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British Airways and the BEAM Emissions Database

by Kevin M Morris

Manager Environment

SYNOPSIS

You often can't see it, touch it or smell it, but emissions from aircraft are now becoming a

major source of interest to the general public. One of the greatest problems is knowing just

how much emissions are actually produced by aircraft engines. This document sets out to

describe the way that British Airways, in conjunction with Warren Springs Laboratory (now

AEA Technology) set about trying to estimate the amount of emissions from British Airways

flight operations, culminating in the construction of the 'BEAM' Emissions Database.

Civil aviation uses significant quantities of fossil fuels, amounting to something like 170

million tonnes per year (1). British Airways itself burns just under 5 million tonnes of

aviation fuel per year (2) to operate its world-wide services. Aircraft are not a major source of

atmospheric pollution, for instance accounting for only some 2½ to 3% of global CO2

production (3). The products of the combustion of aviation fuel does, however, result in

emissions to the atmosphere, that can have an impact at the local, national and global level.

Global warming (the so called 'Greenhouse effect'), stratospheric ozone depletion (the

polar ozone 'holes'), photochemical smog (poor surface level air quality e.g. Mexico city, and

the California basin area), and acid rain (artificial reduction of the pH of rainwater resulting in

defoliation of forests and acidification of lakes), have all become household names, and big

issues for environmental pressure groups. In order to explore the effect of aircraft operations,

and to ascertain whether they pose a major threat to the environment, first it is necessary to

know what contribution aircraft operations make to the various scenarios.

There are a number of problems, however, that arise when looking at the effect of aircraft

emissions in the atmosphere: the nature of the emission species produced; the localised

atmospheric chemistry; the dispersion and dilution properties of the atmosphere; to name but

a few. One of the main problems facing the scientific community is, however, being able to

calculate just how much emissions are actually produced by Aero-engines during their

operating cycle. There are a number of international bodies that are conducting research in

this arena, the most notable being perhaps NASA in the USA in their 'Atmospheric Effects of

Aviation Project' (4); and the ECAC/ANCAT & EC 'Emissions Inventory Database Group'

(5) which has reported to the European 'AERONOX' project (6), and the follow-up project

‘POLINAT’ (7).

British Airways, Operations Engineering department (now A/c Performance Engineering)

became involved in this area, both as a contributor to the European Emissions Inventory

Database Group, and internally in developing, with Warren Springs Laboratory a database for

calculating emissions from British Airways aircraft. These methods were developed and now

form the basis of what has become the 'British Airways Emissions to the Atmosphere

Database' - BEAM.

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IN THE BEGINNING ...

Prior to 1989, environmental issues tended to be centred around noise with a number of

groups within British Airways 'dabbling' in one of a number of aspects. It was noted that there

was a growing interest, both externally and within the airline, about other areas affecting the

environment. In particular, great interest was being shown in the effect of British Airways

emissions from its world-wide aircraft operations, on the atmosphere.

In British Airways, as well as some other airlines, the importance of these environmental

issues was recognised by the formation of a corporate 'Environmental' department, reporting

directly to British Airways board level, to co-ordinate environmental issues. The appointment

of Dr Hugh Somerville as 'Head of Environment', at British Airways in 1989 and the setting

up of the 'Environment branch', gave the airline the ability to focus on all of the issues

affecting the environment, as well as co-ordinating the expertise of the existing specialists

and giving impetus and the support to develop new environmental initiatives.

One of the early requirements to come from the newly formed Environment branch, was to

establish British Airways' environmental performance in the area of aircraft emissions, a task

never before attempted. The information was to be used to check the validity of numerous

statements and studies that were being made by various environmental groups, and later for

inclusion in a proposed 'Environmental Report' (first published in 1992 (8)).

The Operations Engineering, now Aircraft Performance Engineering, department of

British Airways, had a history of expertise in both the areas of noise technology, and aircraft

performance, dealing primarily with fuel flight planning, and the monitoring and reduction of

fuel usage. It was therefore seen as being ideally placed to help with setting up a process for

the calculation of British Airways aircraft emissions.

