no provision for the calculation of PM emissions in the Simple Approach 

(Option A).

A1.6.17 Emission Calculation Simple Approach (B)

A1.6.18 Aircraft Time-in-mode

A1.6.19 As discussed previously, the reference TIM used as part of the ICAO engine 

emissions certification process (and contained in the ICAO Aircraft Engine Emissions Databank) 

are only appropriate for the engine certification process, and are not representative of actual TIM 

aircraft spend in real world operations (see Annex A1.2.1 through A1.2.8). Nonetheless, the 

ICAO default TIM can provide a conservative estimate of aircraft emissions at an airport when 

airport-specific taxi/ground idle TIM data or refined methods of estimating takeoff, climb, and 

approach times are not available. Sensitivity analyses conducted by CAEP determined that 

conducting an aircraft emissions inventory using the ICAO certification TIM (as well as the fuel 

flow and EI) normally yields an overestimation of total aircraft emissions across the entire LTO 

cycle. 

A1.6.20 While ICAO default TIM are applicable primarily to regulated engines, there may 

other default times in mode be available for other engine types (i.e. unregulated turbofan engines, 

turboprop engines, piston engines or helicopters). Sources for such information could include 

national aviation or environmental authorities.

A1.6.21 Emissions Calculation Methodology for NOx, CO, and HC

A1.6.22 Identification of the aircraft type will enable the determination of the number of 

engines and the appropriate engine models. In turn, the engine model will determine the proper EI 

to calculate aircraft emissions.

A1.6.23 To determine the NOx, CO, or HC emissions for a unique aircraft/engine 

combination, the following formula may be used. This method is repeated for each aircraft/engine 

type representing each TIM to establish a complete aircraft emissions inventory.

Ei j = ∑ (TIMjk*60) * (FFjk) * (EIjk) * (Nej) Eq. 

A1-3

where:

Eij = Total emissions of pollutant i (e.g., NOx, CO, or HC), in grams, produced by aircraft 

type j for one LTO cycle

Eijk = The emission index for pollutant i (e.g., NOx, CO, or HC), in grams per pollutant 

per kilogram of fuel (g/kg of fuel), in mode k (e.g., takeoff, climb out, idle and approach) 

for each engine used on aircraft type j

FFjk = Fuel flow for mode k (e.g., takeoff, climb out, idle and approach), in kilograms per 

second (kg/s), for each engine used on aircraft type j
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Appendix C to the Report on Agenda Item 2 2 C-17

TIMjk = Time-in-mode for mode k (e.g., idle, approach, climb out, and takeoff), in 

minutes, for aircraft type j

Nej = Number of engines used on aircraft type j

A1.6.24 If the actual measured TIM for one or more of the operating modes exists and is used, 

then the different flight phases have to be calculated separately and the total emissions for each 

species have to be summed to give the total emissions for each aircraft/engine type.

A1.6.25 ICAO does not have emissions certification standards for SOx. However, SOx 

emissions are a function of the quantity of sulphur in the fuel. The U.S. EPA conducted a survey 

of sulphur content for commercial aviation jet fuel, which resulted in a U.S. average of 1 gram 

per 1,000 grams of fuel consumed (EISOx = 1 g/kg of fuel). This average should not be relied 

upon where validated data is needed, but can be used to perform an emissions inventory of SOx 

emissions using the following equation:

Ek = ∑ (TIMk*60) * (Erk) * (Nek) Eq. 

A1-4

where:

Ek = Total emissions of SOx, in grams, produced by aircraft type k for one LTO cycle

Nek = Number of engines used on aircraft type k

Erk = 1 * (FFk)

where:

Erk = emission rate of total Sox in units of grams of Sox emitted per second per operational 

mode for aircraft k

FFk = the reported fuel flow by mode in kilograms per second (kg/s) per operational mode 

for each engine used on the aircraft type k.

A1.6.26 ICAO does not have emissions certification standards for PM emissions. However, 

CAEP has developed and approved the use of an interim First Order Approximation (FOA) 

method to estimate total PM emissions from certified aircraft engines. At the time of this 

document, FOA version 3 is the most up-to-date and is provided in Appendix D of this section. 

FOA3 provides expressions of volatile PM from fuel organics and sulphur content, as well as a 

relationship between SN and non-volatile PM mass. CAEP is committed to continually updating 

the interim FOA methodology as data and scientific advancements become available, until such 

time as it can be replaced by fully validated and verified measurement data. The FOA 

methodology is to be used for emissions inventory purposes only within the vicinity of airports. 

The FOA methodology should not be relied upon where accurate, validated data is required.

A1.6.27 Emission Calculation Advanced Approach (Options A and B) 

A1.6.28 The advanced emission calculation methods make use of performance models that 

take into account or model ambient and specific aircraft related operational information. As such, 

a number of additional information is needed that could be obtained more easily by the 

modeller from public sources. Such information can include the following: aircraft information 

(take-off mass, actual engine), airport information (airfield elevation, runway usage length), 

ambient information (wind speed and direction, turbulence, pressure, temperature, humidity) and 

operational information (destination, stand, runway, departure route, approach route and glide 

slope, APU usage). The actually needed information depends on the model used and may vary, 

also refer to Table 1 for additional guidance on what parameters to use..
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Appendix C to the Report on Agenda Item 2

A1.6.29 Thrust Levels

A1.6.30 While the certification LTO-cycle suggests specific thrust settings for each mode, any 

operational LTO-cycle may have different modes with more individual power settings (cf. A1.3). 

Specifically, take-off thrust is often less than the certification 100% for performance and costefficiency reasons. Aircraft are more and more operated using flexible thrust rates, sometimes in 

combination with derated thrust options. This could apply to the take-off phase of a flight as well 

as to other flight phases in the landing and take-off cycle. 

A1.6.31 As an option A, an airport average and/or aircraft group specific reduced thrust level 

may be available for primarily the take-off phase, but may also be available for other modes. 

Such information could stem from empirical data, for example, from one aircraft operator, and be 

extrapolated over the total of the operations. 

A1.6.32 In option B, a dedicated aircraft performance model should be utilised that gives an 

operational thrust level using additional, publicly available parameters unique to the model. The 

thrust level could be modelled for take-off only or for all modes in the LTO-cycle. 

A1.6.33 Time in Mode

A1.6.34 As an option A, airports are encouraged to take measurements of the typical taxi 

times unique to the airport's taxiway structure for both taxi-in from runway to the terminal and 

vice versa for taxi-out times, including possible queuing times at departure runways. Using the 

measured taxi time values for the study airport can better reflect emissions for the taxi/idle mode 

of the LTO cycle. Such data could be obtained from e.g. touch-down, on-block, off-block and 

take-off times for either all possible stand/runway combinations or as an airport default.

A1.6.35 As an option B, times in mode could also be modelled for other than just the taxi 

mode. This option would most likely include an aircraft performance modelling approach, giving 

aircraft group or even aircraft type individual times in mode for those modes considered in the 

approach (e.g. more than just the 4 ICAO certification modes).

A1.6.36 Fuel Flow

A1.6.37 For Option A, a relationship has been developed that uses the certification fuel flow 

and thrust data from the ICAO Engine Emissions Databank to determine fuel flow at any thrust 

level desired between 60% and 100%. Note. The thrust levels are % of rated output thrust and 

represent the thrust selected by the pilot. They do not represent the actual thrust delivered by the 

engine (corrected net thrust). This methodology allows for accurate calculation of fuel flow at 

reduced take-off thrust levels which in some instances could be as low as 60% of rated thrust. 

From this fuel flow, corresponding emissions indices can be calculated using the BFFM2 curve 

fitting methodology. A twin quadratic methodology has been developed, and it is described 

below;

A1.6.38 The Twin Quadratic method comprises calculation of fuel flow vs thrust, for thrusts 

above 60% maximum rated thrust. The fuel flow and thrust data required to define the two curves 

is available in the ICAO Engine Emissions databank for certificated engines. The methodology is 

as follows:
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Appendix C to the Report on Agenda Item 2 2 C-19

60% to 85% thrust: defined by a quadratic equation based on the 7%, 30% and

85% thrust and associated fuel flow points

85% to 100% thrust: defined by a quadratic equation based on the 30%, 85% and

100% thrust and associated fuel flow points

These two quadratic equations are uniquely defined by their 3 points and meet at 85% thrust. The 

slopes of the two curves at 85% thrust may be different, (the ―kink‖ shown diagrammatically in 

Figure A1-2 below).

Figure A1-2 Diagrammatic illustration of twin quadratic curve fit

A1.6.39 A quadratic equation to fit through three points on the non-dimensionalised fuel flow 

versus thrust curve has the following parameters:

X = (thrust)/(maximum rated thrust), Quadratic defined by values X1, X2, X3

Y = (fuel flow)/(fuel flow @ maximum rated thrust), values Y1, Y2, Y3

Giving

Y = AX2 + BX + C

With three known points

Y1 = AX12+ BX1 + C

Y2 = AX22+ BX2 + C

Y3 = AX32+ BX3 + C

Allowing solution for A, B and C as :

A = (Y3-Y1)/((X3-X1)*(X1-X2)) – (Y3-Y2)/((X3-X2)*(X1-X2))
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Appendix C to the Report on Agenda Item 2

B = (Y3-Y1)/(X3-X1) – A*(X3+X1)

C = Y3 – A*X3 2- B*X3

A,B and C vary for different engine UIDs

For selected thrusts between 85% and 100% rated thrust: 

Known ICAO Engine Emissions Databank points for the engine UID at 30%, 85% and 100% are 

used to derive A, B and C as above.

These are then used in the generic quadratic equation

Y = AX2+ BX + C

Where X is the (selected thrust)/(maximum rated thrust)

To give Y (= (desired fuel flow)/(fuel flow at maximum rated thrust)) at the selected thrust.

Fuel flow at the selected thrust is obtained but multiplying Y by the ICAO Engine Emissions 

Databank fuel flow at maximum rated thrust

The Upper Quadratic curve is applied between 85% and 100% rated thrust only

For selected thrusts between 60% and 85% rated thrust.

Known databank points for the engine UID at 7%, 30% and 85% are used to derive A, B and C as 

above. These are then used in the generic quadratic equation

Y = AX2+ BX + C

Where X is the (selected thrust)/(max rated thrust)

To give Y (= (fuel flow)/(fuel flow at maximum rated thrust)) at the selected thrust.

Fuel flow at the selected thrust is obtained by multiplying Y by the ICAO Engine Emissions 

Databank fuel flow at maximum rated thrust

The Lower Quadratic curve is applied between 60% and 85% rated thrust only

Example calculation for UID 8RR044, Rolls-Royce Trent 553-61:

1) Determination of quadratic curve between 85% and 100% rated thrust

X1 = 0.30

X2 = 0.85

X3 = 1.00

With ICAO Engine Emissions Databank fuel flows:

Y1 = 0.2844
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Appendix C to the Report on Agenda Item 2 2 C-21

Y2 = 0.8199

Y3 = 1.0000

→ A = 0.3242

→ B = 0.6009

→ C = 0.07491

→ Y = 0.3242 X2+ 0.6009 X + 0.0749 (1)

2) Determination of quadratic curve between 60% and 85% thrust

X1 = 0.07

X2 = 0.30

X3 = 0.85

With ICAO Engine Emissions Databank fuel flows:

Y1 = 0.1090

Y2 = 0.2844

Y3 = 0.8199

→ A = 0.2709

→ B = 0.6622

→C = 0.0613

→ Y = 0.2709 X2+ 0.6622 X + 0.0613 (2)

3) Results for selected thrust (examples)

70% thrust (X = 0.7): equation (2): Y = 0.6576 → multiply with ICAO Engine Emissions 

Databank maximum rated thrust fuel flow → Fuel flow = 1.388 kg/s

90% thrust (X = 0.9): equation (1): Y = 0.8783 → multiply with ICAO Engine Emissions 

Databank maximum rated thrust fuel flow → Fuel flow = 1.853 kg/s

A1.6.40 For Option B, performance model would be utilized to obtain/calculate operational 

fuel flow data using various additional data (e.g. ATOW or stage length or information pertinent 

to fuel flow calculation) in conjunction with the ICAO EEDB. As examples, models such as 

BADA or PIANO or ADAECAM may be used

A1.6.41 Emission Indices

A1.6.42 Option A: Emissions indices for Option A will be calculated from the data in the 

ICAO EEDB using the  ̳linear interpolation on a log-log scale‘ method as employed in the 

BFFM2 method, using the fuel flows calculated by the methodology in section A1.6.39.
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A1.6.43 Option B: The "operational" emission indices are derived from the data in the ICAO 

EEDB using the  ̳linear interpolation on a log-log scale‘ method as employed in the BFFM2 

method, using the operational fuel flows from the method described in section A1.6.40

A1.6.44 Application of Additional Parameters that may Influence Emissions, if 

Appropriate

A1.6.45 Important Caveats For Modelers Using Advanced Methods

A1.6.46 Unlike for the Simple approach, different methods under the heading of Advanced 

methods may already include some aspects of the corrections for additional parameters such as 

ambient conditions. It is important to avoid double-accounting in these cases. Hence, the 

application of the corrections may differ between different methods. It is also important to realize 

that ambient conditions sufficiently far from standard may cause the airplane or engine to reach 

operational limits. For instance, many engines will not be able to provide full flat-rated thrust 

beyond some temperature limit (typically ISA +15C, but this limit varies). The modeler must take 

care not to extrapolate a methodology beyond the conditions for which it is valid.

A1.6.47 Application to Advanced Approach Option B–

A1.6.48 If an aircraft performance model is used to calculate airplane and engine operating 

conditions (Advanced Option B), then it should already include the effects of forward speed on 

the fuel flow. It may, depending on the model, also include the effects of ambient conditions. The 

modeler must be aware of how the model functions. If it is necessary to correct the airplane 

performance model and/or fuel flow further to account accurately for these effects, the modeler 

should do so at this stage.

A1.6.49 After the airplane performance and fuel flow has been correctly determined under 

Advanced Option B, then the emissions indices should be calculated using a fuel flow method. 

One documented6 fuel flow method is the Boeing Fuel Flow Method 2. Depending on the needs 

of the modeler and the available data other methods may be used, although the BFFM2 is 

recommended as a default option.

A1.6.50 As described in SAE AIR5715, the BFFM2 accounts for the effects of ambient 

conditions and forward speed. It is important to recognize that if the effects of ambient conditions 

and forward speed are to be considered, it is not sufficient to only use the initial calculation of the 

emission indices from the curve fitting methods defined for the BFFM2. However, the full 

BFFM2 method includes corrections for both of these effects, so no further corrections to the 

emissions indices would be required if it is used.

A1.6.51 Application to Advanced Approach Option A

A1.6.52 Methods that fall under Advanced Option A, while less sophisticated and precise, may 

also be more complicated to adjust for ambient conditions. First the performance of the airplane 

(thrust, time in mode, etc.) might need to be adjusted to account of ambient conditions. Then, 

 

6

SAE AIR5715
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Appendix C to the Report on Agenda Item 2 2 C-23

since the fuel flow would have been calculated for the relevant thrust level at ISA static 

conditions (as the fuel flow is not based on an aircraft performance model in this option), 

corrections for both ambient conditions and forward speed would need to be implemented. The 

result would be a fuel flow, corrected for both sets of conditions, but without the accuracy (or 

temporal and spatial resolution) of an Option B model.

A1.6.53 The calculation of the emission indices and their correction for ambient conditions 

and forward speed effects could then use the same approach as for Advanced Option B. However, 

because the fuel flow and flight conditions are not known to the same degree of resolution as with 

Option B, the results obtained when applying a method such as the BFFM2 might not be accurate 

or even well-defined. The BFFM2 is only defined at fully specified7 flight conditions and can not 

be directly applied to an entire ―mode‖ such as takeoff or climbout. Either a fully specified flight 

condition could be assumed that represents the airplane for the entire time in mode, or else a 

different method would have to be used to determine the emissions indices. This different method 

might be a modification of BFFM2, or it might be unrelated. Thus the application of corrections 

for forward speed and ambient conditions to an Advanced Option A calculation will depend on 

the details of the model and the requirements of the modeler.

A1.6.54 Altitude Effects

A1.6.55 The effects of altitude on an aircraft engine are governed by the local pressure, 

temperature and humidity. Therefore, the effects of altitude on the engine emissions will be 

correctly treated if the approaches described above are implemented and the ambient conditions 

used are those local to the airplane in flight.

A1.6.56 Engine Deterioration

A1.6.57 While aircraft/engine manufacturers always design their products for peak efficiency 

at delivery, as aircraft enter revenue service some performance degradation may be experienced 

over time due to the harsh environments aircraft and engines will operate at. Erosion, seal 

degradation and dirt build up on finely tuned rotating hardware and airframes over long periods 

of time can lead to performance loss. If left unchecked, the deterioration can result in noticeable 

fuel consumption increases over time. Fuel consumption increases are an un-necessary cost 

increase to the carriers and as a result they will normally perform maintenance on their products 

to keep the level of performance loss at acceptable levels. An analysis done by CAEP Working 

Group 3 has assessed the impact of aircraft/engine deterioration and provides the following 

guidance regarding how and when to apply deterioration in performing airport inventories.

A1.6.58 In-service airframe and engine deterioration for the purposes of airport inventories 

(i.e., the LTO cycle below 3000 feet) is a small but real effect on fuel burn and NOx emissions. 

There is no evidence that indicates deterioration effects on CO, HC, or smoke number.

 

7

Fully Specified: The state vector (3D position, speed, attitude), engine parameters and airframe configuration are 

known.
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Appendix C to the Report on Agenda Item 2

A1.6.59 As a cost savings measure airlines take precautions to keep deterioration effects to a 

minimum by establishing routine maintenance programs. Based on analyses of theoretical and 

actual airline data, the magnitude of deterioration effects can be on a fleet-wide basis as follows:

Fuel consumption +3%

NOx emissions +3%

CO emissions no change

HC emissions no change

Smoke number no change

A1.6.60 For application to modelling, including emission inventories, the appropriate use of 

this deterioration information in modelling activities is model/assumption and input data 

dependent. Specifically, models and assumptions may already include a deterioration allowance, 

either explicitly (i.e., actual engine operational data or calibrated/validated on actual in-service 

data), implicitly (i.e., conservative fuel flow correction factors applied to engine certification 

values), or may already include conservatism which significantly outweighs the fuel consumption 

and NOx emissions deterioration effects. Care must be taken to avoid double accounting.

A1.6.61 The Simple Approach is a significant over-estimate of aircraft emissions and fuel 

consumption. The margin of conservatism for the Simple Approach is large enough to preclude 

the application of deterioration effects.

A1.6.62 The Advanced Approach allows different thrust settings to be applied to fuel flow 

methodologies as well as some sort of aircraft performance calculations. While the results are 

more accurate than the Simple Approach, comparison with FDR data suggests that, for commonly 

used methods, there still is a level of conservatism on a fleet-wide basis on fuel flow calculations 

resulting from use of performance-estimated times-in-mode, take-off weight and throttle settings 

in the LTO cycle. The deterioration factors are considered smaller that the inherent conservatism 

already existing in the method and application is therefore not recommended.

A1.66.3 Where the Sophisticated Approach utilizes actual engine/aircraft operational 

performance data (including operational fuel flow), then that would inherently include actual 

deterioration effects. Again the application of deterioration factors is not recommended. 

A1.6.64 An exception to the recommendation above might occur in using a combination of 

advanced and sophisticated methods using actual engine/aircraft combinations, average or 

measured times-in-mode, TOW and throttle settings, combined with fuel flow rates calculated 

from ICAO certification data. In this case application of deterioration factors is recommended.

A1.6.65 Fuel consumption deterioration should only be applied to modelling in the vicinity of 

airports (i.e., the LTO cycle) and should not be used for global modelling where the deterioration 

factor would be different than the values reported here.

A1.6.66 Start-Up Emissions Calculation Approach 
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Appendix C to the Report on Agenda Item 2 2 C-25

A1.6.67 During the starting sequence there is very little NOx emissions produced compared to 

the LTO cycle due to the very low engine temperatures and pressures, and the only emissions that 

requires consideration during the starting sequence is HC. Aircraft main engine starting can 

generally be broken down into two phases; pre ignition and post ignition. 

A1.6.68 Engine Pre-Ignition

A1.6.69 The Pre-ignition phase represents the time when the engine has been cranked using a 

starter motor and fuel permitted into the combustor to achieve ignition. From starter motor 

initiation to combustor lighting can take several seconds but there is no fuel entering the engine as 

the fuel system primes and the fuel valves are closed. Due to the requirement for quick start 

times, the combustion system is designed so that ignition occurs within the first or second spark 

of the igniter, typically within 1 second of fuel valves being opened and no later than 2 seconds. 

This has also been confirmed from rig testing by manufacturers using optical access to see fuel 

arrive and observed time to ignition. 

A1.6.70 Pre ignition emissions would be purely fuel hydrocarbons, as combustion has not 

been initiated so no fuel is consumed within the combustor. This allows the HC emissions to be 

calculated directly from the fuel flow. During the pre ignition period three things happen

 The fuel valve is opened

 The fuel injector system fills and fuel flow starts

 The igniter begins to spark and lights the combustor 

A1.6.71 Engine Post-Ignition 

A1.6.72 At this point the starting process occurs at low engine loading conditions. At these 

operating points the engine emissions will primarily take the form of HC and CO emissions. 

Direct measurement of starting emissions is made difficult by unburnt and partially burnt fuel 

contaminating gas sampling hardware. After ignition at particularly low engine loading, as would 

be the case during engine starting, emissions of HC dominate. For this reason it is not 

unreasonable to attribute starting emissions to HC alone resulting in a conservative estimate of 

HC emissions. CO emissions can be higher than HC for some engines at 7% idle and below, and 

thus post ignition HC emissions may be significantly lower than the estimate based on 

combustion efficiency. Detailed emissions measurements would be required to provide a more 

precise estimate of HC emissions.

A1.6.73 Post ignition emissions are determined from the point of ignition through the 

acceleration to idle. As the combustor is now burning fuel therefore the rate of consumption must 

be considered to determine emissions accurately. Gas sampling at sub-idle conditions is very 

difficult on engines because there are significant amounts of unburned and partially burnt fuel 

that tends to contaminate the sampling hardware. To get around this issue the analysis is 

performed using combustion efficiency correlations that have been determined by combustor rig 

testing at sub-idle conditions. These correlations are based on combustor inlet temperature, 

combustor inlet pressure, combustor air mass flow, fuel flow and fuel-air ratio. This approach to 

determining combustion efficiency and heat release is common between all engine manufacturers.
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Appendix C to the Report on Agenda Item 2

A1.6.74 The instantaneous combustor efficiency is calculated and the resulting inefficiency is 

allocated as a percentage of unburnt fuel representing the resulting HC emission. Using this 

process throughout the acceleration to idle the sum of the instantaneous HC emissions can be 

utilized to provide a conservative estimation of the total post ignition engine HC emission.

A1.6.75 ICCAIA has performed a detailed analysis of engine starting data from GE, RR , 

P&W and IAE engines and has developed a method to estimate total start up emissions based on 

the rated sea level thrust of the engine in question. The results of this study were presented to 

CAEP WG3 in Working Paper CAEP8-WG3-CETG-WP06. In the paper ICCAIA recommends a 

simple first order linear relationship between HC and the take-off engine thrust rating. The 

recommended equation is:

STARTING HC EMISSIONS (grams) = Rated Take Off Thrust (kN)/2 + 80 Eq. A1-

5

(NOTE: This analysis is based on actual engine testing performed at moderate inlet temperature 

conditions. The methodology to derive the starting HC emissions was conservative because it 

did not account for any CO during starting. In addition, applying the methodology to all engines 

may be optimistic for older engines where fuel distribution controls are not as sophisticated. The 

methodology also considers typical times to light and typical starting times which in practice 

could be quite varied and would be longer at very cold conditions. It would be reasonable to state 

that the uncertainty in the methodology was around +/-50%).

A1.6.76 Advanced Calculation Methodology for NOx, CO and THC

A1.6.77 The calculation of emission masses in the advanced approach makes use of additional 

data, information and existing models. As such, the emission of an aircraft is a function () of the 

key parameters and the chosen options. This results in having a performance based calculation 

using various additional data and information that should yield a more accurate emissions 

inventory that will be unique to the specific airport and study year under consideration. 

A1.6..78 To determine the NOx, CO, or HC emissions for a unique aircraft/engine 

combination, the following formula may be used. This method is repeated for each aircraft/engine 

type and movement.

Ei j = ∑ (TIMjk*60) * (FFjk, EIjk or Thrustjk, Condj, Nej) Eq. 

A1-6

where:

Eij = Total emissions of pollutant i (e.g., NOx, CO, or HC), in grams, produced by a 

specific aircraft j for one LTO cycle

Eijk = The emission index for pollutant i (e.g., NOx, CO, or HC), in grams of pollutant per 

kilogram of fuel (g/kg of fuel), in mode k for each engine used on aircraft j

FFjk = Fuel flow for mode k, in kilograms per second (kg/s), for each engine used on 

aircraft type j

Thrustjk = Thrust level for mode k for the aircraft type j

TIMjk = Time-in-mode for mode k, in minutes, for aircraft j
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Appendix C to the Report on Agenda Item 2 2 C-27

Nej = Number of engines used on aircraft j, considering the potential use of less than all 

engines during taxi operation.

Condj = ambient conditions (forward speed, altitude, p, t, h) for aircraft type j movement

A1.6.79 Emission Calculation Sophisticated Approach

A1.6.80 Parameters

A1.6.81 Under the Sophisticated Approach, the actual and refined data required for the 

analysis is obtained from real-time measurements, reported performance information and/or 

complex computer modeling outputs. At a high level, these data and information characterize the 

actual fleet composition in terms of aircraft types and engine combinations, TIM, thrust levels, 

fuel flows and possibly, combustor operating conditions for all phases of ground-based and takeoff operations. In some cases, correction of engine operating conditions to reference conditions, 

using accepted methods will also be required.8 Additionally, the application of the parameters 

defined in Sections A1.6.42 – A1.6.65 could be considered based on the guidance provided in 

Table 1.

A1.6.82 Listed below are the data and information typically required for computing aircraft 

engine emissions using the Sophisticated Approach. 

 Times-in-mode measurements for different aircraft/engine types under different load, 

route and meteorological conditions.

 Reverse thrust deployment measurements for different aircraft/engine types under 

different meteorological conditions.

 Airport meteorological conditions, where modelling of aircraft/engine performance 

accounts for variation in meteorological conditions.

 Frequency and type of engine test runs.

 Frequency of operational aircraft towing.

 Airport infrastructure and constraints (e.g., runway length).

A1.6.83 Similarly, data measured by operators may be made available, including:

 Typical or actual throttle settings used during reverse thrust operation.

 Actual aircraft/engine configuration data.

 Actual fuel flow data.

 Actual idle engine-type idle speeds.

 Typical or actual throttle settings for approach take off and climb out (e.g. reduced thrust 

take-off procedures).

 Approach and climb profiles.

 Frequency of less than-all-engine taxi operation.

A1.6.84 This measured and actual operator data may supplement or replace elements of 

modeled data.

 

8

Sources for correcting and obtaining these data will be the airlines, engine manufacturers, ICAO Annex 16 

Volume II, SAE AIR 1845, BADA, and ETMS, ETFMS and FDR data.
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A1.6.85 Using actual performance and operational data, engine emissions factors can be 

calculated using programs such as the Boeing Fuel Flow Method 2 or the Deutsches Zentrum für 

Luft- und Raumfahrt Method.

