Research Projects

Emission Factors from Aircraft Auxiliary Power Units

Develop emissions factors for air pollutants emitted from aircraft auxiliary power units for a larger set of APUs than are currently in AEDT.

Background (Describe the current situation or problem in the industry, and how your idea would address it.)

While aircraft main engines are responsible for a large portion of emissions around
airports, there are other emissions sources such as the aircraft auxiliary power unit (APU), ground
support equipment, heating plant, construction equipment and road vehicles. Most of these sources are
dealt with in detail by other sources (e.g. AP-42, MOVES (road vehicles and GSE)). However, there are
relatively few openly-available sources of information giving APU emission factors (kg pollutant per kg
fuel burned) and fuel flow rates (kg/hour), principally because APUs are not included in the ICAO
certification process. The release of detailed APU emission indices is controlled by the APU
manufacturers, but data are released to aircraft operators for the purposes of generating emission
inventories, provided the values for individual APU models are not published. Therefore APU emissions
have limited documentation, especially in the context of the impact of alternative fuels on their
emissions. The existing data within EDMS/AEDT is limited and based on typical APU operating
parameters (where as APU's operate under different loads depending on the amount of power the
aircraft needs). ACRP Report 64 documented different APU operating modes and emission rates (based
on data in the ICAO Air Quality Manual) however both only list values for very generic aircraft (e.g. one
set of values for all narrow bodied aircraft) due to confidentiality issues. Therefore in order to better
estimate the impact of APU emissions better data is needed on APU fuel flow rates per operating mode
and also the related emission indices for a wide variety of APU models. Another associated issue with
calculating APU emissions is availability of actual APU usage times, however, this will vary by airport and
airline, time of day etcetera and so it is not proposed that APU time data should be included.

Objective (What is the desired product or result that will help the airport industry?)

Develop emissions factors for air pollutants emitted from aircraft auxiliary power units for a larger set of APUs than are currently in AEDT.

Voting

2 votes
2 up votes
0 down votes
Idea No. 51