EARLY STUDIES AND SOME RESULTS

Initially, two studies of aircraft emissions, prior to the setting up of the BEAM database, were

undertaken by students working for the Environment branch, as part of their industrial

placement. Operations Engineering were asked to provide the technical expertise to enable

the requirements of the studies to be fulfilled. The first of these was carried out by Sarah

Bond, who, at that time, was studying at Kingston polytechnic, and involved trying to

calculate fuel usage, and emissions from aircraft taxiing operations at a number of UK

airports. The times and fuels required for input into a small database, were taken from data

stored on one of the British Airways corporate databases called the 'Fuel Monitoring

Programme' (FMP). Emissions indices for the emissions species: carbon monoxide (CO),

unburned hydrocarbons (HC), particulate carbon (smoke) and the oxides of nitrogen (NOx),

were obtained straight from the International Civil Aviation Organisation's (ICAO) Emissions

Database (9). (The results from this study together with some other work by another student

Griff Williams, was published as an 'Environment Report' in 1990 (10). Although not part of

the original BEAM database set-up, the methodology became part of a later enhancement, and

proved that something at least was possible in this area.

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The second study (11) was undertaken by Ruud Westgeest, an Engineering undergraduate

from the Technische Hogeschool in Haarlem, and was British Airways first attempt at

estimating NOx emissions over the whole flight operation, in this case for the Boeing 747-

236 fleet. This study proved to be more complex as NOx is produced in the engines

combustor by the oxidation of atmospheric nitrogen, and unlike some of the other emissions

species, is highly dependant on the temperatures and pressures within the combustion system.

As the routine measurements of these parameters was not available in a form that lent itself to

the type of analysis proposed, another method had to be devised. Rolls Royce were

approached, and David Snape, Manager - Project Combustion, was able to provide an

analysis that they had undertaken on a number of different engine types (not just Rolls

Royce!), comparing a combination of the modal emission indices for NOx from the ground

based ICAO emissions certification data, with results from various sources for NOx

emissions during typical cruise and climb conditions (12). Flight and fuel usage information

was again obtained from the British Airways' FMP database. One of the limitations of the

FMP database was, however, that although fuels and times for every flight (take-off to

touchdown) could be calculated accurately, no data was recorded at the top of climb, or top of

descent. FMP did not record the cruise altitude achieved either, although that used to

calculate the flight plan, did form a field in the database. An analysis of a number of flight

plans did however show that the planned flight level was often that actually achieved for the

flight. It was felt that the only way to split the flight profile, was to use manufacturers data

from their 'Operations Manuals'(13) (again this is also used by the flight planning system), for

the climb and descent parts of the flight, and the resulting part left after subtraction of these

from the total recorded was assumed to be the cruise segment.

Figure 1, Flight Profile Assumed in early BEAM study

The Operations Manual tables were reduced to simple quadratic equations giving the fuel

used and time in mode as functions of cruise altitude and take-off weight. Flight data for each

individual flight was averaged by sector (origin - destination pair), and the flight times, fuels

and NOx, for climb cruise and descent were calculated using a simple database. When the

data were summed for the year May 1990 to April 1991 the results below were obtained:

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Flight phase NOx emissions

(tonnes)

Climb 2076

Cruise 6524

Descent 54

Total 8654

This initial attempt at calculating NOx emissions for one particular fleet, was intended to

give a rough 'order of magnitude' estimate only, but as can be seen 8.7 thousand tonnes of

NOx produced by 16 aircraft over one year, is quite a lot, and gave the impetus to develop a

system for calculating the emissions for the rest of the British Airways fleet on a routine

basis.

BEAM DEVELOPMENTS AND IMPROVEMENTS

NOx was by far the hardest emission species to calculate because of its variation with the

ambient conditions. The other ICAO regulated emissions of CO, HC, and smoke, were much

simpler, and were incorporated into the database. At the same time Dr Martin Williams at

Warren Springs Laboratory, Stevenage, was approached to help with the construction of an

'Emissions database', for the whole of the British Airways fleet, and to give further advice on

the calculation of emissions at altitude. The proposals were accepted and Geoff Broughton,

Michael Jackson and Charles Walker, were contracted to construct the database.