A1.6.86 Sophisticated Calculation Methodology for NOx, CO and THC

A1.6.86 Once the actual fleet engine emissions factors, times-in-mode and fuel flows are 

known, the LTO emissions are calculated using the same equation used in the Advanced 

Approach; however with the refined input values.

Ei j = ∑ (TIMjk*60) * (FFjk, EIjk or Thrustjk, Condj, Nej) Eq. 

A1-7

where:

Eij = Total emissions of pollutant i (e.g., NOx, CO, or HC), in grams, produced by a 

specific aircraft j for one LTO cycle

Eijk = The emission index for pollutant i (e.g., NOx, CO, or HC), in grams per pollutant 

per kilogram of fuel (g/kg of fuel), in mode k for each engine used on aircraft j

FFjk = Fuel flow for mode k, in kilograms per second (kg/s), for each engine used on 

aircraft type j

Thrustjk = Thrust level for mode k for the aircraft type j

TIMjk = Time-in-mode for mode k, in minutes, for aircraft j

Nej = Number of engines used on aircraft j

Condj = ambient conditions (forward speed, altitude, p, t, h) for aircraft type j movement

A1.7 Auxiliary Power Unit Emissions

A1.7.1 An auxiliary power unit (APU) is a small gas-turbine engine coupled to an electrical 

generator and is used to provide electrical and pneumatic power to aircraft systems when 

required. It is normally mounted in the tail cone of the aircraft, behind the rear pressure bulkhead, 

and runs on kerosene fed from the main fuel tanks. Not all aircraft are fitted with APU, and 

though their use on transport category jet aircraft is now almost universal, some turboprops and 

business jets do not have an APU fitted. 

A1.7.2 Emissions Calculation Methodology

A1.7.3 Unlike aircraft main engines, APU are not certificated for emissions and the 

manufacturers generally consider information on APU emissions rates as proprietary. As a result, 

little data are publicly available to serve as a basis for calculating APU emissions. Analysis 

performed to date on APU‘s have not been successful in developing Advanced and Sophisticated 

methodologies that more accurately predict APU emissions if more information is available to the 

user. As a result, use of the Simple approach, for all cases, is recommended at this time. 

A1.7.4 Simple Approach

A1.7.5 If very little information is known about the aircraft types operating at the study 

airport, then the Simple Approach for APU emissions may be used. However, the results are 
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Appendix C to the Report on Agenda Item 2 2 C-29

likely to have a large order of uncertainty associated with their use and emissions. Generalised 

emissions for APU have been made public. The information is recommended for use as the 

Simple approach uses averaged proprietary engine-specific values obtained from APU 

manufacturers

A1.7.6 Where the level of detail of aircraft fleet does not allow for this process to be used, the 

following values are considered representative of the APU emissions for each aircraft operation at 

the airport under study (other values may be used if deemed more appropriate):

Aircraft Group Short-haul9 Long-haul

Duration of APU operation 45 min. 75 min.

Fuel burn 80 kg 300 kg

NOx emissions 700 g 2400 g

HC emissions 30 g 160 g

CO emissions 310 g 210 g

PM10 emissions 25 g 40 g

A1.7.7 The previous fuel burn and emission values are based on averaged manufacturer 

APU-specific proprietary data; though do not represent any specific APU type. The operational 

times noted are based on average operating times experienced by a number of operations and do 

not necessarily represent any specific airport operation. It should be noted that APU operating 

times vary considerably at different airports due to a number of factors, and can be significantly 

different to the default values listed in the previous table. If information on actual APU operating 

times is available, either from surveys or as maximum durations from local airport restrictions, 

then the APU fuel burn and emissions may be adjusted by factoring these values in the table by 

the ratio of the survey times with the default values outlined.

A1.7.8 For example, APU NOx emissions for a short-haul aircraft operating for 60 minutes 

would be calculated as follows:

NOx (g/LTO) = (60 minutes per LTO)) x (700 g/ 45 minutes) = 933 g/LTO

A1.7.9 In addition, publicly distributed manufacturer information is available showing aircraft 

and APU combinations including duty cycle average APU EI and fuel burn rates.10 Air Transport 

Association (ATA) estimates of APU operating times also are available; based on a limited, 

informal survey concerning APU usage. Use of the manufacturer APU emissions data, along with 

the ATA estimates on APU operating times will provide a more accurate estimate of APU 

emissions. The ATA estimates on APU operating times provide estimates for narrow and widebody11 aircraft with and without gate power. As examples, these estimates are provided in the 

following table (other values may be used if deemed more appropriate):

 

9 Although there is no common definition of short haul and long haul, in the context of this document we propose a rule 

of thumb that relates the term to aircraft type. The long haul group would include aircraft capable of a maximum 

range of more than 8000km, e.g. A330, A4340, A380, B747, B767-200ER, B763, B764, B777, IL96, MD11. Short 

haul would include all other aircraft.

10 Correspondence from Honeywell Engines & Systems to U.S. EPA Assessment and Standards Division, APU 

Emissions, September 29, 2000.

11 Narrow Body: single aisle aircraft. Wide body: multiple aisle aircraft e.g. A300, A330, A340, A380, B767, B777, 

B747.
2 C-30

CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2

ATA Operating Time (hours/cycle)

Aircraft Type With Gate Power Without Gate Power

Narrow Body 0.23 to 0.26 0.87

Wide Body 0.23 to 0.26 1.0 to 1.5

A1.7.10 APU and aircraft combinations can be found in 1995 FAA technical report entitled, 

Technical Data to Support FAA Advisory Circular on Reducing Emissions from Commercial 

Aviation [FAA 1995]. This document provides an accurate summary of which major APU family 

is used on different aircraft. The document also provides modal EI and fuel flow for specific 

APU; all of which would provide additional detail to the APU emissions calculation.

A1.7.11 For example, APU NOx emissions for a wide body aircraft utilizing a 331-200ER 

without gate power, where the time at load is 1.5 hours, the NOx EI is 9.51 lb per 1000 lb fuel, 

and the fuel flow is 267.92 lb per hour.

NOx (lb/LTO) = (1.5 hours per LTO)) x (9.51 lb/1000 lb fuel)*(267.92 lb fuel/hour) = 3.82 

lb/LTO = 3,466 g/LTO
CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2 2 C-31

Chapter 2

Emissions Inventory

Annex 1

Aircraft Emissions

Appendix A

Example ICAO Engine Emissions Datasheet
2 C-32

CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2
CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2 2 C-33

Chapter 2

Emissions Inventory

Annex 1

Aircraft Emissions

Appendix B

Simplified Aircraft Emission Indices
2 C-34

CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2

Table B-1 LTO Emission Factor by Aircraft

LTO emissions factors/airplane (kg/LTO/aircraft)(10) Fuel consumption 

(kg/LTO/aircraft)

Aircraft(11) CO2

(9) HC NOx CO SO2 (8)

Source: ICAO (2004) (1)

Large Commercial Aircraft (2)

A300 5450 1.25 25.86 14.80 1.72 1720

A310 4760 6.30 19.46 28.30 1.51 1510

A319 2310 0.59 8.73 6.35 0.73 730

A320 2440 0.57 9.01 6.19 0.77 770

A321 3020 1.42 16.72 7.55 0.96 960

A330-200/300 7050 1.28 35.57 16.20 2.23 2230

A340-200 5890 4.20 28.31 26.19 1.86 1860

A340-300 6380 3.90 34.81 25.23 2.02 2020

A340-500/600 10660 0.14 64.45 15.31 3.37 3370

707 5890 97.45 10.96 92.37 1.86 1860

717 2140 0.05 6.68 6.78 0.68 680

727-100 3970 6.94 9.23 24.44 1.26 1260

727-200 4610 8.14 11.97 27.16 1.46 1460

737-100/200 2740 4.51 6.74 16.04 0.87 870

737-300/400/500 2480 0.84 7.19 13.03 0.78 780

737-600 2280 1.01 7.66 8.65 0.72 720

737-700 2460 0.86 9.12 8.00 0.78 780

737-800/900 2780 0.72 12.30 7.07 0.88 880

747-100 10140 48.43 49.17 114.59 3.21 3210

747-200 11370 18.24 49.52 79.78 3.60 3600

747-300 11080 2.73 65.00 17.84 3.51 3510

747-400 10240 2.25 42.88 26.72 3.24 3240

757-200 4320 0.22 23.43 8.08 1.37 1370

757-300 4630 0.11 17.85 11.62 1.46 1460

767-200 4620 3.32 23.76 14.80 1.46 1460

767-300 5610 1.19 28.19 14.47 1.77 1780

767-400 5520 0.98 24.80 12.37 1.75 1750

777-200/300 8100 0.66 52.81 12.76 2.56 2560

DC-10 7290 2.37 35.65 20.59 2.31 2310

DC-8-50/60/70 5360 1.51 15.62 26.31 1.70 1700

DC-9 2650 4.63 6.16 16.29 0.84 840

L-1011 7300 73.96 31.64 103.33 2.31 2310

MD-11 7290 2.37 35.65 20.59 2.31 2310

MD-80 3180 1.87 11.97 6.46 1.01 1010

MD-90 2760 0.06 10.76 5.53 0.87 870

TU-134 5860 35.97 17.35 55.96 1.86 1860

TU-154-M 7040 17.56 16.00 110.51 2.51 2510

TU-154-B 9370 158.71 19.11 190.74 2.97 2970

Regional Jets/Business 

Jets > 26.7 kN thrust

RJ-RJ85 950 0.67 2.17 5.61 0.30 300

BAE 146 900 0.70 2.03 5.59 0.29 290

CRJ-100ER 1060 0.63 2.27 6.70 0.33 330

ERJ-145 990 0.56 2.69 6.18 0.31 310

Fokker 100/70/28 2390 1.43 5.75 13.84 0.76 760

BAC111 2520 1.52 7.40 13.07 0.80 800

Dornier 328 Jet 870 0.57 2.99 5.35 0.27 280
CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2 2 C-35

Gulfstream IV 2160 1.37 5.63 8.88 0.68 680

Gulfstream V 1890 0.31 5.58 8.42 0.60 600

Yak-42M 1920 1.68 7.11 6.81 0.61 610

Source: 

FAEED222 (3)

Low Thrust Jets (Fn 

< 26.7 kN)

Cessna 525/560 1060 3.35 0.74 34.07 0.34 340

Source: FOI (4)

Turboprops

Beech King Air (5) 230 0.64 0.30 2.97 0.07 70

DHC8-100 (6) 640 0.00 1.51 2.24 0.20 200

ATR72-500 (7) 620 0.29 1.82 2.33 0.20 200

Notes:

(1) ICAO (International Civil Aviation Organization) Engine Exhaust Emissions Data Bank (2004) based on average measured certification 

data. 

 Emissions factors apply to LTO cycle only. Total emissions and fuel consumption are calculated based on ICAO standard time in mode and 

thrust levels.

(2) Engine types for each aircraft were selected on a basis of the engine with the most LTOs as of 30 July 2004 (except 747-300 - see text). 

 This approach, for some engine types, may underestimate (or overestimate) fleet emissions which are not directly related to fuel 

consumption (eg NOx, CO, HC).

(3) U.S. Federal Aviation Administration (FAA) Emissions and Dispersion Modeling System (EDMS) noncertified data

(4) FOI (The Swedish Defense Research Agency) Turboprop LTO Emissions database noncertified data

(5) Representative of Turboprop aircraft with shaft horsepower of up to 1000 

shp/engine

(6) Representative of Turboprop aircraft with shaft horsepower of 1000 to 2000 

shp/engine

(7) Representative of Turboprop aircraft with shaft horsepower of more than 2000 

shp/engine

(8) The sulphur content of the fuel is assumed to be 0.05% [Same assumption as in 1996 IPCC 

NGGIP revision]

(9) CO2 for each aircraft based on 3.16 kg CO2 produced for each kg fuel used, then rounded to the nearest 10 

kg.

(10) Information regarding the uncertainties associated with the data can be found in the 

following references:

QinetiQ/FST/CR030440 ―EC-NEPAir: Work Package 1 Aircraft engine emissions certification – a review of the development of ICAO Annex 

16, Volume II‖, by D H Lister and P D Norman

ICAO Annex 16 ―International Standards and Recommended Practices Environmental Protection‖, Volume II ―Aircraft Engine Emissions‖, 

2nd edition (1993)

(11) Equivalent aircraft are contained in 

Table B-3
2 C-36

CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2

Table B-2 Engine Designations by Aircraft

Aircraft ICAO Engine Engine UID

A300 PW4158 1PW048

A310 CF6-80C2A2 1GE016

A319 CFM56-5A5 4CM036

A320 CFM56-5A1 1CM008

A321 CFM56-5B3/P 3CM025

A330-200/300 Trent 772B-60 3RR030

A340-200 CFM56-5C2 1CM010

A340-300 CFM56-5C4 2CM015

A340-500/600 TRENT 556-61 6RR041

707 JT3D-3B 1PW001

717 BR700-715A1-30 4BR005

727-100 JT8D-7B 1PW004

727-200 JT8D-15 1PW009

737-100/200 JT8D-9A 1PW006

737-300/400/500 CFM56-3B-1 1CM004

737-600 CFM56-7B20 3CM030

737-700 CFM56-7B22 3CM031

737-800/900 CFM56-7B26 3CM033

747-100 JT9D-7A 1PW021

747-200 JT9D-7Q 1PW025

747-300 JT9D-7R4G2(66%) RB211-

524D4(34%)

1PW029(66%) 

1RR008(34%)

747-400 CF6-80C2B1F 2GE041

757-200 RB211-535E4 3RR028

757-300 RB211-535E4B 5RR039

767-200 CF6-80A2 1GE012

767-300 PW4060 1PW043

767-400 CF6-80C2B8F 3GE058

777-200/300 Trent 892 2RR027

DC-10 CF6-50C2 3GE074

DC-8-50/60/70 CFM56-2C1 1CM003

DC-9 JT8D-7B 1PW004

L-1011 RB211-22B 1RR003

MD-11 CF6-80C2D1F 3GE074

MD-80 JT8D-217C 1PW018

MD-90 V2525-D5 1IA002

TU-134 D-30-3 1AA001

TU-154-M D-30-KU-154-II 1AA004

TU-154-B NK-8-2U 1KK001

RJ-RJ85 LF507-1F, -1H 1TL004

BAE 146 ALF 502R-5 1TL003

CRJ-100ER CF34-3A1 1GE035

ERJ-145 AE3007A1 6AL007

Fokker 100/70/28 TAY Mk650-15 1RR021

BAC111 Spey-512-14DW 1RR016

Dornier 328 Jet PW306B 7PW078

Gulfstream IV Tay MK611-8 1RR019
CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2 2 C-37

Gulfstream V BR700-710A1-10 4BR008

Yak-42M D-36 1ZM001

Cessna 525/560 PW545A or similar FAEED222

Beech King Air PT6A-42 PT6A-42

DHC8-100 PW120 or similar PW120

ATR72-500 PW127F or similar PW127F
2 C-38

CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2

Table B-3 Representative Aircraft

Generic Aircraft ICAO

IATA 

aircraft 

in group

Airbus A300

A30B AB3

A306

AB4

AB6

ABF

ABX

ABY

Airbus A310 A310

310

312

313

31F

31X

31Y

Airbus A319

A319 319

A318 318

Airbus A320 A320

320

32S

Airbus A321 A321 321

Airbus A330-200

A330 330

A332 332

Airbus A330-300

A330 330

A333 333

Airbus A340-200 A342 342

Airbus A340-300

A340 340

A343 343

Airbus A340-500 A345 345

Airbus A340-600 A346 346

Boeing 707 B703

703

707

70F

70M

Boeing 717 B712 717

Boeing 727-100 B721

721

72M

Boeing 727-200 B722

722

727
CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2 2 C-39

72C

72B

72F

72S

Boeing 737-100 B731 731

Boeing 737-200 B732

732

73M

73X

Boeing 737-300 B733

737

73F

733

73Y

Boeing 737-400 B734

737

734

Boeing 737-500 B735

737

735

Boeing 737-600 B736 736

Boeing 737-700 B737

73G

73W

Boeing 737-800 B738

738

73H

Boeing 737-900 B739 739

Boeing 747-100

B741 74T

N74S 74L

B74R 74R

B74R 74V

Boeing 747-200 B742

742

74C

74X

Boeing 747-300 B743

743

74D

Boeing 747-400 B744

747

744

74E

74F

74J

74M

74Y

Boeing 757-200 B752

757

75F

75M
2 C-40

CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2

Boeing 757-300 B753

Boeing 767-200 B762

762

76X

Boeing 767-300 B763

767

76F

763

76Y

Boeing 767-400 B764

Boeing 777-200 B772

777

772

Boeing 777-300 B773

773

Douglas DC-10 DC10

D10

D11

D1C

D1F

Douglas DC-10 DC10

D1M

D1X

D1Y

Douglas DC-8

DC85 D8F

DC86 D8L

DC87

D8M

D8Q

D8T

D8X

D8Y

Douglas DC-9

DC9 DC9

DC91 D91

DC92 D92

DC93 D93

DC94 D94

DC95

D95

D9C

D9F

D9X

Lockheed L-1011 L101

L10

L11

L15

L1F

McDonnell 

Douglas MD11 MD11

M11

M1F
CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2 2 C-41

M1M

McDonnell 

Douglas MD80

MD80 M80

MD81 M81

MD82 M82

MD83 M83

MD87 M87

MD88 MD88

McDonnell 

Douglas MD90 MD90 M90

Tupolev Tu134 T134 TU3

Tupolev Tu154 T154 TU5

Avro RJ85 RJ85

AR8

ARJ

BAe 146

B461 141

B462 142

B463

143

146

14F

14X

14Y

14Z

Embraer ERJ145 E145

ER4

ERJ

Fokker 100/70/28

F100 100

F70 F70

F28

F21

F22

F23

F24

F28

BAC 111 BA11

B11

B12

B13

B14

B15

Dornier Do 328 D328 D38

Gulfstream IV / V GRJ

Yakovlev Yak 42 YK42 YK2
2 C-42

CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2

Chapter 2

Emissions Inventory

Annex 1

Aircraft Emissions

Appendix C

Definition of Publicly Available Databases for Use in the 

Matching Aircraft Type with Engine Type
CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2 2 C-43

Useful data fields in the IOAG Database:

LveTime = time flight is scheduled to depart origin in local time

LveGMT = time flight is scheduled to depart origin in Greenwich Mean Time 

(GMT)

ArrCode = number representing arrival airport

Arrive = arrival airport alphabetic code (e.g., JFK)

ArrTime = time flight is scheduled to arrive in local time

ArrGMT = time flight is scheduled to arrive in GMT

Equip = type of aircraft, in code (e.g., B738)

FAACarr = abbreviation for air carrier name

FltNo = flight number

Freq = 1/0 code showing days of the week that that flight flies that time slot 

and city pair

ATACarr = carrier name in Air Transport Association Code

IOAGCARR = air carrier company in 2-letter IOAG code

CarrType = commuter or carrier company

ATAEquip = aircraft type in ATA code

EqType = J for Jet, T for Turboprop, P for propeller-driven aircraft

CarrName = air carrier company name spelled out

LveCity = origin city and country/state, spelled out

ArrCntry = destination country or state if the destination is in the US

LveCntry = origin country or state if the origin is in the US

YYMM = year and month of the current schedule

Eday = 0/1 code indicating whether this flight flies on each day of the month 

given by the schedule

FPM = number of times (days) this fight is flown between this city-pair at this 

time slot in a month

Useful data fields in the BACK World Fleet Registration Database:

 Aircraft Type

 Aircraft Serial Number

 Aircraft Manufacturer

 Registration\Tail Number

 Engine Manufacturer

 Engine Model

 Number f Engines

 Aircraft Noise Class (Stage)

 Equipment Category

 Equipment Type (LAR Code)

 Equipment Type (IOAG Code)

 Aircraft Equipment Model

 Operator Category

 Operator Name

 Operator IATA Code

 Operator ICAO Code

 Wing Span (meters)
2 C-44

CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2

 Wing Area (square meters)

 Overall Length (meters)

 Belly Volume (cubic meters)

 Fuel Capacity

 Maximum Takeoff Weight (kilograms)

 Maximum Payload (kilograms)

 Maximum Landing Weight (kilograms)

 Range with Maximum Fuel (kilometres)

 Range with Maximum Payload (kilometres)

Useful data fields in the ASQP Database:

 IATA carrier code

 Flight number

 Depart airport

 Arrival airport

 Date of operation

 Day of week

 IOAG depart time

 Actual depart time

 IOAG arrival time

 CRS arrival time

 Actual arrival time

 Wheels off time 

 Wheels on time

 Aircraft Tail number

 Taxi out time

 Taxi in time

Useful data fields in the JP Airline Fleets Database:

 Operator Name 

 Operator IATA Code 

 Operator ICAO Code

 Aircraft Tail number

 Aircraft type and subtype

 Month and year of manufacturing

 Construction number

 Previous identity

 Number of engines

 manufacturer of engines

 exact type of engines

 Maximum Takeoff Weight (kilograms)

 Seat configuration (or other use than for passenger services)
CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2 2 C-45

APPENDIX

LIST OF REFERENCES

FAA, 1995, Technical Data to Support FAA Advisory Circular on Reducing Emissions from 

Commercial Aviation, http://www.epa.gov/otaq/regs/nonroad/aviation/meta-faa.txt .

IPCC, 1999, Aviation and the Global Atmosphere, Intergovernmental Panel on Climate Change, 

Cambridge University Press, ISBN 0 521 66404 7.

B. Kärcher et al., Particles and cirrus clouds (PAZI) - Overview of results 2000-2003. In: 

Proceed. European Workshop Aviation, Aerosols and Climate, R. Sausen and G.T. Amanatidis 

(Eds.), Air Pollution Research Report No. 83, Commission of the European Communities, 197-

206, 2004.

Hagen, D.E., P.D. Whitefield and H. Schlager (1996) Particle emissions in the exhaust plume 

from commercial jet aircraft under cruise conditions, J. Geophys. Res., 101, 19,551-19,557.

B. Kärcher et al., Particles and cirrus clouds (PAZI) - Overview of results 2000-2003. In: 

Proceed. European Workshop Aviation, Aerosols and Climate, R. Sausen and G.T. Amanatidis 

(Eds.), Air Pollution Research Report No. 83, Commission of the European Communities, 197-

206, 2004.

Coordinating Research Council, Inc., Handbook of Aviation Fuel Properties, Third Edition CRC 

Report No. 635, Alpharetta, GA, USA, 2004.

Hagen, D.E., P.D. Whitefield and H. Schlager (1996) Particle emissions in the exhaust plume 

from commercial jet aircraft under cruise conditions, J. Geophys. Res., 101, 19,551-19,557.

NRC, 1988, Research Priorities for Airborne Particulate Matter: I. Immediate Priorities and a 

Long-Range Research Portfolio, Committee on Research Priorities for Airborne Particulate 

Matter, National Research Council, http://www.nap.edu/catalog/6131.html.

NRC, 2004, Research Priorities for Airborne Particulate Matter: IV. Continuing Research 

Progress, Committee on Research Priorities for Airborne Particulate Matter, National Research 

Council, http://www.nap.edu/catalog/10957.html.

EPA, 2004, Particulate Matter Research Program, five years of progress, 

http://www.epa.gov/pmresearch/pm_research_accomplishments/pdf/pm_research_program_five_

years_of_progress.pdf

NARSTO, 2004, NARSTO (2004) Particulate Matter Assessment for Policy Makers: A 

NARSTO Assessment. P. McMurry, M. Shepherd, and J. Vickery, eds. Cambridge University 

Press, Cambridge, England. ISBN 0 52 184287 5.

Petzold, A. and F.P. Schröder (1998) Jet engine exhaust aerosol characterization, Aerosol Sci. 

Technol., 28, 62-76.

Petzold, A., R. Busen, F.P. Schröder, R. Baumann, M. Kuhn, J. Ström, D.E. Hagen, P.D. 

Whitefield, D. Baumgardner, F. Arnold, S. Borrmann, and U. Schumann (1997) Near field 

measurements on contrail properties from fuels with different sulfur content, J. Geophys. Res.,

102, 29,867-29,880.

Petzold, A., A. Döpelheuer, C.A. Brock, and F.P. Schröder (1999) In situ observations and model 

calculations of black carbon emission by aircraft at cruise altitude, J. Geophys. Res., 104, 22171-

22181.
2 C-46

CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2

Petzold, A. and F.P. Schröder (1998) Jet engine exhaust aerosol characterization, Aerosol Sci. 

Technol., 28, 62-76.

Petzold, A., R. Busen, F.P. Schröder, R. Baumann, M. Kuhn, J. Ström, D.E. Hagen, P.D. 

Whitefield, D. Baumgardner, F. Arnold, S. Borrmann, and U. Schumann (1997) Near field 

measurements on contrail properties from fuels with different sulfur content, J. Geophys. Res.,

102, 29,867-29,880.

Petzold, A., A. Döpelheuer, C.A. Brock, and F.P. Schröder (1999) In situ observations and model 

calculations of black carbon emission by aircraft at cruise altitude, J. Geophys. Res., 104, 22171-

22181.

Petzold A et al, Particle emissions from aircraft engines – a survey of the European project 

PartEmis, Meterologische Zeitschrift, Vol. 14, No. 4, 465-476 (August 2005).

SAE AIR5715, Procedure for the Calculation of Aircraft Emissions, 

http://www.sae.org/technical/standards/AIR5715 , (July 2009).

Schumann U., J. Ström, R. Busen, R. Baumann, K. Gierens, M. Krautstrunk, F.P. Schröder and J. 

Stingl (1996) In situ observations of particles in jet aircraft exhausts and contrails for different 

sulfur-containing fuels, J. Geophys. Res., 101, 6853-6869.

Schumann, U., F. Arnold, R. Busen, J. Curtius, B. Kärcher, A. Kiendler, A. Petzold, H. Schlager, 

F. Schröder, and K.H. Wohlfrom (2002) Influence of fuels sulfur on the composition of aircraft 

exhaust plumes: The experiments SULFUR 1-7, J. Geophys. Res., 107 (10.1029/2001JD000813), 

AAC 2-1 – AAC 2-27.

Whitefield, P.D., D. Hagen, J. Wormhoudt, R.C. Miake-Lye, C. Wilson, K. Brundish, I.A. Waitz, 

S. Lukachko, and C.K. Yam, 2002: NASA/QinetiQ Collaborative Program – Final Report, NASA 

TM-2002-211900 and ARL-CR-0508, NASA, Washington, DC, USA, 193 pp.

EXAMPLES OF MODELLING SYSTEMS

The following list contains examples of modelling systems for airport local air quality studies. 

This list is neither complete nor prescriptive.

Name and Version Availability Website

ADMS Application, publicly available www.cerc.co.uk

ALAQS-AV Experimental, available to Eurocontrol 

member states and other users by 

special agreement.

www.eurocontrol.int

AEDT-EDMS 5.1 Application, publicly available www.faa.gov

LASPORT 2.0 Application, publicly available www.janicke.de
CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2 2 C-47

Chapter 2

Emissions Inventory

Annex 1

Aircraft Emissions

Appendix D

First Order Approximation v3.0 Method

for Estimating PM Emissions from Aircraft Engines
2 C-48

CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2

FIRST ORDER APPROXIMATION V3.0 (FOA3.0) for ESTIMATING PARTICULATE 

MATTER (PM) EMISSIONS from AIRCRAFT ENGINES

Nomenclature

AFR Air-to-Fuel Ratio (mass basis).