Due to the difficulties in obtaining precise operational data required, the methodology of

the original database developed by British Airways for the Boeing 747-236 NOx estimation

was kept. As well as CO, HC, and NOx, the other emissions species of water and carbon

dioxide (CO2), were included, with their emissions indices based on the complete

combustion of kerosene fuel (assumed to be completely composed of C10H22). This actually

overestimates the carbon production slightly as some double accounting due to the calculation

of carbon monoxide is not taken into account, this was considered acceptable as the

philosophy of the database was to be as accurate as possible erring on the conservative side.

A database was then constructed on this basis using the FOXPRO commercially available

software, recommended by the Information Management department of British Airways.

Sulphur emissions, as SO2, were another headache, as a reliable average from British

Airways many sources, did not exist. Until a more reliable figure became available, it was

therefore decided that the fuel specification figure of 0.3% by weight would be used even

though it was suspected that this could be an order of magnitude too high.

In 1992, Warren Springs Laboratory delivered the first version of what was to become

known as the 'BEAM database', to British Airways, Operations Engineering, and a report

detailing the emissions production for the whole of the British Airways subsonic world-wide

operations, between March 1991 and April 1992 (14). Provision was made for Concorde

operations, but due to the nature of the flight profile has yet to be incorporated fully into

BEAM.

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At the end of 1992, work was started in developing BEAM to more completely model the

two terminal phases of the flight. These contain what has normally been assumed to 'belong'

to the airport, that is emissions below the 3000 ft cut-off altitude of the ICAO emissions

certification scheme. This work involved a lot of analysis using manufacturers performance

programmes, information from flight data recorders, flight planning information, and in a few

cases validating with actual flight deck recordings. The emission indices were taken directly

from the ICAO 'Engine Exhaust Emissions Data Bank' (9), but used actual, or best estimates

for times, distances and fuels for the additional modes of: taxi-out; take-off to acceleration

altitude; third segment acceleration and climb to 3000 ft; approach and landing from 3000 ft;

and taxi-in. These are shown visually below:

Figure 2, Changes to flight profile for the improved BEAM database

Unfortunately, these refinements were incorporated just too late for publication in the

1994 British Airways Annual Environmental Review, but fist appeared in the 1995 review,

along with a rerun of the 1993/1994 data to the new format, thus a year-to-year direct

comparison was still possible.

Sulphur was again looked at, and with data provided by the Defence Research Agency

(15), Al Momenthy at Boeing and some help from British Petroleum (BP), a weighted

network average for British Airways operations has been calculated. For the small proportion

of fuel whose origin could not be positively identified, the specification value of 0.3% was

used, and this resulted in an overall value of 0.046%. As expected, this was significantly

lower than the specification value of 0.3%, whilst still adhering to the conservative

philosophy required by the Environment branch.

The major inputs to the BEAM database, along with the current output options are shown

in Figure 3, below:

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In 1996, greater concerns were beginning to be expressed regarding other pollutant

species, notably benzene and small particles of matter with a maximum diameter of 10 m,

known as PM10. AEA Technology were again approached to see if there was a way of using

the BEAM database and additional information, to calculate the levels of these pollutants

additionally for British Airways operations.

Following contract negotiations a method was found for benzene (16), which used a

simple factor applied to the unburned hydrocarbon Emissions Index, contained in the ICAO

Emissions Databank. A methodology for PM10 emissions was also constructed, based on the

ICAO Emissions Databank hitherto unused Smoke Number (17), and an estimation of the

Air:Fuel ratio from advice given by Rolls Royce.

The required coding was developed (18) and input into a redefined BEAM database. At the

same time the opportunity was taken to convert BEAM to run in a windows environment.

This new version of BEAM (BEAM98?), was delivered to British Airways Environment

Branch in June 1998, and was used ‘in anger’ for the first time almost immediately to provide

information for the British Airways Annual Environmental Report for 1998.

THE FUTURE ...

The BEAM emissions database has already proved to be a useful tool. It has been able to

provide an indication of the environmental performance of British Airways aircraft on the

basis of: fleet specific, origin and/or destination specific and sector specific operations. The

data for British Airways world-wide operations has been publicly reported in the British

Airways 'Annual Environmental Reports' for the past five years (the sixth was due to be

published at the time of writing). Sector specific information has been used in validating

some of the European ANCAT Emissions Inventory Database Group's assumptions for the

AERONOX project, with some further study and modifications identified as a result! ICAO

CAEP Working Group 3, has also benefited from some of the output in BEAM, with again a

number of the operational issues being highlighted.

The airport analysis part of the 'New' BEAM has enabled British Airways aircraft fleet

emissions, below 3000 ft (910 m), at specific airports to be estimated routinely for the first

time, allowing a fuller 'environmental audit' to be carried out at various specific British

Airways destinations. These were first published for Heathrow airport, in the 1995 Annual

Environmental Review, with subsequent Reports containing emissions information for other

airports. Another aspect of this airport analysis facility, is to check on the reports of other

bodies, for example the airports and manufacturers, who tend to use to less accurate modal

times of the ICAO Engine Exhaust Emissions Data Bank for their analyses.

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It has always been suspected that 3000 ft was too high a cut-off point for emissions to

reach the ground, and this has been demonstrated using Gaussian plume models by both AEA

Technology and ENTEC, for the Heathrow Terminal 5 air quality assessment, amongst

others. The work so far suggests that above altitudes of a few hundreds of feet (probably 300

ft to 600 ft), any species emitted would not reach ground level. The use of BEAM emissions

data, can therefore be expected to overestimate ground level concentrations, by possibly a

significant amount. In 1996, an evaluation of this was carried out by Martin Leech, of AIR3c,

Department of Trade and Industry, which showed that this was particularly true of NOx

emissions(19). The altitude of 3000 ft has, however, been adopted internationally, as a cut off

for emissions ‘belonging to the airport’, and so this height is still retained in the BEAM

database.

As with all models, however, there are known limitations with BEAM. Improvements to

remove these are constantly being pursued, and would form another paper on their own if

reported in their entirety! The most useful and probable ones, are however listed below:

Emission indices, especially for NOx. A new methodology using fuel flows and the ICAO

data bank levels as the basis, has been developed by Richard Martins (now Doug DuBois)

group at Boeing (20), and has been presented to the ICAO working group 3 (Emissions).

This has been validated against the P3/T3 standard method, with a reported accuracy of

better than 10%! This method lends itself particularly well to incorporation into BEAM.

Reduced thrust take-offs. These form the vast majority of all take-off at all airports,

except under very special circumstances. The use of reduced power for takeoff has a

major effect on NOx emissions, due to the exponential nature of the EI vs. Thrust,

relationship. A study (21) has been started to identify whether a relationship can be

identified between take-off thrust levels and take-off weight, initially for operations at

Heathrow airport.

Analysis so far has suggested that, for the Boeing 747-436 aircraft, the average thrust

level set for take-off from Heathrow airport is about 85% of the maximum assumed by the

ICAO Databank LTO cycle. Figures for the now non-operational Boeing 747-236 and

Boeing 747-136 aircraft, are similar. A few shorthaul types have also been analysed, the

Boeing 767-336, Boeing 757-236 and Boeing 737-436. These tend to show a marked

difference in that about 10% of operations are at full power and the rest average below

80%, and in the case of the 767, well below 80%. Again this information has been

reported to ICAO (22), and additional work is ongoing for other types and other airports

that British Airways operates to.

Step climbs. At present, only one cruise flight level is incorporated into the Fuel

Monitoring Programme (FMP), and therefore no facility for analysing the effect of step

climbs exists. ANCAT are also interested in this area for AERONOX, and a study has

tentatively proposed some 'standard rules' to apply to long sectors to incorporate step

climbs.

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Emissions dispersion modelling in the vicinity of the airport. To model ground level

emissions, a number of consultants have been approached to see if a way can be found to

attach a Gaussian, Lagrangian or Eulerian dispersion model to the output from BEAM.

Ground level pollution concentrations of the various emission species resulting from

British Airways operations, may then be estimated. With emissions input data from other

local sources, it should then be possible to calculate concentrations of various emission

species affecting local air quality.

This study is currently underway for flights to and from London’s Heathrow airport, with

others to follow if this proves feasible. In connection with this BAA (Heathrow), have

expressed an interest in modelling emissions around Heathrow airport, and the intention is

to involve all local stakeholders. A feasibility study is underway to see if BEAM could be

modified to incorporate the type of methodology required to accept data from the

Heathrow Noise and Track keeping system that the BAA operate.