BPR By-Pass Ratio.

CI Carbon Index. A measure of the black carbon mass per

standard volume of flow. The volume is in standard cubic 

meters Standard atmosphere is defined as the volume occupied 

at 273.15 degrees Kelvin and 1 atmosphere of absolute 

pressure). (mg/m3 produced by burning 1 kg fuel).

EI Emission Index. A pollutant emission rate based on one

kilogram of fuel burned. The units of an EI are normally given

as g/kg fuel. However, for convenience the units of mg/kg of 

fuel are used in this document unless explicitly stated

otherwise.

EIHC Emission index for total hydrocarbons as listed in the ICAO

Data Bank. (g/kg fuel)

EIHCCFM56 Emission index for total hydrocarbons for the CFM56-2-C5

engine as listed in the ICAO Data Bank (g/kg fuel).

EIPMvol-orgCFM56 Emission index for CFM56-2-C1 engine as derived in the 

APEX1 measurements. (mg/kg fuel)

EIHCEngine Emission index for total hydrocarbons from the ICAO Data

Bank for the subject engine. (g/kg fuel)

EIPMnvols Emission Index for non-volatile particulate matter primarily

consisting of black carbon. (mg/kg fuel)

EIPMtotal Total particulate matter emission index for both volatile and 

non-volatile components. (mg/kg fuel)

EIPMvol – FSC Emission Index for volatile sulphate particulate matter due to

fuel sulphur. (mg/kg fuel)

EIPMvol-FuelOrganics Emission index for organic volatile particulate matter primarily

due to incomplete combustion of fuel. (mg/kg fuel)

HC Total hydrocarbons.

ICAO International Civil Aviation Organization.

FOA First Order Approximation. FOA3.0 is the latest version of the

methodology to provide emission indexes for particulate matter 

emitted from aircraft listed in the ICAO Data Bank.

FSC Fuel sulphur content. (mass fraction)

LTO ICAO Landing Take-Off cycle.

MWout Molecular weight of SO4

-2

(SVI = 96).

MWSulphur Molecular weight of elemental sulfur (SIV = 32).

PM Particulate Matter.

Qcore Exhaust volumetric flow rate as related to fuel burn (m3/kg

fuel).

QMixed Exhaust volumetric flow rate including that due to fuel burn 

and the bypass air (m3/kg fuel).

SF Scaling factor.
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Appendix C to the Report on Agenda Item 2 2 C-49

SN Smoke Number. The methodology in this document based on 

smoke numbers as defined in Appendix 2 in the ICAO Annex

16 document.

SNmode Smoke number for one of the ICAO defined modes (take-off,

climb-out, approach, or idle).

SNmax Maximum smoke number.

STP Standard temperature and pressure. As used in this

document is 273.15 degrees Kelvin and 1 atmosphere of 

absolute pressure.

ε Fuel sulphur conversion efficiency (mass fraction).

δ Ratio of 

56

56

HC CFM

PM vol orgCFM

EI

EI



as derived for use in Equation 9. 

(mg/kg)

1. Introduction

FOA3.0 is a method for estimating the particulate emissions both non-volatile (soot) and volatile 

in the form of Emission Indices (EIs) as mass emitted per kilogram of fuel.1,2 Currently there are 

three components to the estimation process and each must be calculated separately, with the total 

EI being the sum of the parts. The basic technique for each component of Particulate Matter (PM) 

is as follows.

1.1 Non-volatile PM (EIPMnvols)

The calculation of non-volatile PM is based on the engine‘s Smoke Number (SN), Air Fuel Ratio 

(AFR) and if applicable its by-pass ratio (BPR). The essence of the technique is to convert the SN 

via an experimental correlation into a Carbon Index (CI). The CI is the mass of non-volatile PM 

per unit volume of exhaust. Using the engine AFR and BPR the volume of the exhaust (Q) per 

kilogram of fuel is calculated thence the product CI and Q gives the EI with the unit of mass per 

kilogram of fuel burn. Units as reported in this work are mg/kg of fuel unless otherwise stated. 

The EI must be computed for the various power settings used in the vicinity of airports for 

EIPMnvols.

1.2 Volatile Sulphate PM (EIPMvol – FSC)

Volatile sulphate PM is formed from the fuel sulphur via oxidation of SO2 (SIV) to SO3 (SVI) and 

subsequent hydration, in the exhaust plume, of the SO3 to H2SO4. The EI is calculated from the 

fuel sulphur content and the conversion rate of SIV to SVI (ε). As such, the EI is does not vary by 

power setting.

1.3 Volatile Organic PM (EIPMvol-FuelOrganics)

Measurements of condensable organics in the engine exhaust are very limited. Based on the 

assumption that condensable organics are directly related to unburned hydrocarbons, an estimate 

is made by scaling the engine‘s reported ICAO (International Civil Aviation Administration) 

Hydrocarbon (HC) EI to those of other engines in the database. Making a second assumption that 

modern engines behave in a similar manner, the HC ratio can be multiplied by the volatile 
2 C-50

CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2

organic PM EI for the CFM56-2-C1 engine which was measured during NASA‘s Aircraft Particle 

Emissions Experiment 1 (APEX1).3 The result is an EI that is both engine and power setting 

specific for the volatile organic PM.

1.4 PM from Engine Lubricant

Data are not available to allow prediction of this EI for PM. It is currently assumed, based upon 

measurement results from APEX1, that the present EI volatile organic PM includes a contribution 

due to lubrication oil.

2. Data Sources

2.1 ICAO Engine Emissions Data Bank

Values of SN, EIHC and BPR for engines can be found in the ICAO Data Bank for the four power 

settings of the Landing Take-off cycle (LTO). Unfortunately there are gaps in the data bank for 

SN and BPR values. This problem is being addressed by ICAO‘s Committee on Aviation 

Environmental Protection as follows:

 Addition of new engine data by late 2008.

 Clarification for mixed turbofans as to whether the measurements were made on the 

engine core or over both the core and by-pass flows by late 2008.

 Addition of missing SN data by late 2008.

Since the SN data within the ICAO emissions data bank is fragmentary for many engines, some 

only showing the maximum SN, general guidelines have been developed to help fill-in the data 

gaps. These guidelines apply when instead of a listed value the symbol ―-― or ―NA‖ appears 

which denotes that either the SN was not derived at that particular power setting or it was not 

reported since only the maximum is required. These guidelines were developed by Calvert4and 

are based on analyzing modal trends within groups of engines to derive scaling factors that can be 

used to predict the missing data. A scaling factor is a ratio of a modal SN to the maximum SN for 

an engine:

max

mod

SN

SN SF e



(1)

where SF = Scaling Factor

SNmode = SN for one of the modes (take-off, climb-out, approach, or idle)

SNmax = Maximum SN

In order to reduce the uncertainties in developing the SF values, SNs with values less than 6 were 

excluded from the analysis. The resulting SF values are presented in Table 1. The majority of 

engines are covered by the category non DAC (Double Annular Combustor) engines, however, 

Aviadgatel, General Electric CF34, Textron Lycoming and DAC engines have significantly 

different SF vales from the norm.
CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2 2 C-51

Engine 

Category

Takeoff Climb-out Approach Idle

Most non-DAC 

engines

1.0 0.9 0.3 0.3

Aviadgatel 

engines

1.0 1.0 0.8 0.3

GE CF34 

engines

1.0 0.4 0.3 0.3

Textron 

Lycoming 

engines

1.0 1.0 0.6 0.3

GE and CFM 

DAC engines

0.3 0.3 0.3 1.0

Table 1. Suggested SF Values to Predict Missing SNs within the ICAO Emissions

Databank.

Using these SF values and Equation 1, missing SN data can be reasonably filled-in if at least one 

of the modal SN values for an engine is known.

It is also important to note that in addition to the missing SNs in the ICAO Data Bank, other 

concerns also exist. If a SN is listed as zero (0) by the manufacturers no attempt has been made 

to change the value. In these cases, non-volatile PM estimates will be also be zero which is 

unrealistic but it was considered to be undesirable by the group to change any listed values. In 

some cases the SN for the idle power setting is listed with an asterisk (*) as a superscript. This 

indicates that the SN has been calculated at a power setting other than 7%. Finally, if the value is 

preceded by the symbol ―<‖ the provided value should still be used.

To assist in on-going analysis, a separate table has been included in spreadsheet form (Calvertmethod-Databank-Issue_15-C.xls) as the interim recommended values. Manufacturers are 

working to include all SNs for engines still in production in the ICAO Data Bank and those 

values will replace those included in the table.

2.2 Air-Fuel-Ratio (AFR)

AFR is not included in the ICAO Data Bank. This problem has been overcome by the use of 

average fleet AFRs. These generic values were agreed with representatives of the three main 

engine manufacturers and are shown in Table 2. 

Power Setting AFR

7% (idle) 106

30% (approach) 83

85% (climb-out) 51

100% (take-off) 45

Table 2. Representative Air-Fuel-Ratios Listed by ICAO Power Settings (Mode)
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Appendix C to the Report on Agenda Item 2

2.3 Non-Volatile PM (EIPMnvols)

The calculation of EIPMnvols is accomplished by first computing the CI, which is based on a 

statistical correlation with the ICAO SN being the independent variable. Derivation of the 

appropriate SN when the value is not available in the ICAO Data Bank was described in Section 

2.1. Also of note is that the statistical correlation equation that must be used has two forms 

depending on the value of the SN. The dividing line is a SN value of less than or equal to 30 or 

above 30. 

The independent variable for the derivation of the flow rate is the AFR which was listed for each 

power setting (mode) in Section 2.2. Of note is that two possible choices exist for the appropriate 

flow rate to use. This is due to SNs being listed either by core flow or mixed flow in the ICAO 

Data Bank. The listing in the ICAO Data Bank for Engine Type (TF or MTF) allows the choice 

to be easily made. However, the Data Bank is undergoing changes and the user should be careful 

in their choice. 

The CI must then be multiplied by the appropriate flow rate to determine EIPMnvols.

2.4 Volatile Sulphate PM (EIPMvol – FSC)

Fuel sulphur contents (FSC) can vary widely between different batches of aviation fuel and are 

not included in the ICAO Data Bank. For application to the FOA airport, this input has been left 

as a variable to allow the most applicable value, such as the national and/or international mean 

sulphur contents, should be used. As a guide, typical FSC values rang from 0.005 to 0.068 

weight percent5 with a global average of 0.03 weight percent6. Using a conservative value of 

0.068 weight percent is currently recommended in the absence of more specific FSC data.

There is uncertainty about the SIV to SVI conversion process, the non-linear production of SVI that 

varies with changing FSC and engine operating conditions. The variable for fuel sulphur 

conversion efficiency (ε) may be input directly by the practitioner if detailed information is 

known. However, the value is often unknown and a default value is recommended in these 

situations. Based on the most recent measurements from APEX and PARTEMIS7, the range of 

the sulphur conversion efficiency can range from 0.5 to over 3.5 wt%. A median value of 2.4 

wt%, based on the APEX measurements, is recommended as the default value. The value of the 

fuel sulphur conversion efficiency is still a topic of ongoing research and future refinements are 

expected.

2.5 Volatile Organic Aerosol (EIvol-FuelOrganics)

Organic Volatile PM is calculated from the engine ratio of EIHC reported in the ICAO databank 

with the denominator being the EIHC for the CFM56-2-C5 engine which is the closest value to the 

engine measured during APEX13. This ratio is multiplied by the measured volatile organic PM 

EI from APEX1 for the CFM56-2-C1 engine. The measured values are shown in Table 3.
CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2 2 C-53

LTO Mode EIPMVol-orgCFM56

(mg/kg fuel)

Take-off 4.6

Climb-out 3.8

Approach 4.5

Idle 11.3

Table 3. Measured Volatile EI from Reference 1 Used to Calculate Organic Volatile PM.

3. PM EI Calculation

3.1 Non-volatile PM (EIPMnvols)

The CI at STP for SN ≤ 30 is calculated from Equation 28.

CI 0.0694(SN) mg / m based on 1 kg of fuel burn 1.234 3

(2)

For SN > 30 Equation 3 should be used.

CI 0.0297(SN) 1.802(SN) 31.94 mg / m based on 1 kg of fuel burn 2 3  

(3)

The exhaust volumetric flow rate at STP for the engine core is:

QCore 0.776(AFR) 0.877 m / kg 3 

(4)

Where AFR is the mode specific value from Table 2. 

It should be noted that the constants in this equation have the units of m3/kg of fuel. Similarly, 

constants used for other equations listed in this document will have units.

And for a mixed (core and by-pass) flow:

QMixed 0.776(AFR)(1 BPR) 0.877 m / kg 3  

(5)

EI CI Q mg kg fuel PM nvol ( )( ) /

(6)

3.2 Volatile Sulphate PM (EIPMvol – FSC)

The EI for sulphate PM is calculated from:

mg kg

MW

FSC MW

EI

Sulphur

out

PMvols FSC /

( )( )( )

(10 )

6

















 



(7)
2 C-54

CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2

Where MWout = 96 (SO4

-2

) and MWSulphur = 32. The values of FSC and ε are user defined with 

default values as previously defined.

3.3 Volatile Organic PM (EIPMvol – Fuel Organics)

The EI of the volatile organic PM is calculated from:

EI mg kg

EI

EI

HC Engine

HCCFM

PM vol orgCFM EI ( ) /

56

56

PMvol- Fuel Organics





(8)

Where EIHCCFM56 is the ICAO total hydrocarbon emission index for the CFM56-2-C1 engine. 

EIPMvol-orgCFM56 is the APEX1 measured volatile organics EI from Table 3, and. EIHCEngine is the 

EIHC from the ICAO Data Bank for the subject engine (engine where the EI is being determined). 

Of note is: 1) the units of EIHCEngine and EIHCCFM56 are g/kg fuel as listed in the ICAO Data Bank 

and cancel; and, 2) that the ratio of EIPMvol-orgCFM56 and EIHCCFM56 is a constant for each mode. 

Since only the modal value of the EIHC for the subject engine changes, a simplification can be 

made to Equation 8 which is easier to calculate. This results in:

EI mg kg HC Engine EI ( )( ) /

PMvol- Fuel Organics  

(9)

Where δ is constant ratio by mode. Values of this constant are given in Table 4 for each mode.

LTO Mode δ (mg/g)

Take-off 115

Climb-out 76

Approach 56.25

Idle 6.17

Table 4. Modal Values for the Ratio of EIPMVol-orgCFM56 and EIHCCFM56 in Equation 8

4. Example Calculations

This example is based on calculating PM EIs for the JT8D-217 series engines with an ICAO UID 

of 1PW018. Derived values are presented for all modes while complete calculations are only 

shown for the idle since the process is simply repeated for the other modes using appropriate 

variables. Of course the PM for sulphur does not change by power setting and is the same for all 

modes. HC EI and SN data for the idle mode from the ICAO Emission Data Bank for this engine 

is shown in Table 5.
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Appendix C to the Report on Agenda Item 2 2 C-55

LTO Mode EIHC (g/kg) SN

Takeoff 0.28 13.2

Climb 0.43 Missing

Approach 1.6 Missing

Idle 3.33 Missing

Maximum Value NA 13.3

Table 5. ICAO Data for the JT8D-217 Series Engine, Idle Mode.

To fill-in the missing SN value for the idle mode, a scaling factor of 0.3 from Table 1 

corresponding to ―most non-DAC engines‖ and the idle mode is used:

SNmode (0.3)(13.3)  3.99

To calculate non-volatile PM EI (EIPMnvols) as function of SN, since the SN< 30, Equation 2 is 

used.

1.234 3 CI  0.0694(3.99)  0.383 mg / m

Based on the ICAO Data Bank, the mixed exhaust volumetric flow rate should be used with a 

bypass ratio of 1.73. Using the idle AFR of 106 (Table 2), the exhaust

volumetric flow rate is calculated, via Equation 5, as follows:

Q m kg fuel Mixed 0.776(106)(1 1.73) 0.877 225.436 /

3

   

Hence:

EIPMnvols  (0.383)(225.436)  86.3 mg / kg

or 0.086 g/kg

Assuming a fuel sulfur content of 0.068 wt% (fraction 0.00068) and a SIV to SVI conversion rate 

of 2.4 wt% (fraction 0.024), the modal independent EIPMvol -FSC is calculated as follows:

49.0 mg / kg

32

(0.00068)(0.024)(96)

EI (10 )

6

PMvol- FSC 













or 0.049 g/kg

The EIPMvol – Fuel Organics may be calculated using the values in Table3, Table 5, and the EIHC for the 

specific engine as listed in the ICAO Data Bank corresponding to the idle mode:

(3.33) 20.6 mg / kg

1.83

11.3

EI PMvol-FuelOrganics 

or 0.021 g/kg

Alternatively, the values in Table 5 may be multiplied by the EIHC for the specific engine as listed 

in the ICAO Data Bank as:
2 C-56

CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2

EI PMvol-FuelOrganics (6.17)(3.33)  20.5 mg / kg

In summary, the example calculation results of applying FOA3 to the idle mode for the JT8D-217 

series engine are:

EIPMnvols  86.3 mg / kg EI PMvol- FSC  49.0 mg / kg EI PMvol-FuelOrganics

 20.6 mg / kg

The total EI for all components of PM emissions is then:

EIPMtotal = 86.3 + 49.0 + 20.6 = 155.9 mg / kg of fuel or 0.156 g/kg of fuel burn.

While the EI for sulphur does not change by power setting, the other EIs must be calculated for 

each mode. Table 6 shows the results for all modes. Of note is that the maximum smoke number 

was used for the non-volatile PM EI estimates.

ICAO Defined 

Power Setting 

(mode)

EIPMn-vols EIPMvols - FSC EIPMvolFuelOrganicsTotal PM EI 

by Mode

Idle 86.3 49.0 20.6 155.9

Approach 67.6 49.0 90.0 206.6

Climb-out 161.7 49.0 32.7 243.4

Takeoff 161.2 49.0 32.2 242.4

Table 6. Values of EIPM for the JT8D-217 Series Engine (mg/kg fuel)

5. Uncertainties

As its title suggests FOA3.0 is an approximation. The PM ad hoc group of CAEP Working 

Group 3 has endeavoured to make the methodology as accurate as possible. However, the user 

should be aware that not all physical concepts are well understood and data for many of the 

parameters are sparse. This leads to uncertainties in the estimation methodology including: 

 Lack of data in the ICAO Data Bank, particularly:

o SN.

o Detail of whether the by-pass flow was included in the SN measurement.

 Reliance on average values of the specific engine‘s:

o AFR.

o Fuel sulphur content.

o S

IV to SVI conversion factor.
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Appendix C to the Report on Agenda Item 2 2 C-57

o Combustor technology.

 Extremely limited data on volatile organics.

 No information on the effect of engine lubricants.

 Inaccuracies and measurement differences in reported data:

o Annex 16 states that measured SNs can vary by ± 3.

o Reported mass measurements vary considerably resulting in ranges of values.

The limitations of the Data Bank are being addressed by the engine manufacturers through CEAP 

WG3. Values of engine AFR are unlikely to be available as they are commercially sensitive. 

More confidence in the SIV to SVI conversion factor, volatile organics and the effect of engine 

lubricant will come with more experimental measurements and improved measurement 

techniques.

Since the inception of the FOA process, and it development into FOA3.0, the methodology has 

continued to evolve and the estimate accuracy improved. The FOA process is not static and will 

continue to evolve until measurements are sufficient that the approximation is no longer needed. 

In the interim, CAEP and specifically the ad hoc PM working group will continue to review 

available information to improve the methodology and the input parameters to the degree 

possible.

6. References

1. CAEP, "Particulate Matter Charactisation", Information Paper No. 6, Working Group 3-

Technical Emissions, ICAO Committee for Aviation Environmental Protection (CAEP) meeting, 

February 2007.

2. ICAO, "Airport Air Quality Guidance Manual," Document 9889, ICAO PRELINIMARY 

UNEDITED VERSION - 15 April 2007.

3. NASA. Aircraft Particle Emissions Experiment (APEX). C.C. Wey, U.S. Army Research 

Laboratory, Glenn Research Center, Cleveland, Ohio. ARL–TR–3903. 2006-214382, September 

2006.

4. Calvert, J.W. ―Revisions to Smoke Number Data in Emissions Databank.‖ Gas Turbine 

Technologies, QinetiQ. February 23, 2006.

5. Coordinating Research Council, Inc., Handbook of Aviation Fuel Properties, Third Edition 

CRC Report No. 635, Alpharetta, GA, USA, 2004.

6. IPCC, 1999, Aviation and the Global Atmosphere, Intergovernmental Panel on Climate 

Change, Cambridge University Press, ISBN 0 521 66404 7.
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Appendix C to the Report on Agenda Item 2

7. Katragkoue, E., S. Wilhelm, F. Arnold, C. Wilson, First gaseous Sulfur (VI) measurements in 

the simulated internal flow of an aircraft gas turbine engine during project PartEmis, ISSN 0094-

8276, Geophysical research letters, November, 2003.

8. S. P. Girling, C. D. Hurley, J. P. Mitchell and A. L. Nichols, Development and 

Characterization of a Smoke Generator for the Calibration of Aerosol Emissions from Gas 

Turbine Engines, Aerosol Science and Technology, 13:8-19, 1990.

— — — — — — — —
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Appendix C to the Report on Agenda Item 2

Chapter 4

DISPERSION MODELING

Content

1. Introduction

2. External Requirements and Drivers

3. General Dispersion Concepts

4. Required Model Inputs

5. Dispersion Calculation

6. Model Outputs

7. Modeling Application and Interpretation of Results

8. References

 Annex 4A. Overview of Dispersion Modeling Methodologies

 Annex 4B. Commonly Used Dispersion Models in the Vicinity of Airports

 Annex 4C. Climatological Information Sources

1. INTRODUCTION 

In the emission inventory chapter, guidance on estimating the mass emitted for various 

pollutants was discussed. However, the total mass emitted does not account for mixing in the 

atmosphere which determines local concentrations or how much mass is mixed in the air at 

any given time. Additional modeling is required to estimate these local ambient 

concentrations.

A trace substance that has been released from a source into the free atmosphere will be 

transported by the mean wind field and dispersed by atmospheric turbulence. This process is 

referred to as atmospheric dispersion. Dispersion can be more rigidly defined1as ―the 

scattering of the values of a frequency distribution from an average.‖ It then follows that 

atmospheric dispersion modeling is the mathematical simulation of the scattering or mixing 

process in the ambient atmosphere. The trace substances most often evaluated are regulated 

atmospheric pollutants and were delineated in the emission chapter for airport sources. In an 

airport-related dispersion calculation, the atmospheric mixing of these trace substances or 

pollutants that are emitted from local sources is modelled based on scientific principals and 

the resulting concentration distributions (usually near the ground) are predicted. The results, 

or predicted atmospheric concentrations, form the basis for local air quality (LAQ) impact 

studies and are used to show compliance with required regulations and/or standards.

This chapter presents the needs for dispersion modeling in the vicinity of airports, provides a 

brief overview of dispersion models, summarizes typical practices that occur during 

atmospheric dispersion modeling at airports, and examines how predicted concentrations are 

used to estimate impacts. The chapter has been laid out to follow the procedure established in 

the emission chapter. That is, the required modeling will be discussed in a simple, advanced, 

and sophisticated approach.

2. EXTERNAL REQUIREMENTS AND DRIVERS 
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Appendix C to the Report on Agenda Item 2

This section discusses the need for Dispersion Modeling and the external drivers that both 

cause and affect this need. As described in detail in Chapter 1: Regulatory Frameworks and 

Drivers, air quality assessments for proposed actions at airports are often necessary to comply 

with:

 Worsening air quality leading to reduced margins against existing regulations;

 Increased awareness of health impacts, leading to the production of new regulations, 

including the addition of new pollutant species;

 Development constraints resulting from limitations imposed by the need to meet air 

quality standards;

 Increasing public expectation regarding air quality levels; 

 Public relations exercises carried out by airport and environmental lobbies; and,

 Legislative requirements of the various countries and regions.

Emission modeling to meet these requirements has been previously discussed. Emission 

modeling, a prerequisite to dispersion modeling, allows the change in emissions to be 

reviewed temporally and spatially. However, direct impacts are more related to the ambient 

concentrations and not just the mass of emissions emitted. Ambient air quality standards, 

evaluation of real impacts, and health impacts are better evaluated by the use of ambient 

concentrations than with mass emitted. As previously described, atmospheric mixing of 

emissions results in ambient concentrations most often used to determine local impacts. 

Measurements, described in Chapter 5 of this guidance, can be very costly, only define the 

concentration at a point in space for each measurement, and do not readily reveal the 

fractional contribution from each contributing source. Dispersion modeling allows the 

evaluation of local air quality to be done at a reasonable cost. Regardless, the need for 

dispersion modeling is to determine the ambient mixing as a part of the overall analysis 

process.

Beyond the evident need for dispersion modeling, ordinances or legislation often mandates 

the estimation process be used. The regulations resulting from these legal requirements may 

also specify how the dispersion modeling must be accomplished or how variables are 

considered. The analyst is prompted to review any related requirements to insure the process 

occurs as mandated.

3. GENERAL DISPERSION CONCEPTS 

This section provides a brief overview of the basic physical concepts included in dispersion 

modeling and the process required. References are included to allow interested parties to go 

deeper in exploring these concepts than presented here. The understanding of how the models 

work should lead to more appropriate use of the models. 

When a trace element or pollutant is emitted from a source, the final fate is determined by the 

characteristics of the pollutant, source characteristics, atmospheric motion, and local 

topography. Each of these parameters plays an important role in the local concentrations. A 

pollutant that is released in its final form is called a primary pollutant. Primary pollutants 

that are very slow to react with other gases in the atmosphere are called passive pollutants. 

Primary pollutants such as carbon monoxide (CO) are often called inert because of the very 

long reaction time and residence time in the atmosphere. Secondary pollutants are formed 

in the atmosphere when the original precursor emitted undergoes chemical reactions or other 
CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2 2 C-61

conversion processes in the atmosphere and forms a new pollutant. The pollutant is termed 

secondary since the final composition is not as released from the source. Ozone (O3) is a 

secondary pollutant. 

The pollutant source affects the local concentrations due to the location of the release, the 

total mass flow rate, and the dynamics of the exhaust air due to the effect on the atmospheric 

dispersion in addition to the atmospheric motion. Atmospheric motions determine the overall 

direction the emissions travel and are primarily responsible for the mixing with the ambient 

atmosphere (dispersion), thereby creating a pollutant  ̳plume‘ (or  ̳puff‘). The direction of 

the plume is determined by the large scale motion such as the mean wind flow while mixing 

is more related to small scale eddies in the flow referred to as turbulence. Likewise terrain 

characteristics and local building structures will have an effect on local area concentrations 

due to changes in the wind patterns and the generation of turbulence. All of these parameters 

affect atmospheric dispersion and lead to a three-dimensional, generally time-dependent 

concentration distribution of the emitted trace substance (pollutant). Likewise other 

substance-specific processes may have an effect such as dry and wet deposition.