Concorde. Because of the way Concorde operates, it has been difficult to incorporate into

BEAM. The use of 'standard' flights covering the vast majority of Concorde operations

has been studied, and results calculated. These have then been combined with those from

BEAM for the subsonic fleet, and used for British Airways environmental reporting. Due

to the limited time left in service, it is likely that Concorde emissions will continue to be

modelled externally to BEAM (a supersonic BEAM!).

Flight profiles. A major new database, using flight data recorder (FDR) information for

the recording and storage of flight parameters, at various points during the flight, is

currently under study by Aircraft Performance Engineering. This would allow measured

actual data to take the place of that which currently has to be estimated. This is still at a

very early stage, however, and progress is somewhat slow due to the high costs involved.

The BEAM database has proved to be a useful tool for estimating aircraft emissions

already. With improvements and developments, some of which have already been identified,

it could well become the basis for a standard method for assessing the level of aircraft

emissions in the environment.

Kevin Morris 2003

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REFERENCES

1. International Energy Annual 1992 - DOE/EIA-0219(92), 1994, Energy Information

Administration, US Department of Energy, Table 18.

2. Unpublished internal report, 1997, British Airways Fuel Group.

3. ARCHER, L.J. Aircraft Emissions and the Environment: COx, SOx, HOx & NOx,

1993,Oxfore Institute for Energy Studies.

4. STOLARSKI, R.S. & WESOKY, H.L. The Atmospheric Effects of Stratospheric

Aircraft: A Fourth Program Report, NASA, 1995, NASA Reference Publication

1359.

5. SCHMITT, A. & GARDNER, R.M. A Global Inventory of Aircraft NOx Emissions,

1995, ECAC/ANCAT & EC Working Group.

6. SCHUMANN, U (ed). AERONOX, The Impact of NOx Emissions from Aircraft

Upon the Atmosphere at Flight Altitudes 8-15 km, 1995, EC-DLR publication related

to Aeronautics and Environment.

7. SCHUMANN, U (ed). Pollution from Aircraft Emissions in the North Atlantic Flight

Corridor (POLINAT), 1996, EC publication - Air Pollution Research Report 58.

8. WOODS, I., MARPLES, A., SHIRLEY, D. & PYKE, D.R. British Airways

Environmental Review, 1991, British Airways Environment Branch Report 1-3/91.

9. LISTER, D. ICAO Engine Exhaust Emissions Data Bank, First Edition, 1993,

Defence Research Agency.

10. WILLIAMS, G. Aircraft Emissions, 1990, British Airways Environment Branch

Report 10/91.

11. WESTGEEST, R. Provisional Estimates of NOx Emissions from the British Airways

747-236 fleet, 1991, British Airways Environment Branch Report 15/91.

12. Unpublished internal report, 1991, Rolls Royce.

13. 747 Operations Manual - Part 3, -200/RB211-524D4 CAA., at amendment May

29/90, ref: 747-K29C. Boeing Commercial Airplane Group

14. WALKER, C.T. British Airways Emissions From Aircraft Database,1993, Warren

Springs Laboratory.

15. BROOK, P.S., RICKARD, G.K. & TUCKER, A. The quality of aviation turbine

fuels available in the United Kingdom Annual survey 1993, 1994, Defence Research

Agency.

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16. SHAREEF, G.S. et al. Air emissions species manual Volume 1. Volatile Organic

Compound Species Profiles, 1988, Radian Corporation.

17. CHAMPAGNE, D.L. Standard measurement of aircraft gas turbine engine exhaust

smoke, 1971, ASME 71-GT-88.

18. UNDERWOOD, B.Y. & WALKER, C.T. Extension of BEAM to Benzene and PM10

Emissions, 1998, AEA Technology.

19. LEECH, M. Emissions from British Airways Aircraft during Take off and Landing at

Heathrow, Gatwick and Manchester Airports, 1996, Department of Trade and Industry

20. MARTIN, R.L. Presentation to CAEP Working Group III, Certification Subgroup,

1995, Boeing Commercial Airplane Group.

21. MORRIS K.M. Presentation to CAEP Working Group 4, Emissions - Operational

Issues, 1999, British Airways, plc.

22. MORRIS K.M Take-off at less than Full Power. Working Paper 10/10 for ICAO

CAEP Working Group 3, AEM Task Group, 27-28 June 2002, British Airways, plc.