The quantities that determine atmospheric dispersion resulting in a local concentration can be 

grouped as follows:

 Q1 Source parameters (location, shape, dynamics of the exhaust air);

 Q2 Emission parameters (emission strength of each trace substance for each source);

 Q3 Substance parameters (e.g. conversion or deposition properties);

 Q4 Atmospheric parameters (e.g. wind speed, wind direction, turbulence properties, 

and temperature); and,

 Q5 Terrain parameters (e.g. surface roughness, terrain profile, obstacles).

Not all of the above parameters are independent and most of the parameters are timedependent. It is evident that the parameter set includes additional information than was 

required for emission calculations, even when emission allocation has been conducted as 

described in Chapter 3.

At airports, the relevant sources can be grouped as follows:

 S1 Aircraft, including Auxiliary Power Units (APUs);

 S2 Aircraft Handling Sources (e.g. Ground Support Equipment (GSE), aircraft 

fueling, airside vehicles);

 S3 Stationary and area sources (e.g. power plants, fire training); and,

 S4 Airport access traffic (e.g. landside motor vehicles). 

The dispersion methodologies used are of course only for those sources directly included in 

the model. Regional or background contributions also add to the total local concentration to 

produce the total concentration. The total concentration is needed to compare to the 

applicable criteria or standards. These background sources can be substantial and come from 

sources at varying distances from the airport. How background sources and the resulting 

concentrations are accounted for needs to be considered based on the spatial resolution of the 

modeling area and data sources to be used such as long-term ambient monitoring stations. 

This stands in contrast to noise assessments, where the airport contribution is usually by far 

the dominating component. To account for the overall concentration the background 

concentration must be added to the concentration predicted by the models. This results in:
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[4.1]

Where: c = concentration with the subscripts t, s and b representing total, 

source, and background, respectively.

The summation in Equation 4.1 represents the concentration at a point in space from all 

sources and is the value that is compared to applicable ambient air quality standards. Of note 

is that concentration, c, is pollutant specific. That is, pollutants of different species cannot be 

added.

Figure 4.1 shows an a) an overview of the modeling process and b) the detailed steps 

required.

a. Process Overview

b. Detailed Breakdown of Atmospheric Concentration Due to S1 – S4

Figure 4.1. Inputs and Outputs of Dispersion Modeling.2

Several approaches to dispersion modeling have been applied at various airports around the 

world to predict local concentrations. As the science continues to evolve, so will the airport 

models. As such, this chapter will concentrate on the common methodologies currently used 

rather than on specific models.

The actual formulation for these models may vary. To assist the reader in a more 

comprehensive understanding of dispersion model methodologies, model formulations are 

briefly discussed in Annex A. Computer models in commons use for airport dispersion 

modelling are listed in Annex B.

S1-S4

Q1+Q2 Q4 Q5

Q3 Dispersion 

Model Receptors

Atmospheric Concentration at 

Receptors
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4. REQUIRED MODEL INPUTS 

This section provides information on variables needed to perform a dispersion analysis. 

While this is a general overview to provide understanding for the reader, variables required 

will vary by modeling effort (simple, advanced, sophisticated) and the specific model used. 

Additionally, each airport is unique and this large variability, the differences in the 

availability of data, and the desired final product also result in different data sets for each 

airport. 

4.1 Emission Source Information

A brief overview of the information that will be needed to complete the concentrations 

analysis is included in this section. 

4.1.1 Airport Emission Sources

Air pollution sources at airports are many and varied. In order to perform concentration 

modeling, for each source studied, the emission strength for each of the modelled substance 

must be available. A detailed description on the emission sources found at an airport is given 

in Chapter 2 of this guidance manual. 

4.1.2 Airport Temporal and Spatial Considerations (e.g., taxiways, runways, gates)

When performing an emission inventory, spatial and temporal allocations are not always 

required or completed. However, spatial and temporal allocations are of prime importance 

during dispersion modeling since local concentrations will be calculated. These local 

concentrations depend upon the distance to a source and its time of operation. This requires 

not only the emission data, but explicit detail on when and where and in which way the 

emissions occur. Airport spatial and temporal variation was previously discussed during 

emission allocation in Chapter 3. 

Dispersion modeling often relies on Cartesian coordinates (x,y,z) where x and y are the 

horizontal distances and z is the vertical distance from an established datum point. A 

common practice, for easy transfer to maps, is to set the positive y axis is in the north 

direction. A thorough understanding of the airport operation is required for detailed 

dispersion modeling (see Chapter 3). For all but the simple approach, all source locations 

must be established (see Chapter 3) and for dispersion modeling, a new component, the 

receptor must be added as discussed in Section 4.4. The receptor location must be exactly 

specified, as with the source, leading to the use of coordinates such as the Cartesian 

coordinate system. The defined receptor location determines where the concentration will be 

predicted using the dispersion models. This is most often at locations of frequent human use. 

Some dispersion models are based on specific time periods since their dispersion parameters 

change with time after release. This is often an internal parameter, transparent to the user, 

and can be adapted based on the output needs to compare to ambient air quality standards. 

4.1.3 Emission Factors 

Emission factors are needed to determine the rate of release for emissions from each source. 

Emission factors are both source and pollutant specific. The reader is referred to Chapter 2 

for a complete discussion of emission factors.
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4.2 Meteorology

Meteorology is an essential input for the dispersion calculation. Without an input for the local 

weather, it is not possible to perform dispersion modeling except in the simple cases. For all 

modeling of any sophistication, the parameters for the planetary boundary layer (PBL) must 

be known. As with other variables, the degree of sophistication of the modeling process can 

vary but a general listing of needs is discussed here. Additionally, some common sources for 

this data are listed in Annex C.

4.2.1 Wind Data

The horizontal wind speed (velocity) and direction generated by the geostrophic wind 

component and altered by local surface characteristics and other parameters such as terrain is 

of primary importance in all but the simple case. In the advanced and sophisticated approach, 

local climatology must be established in more detail and may include wind data from multiple 

elevations and/or vertical wind gradients. Often this historical data is available from existing 

records (see Annex C). The wind speed and direction will vary by surface characteristics and 

topography, local buildings, surface cover, and nearby influences such as large bodies of 

water, to establish a suitable wind field depending on model requirements. 

4.2.2 Turbulence and Atmospheric Stability

The atmospheric stability can be simply defined as the turbulent status of the atmosphere 

and has a significant effect on the dilution rate of pollutants. Turbulence refers to the small 

motions of the atmosphere, generally circular in nature and referred to as eddies. These 

eddies vary dramatically in size depending on atmospheric stability. Small eddies can ―rip‖ 

apart the plume and cause mixing with the local air while large eddies tend to move the entire 

plume.

Turbulence can be characterized in several ways including empirical methods (e.g., the 

Pasquill-Gifford Stability Classes), the flux Richardson number, the gradient Richardson 

number, or the Monin-Obukhov length. While each requires different inputs to determine, the 

basic meteorological information needed is wind speed by height (wind shear), temperature 

by height (lapse rate), wind velocity fluctuations, and surface characteristics.

Turbulence is often broken into the categories of stable (vertical mixing of pollutants is 

hindered), neutral (vertical motion of the atmosphere is nether hindered or enhanced), and 

unstable (vertical motion of the atmosphere is enhanced).

4.2.3 Upper Air Data

In the advanced and complex analysis it is recognized that the atmospheric conditions change 

with height. To account for this change, meteorological data at greater heights (up to some 

hundred metres) than surface data are often used, although some models can approximate the 

change with height based on surface data and use boundary layer parameterization. If the 

measured data are used, these data come from acoustic soundings, release of balloons with 

instrument packages, and reports by aircraft. 

4.2.4 Temperature

The ambient temperature has an effect on the rate of chemical reactions and may be needed in 

the sophisticated approach. The change of temperature with height (lapse rate) may be 
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needed by models to assist in determining atmospheric stability and could be needed for both 

the advanced and sophisticated approach.

4.2.5 Cloud Cover

Cloud cover has the direct effect of changing the albedo and is often used indirectly for 

atmospheric stability in the advanced approach.

4.2.6 Derived Parameters (Model Specific)

Many parameters may be important depending upon the model chosen (e.g., sensible heat 

flux, surface friction velocity, convective velocity scale, vertical potential temperature 

gradient, Monin-Obukhov length, and the Bowen ratio). Often these parameters can be 

derived from the basic meteorological data listed above. The parameters are not described 

here but if not computed directly by the dispersion model selected, the user should take great 

care to understand these parameters and how they may be derived. 

4.3 Surface Roughness

Different types of surfaces change the frictional characteristics of the surface and affect the 

vertical wind profile and the turbulence characteristics. For airports this is often a vegetative 

flat relief near the runways. But the location and height of buildings such as the terminal, tree 

lines, and for some airports significant changes in the surface profile must all be determined. 

After this determination, charts may be used to determine the value of the surface roughness 

parameter (z0) to be included in the model. Table 4.1 shows an example of values that can be 

selected. Of note is that this is a parameter and not a true length of the objects on the surface.

Table 4.1 Surface Roughness Length, z0,for Typical Surfaces3

Terrain Description Z0 (m)

Water 0.0001

Grassland (winter) 0.001

Grassland (summer) 0.1

Cultivated Land (winter) 0.01

Cultivated Land (summer) 0.2

Swamp 0.2

Desert Shrubland 0.3

Deciduous Forest (winter) 0.5

Deciduous Forest (summer) 1.3

Coniferous Forest 1.3

Urban 1.0 – 3.0

4.4 Receptor Information

A receptor is a location in space that may represent human occupation or simply a location of 

interest. Receptors can also simply be a predetermined grid of a specific size, centered on an 

established airport reference point. Airport receptor locations may be defined on or off of the 

airport. These are chosen by a review of the airport with particular interest in locations where 

normal human activity occurs or in other locations for example nature reserves. The choice of 

receptor locations will result in modelled concentrations at these points used to determine the 

overall impact at that location. 
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4.5 Background Concentrations

As previously discussed (Equation 4.1), background concentrations are due to sources not 

considered during the modeling process. These concentrations must be added on a pollutant 

specific basis to the model results to obtain the total concentration of any pollutant. The 

background concentrations are generated by nearby roadways, industry, commercial 

operations, residential areas, and long-range transport. The background concentration is most 

often determined by long-term measurement stations in the area since the sources are too 

numerous to be modelled during an airport evaluation. The averaged upwind concentration to 

the airport is often used and may be temporally allocated to account for diurnal changes in the 

other local sources. Depending on the pollutant, significant percentages of the overall 

(measured) concentrations may be from background concentrations sometimes brought into 

the study area from large distances.

4.6 Atmospheric Chemistry

As previously mentioned, pollutants may react with other components in the atmosphere after 

being emitted by the source. This causes a change in precursors and creates new pollutants. 

This is particularly important for aircraft emissions where secondary gas and particulate 

matter pollutants are created. This is an advanced topic and will most often be built into the 

model used or may even be ignored depending upon the scope of the study. Chemical 

reactions are always ignored in the simple approach defined here. In the case where 

atmospheric chemistry is not explicitly considered, ratios based on historic data can be 

applied and this is defined in this document as the advanced approach. For example, the ratio 

of NO to NO2 is important. Historic data may provide a typical ratio. This ratio can then be 

applied to the NOx prediction (NO + NO2) which is predicted by models without chemical 

algorithms. If not performed by the model, speciation of hydrocarbons may also be 

approximated in this manner based on the total hydrocarbon prediction and historic data.

Chemical reactions proceed at different rates and are affected by ambient concentrations, 

transport time, and ambient conditions with all being considered in the sophisticated 

approach. The time for the reaction to occur is different for each pollutant and the reaction 

rate is necessary for dispersion modeling of reactive pollutants. 

5. DISPERSION CALCULATION 

Annex A contains a very general overview of the dispersion methodologies while Annex B 

lists models commonly used for airport analysis. The purpose of this section is not to provide 

detailed directions on the use of these methodologies or concepts and the reader is directed to 

the appropriate texts or user manuals for the specific methodology/method chosen. The 

fundamental approach for simple, advanced and sophisticated is described in this section. The 

choice of which method is best suited for the analysis will depend on the data available and 

the desired use of the results.

5.1. Analysis and Level of Effort

As the analyst proceeds from the simple, to the advanced, and to the sophisticated approaches, 

the data requirements increase as well as the analysis time. However, the accuracy increases 

with the additional effort required if the input data is of good quality. Simple approaches 

should be conservative in nature while the advanced and sophisticated approaches will 

provide results that permit the impact analysis to be more realistic. Table 4.2 shows the input 
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variables that may be needed if the simple, advanced or sophisticated approach is chosen. 

Exact needs are determined by the model selected.

Table 4.2 Input Data Needed Depending Upon Approach Taken

Key Parameters Simple Approach Advanced 

Approach

Sophisticated 

Approach

Emissions As described in Chapter 2 of the guidance

Spatial resolution For Case 1: No 

differentiation; 

airport as one 

"emission bubble". 

For Case 3, very 

large mesh size using 

single source 

location such as 

runways.

Defined receptor 

positions with spatial 

resolution on a 

coarse grid (e.g. not 

less than 500m mesh 

size)

Defined receptor 

positions with fine 

grid on a 10 by 10 m 

mesh size, but not 

more than 500 by 

500 m mesh size

Temporal 

resolution

Annual total Monthly or daily 

resolution

Hourly or smaller 

resolution

Meteorological 1. No weather data.

2. Wind speed is 1 

m/s. Wind direction, 

very stable 

atmosphere for 

ground level sources, 

and no plume rise is 

used to predict a 

conservative 

estimated (often 

referred to as ―worst 

case‖) concentration 

calculated at the 

receptor. Mixing 

height not 

considered.

Climatological data 

for multiple 

parameters ranging 

from an hourly to 

daily average 

Turbulence as a 

single parameter 

such as a stability 

classification 

generally from only 

wind speed and cloud 

cover considerations. 

Average mixing 

height for area, 

generally assumed to 

be 914 meters (3000 

feet). 

Detailed 

climatological data 

on a small time scale 

including upper air 

and specific mixing 

height data. Multiple 

derived parameters 

requiring additional 

data such as cloud 

cover and 

temperature 

gradients.

Surface Roughness Assume all area is 

flat and grass.

Consideration of 

major topographical 

features.

Consideration of 

topographical 

features, ground 

cover, and local 

buildings.

Receptor 

Information

General locations at 

ground level.

Specific locations at 

ground level. 

Specific locations 

with varying 

horizontal and 

vertical locations.

Background 

Concentration

1. Not considered.

2. Single value for 

airport area.

Single value for 

airport area.

Temporal and spatial 

considerations 

included.

Atmospheric 

Chemistry

None Typical (analytical) 

transformation ratios 

from established 

studies.

Detailed reaction rate 

constants with 

consideration of local 

ambient 
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concentrations of 

reacting chemical 

species.

The designation 1 in the simple approach refers to the rollback model approach while 2 is a 

conservative analysis often referred to as the “worst” case analysis.

It is again noted that many models will not support all variables or require very specific 

information and it is the responsibility of the analyst to determine which variables are 

required by any model.

5.1 Simple Approach

The simple approach can be thought of in two distinct ways: 1) use of a rollback model in 

which airport data is lacking except for the overall change in operations; and, 2) a simplistic 

so called ―worst case‖ analysis. As in Chapter 2 for emissions, the simple approach is only 

recommended when limited data are available or for initial assessments.

5.1.1. Rollback Approach

The rollback approach is the most simple and requires the least data and as such can be 

performed very quickly. It is also represents the greatest error. In this approach, which is not 

actually dispersion modeling, known emissions and concentrations are scaled according to 

overall changes in the aircraft operations. This assumes all other sources grow or decrease at 

the same rate as the aircraft operations. Equation 4.2 represents the idea numerically:

( / ) 2  1 O2 O1

[4.2]

Where: Δ2 = Total Emissions or Local Area Concentration at Time 2

Δ1 = Total Emissions or Local Area Concentrations at Time 1

O1,2 = Aircraft Operations in LTOs for time 1 and 2, respectively

5.1.2. Worst‖ Case Analysis

In this analysis, wind speed is assumed to be the smallest value that provides reasonable 

answers in a model, typically a constant 1 m/s. The wind is also assumed to be from a 

direction that produces the greatest concentration at the receptor location. The atmospheric 

stability is considered to be very stable for ground level sources and the mixing height is not 

considered. Background concentrations are assumed to be a single, conservative value. Use 

of these parameters results in a so-called ―worst case‖ analysis in that in reality the 

concentrations would rarely, if ever, be this high. These assumptions lead to the logic that if 

criteria or standards are not shown to be exceeded in this conservative estimation where 

predicted concentrations are most likely at a level greater than would normally occur, then 

there is not a substantial impact. Simple models can be used and as such this method can be 

coded into a spreadsheet (such as the use of the Gaussian formulation included in Annex A) 

or graphs and tables may be used. Simple computer models may also be used. The 

advantage is only a small set of data is needed and quick results. The disadvantage is a very 

conservative prediction that overestimates impacts.

Advanced Approach

In this approach, computer coded models are a must. Specific models may be required by the 

reviewing agency, some models are available in the open domain, or proprietary models may 
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be purchased. Each model will have a user guide and most will have a technical manual for 

the interested analyst. The analyst must completely review the user manual and be sure of 

input. The old adage ―garbage in equals garbage out‖ is very true in this case and the result, 

even for the most complete model is only as good as the input data used. Some models may 

include an interactive graphical user interface (GUI) to allow input more easily included. If 

not, input files will have to be created. Some models may have the needed emission factors 

(or in the case of aircraft emission indices) included to also make input easier. In these cases 

the emission inventory may also be accomplished directly in the model. If this information is 

not included, the emission inventory will have to first be completed externally. Temporal and 

spatial allocation may occur at the emission inventory phase or postponed until the dispersion 

analysis.

These models may be the same as in the sophisticated approach with the difference being a 

greater use of default values for input variables, less complete operational data, non-varying 

background concentrations, and a lesser degree of spatial and temporal definition. Models 

inputs contain a large amount of ―default‖ values, that is typical values for airports but not 

actual for the defined airport. Typical models used in the advanced approach for modeling in 

the vicinity of airports include ALAQS-AV, AEDT/EDMS4, ADMS-Airport5, and 

LASPORT6. 

Sophisticated Approach

This approach requires the most extensive data collection effort to define inputs. Default 

values are replaced with real data and this is especially true of meteorological input. 

Operational data is very complete with a much greater emphasis on spatial and temporal 

resolution. The models may be the same as in the advanced approach but with the actual data 

and a much greater use of options. Typical models used in the sophisticated approach for 

modeling in the vicinity of airports include ALAQS-AV, AEDT/EDMS, ADMS-Airport, and 

LASPORT. 

Hybrid Approach

As with emissions, the three basic approaches can be mixed according to need and available 

data. The simple approach, because of the large simplifications that are made, does not lend 

itself to the hybrid approach except in very special situations. The advanced and 

sophisticated approaches are often mixed. This is especially true when the same model is 

used first with a high number of defaults input values for a high level assessment and then 

refined to allow more detailed modeling.

6. MODEL OUTPUTS 

Each model has different outputs but some are common to all models. The first is an echo file 

of the input data when computer models are used. This is an important component of the 

output because it allows the user to check the input data to 1) be sure of the accuracy of input; 

2) make sure the model has interpreted the data input correctly (very important for fixed field 

inputs); 3) evaluate derived parameters by the model which will be reported with the input; 

and, 4) allow the analyst to store the results and later understand the inputs used.

The most important output of course from all models is the calculated concentrations. The 

concentrations will be output as a certain time average (e.g. annual mean or series of daily 

means), possibly supported by some statistics (e.g. percentiles or exceedance frequencies) or 
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even by complete time series (e.g. hourly means at given receptor points). The units of the 

concentrations will typically be either parts-per-million (ppm) or micro-grams-per-cubicmeter (μg/m3

). In the case of particulate matter, only μg/m3 is valid. The calculated or 

predicted concentrations including background should then be compared to the ambient air 

quality standards or criteria with the correct time frame and units.

Some models may also include graphical outputs to assist in determining problem areas or to 

allow a visualization of changes, for example during mitigation modeling. In the 

sophisticated approach multiple derived parameters will also be available in the output.

7. MODELING APPLICATION AND 

INTERPRETATION OF RESULTS 

The analyst should be aware of the fidelity of the results. This depends on the model used, 

the accuracy of the input data, and any assumptions applied.

Uncertainty in Dispersion Modeling

Since air pollution dispersion models vary from the simple to the very complex, there is a 

large difference in the uncertainty from model to model. Hanna7points out that total model 

prediction uncertainty is a combination of parameters including: model physics errors, natural 

or stochastic uncertainty, and data errors. As the number of parameters increases, the natural 

or stochastic uncertainty decreases and the model‘s representation of the physical reality 

becomes better. This leads to more complex models and a greater need for high fidelity input 

data. However, as the number of input parameters increases, the input data errors may 

increase. Poor input data could cause the more complex model outputs to be equal or even 

inferior to using more simplistic models. In addition, model adjustments based on limited data 

sets can lead to additional error.

This makes it extremely difficult to quantify the uncertainty. Models may perform well in 

predicting the maximum occurrences but may do poorly when trying to predict concentrations 

in time and space when compared to measurements. 

Limit values and required model results often refer to statistical quantities like percentiles, 

long-time averages like annual means, or maximum concentrations independent of their 

specific occurrence in time or their accurate location. A model may yield reliable results with 

respect to these quantities even if it shows poor performance in a point-by-point comparison, 

for example with a measured time series at a given location.

Verification Based on Measurements

Complex dispersion models are applied in form of computer programs. In view of quality 

assurance it is required to verify and validate such programs. The verification checks whether 

the program correctly implements the mathematical formulation (algorithms) of the model. 

The validation then checks how well the model respectively the program describes the reality, 

usually by a comparison with measured data sets.

For the validation it is important that these data sets are sufficiently complete, i.e. that the 

validation test can be performed with the smallest amount of additional assumptions. If 

assumptions are required or if assumptions have been implemented in the model or the 

program, it is of importance whether they are based on general grounds or adjusted for 
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example to a specific airport or situation. With regard to input data, complex models are 

usually better able to account for specific airport details and are thus more flexible for 

validation against measured data.

Comparison to Applicable Standards and Criteria

The term impact has been used throughout this chapter. This is because impacts are most 

often evaluated by comparing the predicted concentrations from the dispersion models to 

standards and/or criteria which most often are time-averaged concentrations based on health 

effects. The use of these standards has been addressed in earlier chapters and will not be 

repeated here. However, it is important to realize the connection between dispersion 

modeling and impact assessment. Results from the emission inventory do not allow this 

direct impact analysis. It has also to be considered that usually only by conducting dispersion

modeling of all contributing sources plus the inclusion of all background concentrations will 

results be produced that may be directly compared to applicable standards. Modeling 

uncertainties must still be considered with respect to reporting direct impacts. 

Use of Multiple Runs During Mitigation Considerations

Both the emission inventory and the dispersion analysis results may be used for mitigation 

purposes. The big difference, as noted in the preceding section, is that the dispersion analysis 

results that compare the existing case and multiple future scenarios allows evaluation of 

changes in local area concentration and directly the changes in impacts that are health related.

Future Advancement in Models

As the understanding of the emission and dispersion of airport-related source systems 

increases, models will be improved to reflect and incorporate these advancements. 

In addition to model development, combination of microscale (the ones discussed here) and 

regional modeling are occurring to allow evaluation of the impact at larger distances from the 

airport and a more detailed consideration of background concentration at the airport.

As advancements occur, agencies and airport authorities will be faced with the need to 

evaluate and implement modeling practices that provide the best impact analysis for the 

airport. As such, this field is dynamic and any documents such as this one will need to be 

evaluated over time for possible updating.
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8. REFERENCES

1 Merriam-Webster Online Dictionary. http://www.merriamwebster.com/dictionary/dispersion.

2 Draper, J., S. Webb, Augustine, Pernigotti, J. Plante, Liang, Air Quality Procedures For 

Civilian Airports and Air Force Bases, Appendix I: Dispersion Modelling, FAA-AEE-97-

03, Arlington, VA., April, 1997.

3 Turner, D.B., Workbook of Atmospheric Dispersion Estimates, An Introduction to 

Dispersion Modeling, 2nd Ed., Lewis Publishers, Boca Raton, FL., 1994.

4 U.S. EPA, AERMOD, AERMIC Dispersion Model, 

http://www.epa.gov/scram001/7thconf/aermod/mod-desc.txt, last visited May 

31, 2005.

5 CERC, ADMS 3, http://www.cerc.co.uk/software/adms3.htm, last visited May

31, 2005.

6

Janicke Consulting, LASPORT 2.0, A program system for the calculation of 

airport-induced pollutant emissions and concentrations in the atmosphere,

Germany, 2009http:///, http://www.janicke.de/en/lasport.html, last visit September 23, 

2009.

 7 Hanna, S.R., Plume dispersion and concentration fluctuation in the atmosphere, 

 Encyclopedia of Environmental Control Technology, Volume 2, Air Pollution 

 Control, Gulf Publishing Company, Houston, Texas, 1989.

8

Pasquill, F., Atmospheric Diffusion, Van Nostrand, New York, 1962.

Dispersion modeling is a relatively new science and development is continuing. In 1895, 

Reynolds produced a paper discussing laminar to turbulent flow in pipes and has been 

considered by some to be the starting point of dispersion modeling. Taylor produced one of 

the first papers on turbulence in the atmosphere in 1915 and in 1921 produced the  ̳Taylor 

theory of turbulent diffusion‘ which provided a basis for describing dispersion with constant 

eddy diffusivity. Development continued and in 1962, Pasquill published the landmark book 

―Atmospheric Dispersion‖8. This work summarized what had been done to that time and is 

the basis of modern Gaussian plume models based on the horizontal and vertical spread of the 

plume being determined experimentally as a function of atmospheric stability and distance; 

the now well known sigma values. The sigma values are in reasonable agreement with the 

Taylor theory.

There are different types of dispersion modeling methodologies for a dispersion calculation, 

with different features and capabilities. In the 1960s work on dispersion modeling continued 

to expand and formalize the dispersion modeling process including plume rise considerations. 

This resulted in the basis of the Lagrangian (moving coordinate axis) and Eulerian (fixed 

axis) modeling we know today. The science has become an accepted approach to prediction 

of concentrations of pollutants in the vicinity of airports which is directly connected with 

impact on public health and welfare. Performance of dispersion modeling requires key 

variables to be carefully assembled and various methodologies have occurred. A very brief 

description of each is included here.
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A.1 Gaussian Formulation.

The Gaussian formulation is still used more than any other approach. This Lagrangian 

approach assumes downwind dispersion to be a function of stability class and downwind 

distance and applies the Gaussian probability density function to account for plume 

meandering and diffusion. It was released in various forms by the U.S. EPA as part of the 

UNAMAP series in late 1960s and developments still are on-going worldwide. It can be 

applied to plumes or individual puffs and as such provides needed flexibility for local air 

quality modeling. It has been adapted for point, line and area sources. In its basic point 

source form, for a plume, the concentration (c) is predicted with the following mathematical 

expression:

where: Q = source strength

u = wind speed

h = stack height

ζy, ζz = horizontal and vertical dispersion coefficients

Of note is that x, the distance downwind, is included implicitly in the horizontal and vertical 

dispersion coefficients that increase with downwind distance.

More recent Gaussian model formulations have used a bi-Gaussian distribution in the vertical 

to better account for vertical mixing in convective conditions. This results in more accuracy 

but also a more complex model.

A.2 Eddy Diffusivity based on Mass Conservation Formulation. 

In this Eulerian approach, the approximate solution of the mass conservation governing 

equations are used with simplifying assumptions that relate turbulent fluxes <u‘c‘> to 

concentration gradients, ∂c/∂xi by including an eddy diffusivity term, Ki. This results in:

<u‘c‘> = -Ki (∂c/∂xi)

This approach is used for widely or uniformly distributed pollutants where large individual 

plumes are not dominant. This occurs for such pollutants as carbon monoxide. This approach 

has been applied in regional modeling in the form:









































c

t

u

c

x

u

c

y

u

c

z x

K

c

x y

K

c

y z

K

c

z

i

x

i

y

i

z

i

x

i

y

i

z

i

   











 











 













 R c c c   E x y z t  S x y z t i 1 2 n i i, ,..., , , , , , ,

where: ux, uy, uz = velocity

ci = concentration of ith species

Ri = chemical generation rate of species i

Ei = emissions flux

Si = removal flux
2 C-74

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Appendix C to the Report on Agenda Item 2

A.3 Box Model. 

The box model is a simplistic mathematical representation of a defined, well-mixed volume 

of air (the box) that includes inputs and outputs into the volume. Since the box is well mixed, 

the output concentration is equivalent to the concentration inside the box. Multiple boxes 

may be used in the horizontal or vertical with the output of one box representing the input of 

the next in a grid approach. Chemical reactions can be considered in each box. This allows 

the mass conservation formulation to be used for each box in this Eulerian method.

A.4 Trajectory Models. 

These models, based on the Lagrangian approach, provide an approximate solution by using 

the governing equations of mass conservation and a coordinate system that moves with the 

average wind velocity. This approach implies that parcel integrity is reasonably maintained 

for the length of time of model simulation and assumes that horizontal wind shear, horizontal 

turbulent diffusions and vertical advective transport are negligible. This model is not 

generally accepted for general use for regulatory applications in the U.S.

A.5 Mass and Momentum Models. 

In this type of model, governing equations of mass and of momentum are applied using first 

order principles. For example, approaches may begin with the fundamental Navier-Stokes 

equation and include turbulence based on Reynolds averaging. The result is more 

scientifically rigorous with complex procedures that avoid the K-theory simplification but are 

often computer and data intensive and specific to a particular case. As such, this category of 

models tends to be more research oriented and not in common use.

A.6 Lagrangian Particle Models. 

In contrast to Gaussian models which are based on an analytical solution of the classical 

dispersion equation and Eulerian models which solve this equation numerically, Lagrangian 

particle models simulate the transport process itself. 

Out of the huge number of particles (gas, aerosol, dust) usually emitted by a source, only a 

representative, small sample is considered. The sample size is typically of the order of some 

million particles, depending on the problem and available computer resources. The trajectory 

of each of these particles is calculated on the computer by a stochastic process (Markov 

process in phase space). From these trajectories the three-dimensional, time-dependent, nonstationary concentration distribution is derived. 

The core of a Lagrangian particle model, as for example specified in the guideline VDI 

3945/3 (English/German, see www.vdi.de), does not contain tuneable parameters. It relies on 

meteorological parameters that can be determined without dispersion experiments. Time 

scales typically range from some minutes to one year with a time resolution down to some 

seconds, spatial scales range from some metres to some 100 kilometres.

Increased research and application to atmospheric physics started about 20 years ago and 

Lagrangian particle models have become more widely used with increased computer speeds 

and memory storage. Today the technique is routinely applied in air quality control.
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Appendix C to the Report on Agenda Item 2 2 C-75

A.7 Plume-in-Grid Approach. 

This method is a hybrid between the Lagrangian and Eulerian approaches. The Eulerian 

approach is adapted by using trajectory models or Gaussian dispersion techniques to preserve 

trace specie concentration to overcome the deficiencies regarding instant mixing of pollutants 

in the grid.

A.8 Closure Models. 

In Eulerian models, vertical diffusion must be addressed. Two different turbulence closure 

schemes are typically used: local closure and non-local closure. Local closure assumes the 

turbulence is similar to molecular diffusion while non-local closure assumes the turbulent flux 

to be similar to mean quantities at different layers and an exchange of mass is allowed. 

Closure models are often discussed in terms of first-order for prognostic equations for the 

mean variables (i.e., wind or temperature) or higher order models which are more complex. 

This type of modeling is closely related to eddy diffusivity models previously described.

A.9 Statistical Models. 

This idea is based on statistical analysis of ambient pollutant measurements and other 

emissions information. This approach is best used when detailed source information is 

available, as these models have difficulty in applying results as location parameters change. 

One subset if this type of modeling is receptor modeling which has been used to predict 

particulate matter in the U.S. and in the U.K. Receptor modeling uses multivariate statistical 

methods to identify and quantify the apportionment of air pollutants to their sources.

In sum, this partial listing of procedures is meant to provide a background for the discussion 

of dispersion modeling allowing the analyst to better understand the process.
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Appendix C to the Report on Agenda Item 2

ANNEX 4B. Commonly Used Dispersion Models in the Vicinity of Airports

The purpose of this annex is not to recommend any particular model or to show detailed 

information on any model. The analyst is expected to choose the appropriate model based on 

legislative requirements, data available, and intent of use.

Table B.1 shows computerized modeling packages that have been commonly used at airports. 

Of note is that there are many models that have been used and the table is not all inclusive.

TABLE B.1. Commonly Used Dispersion Models at Airports

Airport Air Quality 

Model

Fundamental Type of 

Dispersion Model

Model Information

AEDT/EDMS Bi-Gaussian Sponsoring Organization: United 

States

Model Developer: Federal Aviation 

Administration

ADMS-Airport Bi-Gaussian Sponsoring Organization: United 

Kingdom

Model Developer: CERC

ALAQS-AV Bi-Gaussian / Lagrangian Sponsoring Organization: France

Model Developer: EUROCONTROL

LASPORT Lagrangian Sponsoring Organizations: Germany 

and Switzerland 

Model Developer: Janicke Cons.

Obvious in all of these reports are that no one modeling approach totally meets all current 

modeling needs, especially if cost, practicality and complexity are considered. This results in 

either multiple models being used and selected on a case-by-case basis or 

adaptations/simplifications of the selected model inputs.

The analyst should carefully review any legislative requirements, sources to be modelled, 

inputs needed for any specific model, and limitations of any model when selecting the 

appropriate dispersion model.
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Appendix C to the Report on Agenda Item 2 2 C-77

ANNEX 4C. Climatological Information Sources

Dispersion modeling using the Advanced or Sophisticated Approach requires detailed 

meteorological data. Care should be taken in selecting this data. Short term data may not 

accurately display trends and may not be representative of the seasonal variations, dominant 

wind patterns, or diurnal variations.

The World Meteorological Organization (WMO) (http://www.wmo.int/pages/index_en.html) 

includes:

―more than 10000 manned and automatic surface weather stations, 1000 upper-air 

stations, over 7000 ships, more than 100 moored and 1000 drifting buoys, hundreds 

of weather radars and over 3000 specially equipped commercial aircraft measure key 

parameters of the atmosphere, land and ocean surface every day.‖

Information is available for multiple years and data bases were established prior to 1950.

The World Data Center for Meteorology with 52 centers in 12 countries 

(http://www.ncdc.noaa.gov/oa/wdc/index.php) represents a huge number of monitoring 

stations worldwide.

Individual countries may also maintain the required climatological data for a region or 

country. These include the British Atmospheric Data Centre 

(http://badc.nerc.ac.uk/home/index.html) in the U.K. and the National Climatic Data Center 

(NCDC) (http://lwf.ncdc.noaa.gov/oa/climate/climatedata.html) in the U.S. For example 

NCDC has directly downloadable surface data, upper air data, and other useful information in 

multiple formats. Of importance are the historical records over many years that helps to 

avoid errors due to incorrect input parameters. The data are available from the 1800s to the 

present for over 8000 locations in the U.S. and 15,000 worldwide stations depending upon the 

data needed.

Climatological data can be found at many universities world wide as well and often may 

provide unique data for a region. It is suggested the analyst explore this possibility of 

information.

— — — — — — — —
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Appendix C to the Report on Agenda Item 2

Chapter 5:

AIRPORT MEASUREMENTS

Table of Contents

5.1 Introduction

5.2 Requirements and Drivers for Measurement

5.3 Measurement Plan

5.4 Analysis of Data 

5.5 Measurement Quality Assurance / Quality Control

Annexe 5A1 Description of Measurement Methods

Annexe 5A2 Examples of Measurement Methods

Annexe 5A3 References

Introduction

5.1.1 Airports are an important part of the economic infrastructure of the cities they serve; passenger 

and cargo activity at an airport support local air transportation needs. However as part of that 

infrastructure, airports are a magnet for many types of activities that contribute air pollution to the local 

area: aircraft, automobiles, ground support equipment, stationary sources, etc. Often responding to 

various objectives and requirements, airports and/or local authorities seek to obtain an understanding the 

contribution of airport-related pollutant sources to the local air quality. While modeling tools are 

available, some airport locations seek to quantify airport-related emissions through the conduct of actual 

air measurements. It is important that measurements conducted for airports comply with the appropriate 

measurement protocols. This chapter describes the various elements for ambient air quality 

measurements for airports.

Requirements and Drivers for Measurements

5.2.1 Chapter 1 of this guidance material describes the general local air quality regulatory framework 

and drivers influencing the aviation industry to provide information or undertake action related to air 

quality. Specific to ambient air quality measurements, numerous requirements and drivers influence the 

need for airport ambient air quality measurements to be conducted. Measurements are often conducted in 

order to meet legal obligations, as part of voluntary programs, or for model verification.

5.2.2 Legal Compliance: To comply with applicable ambient air quality regulations and accompanying 

standards or targets for particular pollutants, airports and in some place local authorities may be required 

to conduct ambient measurements. An airport or local authority might also be under the obligation (e.g. 

for baseline assessment or in the context of expansion projects) to perform measurement on a regular or 

irregular basis.

5.2.3 Voluntary Programs: For example, public and community concerns often trigger the need for 

measurements to obtain actual information about air quality in the local vicinity. Alternatively, an airport 

may voluntarily conduct measurements and report as part of their environmental policy and management 

activities.

5.2.4 In addition to public and community concerns, new scientific evidence or hypotheses may 

emerge that suggest initiating measurement campaigns at or around airports to seek clarifications or 

obtain further information. 
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Appendix C to the Report on Agenda Item 2 2 C-79

5.2.5 Model Verification: Sometimes, model results are calibrated with measured results to determine 

the ability of a model to characterize current conditions with some degree of confidence. Once a 

particular model is verified for baseline conditions, it can be used with greater confidence to predict 

future scenarios accurately. This is particularly important when an airport is considering potential action 

(e.g., infrastructure development) and needs to analyze the potential impact of the action and any 

potential mitigation measures.

5.2.6 The major caveat associated with the model verification is the fact that the model usually 

predicts concentrations from one or several emissions sources but not necessarily from all contributing 

sources. In this case it might be difficult to compare modeled concentrations to measured values, and 

complex procedures have to be applied for the purpose of actually performing model verifications.

Measurement Plan

5.3.1 Design Process of a Measurement Plan

5.3.1.1 The measurement plan for local or regional air quality measurements is determined by external 

and/or internal requirements and the necessary resources available. The following main elements in a 

plan should be addressed (see also Figure 5-1):

1. Objectives and requirements for measurements (as described in section 2)

2. External factors

3. Measurement locations (with respect to the airport premises)

4. Measurement methods

5. Management planning

Figure 5-1: Measurement Plan Elements

5.3.1.2 The requirements and drivers for local airport air quality measurements are outlined in section 

Objectives / Requirements

Legislative or authoritative 

Requirements

Public Concerns

Voluntary Programs

Scientific Issues

Measurement 

Locations

Measurement 

Systems

Management

Planning

External Factors
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Appendix C to the Report on Agenda Item 2

5.2. Following the external requirements, airports may have a single or multiple objectives for the 

measurements. Objectives can include the desire to obtain factual information on the actual ambient air 

quality concentrations at specific receptor locations for communication purposes or to establish long-term 

trend analysis to observe the development of air quality at the measurement sites in response to the 

emission developments. 

5.3.2 External Factors

5.3.2.1 The key external factors to be considered in ambient air quality measurements are potentially 

existing measurement standards, recommendations and guidelines. If applicable, practicable, or available, 

local or national framework documentation for ambient air quality measurements should be used. This 

can range from general issues like measurement principles or quality assurance to prescribed 

measurement systems that have to be put in place. 

5.3.2.2 In some cases, airports will have to bear the responsibility and costs for air quality 

measurements. To this end, the available resources, technical skills and budget may be factors that 

determine the possible scope of air quality measurements. 

5.3.2.3 An air quality monitoring network may already be in place that is operated by local authorities or 

other entities. In this case it would be advisable to coordinate or even harmonise potential measurement 

plans to avoid duplication of similar or identical measurements or to avoid inconsistencies or even 

contradictions. 

5.3.3 Measurement Locations

5.3.3.1 The objectives and requirements as described in section 2 will help determine the locations of 

monitoring stations. The generic measurement site selection plan in Figure 2 and Table 1 identify the 

various site characteristics and their relevance within the measurement concept. Air measurements 

should be conducted upwind and downwind from the airport/airport sources while at the same time 

striving to achieve a source distribution discrimination. To achieve source distribution discrimination, 

locations should be defined that are most likely dominated by a specific emission source, while other 

sources may contribute only marginally to the overall concentrations.

5.3.3.2 The following questions are associated with the choice of the measurement locations:

 What are the current (past) pollution concentrations of relevant species near the airport?

 Can airport induced impacts be - at least to some degree - singled out?

 What is the trend of the pollution concentrations?

5.3.3.3. A generic yet typical site selection plan is illustrated in figure 5-2 with each location described 

and justified in table 5-1. This site selection plan may vary from airport to airport, depending on the 

actual regional land uses, infrastructure, and development. 
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Appendix C to the Report on Agenda Item 2 2 C-81

Figure 5-2: Generic Measurement Site Selection Plan (circled arrow: prevailing wind direction)

Industry

Residential

Airport

Terminal









 

a

b
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Appendix C to the Report on Agenda Item 2

Table 5-1: Description of Generic Measurement Sites

Number Description of Site Justification

1 Background concentration site, 

undisturbed by any polluting 

activities

This station provides the background and baseline 

data for the region where the airport is located.

2 All stations (including a and b) are 

located within the airport area with 

intense airport activities. Optionally, 

stations are located directly upwind 

and downwind (and sideline) of the 

runways, often at the airport 

boundary.

It can be expected that these stations will most 

likely best reflect the airport activities (aircraft 

and/or handling and infrastructure). Those activities 

will dominate the pollution concentrations and 

significant concentration changes will likely be 

caused by these sources. 

3 This station is located in a residential 

area that is located downwind of the 

airport, but without a dominant 

emission source in its proximity. 

This station will give the average situation of a 

residential area with permanent housing closest to 

the airport and downwind from it. A source 

attribution might not be possible, but is not 

necessary.

4 This station is located next to a major 

traffic road, but still in the proximity 

of the airport.

Road traffic is an important emission source in 

general. This station reflects road traffic impacts on 

local air quality in the vicinity of the airport. There 

is no discrimination for airport related traffic versus 

any other traffic.

5 This station is located in another 

residential area, but downwind of an 

industrial area with emissions.

Residential areas could still be subject to increased 

concentrations. In this case it is important to 

discriminate emission sources that are not airport 

related but can impact areas close to the airport.

6 This station is located further away 

from the airport, but again in 

residential areas downwind of the 

airport.

It can be expected that further downwind from the 

airport, concentrations will decrease, provided no 

other significant emission sources are present. 

5.3.3.4 In choosing the locations at and around the airport with regard to most likely dominant pollution 

contributors, it can be possible to estimate qualitatively the relevance of air traffic and airport induced 

impacts.

5.3.4 Measurement Methods

5.3.4.1 Various measurement methods are available that can range between simple (in terms of location 

site and handling) to sophisticated. The choice of each instrument must be made according to the 

expected measurement exigency. This exigency definition rests on the analysis of customer or authority 

demand when it is not compulsory by law. In any case, the risk of providing a wrong result when 

comparing to a threshold must be discussed and accepted by all "parties".

5.3.4.2 The main difference between measurement systems is whether they are active (system collects 

air samples and analyses continuously) or passive (ambient air is reacting with the system and results will 

be obtained remote). Table 5-2 discusses both systematic approaches for various parameters that need to 

be considered when evaluating measurement systems.
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Appendix C to the Report on Agenda Item 2 2 C-83

Table 5-2: Active and Passive Measurement Systems

Parameter Active System Passive System12

Possible Systems Optical Path:

 DOAS (differential optical 

absorption spectroscopy) 

Continuous Point 

 TEOM (Tapered Element 

Oscillating Microbalance)

 Beta-Attenuation Mass Monitor

 High Volume Samplers

 Chemiluminescence

 Bag/Canister

 Passive Diffusion Tubes

 Filter papers

Pollution species to 

be measured

Usually multiple species can be 

measured in one station (e.g. NO2, 

O3, PM10) by using several analysers 

in one location.

Usually only one pollutant can be 

measured; some pollutants cannot be 

measured at all (reactivity).

Analysis Air samples are usually analysed 

directly in the station and when 

sampled.

Samples are usually analysed remote 

in a laboratory and after collection.

Measurement 

Intervals

Depending on the equipment, the 

measurement intervals can be short, 

e.g. samples can be analysed every 

few seconds or minutes.

Intervals are usually long (e.g. twoweek-intervals) or only one-time 

measurements.

Data Accuracy The accuracy of the data obtained is 

usually fairly high, provided proper 

installation and maintenance of the 

systems.

The accuracy of the measured data is 

fair. However, for trend or 

comparison analysis with a larger 

number of sites, the accuracy may be 

sufficient. 

Site requirements The measurement site requires an 

unobstructed location (with regard to 

air flow), a sheltered room for the 

equipment and analysers and access 

to electrical power. Depending on the 

system, communication lines for 

remote operations are also needed. 

Some access restrictions should 

apply.

Such a system can also be mobile for 

measurement campaigns.

The measurement site requires an 

unobstructed location (with regard to 

air flow). Only limited infrastructure 

is required to install the measurement 

system (no shelter, no power).

Maintenance An increased level of maintenance on 

electrical / electronic and precision 

parts is required to obtain and 

maintain a reliable level of 

operability. This may include regular 

calibration or exchange of critical 

parts.

Maintenance efforts are usually low 

as no or only limited electrical / 

electronic or high precision parts are 

involved.

Costs Medium to high (investments) and 

medium (maintenance).

Low (investments and maintenance).

 

12 Bioindicators/bioaccumulators: This category is more a hybrid of an active system and long-term exposition. A limited 

description is given in the Annexe. 
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Appendix C to the Report on Agenda Item 2

5.3.4.3 By considering potential sites in combination with measurement systems, it can be concluded 

that sites at the airport could be equipped with active and/or passive systems, while air quality 

measurements in the airport region are performed with passive systems.

5.3.5 Management Planning

5.3.5.1 An important element of ambient air quality measurement is assuring that implementation and 

actual execution is properly accounted for. To this end, several elements have to be addressed, defined 

and documented in the management planning. These include the following:

 Project Responsibility

 Maintenance

 Data Management

 Communication

 Quality Assurance and Quality Control

5.3.5.2 The project responsibility includes, but is not limited to the elements of drafting of the 

measurement concept, acquiring the necessary budget for acquisition, installation, operation and 

maintenance of the measurement equipment, organising the data management (evaluation, verification, 

storage) and managing potential third party contracts. It defines the roles and responsibilities of all 

involved parties.

5.3.5.3 Maintenance involves all of the elements of regular and preventative maintenance of the 

measurement equipment, as well as the repair and potential contingency planning by having spare 

equipment available. It also deals with the aspects of calibration of the equipment following 

manufacturer instructions or general guidelines and recommendations. 

5.3.5.4 The data management comprises the data acquisition (automatically or manually), the data 

storage, and the data transfer (e.g. from remotely controlled stations). Once the raw data is obtained, it is 

subject to a quality check that needs to be predefined where inappropriate data is being identified and 

either marked or removed from the data series. Depending on the data acquisition system and required 

evaluation and reporting interval, the data might have to be aggregated into a different interval (e.g. 

hourly value).

5.3.5.5 Once the data is available for proper interpretation, there might be requirements for 

communication and /or publication. Public or restricted measurement reports may be produced and 

distributed by means of printed or electronic reports. In addition, communication to authorities or local 

stakeholder might be pre-defined.

5.3.5.6 In order to ensure long term quality of measured data, a quality assurance process is 

recommended where all elements influencing the quality of the data are addressed. Such a quality control 

system is developed and implemented to ensure that the required level of confidence in the system and its 

results are achieved.

5.4 Analysis of Data 

5.4.1 Introduction

5.4.1.1 Ambient air measurement data can be used in a variety of ways, such as:

 Describing existing conditions in an area or a site, and demonstrating whether or not ambient air 

quality standards are being met

 Determining hourly, daily, monthly, and seasonal variation

 Determining trends

 Spatial

 Temporal
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Appendix C to the Report on Agenda Item 2 2 C-85

 Identifying major sources that contribute to measured concentrations

5.4.1.2 How the data can be used is dependent on the:

 specific pollutants or constituents that were measured

 duration (days, weeks, months, or years) of the measurements

 time resolution (seconds, minutes, hours, or longer) of the measurements

 number and location of monitoring sites used to collect the measurements

 meteorological data (e.g., wind speed and direction)

5.4.2 Describing Existing Conditions vs. Ambient Air Quality Standards

5.4.2.1 Ambient air quality monitoring is the traditional method for demonstrating that an area currently 

meets the applicable air quality standards. Often, monitoring must be conducted for one to three years 

prior to a formal designation and determination that an area attains or does not attain a standard. 

Regulatory agencies have defined how the data may be used in comparing the monitored results with the 

air quality standards.

5.4.2.2 Monitoring at one or more sites near an airport provides information regarding local air quality in 

the vicinity of the airport. This data may be used for defining the existing or baseline conditions in an 

environmental disclosure document for a proposed future project. Since air quality standards include the 

averaging period, and the averaging periods for certain standards are up to one year, monitoring must be 

conducted for the period appropriate to the standard in which the data will be compared. Longer 

monitoring may be required if the standard is based on a limited number of measurements that can be 

exceeded over a number of years. 

5.4.3 Determining Periodic Variations

5.4.3.1 Periodic variations may give some clues as to which sources may be contributing to the 

measured concentrations. Each source at an airport has associated peaking characteristics. For example, 

regional surface traffic often follows a morning or evening work-related period peak. Aircraft operations 

often have distinct peaks. Ground vehicle access to an airport may peak 60-90-minutes before and after 

the peak aircraft operations. If hourly monitored data are available, and these data show pollutant 

concentration peaks corresponding in time with the rush hour periods, then traffic is likely a major 

contributor to the measured values. Note that this assumes one is looking at a relatively inert pollutant 

(such as CO, PM10, or total NOx).

5.4.3.2 The variation may also be by day-of-week, month-of-year, or seasonal. These variations may 

also help point to the sources or source types that may be substantial contributors to the measured 

concentrations. However, one should note the periodic variations may also be associated with 

meteorological effects, such as temperature, mixing height, or relative humidity that actually change 

either the pollutant emissions from sources. For example, combustion sources produce more NOx and 

less CO when the ambient air temperature is higher producing both diurnal hourly fluctuations and 

seasonal variations.

5.4.3.3 A typical example of a source dependent variation is the pollution concentration of aircraft. 

There might be airports with distinct seasonal traffic (e.g. winter sports destination) of even weekend 

traffic. A typical example of a variation that corresponds with meteorological conditions might that of an 

airport power plant that operates at fairly regular load conditions throughout the year.

5.4.4 Trend Analyses

5.4.4.1 Spatial gradient analysis uses ambient air measurements of a single pollutant made at multiple 

locations to identify and locate emission sources that contribute to the measurements. 
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Appendix C to the Report on Agenda Item 2

5.4.4.2 Time series analysis uses ambient air measurements of a single pollutant made at multiple 

locations to identify patterns of pollutant concentrations over time. 

5.4.4.3 Long-term (multiple years) data collection at one location can provide information on the general 

trends in pollution emission. In many areas where on-going pollution control programs have been in 

place, the long-term trend show steady reductions in measured pollutant concentrations over time.

5.4.5 Source Apportionment

5.4.5.1 Source apportionment is the use of monitored or modeled concentrations, with or without 

meteorological data, to determine the sources, source types, and/or source locations that contribute 

substantially to measured values. The spatial gradient and time series analyses discussed above are 

possible source apportionment methods. Others include the chemical mass balance or the positive matrix 

factorization. 

5.4.5.2 The use of monitored data to determine sources that contribute to the measurements is referred to 

as receptor modeling. The receptor (monitoring station) data is analyzed along with either wind speed 

and wind direction data or assumed source type emission profiles and characteristics to tease out 

information about which sources or source types are generating the emissions that get measured at the 

station. 

5.4.5.3 Measurements at a point do not allow one to distinguish from different contributing sources 

unless a tracer substance can be isolated that is emitted from a specific source only. Therefore, it is 

important to conduct modeling in conjunction with measurements in order to estimate the contribution 

from individual sources or groups of sources (e.g., an airport). 

5.4.6 Handling of Missing Data

5.4.6.1 Local or national guidelines usually set forth the required conditions under which measured time 

series are valid. For longer-term measurements (e.g. annual), a maximum number of days without data is 

allowed where no specific action has to be taken. Gaps beyond this tolerance will lead to invalid 

measurement series or averaging periods. The obtained data can be used for information purposes, but 

may not be used for legal reporting or justification for mitigation programs. Where such guidelines 

allow, missing data can be inserted by ways of interpolation. In all cases, data gaps should clearly be 

documented.

5.4.6.2 Interpolation of one or several missing data points can be done by consulting a valid 

measurement period from a nearby station with comparable meteorological conditions and to use the 

variation in the measurement points in a corresponding manner. In any case, any interpolated data has to 

be marked as such.

5.5 Measurement Quality Assurance/Quality Control 

5.5.1 Quality Management Guidelines

5.5.1.1 One of the main targets in quality management is to provide confidence that the measurements 

are accurate to avoid criticism when communicating the results. The quality management process will 

help to minimize uncertainty by optimizing equipments performance as well as the technician 

capabilities. Furthermore, the monitoring results must be readily available; it must be traceable, well 

identified, documented and unique in time and location.

5.5.1.2 There may be a number of guidelines available. This could include, but is not limited to 

manufacturer specification, local or national guidelines or international guidelines (International 

Standards Organization). ISO 9001: the reference for quality management, deals with the processes for 

organizing the measurement information that allows for customer satisfaction. ISO 17025: based on the 
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Appendix C to the Report on Agenda Item 2 2 C-87

same quality management organization and goal as the ISO 9001 standard, and specially built for 

measurement activities, adds the technical capability evaluation and is much more constraining than ISO 

9001.

5.5.2 Technical Competence

5.5.2.1 An important factor in assuring the quality of measurements is the skill and expertise of staff 

performing the measurements. As such, adequate technical skills need to be achieved for all elements of 

air quality monitoring: equipment installation, operation, maintenance and repairs and data handling: 

obtaining, storing, validating and interpreting. The minimum educational level should be defined in 

advance and documented.

5.5.2.2 In order to assure the required level of expertise, a training schedule can be developed that 

includes internal and external training e.g. by the equipment manufacturer or environmental authorities. 

This is particularly true for complex analysis instruments with frequently changing technologies. It is 

recommended to document all training programs (e.g. according to ISO 9001). Training programs have 

to be on a repetitive basis. 

5.5.3 Equipment Accuracy

5.5.3.1 The necessary (preventative) maintenance procedures including the periodicity have to be 

prescribed by the equipment manufacturer. Preventive maintenance must be programmed regularly for 

the equipment to assure optimum performance during operation, particularly during continuous 

monitoring and communication of the data. Preventative maintenance could include cleaning, change of 

specific equipment parts, software updates and others. All maintenance activities must be scheduled and 

documented, as well as the findings after each performed maintenance.

5.5.3.2 Calibration of the equipment is an important, necessary step, and is done to assure that the 

measurements are accurate and within the given range of the equipment. Calibration is done after regular, 

pre-defined intervals after each preventative maintenance and repair. When additional calibration

equipment or substances (e.g. reference gases) are used, they must be quality assured or certified (e.g. 

expiration date on reference gases). Controlled temperature and humidity may be necessary for specific 

calibrations and they have to be respected. All information pertaining to the calibration of the equipment 

has to be logged. 

5.5.3.3 Despite all maintenance and calibrations, some uncertainty might remain. It is important to 

understand the magnitude of such uncertainty and the level of impact it has on the overall measured 

values in order to determine the degree of fidelity of the final data. An uncertainty study could help 

determine the various factors and their relevance for ambient measurements and could also suggest ways 

to minimize the uncertainty of the data.

5.5.4 Data handling

5.5.4.1 Depending on the way of monitoring, a large volume of raw data may be compiled over time that 

requires specific data management. It has to be decided whether both raw and validated/processed data 

need to be kept and over what period of time. A suggested way forward would be to keep the raw data for 

a period of at least 10 years, while the processed data (validate, aggregated, etc) could be kept for more 

than 10 years.

5.5.4.2 Data storage will require a maintenance process, such as regularly recopying the data from one 

medium to another and at the same time crosschecking for data faults (missing, falsified). This data 

management process has to be documented as well. 

5.5.5 Accreditation and Certification
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5.5.5.1 Periodical checks must be done to be sure that the management procedures are conveniently 

applied. Internal auditors could be recruited among the employees and trained for this activity. 

5.5.5.2 Even if external companies have an established and maintained quality system, the customer (e.g. 

the airport) would have to have the confidence in such a system. To this end, the current minimum 

standard is an ISO 9001 certification label. In addition, the ISO 17025 standard is specifically adapted to 

the measurement activity and, as it combines quality management based on ISO 9001 guidelines with a 

clear focus on the technicians‘ capability, it is the best way to ensure the customers‘ confidence.

Annexe 5A1 Description of Selected Measurement Methods

A. Active Systems

1. Differential Optical Absorption Spectroscopy (DOAS)

With the DOAS-system it is possible to obtain automatic measurements along a path with high 

resolution. The principle is based on the wavelength dependent absorption of light caused by gases. The 

DOAS-equipment includes an emitter and a receiver unit. A light beam with a wavelength between 200 

and 700 nm is projected from the emitter to the receiver and passes to an analyzer through a fiber optic 

cable. In the path, specific gases will absorb light from known parts of the spectrum. This allows the 

analyzer‘s computer to measure gases through a spectrometer. Within the spectrometer a grater set splits 

the light stepwise into the different spectra. The resulting spectrum is now compared with a reference 

spectrum and the difference calculated to a polynomial. With additional calculations the differential 

absorption spectrum and finally the concentration of the particular gas is determined. These single 

measurements are summarized to 30 minutes values. This system can be used for a range of pollutants 

including nitrogen dioxide, ozone and sulphur dioxide.

2. Tapered Element Oscillating Microbalance (TEOM)

The TEOM (Tapered Element Oscillating Microbalance) allows one to determine the PM10-fraction of 

dust. The TEOM-method is based on the principle that the frequency of an oscillating filter changes with 

increasing mass. The TEOM takes air samples of known volume, which passes through a filter on the 

top of the sampling unit. Here all particulate matter with a particle-size lager than 10 μm is separated. 

The air sampling then passes through a second filter on which the particles smaller than 10 μm drop 

behind. The concentration of PM10 is calculated from the changes of the frequency of the filteroscillation. The single measurements are summarized to 30 minutes values.

2a. Beta-Attenuation Mass Monitor (BAM)

The BAM is a more rugged and less expensive continuous monitor for PM10 and for PM2.5 than the 

TEOM. It has USEPA certification (EFQM-0798-122) as an Equivalent Method to the standard method 

for monitoring ambient air PM10 and PM2.5. The BAM method uses a stable radio-active carbon source 

(

14C, 60 uCi), and it measures attenuation of Beta radiation by particulate matter deposited on a filter 

medium and relates the attenuation to the mass deposited on the filter. PM10 or PM2.5 levels are measured 

separately, depending on the particle size discriminator placed before the filter collection device. 

3. NOX-Analyzer

The NOX-analyzer is used to measure the NO2-concentration. The analyzer takes two air samples. One 

stream passes through and the other stream passes through a convertor that reduces NO2 to NO. Both 

samples are analyzed for NO in a single reaction cell, where the chemiluminescence produced by the 

reaction between NO and O3 is measured. The instrument alternately measures the total NOx and NO. 

The difference between the two readings results in a computed NO2 value in the ambient air.
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Appendix C to the Report on Agenda Item 2 2 C-89

4. O3-Analyser

In the O3-analyser, two air samples are collected. The first one passes through a catalyst which converts 

O3 to O2. The second sample goes directly into an absorption cell (reference measurement). A detector 

measures the amount of ultraviolet (UV) radiation transmitted. The O3 concentration is calculated from 

the two reference values. The interval of measurement is 30 minutes.

Conclusions

Automated analyzers allow for the continuous, automated, on-line and time-resolved measurement of air 

pollutants, producing high-resolution measurements of hourly pollutant concentrations or better, at a 

single point. The major drawback of a continuous point/optical path method, such as the DOAS method, 

is the high cost associated with purchase and maintenance of the analyzers. Consequently, low network

density and low spatial resolution of the measurements may result. Mobile laboratories equipped with 

automated analyzers constitute a useful application of this technique as a tool for measurement programs 

covering several locations of interest.

B. Passive Systems

1 1. Diffusion Tubes

Diffusion tubes are the simplest and cheapest way to evaluate local air quality of gaseous pollutants and 

can be used to give a general indication of average pollution concentrations over longer time periods 

ranging from a week or more. They are most commonly used for nitrogen dioxide and benzene (often 

with toluene, ethyl-benzene, m+p-xylene and o-xylene as BTEX), but are also useful for measuring a 

number of other pollutants such as 1,3 butadiene, ozone, sulphur dioxide, etc.

Diffusion tubes generally consist of a small tube (test-tube size) normally made of stainless steel, glass 

orinert plastic, one end containing a pad of absorbent material and the other end is opened for a set 

exposure time. After exposure, the tubes are sealed and then sent to a laboratory where they are analysed 

using a variety of techniques including chemical, spectrographic and chromatographic processes.

It should be noted that diffusion tubes are an indicative monitoring technique that do not offer the same 

accuracy as the more sophisticated automatic analysers. Also, since the exposure periods can be several 

weeks, the results cannot be compared with air quality standards and objectives based on shorter 

averaging periods such as hourly standards - it is not possible to detect peak events using diffusion tubes 

for the same reason. As a result, although diffusion tubes can be used for shorter period assessments, it is 

recommended that NO2 diffusion tube monitoring, in particular, be carried out over a full year as 

assessments against objectives for annual mean concentrations can then be made. 

Diffusion tubes can be affected by a number of parameters that may cause them to over-read, or underread, relative to a reference measurement, and for this reason, best practise is to use three or more tubes 

at each monitoring point, and co-locating one set with an existing reference continuous monitor. This 
2 C-90

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Appendix C to the Report on Agenda Item 2

way any bias can be corrected by referring the results back to the continuous monitor (e.g. chemiluminescant monitor for NO2), and comparison between the tubes will identify any anomaly. 

It is important to choose sites for diffusion tube monitoring correctly, and the area around the tube 

location should allow for the free circulation of air around the tubes, while avoiding areas of higher than 

usual turbulence such as corners of buildings etc. Care should also be taken to avoid surfaces that may 

act as local absorbers for the pollutant being measured, and for this reason diffusion tubes should not be 

fixed directly on walls or other flat surfaces. Other localised sources or sinks such as heater flues, air 

conditioning outlets, extractor vents, etc as well as trees and other areas of heavy vegetation, should also 

be avoided. 

The relatively low cost of diffusion tubes means that sampling is feasible at a significant number of 

points over a large area, and this can be useful for identifying relative trends, and also regions of high 

concentrations where more detailed studies can then be carried out. Under these circumstances, the cost 

and difficulty of using more accurate continuous monitoring to carry out the same study would almost 

certainly prove prohibitive.

2. Bags/Canisters

For this measurement technique, a "whole air" sample is collected at selected measurement sites by 

drawing an ambient air sample into some sort of container. Most commonly, this could be a bag, glass 

bulb, steel "bomb" or a stainless steel canister. Stainless steel canisters and bags are the most common 

collection systems. The collection of an air sample may be enhanced with a small electric pump that 

actively fills the canister with the ambient air sample. 

Once the gas is collected in the canister, it is analyzed off-site by several different methods (e.g. using 

solution chemistry). Measured ambient air components are often various hydrocarbon species. 

Data quality issues usually revolve around the recovery of contaminants from the collection vessel. 

Recovery is a function of several parameters including, the chemical nature of the contaminant and the 

surface properties of the vessel, the vapor pressure of the contaminant, the influence of various other 

compounds contained in the matrix, and the ability to start with a vessel free of contamination.

Conclusions

Passive sampling methods are simple and cost-effective methods which provide a reliable air quality 

analysis giving a good indication of average pollution concentrations over a period of weeks or months. 

Other methods include the use of bubblers for gaseous pollutants and the analysis of heavy metals 

contained in the suspended particulate matter filtrate.

C. Other Methods

1. Bioindicators 

Biological indicators, or bioindicators, are plant or animal species which provide information on 

ecological changes in site-specific conditions based on their sensitive reactions to environmental effects. 

Bioindicators can provide signs of impending environmental problems such as air and water pollution, 

soil contamination, climate change or habitat fragmentation. They can also provide information on the 

integrated effect of a variety of environmental stresses and their accumulative effects on the health of an 

organism, population, community and/or ecosystem. Lichen species are a commonly-used bioindicator 

for air quality.

Various methods of investigating indicator species exist, and at the individual organism level the effects 

of bioaccumulation can be studied. At the population level, studies of morpho-physiological changes, 

changes in life cycles, relative health of populations, and population and community structures can all be 

conducted. Marking and recapturing, establishing sex and age ratios, point, line, plot or plotless surveys 
CAEP/8-WP/80

Appendix C to the Report on Agenda Item 2 2 C-91

of vegetation cover and plant frequencies, etc. are examples of the ecological field methods which are 

used.

The data obtained from traditional measurements methods permit control of compliance with current air 

quality standards and limit values. Data on ambient pollutant concentrations, however, do not allow for 

direct conclusions to be drawn on potential impacts on humans and the environment. Evidence of 

harmful effects can more accurately be provided through use of bioindicators. Bioindicators also 

integrate the effects of all environmental factors including interactions with other pollutants or climatic 

conditions. This permits the risk of complex pollutant mixtures and chronic effects that can even occur 

below threshold values. 

The use of bioindicator plants to assess air pollution effects is not very well established. Insufficient 

standardization of the techniques and, consequently, the low comparability of the results is one of the 

major reasons for the poor acceptance of this air quality monitoring methodology.
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Appendix C to the Report on Agenda Item 2

Annexe 5A2 Examples of Measurement Methods

Table 5-A2: Example table of measurement methods (from Europe and US)

Pollutant Reference Method Other Methods

Sulfur Dioxide Ultraviolet Fluorescence DOAS

Nitrogen Dioxide and Oxides of 

Nitrogen

Chemiluminescence DOAS

PM10 Gravimetric TEOM (Advanced)

Beta Attenuation

Sticky Tape (Simple)

PM2.5 Gravimetric

Lead Gravimetric

Carbon Monoxide Gas Filter Correlation

Non-Dispersive Infrared 

Spectroscopy (EU)

Ozone Ultraviolet Photometry DOAS
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Appendix C to the Report on Agenda Item 2 2 C-93

Annexe 5A3 References (selection)

Aeroport De Paris – Charles De Gaulle, 2006. ―Campagne De Prelevement De Dioxyde D‘azote Par 

Tubes Passifs‖

Carslaw, D.C., S.D. Beevers, K. Ropkins, and M.C. Bell, 2006. ―Detecting and quantifying aircraft and 

other on-airport contributions to ambient nitrogen oxides in the vicinity of a large international airport,‖ 

Atmospheric Environment 40:5424–5434.

Chow, J.C., L.W.A. Chen, J.G. Watson, D.H. Lowenthal, K.A. Magliano, K. Turkiewicz, and D.E. 

Lehrman, 2006. ―PM2.5 chemical composition and spatiotemporal variability during the California 

Regional PM10/PM2.5 Air Quality Study (CRPAQS),‖ Journal of Geophysical Research, Vol. 111, 

D10S04, 17 pages.

EPA‘s ambient air quality measurements guidance, http://www.epa.gov/ttn/amtic/cpreldoc.html

FAA, Air Quality Procedures For Civilian Airports & Air Force Bases, April 1997, and 2004 Addendum,

http://www.faa.gov/regulations_policies/policy_guidance/envir_policy/airquality_handbook/media/Hand

book.PDF

Fanning, E., R.C. Yu, R. Lu, and J. Froines, 2007. ―Monitoring and Modeling of Ultrafine Particles and 

Black Carbon at the Los Angeles International Airport, Final Report,‖ ARB Contract No. 04-325, 

prepared for the California Air Resources Board and the California Environmental Protection Agency, 

Sacramento, CA (June 20).

Henry, R.C., 2002. ―Receptor Modeling,‖ Encyclopedia of Environmetrics, A.H. El-Shaarawi and W.W. 

Piegorsch, Editors, John Wiley & Sons, Ltd, Chichester.

Henry, R.C., Y.-S. Chang, and C.H. Speigelman, 2002. ―Locating nearby sources of air pollution by 

nonparametric regression of atmospheric concentrations on wind direction,‖ Atmospheric Environment

36:2237–2244.

Henry, R.C., 2008. ―Locating and quantifying the impact of local sources of air pollution,‖ Atmospheric 

Environment 42:358–363.

RWDI, 2003. ―Air Quality Study: Phase 4 - Ambient Air Quality Monitoring,‖ Toronto Pearson 

International Airport, Toronto, Ontario, Canada (November 12).

Unique (Flughafen Zürich AG), 2007: "Air Pollution Monitoring," Concept and Description 

(www.unique.ch), 

Watson, J.G., J.C. Chow, J.L. Bowen, D.H. Lowenthal, S. Hering, P. Ouchida, and W. Oslund, 2000. 

―Air Quality Measurements from the Fresno Supersite,‖ J. Air & Waste Manage. Assoc. 50:1321-1334.

Yu, K.N., Y.P. Cheung, T. Cheung, Ronald C. Henry, 2004. ―Identifying the impact of large urban 

airports on local air quality by nonparametric regression,‖ Atmospheric Environment 38:4501–4507.

www.heathrowairwatch.org.uk

— — — — — — — —
 

 English only

Revised text for the Guidance Manual

Road Vehicle Inventory Chapter
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Appendix C to the Report on Agenda Item 2 2 C-95

A4.3.4 For airport-related vehicles, emission factors are available from the following 

sources:

 U.S. EPA MOBILE6.

 California‘s EMFAC2002.

 CITEPA method based on COPERT-IV.

 EUROCONTROL ALAQS method based on COPERT-IV.

A4.4 Model Variations of Pollutant Emission Factors

A4.4.1 The vehicle emissions models cited in A4.3.4 are provided as sources of current 

and future road vehicle emission factors, but were originally designed for the purpose of 

monitoring the effect of national and/or local air quality legislation [MOBILE6, CITEPA]. 

These models estimate a number of exhaust pollutants including CO, HC, NOx, PM, SOx, 

select HAP and carbon dioxide CO2. Evaporative emissions from fuel and PM emissions from 

brake- and tire-wear are also provided in many cases.

A4.4.2 The pollutants relevant to road vehicle emissions are divided in legislated and 

non-legislated groups. The pollutant species that are typically modelled are shown in the 

following tables. When selecting a model it is important to note that some vehicle emissions 

models will report pollutants differently, e.g. some might provide a breakdown of 

Hydrocarbons and volatile pollutants, whilst others might aggregate these as one pollutant. 

Among other pollutants that are not included, lead may need to be calculated if leaded fuel is 

still in use and if a leaded fuel emissions factor is available.

Base pollutant Set – Legislated

The listed in the table indicate the pollutants subject to air quality legislation in one more 

nations.

Pollutant Remarks

CO

HC Some models may provide results per component 

pollutant – see extended set of pollutants below

NOx (NO2 + NO) Some models may report NO2 and NO separately. 

SOx

PM10

PM2.5 May be included in the report for PM10

Extended Set – non-legislated

Some models are able to report an extended set of pollutants if the appropriate indices are 

available. 

Pollutant Remarks

1.3 Butadiene

Acetaldehyde

Acrolein

Benzene

CO2 Most models will calculate fuel burn, hence CO2

can be derived. But as CO2 is not a LAQ gas we 

include it in the extended set.
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Appendix C to the Report on Agenda Item 2

Pollutant Remarks

CH4

Cu

CHCO

HCB Maybe included in HC

N2O

NH3

MTBE

PAH : BaP, BbF, BkF, 

IndPy

Maybe included in HC

PCDD-F Maybe included in HC

TSP

— — — — — — — —
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Appendix D to the Report on Agenda Item 2 2 D-1

APPENDIX D

Report on the Use of Environmental 

Management Systems (EMS) in

the Aviation Sector

International Civil Aviation Organization (ICAO)

Committee on Aviation Environmental Protection (CAEP)

February 2010
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2 D-2 Appendix D to the Report on Agenda Item 2

Table of Contents

Executive Summary i

Chapter 1. Introduction 1

1.1. Background 1

1.2. Methodology 2

1.3. Questionnaire Data 3

1.4. Introduction to EMS 3

Chapter 2. Questionnaire Participation 5

2.1. Introduction 5

2.2. Sector Characterization 5

Chapter 3. Environmental Management Drivers 7

3.1. Introduction 7

3.2. Priority Environmental Issues or Impacts 7

Chapter 4. Approaches to Environmental Management 8

4.1. Introduction 8

4.2. Application of EMS Standards or Guidelines 8

4.3. Scope of EMS 10

4.4. Other Management Systems in Place 11

Chapter 5. Performance Monitoring and Communication 13

5.1. Introduction 13

5.2. Performance Monitoring 13

5.3. Communication Methods 14

Chapter 6. Implementation and Maintenance 16

6.1. Introduction 16

6.2. EMS Implementation 16

6.3. EMS Maintenance 18

Chapter 7. Benefits and Challenges 21

7.1. Introduction 21

7.2. Implementation Challenges 21

7.3. Benefits of EMS Implementation 21

7.4. Trade-off Analysis 22
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Appendix D to the Report on Agenda Item 2 2 D-3

Chapter 8. Organizations Without an EMS 23

8.1. Introduction 23

8.2. Environmental Program Elements or Principles 23

8.3. Performance Monitoring 25

8.4. Communication Methods 28

8.5. EMS Application and Development Issues 29

Chapter 9. Recommendations 32

9.1. Recommendations 32

Chapter 10. Conclusion 33

References 34
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2 D-4 Appendix D to the Report on Agenda Item 2

Executive Summary

Pressure on the aviation industry to balance increasing demand with environmental protection is at an all 

time high. Therefore, an effective approach to sustain operations and meet future environmental 

requirements is critical. The International Civil Aviation Organization‘s (ICAO) Committee on Aviation 

Environmental Protection (CAEP) is the international forum of expertise for the study and development 

of proposals to minimize the impact of aviation on the environment. 

At the seventh Meeting of CAEP (CAEP/7) in February 2007, the Land Use Planning and Noise 

Management Task Group (TG) was asked to deliver a report at the Eighth Meeting of CAEP in February 

2010 providing information on the use of environmental management systems (EMS) and, as appropriate, 

make recommendations on how the committee could promote the use of EMS within the aviation system. 

In response, the TG developed an industry questionnaire to learn more about the application and potential 

value of EMS to aviation organizations. The questionnaire and accompanying introductory state letter 

were distributed worldwide by member states and industry associations in May 2008. Approximately 326 

organizations responded to the questionnaire; these organizations were categorized into five different 

sectors, including air navigation service providers (ANSPs), airlines, airports, manufacturers, and other 

aviation organizations. After validating the questionnaire data, information from 233 responses formed 

the basis of this report to CAEP/8 and supported the development of recommendations.

Approximately 50 percent of questionnaire respondents (a total of 117) apply EMS standards or 

guidelines, with the majority having an ISO-14001 v2004 certified EMS in place. The remaining 116 

respondents that have other environmental programs in place have many of the same principles and 

practices that are required as part of a formal EMS. For those organizations with an EMS, 82 percent 

have additional management systems in place—approximately 51 percent of these additional systems are 

integrated or coordinated with the organization‘s EMS. Over the past ten years, EMS implementation has 

been relatively consistent in the aviation industry. On average, respondents indicated that 6-12 months are 

needed to successfully develop and implement an EMS. Approximately 71 percent of organizations had 

assistance with EMS implementation from a consulting or contracting firm. 

Regardless of whether the respondent organization had an EMS in place, measuring environmental 

performance is important for ensuring compliance. On average, the majority of questionnaire respondents 

communicate environmental performance through a corporate social responsibility report or through their 

organization‘s website. Environmental areas of regulatory concern were a primary focus of organizations 

regardless of whether they implemented an EMS or not. 79 respondent organizations without an EMS 

plan to implement one in the future. These organizations indicated that the most common reason for not 

implementing an EMS was unfamiliarity with EMS approaches. As a result, aviation industry specific 

EMS implementation guidance was requested by these organizations.

The information provided by respondents forms the basis of two recommendations. These focus on 

increasing awareness of EMS principles and best practices in the aviation sector and establishing practical 

guidance to assist those organizations that choose to use EMS to enhance the way they manage 

environmental issues. Awareness and guidance materials should integrate existing ICAO environmental 

tools, guidelines, and manuals. Where possible they should encourage organizations to support higherlevel ICAO environmental objectives, consider the collaborative nature of the aviation industry, and 

account for variance in operation type (i.e., sector type) and the level of EMS maturity at the organization.
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Appendix D to the Report on Agenda Item 2 2 D-5

Recommendations

Disseminate Report Information. Within the first year of the CAEP/9 cycle, ICAO should make the 

information contained in this report publicly available. A report should be distributed specifically to 

those organizations who responded to the questionnaire and more broadly, via member states, to the 

aviation sectors in their state. 

Develop EMS Guidance. Stand alone EMS guidance should be developed for the end of the CAEP/9 

cycle. This should assist organizations to determine how EMS elements and principles can be used to 

enhance the way they manage environmental issues and provide practical guidance on how these EMS 

elements and principles can be implemented/integrated into existing management systems and business 

processes. 
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2 D-6 Appendix D to the Report on Agenda Item 2

Main Report

Chapter 1. Introduction

1.1. Background

Global demand for air travel is estimated to increase significantly in the future. While the benefits of this 

growth will be substantial, it is likely to be accompanied by an increase in aviation-related environmental 

impacts. Local air quality, ambient noise levels, water quality, energy use, and climate change are some 

of the most prominent impacts of concern. Pressure on the aviation industry to balance increasing 

demand with environmental protection is at an all time high. Therefore, an effective approach to sustain 

operations and meet future environmental requirements is critical. Identifying the significant 

environmental impacts of aviation, and effectively managing these impacts efficiently through the use of 

technology, procedures, and policy is likely to play an important role in the sustainable growth of the 

aviation industry. 

1.1.1. ICAO and the Environment

The International Civil Aviation Organization (ICAO) is a specialized agency of the United Nations 

created in 1944 to promote the safe and orderly development of global air transport. ICAO‘s work on the 

environment focuses primarily on those problems that benefit most from a common and coordinated 

approach on a worldwide basis, namely aircraft noise and engine emissions. The following 

environmental goals have been established by ICAO:

 limit or reduce the number of people affected by significant aircraft noise;

 limit or reduce the adverse impact of aviation emissions on local air quality; and

 limit or reduce the impact of aviation greenhouse gas emissions on the global climate.

ICAO‘s Committee on Aviation Environmental Protection (CAEP) is the international forum of expertise 

for the study and development of proposals to minimize the impact of aviation on the environment. 

Membership consists of experts from members and observers from states, including intergovernmental 

and non-governmental organizations representing aviation industry and environmental interests. CAEP is 

responsible for conducting studies and recommending measures to minimize and reduce aviation‘s impact 

on the environment, and for maintaining certification standards for aircraft noise and aircraft engine 

emissions. Recommendations made by CAEP are reviewed and adopted by the ICAO Council. The 

Council reports to the ICAO Assembly where the main policies on aviation environmental protection are 

defined and translated into Assembly Resolutions.

Since its creation in 1983, the role of CAEP has progressively expanded from one of basic standards 

setting, to the development of broad policy measures such as the balanced approach to limit or reduce the 

impact of aircraft noise, and the creation of market-based measures to handle noise and emissions charges 

and emissions trading. In order to achieve a greater understanding of the environmental impacts of 

aviation, CAEP encourages research through the collection, generation, analysis, harmonization, 

exchange, and dissemination of information related to aviation environmental issues. CAEP‘s work often 

results in published reports, guidance material, and/or specific studies.
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Appendix D to the Report on Agenda Item 2 2 D-7

1.1.2. CAEP/8 EMS Task

Environmental management systems (EMS) provide a methodology and framework to systemically 

identify and cost-effectively manage significant environmental aspects of aviation organizations‘ 

operations. They have proven effective across a wide range of organizations, including airports, air 

carriers, manufacturers, and government agencies. As a result, international recognition of the potential 

value of EMS as a tool to help aviation organizations manage their environmental issues is increasing. 

ICAO would like to further understand the application of EMS by aviation organizations, encourage 

implementation where this may help organizations overcome environmental challenges, and better use 

environmental opportunities. 

At the Seventh Meeting of CAEP (CAEP/7) in February 2007, the Land Use Planning and Noise 

Management Task Group (TG) was asked to deliver a report at the Eight Meeting of CAEP in February 

2010 providing information on the use of environmental management systems (EMS) and, as appropriate, 

make recommendations on how the committee could promote the use of EMS within the aviation system. 

In response, the TG formed an ad hoc group to perform the task and proposed a questionnaire to gather 

information for the report. The US Federal Aviation Administration agreed to lead the effort and an ad 

hoc group was formed with representatives from Transport Canada, Italy, International Coordinating 

Council of Aerospace Industries Associations, International Air Transport Association, and Airports 

Council International.

The TG developed an industry questionnaire to learn more about the application and potential value of 

EMS to aviation organizations. The questionnaire and accompanying introductory state letter were 

approved by the ICAO Secretary General on 16 May 2008. The questionnaire and letter were distributed

worldwide by member states and industry associations. Approximately 326 organizations responded to 

the questionnaire over a period of six months. After validating the questionnaire data, information from 

233 responses formed the basis of the report to CAEP/8 and supported the development of 

recommendations.

1.1.3. Objectives

The CAEP/8 task was to: 

 “deliver a report providing information on the use of EMS among airports, airlines and air 

navigation providers in order to give a base of understanding in the aviation sector;” and

 “based on the report, as appropriate, make recommendations on how the committee could 

promote the use of EMS with in the aviation sector.”

1.2. Methodology

TG1 developed an industry questionnaire based widely on input from members of the working group to 

gain an understanding of environmental management practices in the aviation sector. This questionnaire 

was divided into eight sections that seek to understand the responding organization and their 

environmental management practices by inquiring about the following:

 environmental management drivers;

 approach to environmental management;

 performance monitoring and communication methods; 

 resources required for implementation and maintenance; and

 lessons learned.
CAEP/8-WP/80

2 D-8 Appendix D to the Report on Agenda Item 2

After several revisions by the TG, the questionnaire was finalized and an electronic version of the survey 

was developed so respondents could submit their responses online. On 16 May 2008, the questionnaire 

was distributed by states and industry associations with an accompanying introductory letter signed by the 

ICAO Secretary General.

Over a six month time period, responses were received via mail, fax, email, or through the questionnaire 

software program. All questionnaire responses were input into the questionnaire software program, either 

manually or directly depending on the method of submission. Once all responses were input into the 

questionnaire software program, the response data was validated based on the resolutions that were 

agreed on by the TG (Section 1.3. outlines the validation process that was used).

Following validation, individual sector data was forwarded to the appropriate industry association so a 

summary analysis could be conducted to characterize the respondents in a given sector. After the 

response data was validated and characterized by the appropriate industry association, the remaining 

response data was analyzed and formed the basis of the report to CAEP/8.

1.3. Questionnaire Data

As a result of the number and range of organizations from different countries that responded to the 

questionnaire, variation in the data exists. Common inconsistencies found among questionnaire responses 

included the submission of partially completed surveys; receiving multiple, different responses from the 

same organization; and having questionnaires with response data for both question sets, those for 

organizations with EMS and those for organizations without EMS. It was critical that data be as 

consistent as possible for strong informative analysis. Therefore, the TG developed resolutions for how 

common inconsistencies should be addressed prior to analysis. The resolutions agreed on by TG were as 

follows:

1. Delete those responses from the data set that provide no information on the organization‘s 

environmental management practices.

2. Delete those responses from the data set that are exact duplicates.

3. Request clarification from industry group or respondents for those responses that are from the 

same organization, but not exact duplicates.

4. Review data specifically by sector to see what can be done about inconsistent financial figures.

5. Request clarification from industry group or respondents for those responses that claimed they do 

not apply EMS standards/guidelines, but completed both sets of questionnaires for organizations 

with EMS and without EMS.

6. Delete the completed question set for organizations without an EMS for those organizations that 

claim to have an EMS and completed the question set for organizations with an EMS.

7. Change the organization‘s response to the question regarding whether or not they have an EMS to 

reflect the question set that they answered.

8. Delete those responses from the data set that do not provide sufficient information on the 

organization to validate that the response is accurate.
CAEP/8-WP/80

Appendix D to the Report on Agenda Item 2 2 D-9

Of the 326 responses received, approximately 93 were not considered for analysis as a result of the agreed 

upon resolutions. The remaining 233 responses form the basis of the report to CAEP/8 and support the 

development of recommendations.

In addition to variation in the data, it should also be noted that the questionnaire respondents do not make 

up a random sample. The questionnaire and accompanying introductory letter that was distributed to 

industry associations and states encouraged the participation of all organizations in the aviation sector. 

However, since questionnaire participation was voluntary, those organizations who responded to the 

survey were more likely to have an environmental program in place. As a result, the sample of 

respondents is not representative of the aviation industry as a whole.

1.4. Introduction to EMS

As one of the most environmentally friendly forms of transportation, aviation organizations are 

increasingly using EMS among other approaches to meet their environmental challenges. A formal 

definition of EMS, developed by Transport Canada, is as follows:

“A systematic approach for organizations to bring environmental considerations into decision-making 

and day-to-day operations. It also establishes a system for tracking, evaluating and communicating

environmental performance. An EMS helps ensure that major environmental risks and liabilities are 

identified, minimized and managed.”

Formal Environmental Management Systems (EMS) emerged in the early 1990s to provide organizations 

with a proactive, systematic approach for managing the potential environmental consequences of their 

operations. Such systems have been widely adopted by industry and Government and have been effective 

at improving an organization‘s regulatory compliance and environmental performance. Although several 

recognized EMS frameworks exist, most are based on the International Organization for Standardization‘s 

ISO-14001 EMS standard, described by Figure 1.1.

 Figure 1.1: ISO-14001 Framework
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2 D-10 Appendix D to the Report on Agenda Item 2

Environmental Policy

The organization establishes an environmental policy which provides an overaching vision and 

framework for environmental management at the organization.

Planning

The organization identifies how its operations might harm the environment, and develops objectives, 

targets, and programs to reduce this harm.

Implementation and Operation

The organization implements the systemic measures to control operations and reduce environmental 

impacts across all levels and functions of its operations.

Checking

The organization assesses its environmental performance and the effectiveness of its management system 

elements. 

Management Review

Based on its assessment of the implemented systemic measures, the organization undertakes actions to 

make system adjustments and to promote continual improvement.

The EMS continually moves through this cycle, fine-tuning the management of those operations that 

harm the environment. This ―continual improvement cycle‖ is a fundamental characteristic of the EMS; it 

allows the system to adapt to the dynamic nature of the organization‘s operations and external conditions.

Chapter 2. Questionnaire Participation

2.1. Introduction

With the assistance of CAEP member states, observer organizations, and industry associations, 

questionnaires were disseminated worldwide to a wide range of stakeholders within the aviation industry. 

A total of 326 responses were received over a six month time period. Following validation, 233 of these 

responses were analyzed to form the basis of this report. This chapter will discuss and analyze the 

breakdown of these 233 responses by industry sector and geographic location.

Figure 2.1: Number of valid survey respondents within each aviation industry sector.

Sector Characterization

Airlines 80

Air Navigation Service Providers 24

Airports 96

Manufacturers 10

Other 44

TOTAL 254

Note: CAEP received a total of 233 unique 

survey responses. When selecting a sector, 

respondents were able to choose multiple 

options.
CAEP/8-WP/80

Appendix D to the Report on Agenda Item 2 2 D-11

Asia & Pacific

Eastern & Southern Africa

Europe & North Atlantic

Middle East

South America

Western & Central Africa

North America, Central America

& Caribbean

Figure 2.2: Number of CAEP survey respondents within each ICAO region.

2.2. Sector Characterization 

Individual sector response data was forwarded to the appropriate industry association for completion of a 

summary analysis that characterized the respondents in a given sector. These analyses contain statistical 

data specific to the questionnaire respondents and offer some insight on how representative these 

respondents are of the industry as a whole. In addition, each analysis provides an illustration of the 

geographic location of questionnaire respondents by sector.

2.2.1. Airlines

A total of 80 questionnaire respondents out of 233 were from passenger, cargo, or passenger and cargo 

airlines. These  ̳Airline‘ respondents transported an estimated 1.1 billion passengers and 55 billion ton 

kilometers of cargo in 2008. This represents approximately 67% of total system-wide scheduled 

passengers and 33% of total system-wide scheduled cargo carried by IATA member airlines in that year. 

Of the 80 airline respondents, 57 (or 71%) were IATA members.

2.2.2. Air Navigation Service Providers

A total of 24 questionnaire respondents out of 233 were from air navigation and air traffic service 

providers. Of the 24  ̳Air Navigation Service Provider (ANSP)‘ respondents, 18 are members of the Civil 

Air Navigation Services Organization (CANSO). Together, the CANSO member respondents move an 

estimated 57,370,000 aircraft per year. 

2.2.3. Airports

A total of 96 questionnaire respondents out of 233 were from airport companies, airport authorities, and 

government and city departments that operate one or more airports. These  ̳Airport‖ respondents operate 

a total of 231 airports that have an estimated annual passenger throughput of approximately 1.15 billion.

The 96  ̳Airport‘ respondents represent approximately 17 percent of Airport Council International‘s 

(ACI‘s) 597 member organizations, and 5.7 percent of the 1,680 airports in ACI. In terms of passenger 

numbers, the 96 responses cover almost a quarter of the 4.8 billion passengers handled at ACI member 

airports annually.

41

16

121

16

5

4

30
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2 D-12 Appendix D to the Report on Agenda Item 2

2.2.4. Manufacturers

A total of 10 questionnaire respondents out of 233 are from aircraft and engine manufacturers. These 

 ̳Manufacturer‘ respondents represent approximately 50 percent of the International Coordinating Council 

of Aerospace Industries Association (ICCAIA) membership.

2.2.5. Other

A total of 44 questionnaire respondents out of 233 were from a variety of  ̳Other‘ organizations including 

fixed base operations, corporate aviation flight departments, aviation academies and flight schools, and 

aircraft and engine maintenance organizations. When completing the questionnaire, respondents were 

able to identify themselves as belonging to multiple sectors. As a result, approximately 83 percent of 

those that identified themselves as  ̳Other‘ also identified with one or more of the alternative sectors as 

well.

Chapter 3. Environmental Management Drivers

3.1. Introduction

The projected growth of aviation and accompanying environmental effects has changed the priority of 

some traditional aviation-related environmental issues and resulted in the emergence of some new 

concerns. This chapter discusses and analyzes the priority of environmental issues and impacts to 

aviation organizations including those that are currently most important. Where applicable, the analysis 

and discussion investigates trends by industry sector.

3.2. Priority Environmental Issues or Impacts

Respondents were asked to rate the importance of various environmental issues or impacts to their 

organization. Rating scores were tallied and the level of importance with the highest percentage of votes 

for each issue or impact was identified. Figure 3.1 lists those environmental issues with agreement across 

each of the five sectors as to their level of importance. According to the respondents, these are the 

environmental issues of highest and medium importance to the aviation industry today. There was no 

consensus across industry sectors as to the issues or impacts that might be of importance in five or 10 

years time, or of those that will never be important.

Figure 3.1: Areas of environmental concern across all aviation industry sectors.

Environmental Issue or Impact Importance Today

High Medium

Aircraft Noise 

Noise from ground activities 

Fuel efficiency 

Financial 

Compliance with laws and regulations 

State/country policies 

Company core values and ethics 

Global climate change 

Non-governmental organizations 

Corporate commitment and vision 

Capacity and growth constraints 

Soil and water protection 
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Appendix D to the Report on Agenda Item 2 2 D-13

Energy management 

Materials and chemicals management 

Operational efficiency 

Customers and other stakeholders' concerns 

Note: Agreement was identified through comparison of categories with 

the highest respondent percentage across all five sectors.

Respondents rated each environmental issue against six levels of importance: very important now, 

medium important now, likely to be important in 5 years, likely to be important in 10 years, will never be 

very important, and not applicable. Only one level of importance could be assigned to each 

environmental issue or impact.

Chapter 4. Approaches to Environmental Management

4.1. Introduction

Aviation organizations are increasingly challenged to meet new market demands in a manner that is 

environmentally sustainable. In response to this challenge, organizations are using EMS approaches to 

manage environmental issues. This chapter discusses and analyzes the approaches that aviation 

organizations are using to manage their environmental issues. Where applicable, the analysis and 

discussion investigates trends by industry sector.

4.2. Application of EMS Standards or Guidelines

EMS standards or guidelines are employed by 117 or approximately 50 percent of the questionnaire 

respondents across all five sectors. The number of organizations within each sector that apply EMS 

standards or guidelines is illustrated below in Figure 4.1.

Figure 4.1: Organizations that use EMS standards or guidelines within each aviation industry sector.

Aviation Industry Sector Use of EMS

Air Navigation Service Providers 6

Airlines 42

Airports 54

Manufacturers 8

Other 19

129

Note 1:Of the 129 organizations that use EMS 

standards or guidelines, 117 are 

unique respondents. 12 respondents 

were included in multiple sectors. 

Note 2: CAEP received a total of 233 survey 

responses from across all five sectors.

The types of EMS standards or guidelines used by respondents in each sector are displayed in Figure 4.2 

below. The majority of respondents (57 total) in four of the five sectors have implemented an ISO-14001 

v2004 certified EMS. Other commonly used EMS standards include the application of organization 

appropriate EMS elements (27 total) and the implementation of a formal EMS based on ISO-14001 or the 

Eco-Management Audit Scheme (EMAS) but without third-party certification (24 total). Across all five 

sectors, eight organizations were registered to EMAS.
CAEP/8-WP/80

2 D-14 Appendix D to the Report on Agenda Item 2

6

2

2

8 25

13

7

4

Figure 4.2: EMS approaches to managing environmental issues by aviation industry sector.

2

2

1

1

2

7

5

15

13

9

2

4

10

5

1

2

4.2a – Air Navigation Service Providers 4.2b – Airports

4.2c – Airlines 4.2d – Manufacturers

4.2e – Other

ISO-14001 certified

EMAS registered

Self-declare (ISO-14001 or EMAS)

Mixed (ISO-14001 certified / self-declare)

Apply EMS elements as appropriate

Other
CAEP/8-WP/80

Appendix D to the Report on Agenda Item 2 2 D-15

4.3. Scope of EMS

In order to understand the extent of EMS implementation within respondent organizations, survey 

participants were asked to identify the elements of their organization currently within the scope of their 

EMS. Figure 4.3 illustrates how much of the respondents organization was included within the scope of 

their EMS (e.g., is the entire organizations and all its operations included within the EMS scope or are 

only select facilities or operations covered by the EMS). Most respondents indicated that 100% of their 

organization (i.e., all facilities and operations) were covered by the scope of their EMS. 

Figure 4.3: The percentage of the organization included in the scope of the EMS.

Sector Percentage of the Organization Included in the Scope of the EMS

< 30% 30%-60% 60-90% 90-100% 100%

ANSPs 1 0 0 0 3

Airports 4 3 1 5 37

Airlines 2 6 4 5 8

Manufacturers 0 0 1 0 4

Other 1 0 0 3 10

Respondents were also asked to identify the activities or operations that they currently include in their 

organization‘s EMS. Figure 4.4 lists those functions that were included or excluded from EMS scopes 

across each of the five sectors. Note that of the 28 activities and operations included in the questionnaire, 

 ̳Catering centers‘ is the only item typically excluded from an EMS‘s scope.
CAEP/8-WP/80

2 D-16 Appendix D to the Report on Agenda Item 2

Figure 4.4: Activities and operations concurrently included or excluded from the EMS scope across all 

aviation industry sectors.

Organization’s Activity or Operation EMS Scope

Included Excluded

Engineering/maintenance operations 

Catering centers 

Facility management 

Staff environmental training 

Organization organizational structure and policies 

Environmental accounting 

Environmental performance criteria 

Environmental auditing 

Energy management 

Soil and water protection 

Waste management 

Materials and chemicals management 

Air quality monitoring 

Noise exposure monitoring 

Ground transportation 

Procurement policies/supplier requirements 

Ecology conservation 

Note 1: Agreement was identified through comparison of categories with the 

highest respondent percentage across all five sectors.

Note 2: An activity or operation was listed as „Excluded‟ if the highest 

respondent percentage across all five sectors was „Don‟t know / Not 

applicable‟.

Respondents categorized each function based of the following scope options: included in EMS, likely to 

be included within 5 years, likely to be included within 10 years, and don‘t know/not applicable. Only 

one scope option could be assigned to each activity or operation.

4.4. Other Management Systems In Place

Out of 117 respondents with an EMS, 82 percent have one or more additional management systems in 

place. The percentage of respondents with either a Safety Management System (SMS) or a Quality 

Management System (QMS) is high for all sectors (See Figure 4.5). However, in four of the sectors 

(Airports, Airlines, Manufacturers, and Others) the most common addition to an EMS was a QMS.
CAEP/8-WP/80

Appendix D to the Report on Agenda Item 2 2 D-17

Figure 4.5: Management System types in addition to EMS within each aviation industry sector.

4.5a – Air Navigation Service Providers 4.5b – Airports

Additional Management System in Place

Safety Management System (SMS) 48%

Quality Management System (QMS) 52%

Other Management System 13%

No Additional Management System 26%

Note: Percentages based on 54 Airport 

responses.

4.5c – Airlines 4.5d – Manufacturers

Additional Management System in Place

Safety Management System (SMS) 75%

Quality Management System (QMS) 100%

Other Management System 13%

No Additional Management System 0%

Note: Percentages based on 8 Manufacturer 

responses.

4.5e – Others

Additional Management System in Place

Safety Management System (SMS) 37%

Quality Management System (QMS) 74%

Other Management System 11%

No Additional Management System 21%

Note: Percentages based on 19 Other 

responses.

Approximately 51 percent of respondents with additional management system(s) in place have integrated 

or coordinated it with their EMS. Most respondents with integrated systems suggested the greatest 

benefits to be:

1. the sharing of system procedures and processes, which helps to avoid duplications of effort and 

increase efficiency; and

2. the ability to manage diverse operations in a more integrated manner.

Additional Management System in Place

Safety Management System (SMS) 67%

Quality Management System (QMS) 50%

Other Management System 17%

No Additional Management System 17%

Note: Percentages based on 6 ANSP 

responses.

Additional Management System in Place

Safety Management System (SMS) 64%

Quality Management System (QMS) 95%

Other Management System 19%

No Additional Management System 5%

Note: Percentages based on 42 Airline 

responses.
CAEP/8-WP/80

2 D-18 Appendix D to the Report on Agenda Item 2

Chapter 5. Performance Monitoring and Communication

5.1. Introduction

As aviation organizations adapt to meet industry demands in an environmentally sustainable way, 

demonstrating and communicating environmental performance to stakeholders is becoming increasingly 

important. This chapter discusses and analyzes the value of EMS in assisting aviation organizations to 

manage a broad range of environmental issues, impacts, and regulations. It also describes the types of 

environmental targets that aviation organizations set, the approaches used to measure performance, and 

the methods that are employed to communicate their EMS. Where applicable, the analysis and discussion 

investigates trends by industry sector.

5.2. Performance Monitoring

Respondents that have an EMS in place were asked to rate how helpful their EMS is in managing and 

controlling their organization‘s various environmental issues. Figure 5.1 lists those environmental issues 

with consensus across each of the five sectors as to their level of helpfulness. According to the 

respondents, these are the areas of environmental concern in which EMS is most helpful to the aviation 

industry today. There was no consensus across industry sectors as to the helpfulness of EMS in managing 

environmental issues of medium importance today, those that might be of importance in five or 10 years 

time, or of those areas in which EMS will never be helpful.

Figure 5.1: Consensus areas of EMS helpfulness towards managing and controlling environmental 

concerns across all aviation industry sectors.

Environmental Issue or Impact Very Helpful 

Today

Compliance with laws and regulations 

State/country policies 

Company core values and ethics 

Corporate image 

Soil and water protection 

Waste management 

Energy management 

Note: Agreement was identified through comparison of 

categories with the highest respondent percentage 

across all five sectors.

Respondents rated each environmental issue against six levels of EMS helpfulness: very helpful now, 

medium helpful now, likely to be helpful in 5 years, likely to be helpful in 10 years, will never be very 

helpful, and not applicable. Only one level of helpfulness could be assigned to each environmental issue 

or impact.

Respondents indicated that one of the most important reasons why environmental performance is 

measured is to ensure compliance. The questionnaire asked participants to list the five most important 

environmental regulations in which their organization‘s EMS ensures compliance. As a result of global 

participation in the questionnaire, various environmental regulations were identified as important and 

there was no clear consensus on which laws were the most significant. The results were therefore 
CAEP/8-WP/80

Appendix D to the Report on Agenda Item 2 2 D-19

categorized into areas of environmental concern, which were then tallied and ranked to identify the top 

five areas in which the survey respondents ensure compliance (Figure 5.2).

Figure 5.2: Top five areas of environmental regulatory concern.

Important Environmental Regulation Areas

Hazardous/solid waste 54%

Water 40%

National environmental regulations 38%

Air 34%

Noise 26%

Note: Percentages based on 115 respondents.

The management and disposal of hazardous and solid waste is the most important environmental area in 

which respondent organizations ensure compliance. Second, legislation that regulates the quality, 

management, and use of storm water, waste water, and drinking water was important to 40 percent of 

questionnaire respondents. Many respondents indicated that they ensure compliance with the national 

environmental legislation in place in each country in which their organization operates. The national 

environmental legislation that was identified by respondents typically regulated general environmental 

concerns such as environmental protection and conservation. The fourth most important regulated 

environmental area was the quality and management of air emissions, in particular carbon dioxide. 

Lastly, respondents indicated that regulations that focused on noise were also important.

In addition to compliance, questionnaire respondents stated that other important reasons to measure 

environmental performance include the tracking and monitoring of progress towards achievement of 

environmental objectives and for the purpose of reporting performance to stakeholders and the public. 

Respondent organizations typically measure performance through environmental audits and the use of key 

performance indicators. The environmental targets set by questionnaire respondents are directly aligned 

with the environmental areas in which organizations ensure compliance. In general, respondents are 

looking to reduce their consumption of energy, waste, water, emissions, and noise. On average, 

environmental targets and objectives are set no more than five years into the future.

5.3. Communication Methods

As depicted in Figure 5.3 below, the most common methods of communicating environmental 

performance across all five sectors are through the use of sustainability or corporate social responsibility 

(CSR) reports and through the organization‘s website. The third most common method of external 

communication employed by Airport and ANSP respondents is to use community meetings as a forum for 

informing stakeholders and the public. In contrast, Manufacturer, Airline, and Other respondents prefer 

the use of newsletters over community meetings. In all sectors there were some organizations who listed 

other means of communicating environmental performance, these include: presentations at conferences, 

internal meetings, press releases, and magazines and other publications.
CAEP/8-WP/80

2 D-20 Appendix D to the Report on Agenda Item 2

Figure 5.3: Methods for communicating environmental performance used by organizations within each 

aviation industry sector that have implemented an EMS.

5

1

3

3

6

33

17

15

23

34

5.3a – Air Navigation Service Providers

5.3c – Airlines 5.3d – Manufacturers

44

12

26

20

40

7

2

2

4

7

5.3b – Airports
CAEP/8-WP/80

Appendix D to the Report on Agenda Item 2 2 D-21

15

7

4

8

12

Chapter 6. Implementation and Maintenance

6.1. Introduction

A wide range of approaches can be used to implement an EMS depending on the nature of the 

organization‘s operations and future plans. This chapter discusses and analyzes the resources and time 

needed for EMS implementation, including training. It also discusses the resources needed to operate and 

maintain an EMS, as well as the length of time the organization has operated their EMS. Where 

applicable, the analysis and discussion investigates trends by industry sector.

6.2. EMS Implementation

Respondents were asked to indicate when their EMS was implemented as well as the length of time they 

felt was necessary to successfully implement the system within their organization. The same trends were 

found among all five sectors; and therefore responses were aggregated at the industry level. Figure 6.1 

shows EMS implementation to have been relatively consistent within the industry for the past 10 years.

Figure 6.1: Average length of time EMS has been in place across all aviation industry sectors.

28

18

30

29

12

Figure 6.2 below indicates that most organizations (46 total) required 6–12 months to fully develop and 

implement their EMS. Very few organizations (8 total) were able to accomplish this task in less than six 

5.3e – Other

Sustainability / CSR Reports

Websites

Newsletters

Community Meetings

Other

0-2 years

2-3 years

3-5 years

6-10 years

> 10 years
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2 D-22 Appendix D to the Report on Agenda Item 2

months, and many (63 total) needed one to two years to fully deploy their systems. EMS implementation 

typically takes longer in large organizations and those with complicated operations. Approximately, 71 

percent of the 117 respondents with an EMS in place sought outside assistance from a consulting or 

contracting firm in order to implement the system.

Figure 6.2: Average time taken to implement EMS across all aviation industry sectors.

46

23

20

20

8

Figure 6.3 provides a rough estimate of the average level of resources necessary for EMS implementation 

within each of the five sectors. Note that the averages for each sector are based on the total number of 

question respondents and do not necessarily reflect all questionnaire respondents for each sector. The 

estimates provided by respondents on the length of time necessary for implementation are higher than 

those identified in Figure 6.2. The Airline, Airport, and Other sector results indicate that implementation 

takes approximately 14–15 months. Manufacturers and ANSPs provided estimated longer 

implementation times with ANSPs estimating about 3.5 years for implementation. The results indicate 

that, on average, a minimum of five employees are required during EMS implementation. Both Airports 

and Manufacturers provided larger estimates of 26 and 34 employees necessary for implementation, 

respectively. All five sectors estimated the need for at least two additional employees during EMS 

implementation with the Manufacturing sector respondents going so far as to estimate an average need for 

20 additional staff. Within each sector, the estimates for the number of employees necessary for 

implementation varied by organization size. 

0-6 months

6-12 months

12-18 months

18-24 months

> 24 months
CAEP/8-WP/80

Appendix D to the Report on Agenda Item 2 2 D-23

Figure 6.3: Average resource use for EMS implementation within each aviation industry sector.

6.3a – Air Navigation Service Providers 6.3b – Airports

Implementation Resource Average

Implementation time (months) 15.3

Employees used 26.3

Employees hired for implementation 2.3

Contractor support costs (USD) $62,950

Equipment costs (USD) $209,114

Certification / registration costs (USD) $9,966

Note: Averages based on 54 Airport responses.

6.3c – Airlines 6.3d – Manufacturers

Implementation Resource Average

Implementation time (months) 21.4

Employees used 33.5

Employees hired for implementation 19.6

Contractor support costs (USD) $42,500

Equipment costs (USD) $0

Certification / registration costs (USD) $120,000

Note: Averages based on 8 Manufacturer 

responses.

6.3e – Others

Implementation Resource Average

Implementation time (months) 15.2

Employees used 11.2

Employees hired for implementation 5.8

Contractor support costs (USD) $89,591

Equipment costs (USD) $33,344

Certification / registration costs (USD) $9,778

Note: Averages based on 19 Other responses.

Contract support costs ranged between $42,000–$90,000 for four of the five sectors (Airports, Airlines, 

Manufacturers, and Others). ANSP respondents indicated an average cost for contractor support of more 

than $500,000. Estimates for the average cost of equipment ranged from $10,000–$34,000 for three of 

the five sectors (ANSPs, Airlines, and Others). Manufacturer sector respondents did not provide an 

estimate for their equipment costs and Airports sector respondents estimated an average equipment cost of 

$209,114. EMS certification and registration costs for three of the five sectors (Airports, Airlines and 

Others) ranged from $9,700–$13,000. ANSP and Manufacturer sector respondents estimate average EMS 

certification and registration costs to be much higher at $100,000 and $120,000 respectively. However, it 

is important to note that the monetary figures provided as part of the survey responses were rough 

estimates and caution should therefore be taken when using them to represent industry or sector trends.

6.3. EMS Maintenance

Implementation Resource Average

Implementation time (months) 41.0

Employees used 5.7

Employees hired for implementation 4.3

Contractor support costs (USD) $544,429

Equipment costs (USD) $10,000

Certification / registration costs (USD) $100,000

Note: Averages based on 6 ANSP responses.

Implementation Resource Average

Implementation time (months) 13.9

Employees used 9.5

Employees hired for implementation 2.9

Contractor support costs (USD) $51,542

Equipment costs (USD) $19,699

Certification / registration costs (USD) $12,976

Note: Averages based on 42 Airline responses.
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2 D-24 Appendix D to the Report on Agenda Item 2

Figure 6.4 provides a rough average estimate of the level of resources necessary for EMS operation and 

maintenance (O&M) for each of the five sectors. Note that the averages for each sector are based on the 

total number of question respondents and do not necessarily reflect all questionnaire respondents for each 

sector. For three of the five sectors (Airports, Airlines, and Other), time necessary for operation and 

maintenance ranges from 1–2 years. Estimates provided by ANSP and Manufacturer sector respondents 

were on both sides of this range with Manufacturers on average spending less than six months on O&M 

and ANSPs needing three years. As for the number of employees needed for EMS O&M, the estimates 

varied by sector and are as follows: five for ANSPs, 28 for Airports, 15 for Airlines, 30 for 

Manufacturers, and 16 for Others.

Figure 6.4: Average resource use for EMS O&M within each aviation industry sector.

6.4a – Air Navigation Service Providers 6.4b – Airports

O&M Resource Average

O&M time (months) 22.2

Employees used 27.7

Contractor support costs (USD) $22,577

Equipment costs (USD) $21,554

Certification / registration costs (USD) $5,020

Note: Averages based on 54 Airport responses.

6.4c – Airlines 6.4d – Manufacturers

O&M Resource Average

O&M time (months) 3.8

Employees used 29.5

Contractor support costs (USD) $5,000

Equipment costs (USD) $25,000

Certification / registration costs (USD) $77,000

Note: Averages based on 8 Manufacturer 

responses.

6.4e – Others

O&M Resource Average

O&M time (months) 14.3

Employees used 16.0

Contractor support costs (USD) $63,511

Equipment costs (USD) $30,000

Certification / registration costs (USD) $6,636

Note: Averages based on 19 Other responses.

O&M Resource Average

O&M time (months) 36.0

Employees used 5.0

Contractor support costs (USD) $275,000

Equipment costs (USD) $10,000

Certification / registration costs (USD) $36,653

Note: Averages based on 6 ANSP responses.

O&M Resource Average

O&M time (months) 17.0

Employees used 14.8

Contractor support costs (USD) $14,500

Equipment costs (USD) $36,407

Certification / registration costs (USD) $7,704

Note: Averages based on 42 Airline responses.
CAEP/8-WP/80

Appendix D to the Report on Agenda Item 2 2 D-25

The range of contract support costs were estimated to be $5,000–$22,577 for three out of five sectors 

(Airports, Airlines, and Manufacturers). Other sector respondents estimate an average cost of $63,500 for 

contract support and ANSPs estimated an average cost of $275,000. The cost of equipment for four out 

of five sectors (Airports, Airlines, Manufacturers, and Others) was estimated to be between $21,000–

$36,000. Equipment costs for ANSPs were estimated to be $10,000 on average. Lastly, three out of five 

sectors (Airports, Airlines and Others) estimate average EMS certification and registration costs to be in 

the range of $5,000–$7,704. Manufacturers and ANSPs had higher estimates for EMS certification and 

registration costs. Manufacturers estimated $77,000 for EMS certification and registration costs and 

ANSPs estimated about $37,000. Once again, it is important to note that the monetary figures provided 

were rough estimates and caution should be taken in using the data as representative of industry or sector 

trends.

Staff training is necessary for both EMS implementation and maintenance. Questionnaire respondents 

were asked to indicate the types of staff training required for their EMS. The training of management and 

office personnel and engineering and maintenance staff had the highest respondent percentages across all 

five sectors. Sector differences were apparent in the additional types of training that were required for 

EMS implementation and maintenance (Figure 6.5). For example, airlines required both ground 

operations personnel and cabin crew training, airports required ground operations personnel training, and 

manufacturers required manufacturing personnel training.

Figure 6.5: Staff training required as a result of the EMS within each aviation industry sector.

6.5a – Air Navigation Service Providers 6.5b – Airports

Implementation Resource Average

Management & office staff 91%

Engineering & maintenance staff 83%

Manufacturing staff 11%

Ground operations staff 39%

Air traffic controller staff 9%

Cabin crew staff 0%

Other staff 17%

Note: Percentages based on 46 Airport 

responses.

6.5c – Airlines 6.5d – Manufacturers

Implementation Resource Average

Management & office staff 88%

Engineering & maintenance staff 88%

Manufacturing staff 88%

Ground operations staff 38%

Air traffic controller staff 0%

Cabin crew staff 0%

Other staff 25%

Note: Percentages based on 8 

Manufacturer responses.

Staff Requiring EMS Training

Management & office staff 80%

Engineering & maintenance staff 80%

Manufacturing staff 0%

Ground operations staff 20%

Air traffic controller staff 40%

Cabin crew staff 0%

Other staff 40%

Note: Percentages based on 5 ANSP 

responses.

Implementation Resource Average

Management & office staff 84%

Engineering & maintenance staff 76%

Manufacturing staff 8%

Ground operations staff 63%

Air traffic controller staff 8%

Cabin crew staff 45%

Other staff 47%

Note: Percentages based on 38 Airline 

responses.
CAEP/8-WP/80

2 D-26 Appendix D to the Report on Agenda Item 2

6.5e – Others

Implementation Resource Average

Management & office staff 29%

Engineering & maintenance staff 24%

Manufacturing staff 12%

Ground operations staff 24%

Air traffic controller staff 0%

Cabin crew staff 6%

Other staff 12%

Note: Averages based on 17 Other 

responses.

Chapter 7. Benefits and Challenges

7.1. Introduction

While organizations differ, there are lessons-learned from every EMS implementation. This chapter 

discusses and analyzes the benefits and challenges perceived by respondents to implementing EMS. 

Analysis and discussion of trends has been aggregated for all sectors.

7.2. Implementation Challenges

Respondents, regardless of sector, identified many of the same challenges with EMS implementation. 

Figure 7.1 outlines the top three challenges experienced by questionnaire respondents. The greatest 

challenges identified were the amount of resources and the degree of culture change necessary for 

successful EMS implementation. Respondents stated that it was difficult to alter employee behavior 

towards incorporating environmental considerations and responsibilities into decision making and day to 

day operations.

Figure 7.1: Top three EMS implementation challenges.

EMS Implementation Challenges

Resources (time, finances) 26%

Culture change 26%

Employee awareness / training 23%

Management commitment 16%

Note: Percentages based on 110 survey 

respondents.

Another common challenge respondents faced was adequately training employees to be aware of the EMS 

and their responsibilities with regards to system maintenance. Lastly, lack of management commitment 

was cited as the third most common challenge among respondents. In addition to those included in 

Figure 7.1, respondents identified EMS alignment within the larger organization and recordkeeping 

requirements during EMS implementation as further implementation challenges. It is important to note 

that the challenges identified above are often the most common issues with EMS implementation. 
CAEP/8-WP/80

Appendix D to the Report on Agenda Item 2 2 D-27

7.3. Benefits of EMS Implementation

The three most common benefits of EMS implementation are illustrated below in Figure 7.2. 

Respondents indicated that the greatest benefit of EMS implementation is that it enhances the reputation 

and image of the organization. In addition, respondents noted that this enhanced reputation improved 

their relationship with stakeholders. Another benefit of EMS implementation is improved compliance 

with environmental regulations. Also, since EMS is a proactive approach to environmental management, 

risk to the organization is mitigated. Lastly, respondents cited that improving the environment, or 

lessening their organization‘s impact on the environment, was an important benefit of EMS 

implementation. Other benefits of EMS implementation included the ability to track environmental 

performance, a reduction in costs, and an increase in awareness and efficiency.

Figure 7.2: Three most frequently cited benefits of EMS implementation.

EMS Implementation Benefits

Enhance reputation / image 34%

Enhance compliance / mitigate risk 33%

Environmental improvements 25%

Note: Percentages based on 110 survey 

respondents.

7.4. Trade-off Analysis 

According to the sector respondents, the benefits of EMS implementation far outweigh the 

implementation and maintenance challenges. Approximately 96 percent of questionnaire respondents 

recommend that other organizations establish EMS. Many respondents stated that they would be willing 

to share some of their EMS materials including environmental policies, environmental/sustainability 

reports, performance metrics, and objectives and targets. However, organizations were not willing to 

share EMS documentation that may contain proprietary information such as audit reports and complete 

EMS Manuals.

Chapter 8. Organizations without an EMS

8.1. Introduction

Some organizations have not implemented an EMS, but do have other environmental programs in place to 

manage their environmental issues. This chapter discusses and analyzes responses from those 

organizations that have not implemented an EMS. It reviews the approaches that are used to manage 

environmental issues and impacts including those that are common to EMS and it analyzes the 

environmental issues and impacts that are most important to these organizations now. In addition, it 

investigates the metrics and targets that are established to measure performance and the types of guidance 

that would be helpful to assist them in implementing an EMS. Where applicable, the analysis and 

discussion investigates trends by industry sector.

8.2. Environmental Program Elements or Principles

A total of 116 questionnaire respondents do not apply EMS standards or guidelines. However, these 

respondents have environmental programs in place that have many of the same elements or principles 

required for an EMS. Respondents without a formal EMS were asked to identify whether or not EMS 

elements were included in their environmental program. Figure 8.1 illustrates the percentage of 
CAEP/8-WP/80

2 D-28 Appendix D to the Report on Agenda Item 2

respondents, by sector, whose environmental program includes certain elements or principles consistent 

with EMS.

Figure 8.1: Environmental program elements of organizations that do not apply EMS standards or 

guidelines.

8.1a – Air Navigation Service Providers 8.1b – Airports

Environmental Program Elements

Environmental Vision / Policy 68%

Goals, Objectives or Targets 66%

Management Programs 58%

Operational Controls 84%

Environmental Metrics 53%

Performance Reporting 63%

External Communication Programs 39%

Employee Awareness Training Programs 61%

Compliance Audits / Inspections 61%

Systems / Process Audits 39%

Emergency Preparedness 68%

Management Structure or Framework 50%

Top Management Performance Reviews 34%

Note: Percentages based on 38 Airport 

responses.

8.1c – Airlines 8.1d – Manufacturers

Environmental Program Elements

Environmental Vision / Policy 100%

Goals, Objectives or Targets 100%

Management Programs 50%

Operational Controls 100%

Environmental Metrics 100%

Performance Reporting 100%

External Communication Programs 100%

Employee Awareness Training Programs 100%

Compliance Audits / Inspections 100%

Systems / Process Audits 50%

Emergency Preparedness 100%

Management Structure or Framework 100%

Top Management Performance Reviews 50%

Note: Percentages based on 2 Manufacturer 

responses.

Environmental Program Elements

Environmental Vision / Policy 63%

Goals, Objectives or Targets 44%

Management Programs 19%

Operational Controls 75%

Environmental Metrics 19%

Performance Reporting 38%

External Communication Programs 25%

Employee Awareness Training Programs 38%

Compliance Audits / Inspections 31%

Systems / Process Audits 31%

Emergency Preparedness 38%

Management Structure or Framework 13%

Top Management Performance Reviews 13%

Note: Percentages based on 16 ANSP 

responses.

Environmental Program Elements

Environmental Vision / Policy 89%

Goals, Objectives or Targets 74%

Management Programs 51%

Operational Controls 63%

Environmental Metrics 34%

Performance Reporting 49%

External Communication Programs 37%

Employee Awareness Training Programs 57%

Compliance Audits / Inspections 60%

Systems / Process Audits 37%

Emergency Preparedness 57%

Management Structure or Framework 34%

Top Management Performance Reviews 26%

Note: Percentages based on 35 Airline 

responses.
CAEP/8-WP/80

Appendix D to the Report on Agenda Item 2 2 D-29

8.1e – Others

Environmental Program Elements

Environmental Vision / Policy 82%

Goals, Objectives or Targets 73%

Management Programs 64%

Operational Controls 86%

Environmental Metrics 41%

Performance Reporting 64%

External Communication Programs 50%

Employee Awareness Training Programs 77%

Compliance Audits / Inspections 77%

Systems / Process Audits 55%

Emergency Preparedness 77%

Management Structure or Framework 64%

Top Management Performance Reviews 50%

Note: Percentages based on 22 Other responses.

It is evident from the data that respondents across all five sectors have many elements of an EMS in place. 

Respondent percentages were high across all sectors for the following elements:

 Environmental vision/policy;

 Environmental goals, objectives or targets;

 Operational controls;

 Employee awareness training programs;

 Compliance audits/inspections; and

 Emergency preparedness.

On average, top management performance reviews had the lowest respondent percentage across all five 

sectors. This is important to note because management commitment is imperative for organizations to 

effectively manage their environmental impacts. Organizations with an EMS indicated that management 

commitment is one of the biggest challenges of EMS implementation. Lastly, it is important to note that 

there were only two respondents from the manufacturing sector. 

8.3. Performance Monitoring

Respondents that use an environmental program rather than a formal EMS were asked to rate how helpful 

it is in managing and controlling 28 specific environmental issues or impacts. Figure 8.2 includes five 

tables that list those environmental issues most commonly identified as helpful today by respondents in 

each sector. Generally, there was not a strong level of agreement on the level of helpfulness across all 

five industry sectors.

Although there was no agreement across the aviation industry, four out of five sectors (ANSPs, Airlines, 

Manufacturers, and Others) agreed that their environmental programs were helpful in managing and 

controlling compliance with laws and regulations today. Four out of five sectors (ANSPs, Airports, 

Airlines, and Others) also agreed that their environmental program was helpful in managing customer and 

other stakeholder concerns, fuel efficiency, financial, and company core values and ethics. (Note: Only 

two respondents were identified as part of the manufacturer sector.)
CAEP/8-WP/80

2 D-30 Appendix D to the Report on Agenda Item 2

Figure 8.2: Areas of environmental concern in which use of an environmental program is seen as helpful 

by organizations that do not apply EMS standards or guidelines for management.

8.2a – Air Navigation Service Providers

Environmental Issue or Impact Helpful Today Not 

High Medium Applicable

Aircraft Noise 

Emissions from ground activities 

Noise from ground activities 

Fuel efficiency 

Financial 

Compliance with laws and regulations 

State/country policies 

Competitive pressures 

Company core values and ethics 

Media pressure 

Corporate image 

Local community concerns 

Non-governmental organizations 

Capacity and growth constraints 

Soil and water protection 

International public perceptions 

Waste management 

Materials and chemicals management 

International policy 

Customers and other stakeholders' concerns 

Shareholders appreciation or rating agencies 

Note: Areas of helpfulness determined through identification of categories with single 

highest respondent percentage within the ANSP sector.

8.2b – Airports

Environmental Issue or Impact Helpful Today Helpful in 5 

Medium years

Aircraft Emissions 

Noise from ground activities 

Fuel efficiency 

Financial 

Competitive pressures 

Company core values and ethics 

Media pressure 

Local air quality 

Energy management 

Operational efficiency 

Customers and other stakeholders' concerns 

Note: Areas of helpfulness determined through identification of categories with single 

highest respondent percentage within the Airport sector.
CAEP/8-WP/80

Appendix D to the Report on Agenda Item 2 2 D-31

8.2c – Airlines

Environmental Issue or Impact Helpful Today

High Medium

Aircraft Emissions 

Aircraft Noise 

Emissions from ground activities 

Noise from ground activities 

Fuel efficiency 

Financial 

Compliance with laws and regulations 

State/country policies 

Competitive pressures 

Company core values and ethics 

Media pressure 

Corporate image 

Ecological conservation 

Local community concerns 

Global climate change 

Non-governmental organizations 

Corporate commitment and vision 

Capacity and growth constraints 

Soil and water protection 

International public perceptions 

Waste management 

Materials and chemicals management 

Operational efficiency 

International policy 

Customers and other stakeholders' concerns 

Note: Areas of helpfulness determined through identification of categories with single 

highest respondent percentage within the Airline sector.

8.2d – Manufacturers

Environmental Issue or Impact Helpful Today Not Applicable High

Compliance with laws and regulations 

Non-governmental organizations 

Note 1: Areas of helpfulness determined through identification of categories with single 

highest respondent percentage within the Manufacturer sector.

Note 2: Only 2 of the responses that CAEP received were from organizations that identified 

themselves as manufacturers without an EMS currently in place.
CAEP/8-WP/80

2 D-32 Appendix D to the Report on Agenda Item 2

8.2e – Others

Environmental Issue or Impact Helpful Today

High Medium

Aircraft Emissions 

Aircraft Noise 

Noise from ground activities 

Fuel efficiency 

Financial 

Compliance with laws and regulations 

State/country policies 

Competitive pressures 

Company core values and ethics 

Media pressure 

Corporate image 

Ecological conservation 

Local community concerns 

Local air quality 

Non-governmental organizations 

Capacity and growth constraints 

Soil and water protection 

International public perceptions 

Waste management 

Energy management 

Materials and chemicals management 

Operational efficiency 

Customers and other stakeholders' concerns 

Shareholders appreciation or rating agencies 

Note: Areas of helpfulness determined through identification of categories with single 

highest respondent percentage within the Other sector.

Respondents rated each environmental issue against six levels of environmental program helpfulness: 

very helpful now, medium helpful now, likely to be helpful in 5 years, likely to be helpful in 10 years, 

will never be very helpful, and not applicable. Only one level of helpfulness could be assigned to each 

environmental issue or impact.

Similar to respondent organizations with an EMS, respondents without an EMS indicated that it is 

important to measure environmental performance to ensure compliance. In addition, respondents also 

indicated that it is important to minimize the organization‘s impact on the environment. Environmental 

performance is typically measured through the continuous monitoring and measurement of specific 

elements important to the organization. In addition, performance is also measured through yearly reviews 

and inspections as well as by number of incidents that occur per year. The environmental targets set by 

respondent organizations tend to focus on the reduction of water, fuel, energy, and waste consumption.

Respondents without a formal management system were asked to list the five most important 

environmental regulations with which their organization‘s environmental program helps ensure 

compliance. As a result of having questionnaire respondents from all over the world, various 

environmental regulations were identified as important, and there was no clear consensus on specific 

legislation. As with the analysis performed on respondents who have an EMS in place (Section 5.1 of 
CAEP/8-WP/80

Appendix D to the Report on Agenda Item 2 2 D-33

this report), results were categorized into areas of environmental concern, which were then tallied and 

ranked to identify the top five areas respondents without an EMS ensure compliance (Figure 8.11)

Figure 8.11: Five most frequently cited areas of environmental regulatory concern.

Important Environmental Regulation Areas

Hazardous/solid waste 54%

Air 49%

Water 47%

Noise 39%

National environmental regulations 17%

Note: Percentages based on 87 respondents.

The five environmental areas identified as important by respondents without an EMS are identical to 

those identified by organizations with an EMS. The management and disposal of hazardous and solid 

waste is the greatest priority to organizations with and without an EMS. Second, legislation that regulates 

the quality and management of air emissions, in particular carbon dioxide was important to 49 percent of 

questionnaire respondents. The third most important environmental area concerns the quality, 

management, and use of storm water, waste water, and drinking water. Managing the level of noise was 

also deemed important by all five sectors. Lastly, a few respondents indicated that they ensure 

compliance with other types of country specific national environmental legislation.

8.4. Communication Methods

Respondents were asked to identify the methods used by their organization to communicate about its 

environmental program. As the same trends were found among all five sectors, the results were 

aggregated at the industry level. Figure 8.12 provides a breakdown of the communication methods used 

by respondent organizations with an environmental program in place, but no formal EMS framework.

Figure 8.12: Methods used by organizations across the aviation industry that have not implemented an 

EMS for communicating the performance of their environmental program.

Sustainability / CSR Reports

Websites

Newsletters

Community Meetings

Other

46 44

39

38

53
CAEP/8-WP/80

2 D-34 Appendix D to the Report on Agenda Item 2

26

5

13

8

2

6

1

2

It is evident that all the communication methods outlined in the figure above are applied fairly 

consistently among the respondents. While the use of websites appears to be the most common means of 

communication, other methods identified include: posters and brochures, internal meetings, presentations 

at seminars, and email.

8.5. EMS Application and Development Issues

A variety of reasons exist as to why organizations do not apply EMS standards or guidelines. According 

to the questionnaire‘s respondents, most (79 total) are planning to implement EMS in the future. Airlines 

(28 in total) and airports (26 in total) make up the majority of respondents who are planning to implement 

EMS in the future. 

The reasons why respondent organizations across the aviation industry do not apply EMS standards or 

guidelines are outlined below in Figure 8.13. The most frequent reason for not implementing an EMS is 

that the organization is not familiar with the EMS approach. Of the five sectors, airlines (11 in total) and 

airports (8 in total) had the highest response rate for not being familiar with EMS approaches. 

Figure 8.13: Primary reasons for not applying EMS guidelines or standards cited by organizations 

within each aviation industry sector.

7

1

1

6

2

4

28

7

11

1

5

8.13a – Air Navigation Service Providers 8.13b – Airports

8.13c – Airlines 8.13d – Manufacturers
CAEP/8-WP/80

Appendix D to the Report on Agenda Item 2 2 D-35

16

3

2

5

2

3

Of the 116 respondent organizations that do not apply EMS standards or guidelines, 79 plan to implement 

an EMS in the future. Respondents were asked to list those environmental issues their organization 

would focus on if they were to implement an EMS. Figure 8.14 outlines the top five environmental issues 

in which respondent organizations would focus their organization‘s EMS.

Figure 8.14: Top five environmental issues for inclusion in future EMS.

Important Environmental Issues

Air emissions 73%

Hazardous/solid waste 51%

Noise 50%

Fuel efficiency 30%

Energy 23%

Note: Percentages based on 86 respondents.

The environmental issues identified in figure 8.14 closely resemble the list of important regulated 

environmental areas in Figure 8.11. According to survey respondents, air emissions are the most 

important issue on which to focus their organization‘s EMS. Other important elements to focus on 

include the consumption of fuel and energy.

In order to become more familiar with EMS, respondent organizations have requested guidance to help 

assist with EMS implementation. Figure 8.15 illustrates the types of CAEP guidance requested by 

respondents.

8.13e – Other

Plan to implement EMS in future

EMS not appropriate to organization

Not familiar with EMS approaches

Lack sufficient financial resources

Don't believe EMS will add value

Other
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2 D-36 Appendix D to the Report on Agenda Item 2

Figure 8.15: Usefulness of CAEP guidance types in assisting aviation industry organizations with 

EMS implementation.

58

5

68

62

72

8

Figure 8.15 indicates that respondents thought that all the guidance materials suggested by the 

questionnaire could be useful in assisting them with EMS implementation. However, the most useful 

type of guidance that ICAO-CAEP could provide appears to be aviation industry EMS implementation 

guidance.

Chapter 9. Recommendations

The following two recommendations are based on information summarized in the report above and input 

from CAEP TG members. These recommendations focus on increasing awareness of EMS principles and 

best practices in the aviation sector and establishing practical guidance to assist those states and 

organizations that chose to use EMS to enhance the way they manage environmental issues. Awareness 

and guidance materials should integrate existing ICAO environmental tools, guidelines, and manuals. 

Where possible they should encourage organizations to support higher-level ICAO environmental 

objectives, consider the collaborative nature of the aviation industry, and account for variance in types of 

organizations in the aviation sector and the level of EMS (or environmental program) maturity at the 

organization.

1. Disseminate Report Information. Within the first year of the CAEP/9 cycle, disseminate the 

CAEP/8 EMS report information to States, questionnaire respondents, and the public through various 

mechanisms (e.g., State letter, Assembly resolution language promoting EMS and/or principles, 

website, workshop, presentation). 

2. Develop EMS Guidance. Stand alone EMS guidance should be developed for the end of the CAEP/9 

cycle. This should assist organizations to determine how EMS elements and principles can be used to 

enhance the way they manage environmental issues and provide practical guidance on how these 

EMS elements and principles can be implemented/integrated into existing management systems and 

business processes. 

General EMS guidance

Aviation industry EMS implementation guidance

Aviation industry EMS guidance on important 

focus areas

Aviation industry EMS best practice & guidance 

repository

No guidance necessary

Other
CAEP/8-WP/80

Appendix D to the Report on Agenda Item 2 2 D-37

Chapter 10. Conclusion

In February 2007, the TG was assigned a project for the CAEP/8 work program to deliver a report 

providing information on the use of EMS and, as appropriate, make recommendations on how the 

committee could promote the use of EMS within the aviation system. As a result, the TG developed an 

industry questionnaire to learn more about the application and potential value of EMS to aviation 

organizations. A total of 233 responses from air navigation service providers, airlines, airports, and 

manufacturers formed the basis of this report and supported the development of recommendations.

Approximately 50 percent of questionnaire respondents (a total of 117) apply EMS standards or 

guidelines, with the majority having an ISO-14001 v2004 certified EMS in place. The remaining 116 

respondents that have other environmental programs in place have many of the same principles and 

practices that are required as part of a formal EMS. For those organizations with an EMS, 82 percent 

have additional management systems in place—approximately 51 percent of these additional systems are 

integrated or coordinated with the organization‘s EMS. Over the past ten years, EMS implementation has 

been relatively consistent in the aviation industry. On average, respondents indicated that 6-12 months are 

needed to successfully develop and implement an EMS. Approximately 71 percent of organizations had 

assistance with EMS implementation from a consulting or contracting firm. Respondents indicated that 

the three most common benefits of EMS implementation are enhanced reputation or image, enhanced 

compliance and mitigation of risk, and environmental improvements.

Regardless of whether the respondent organization had an EMS in place, measuring environmental 

performance is important for ensuring compliance. On average, the majority of questionnaire respondents 

communicate environmental performance through a corporate social responsibility report or through their 

organization‘s website. Environmental areas of regulatory concern were primarily a focus of 

organizations regardless of whether or not they implemented an EMS. 79 respondent organizations 

without an EMS plan to implement one in the future. These organizations indicated that the most 

common reason for not implementing an EMS was unfamiliarity with EMS approaches. As a result, 

aviation industry specific EMS implementation guidance was requested by these organizations.

Recommendations were made on how ICAO-CAEP could promote the use of EMS within the aviation 

industry based on questionnaire results. The recommendations were to disseminate the CAEP/8 EMS 

report information to States, questionnaire respondents, and the public through various mechanisms, and 

consider development of EMS guidance. Any guidance should consider the collaborative nature of the 

aviation industry. This report is disseminated to States, questionnaire respondents, and the public in order

to further increase awareness of EMS principles and best practices in the aviation sector.
CAEP/8-WP/80

2 D-38 Appendix D to the Report on Agenda Item 2

References

International Civil Aviation Organization. Assembly Resolutions in Force (as of 28 September 2007). 

September 2007. http://www.icao.int/icaone1t/dcs/9902/9902_en.pdf

International Civil Aviation Organization. Environmental Issues Related To Implementation of CNS/ATM 

System. CNS/MET-ATM-IP/33. July 2003

International Civil Aviation Organization, Committee on Aviation Environmental Protection. 

Environmental Management Systems. CAEP/7-WP/54. February 2007

International Civil Aviation Organization. ICAO Environmental Report 2007. 2007. 

http://www.icao.int/env/pubs/Env_Report_07.pdf

International Civil Aviation Organization, Committee on Aviation Environmental Protection. Update on 

Environmental Management System (EMS) Task. CAEP8_WG2_LUPTG2_WP03. October 2007

International Organization for Standardization. ISO 14001 Environmental management systems —

Requirements with guidance for use, November 2004 (2nd edition).

— END —