Aviation Emissions and Air Quality Handbook  Aircraft  Aircraft Fleet and Operations  Times in Mode  Aircraft emissions for a criteria pollutant emissions inventory are computed in EDMS/AEDT by  factoring total aircraft operational activity against a database of aircraft/engine-specific emission  factors based on engine manufacturer, model, and aircraft operational mode within the cycle. For the purposes of emissions inventory, an LTO cycle consists of operational modes:  EDMS/AEDT calculation of emissions within the LTO relies on two main categories of input: (i)  aircraft fleet and operations, and (ii) time within each mode of the LTO cycle.  At a minimum, EDMS/AEDT requires definition of an aircraft fleet (i.e., the types of aircraft  using the airport and their assigned engines) and a level of operations (i.e., arrivals/departures/touch-and-go’s, or LTO) assigned to each member the a ircraft fleet.  EDMS/AEDT can accept varying levels of detail depending on the extent to which aircraft  operational parameters at a given airport are available or known. These range from the selection  of a generic aircraft fleet with “default” engines selected by EDMS/AEDT, to  the identification  of specific airframes and engines based on an air carrier’s market information, to the modeling of  individual flights based on a flight schedules or radar data. Typical sources of data that can be  used to identify and define these parameters can be found within  Appendix F  ( Data and  Information Sources ).  EDMS/AEDT functionality currently calculates a performance- based time in mode for  the  takeoff, approach and climb out (i.e., the aloft) components of the LTO cycle, which is based  upon aircraft flight profiles, characteristics of individual aircraft, and meteorological conditions.  Users are allowed to modify some of this information, such as aircraft takeoff and weights or the local meteorology, allowing for a more site-specific characterization of emissions  aloft. Further, EDMS/AEDT currently only consider takeoff, climb out and approach emissions  up to the atmospheric  “mixing height” for the area, defined as the vertical extent in atmosphere over which pollutants no longer mix downward to ground level.  39$_{ }$ • Approach : The airborne segment of an aircraft’s arrival extending from the start of the  flight profile (or the mixing height) to touchdown on the runway;  • Taxi In : The landing ground roll segment (from touchdown to the runway exit) of an  arriving aircraft, including reverse thrust, and the taxiing from the runway exit to a gate;  • Startup : Aircraft main engine startup (for VOC only) occurs at the gate and is considered  in EDMS/AEDT for ICAO certified engines only;  • Taxi Out : The taxiing from the gate to a runway end;  • Takeoff : The portion from the start of the ground roll on the runway, through wheels off,  and the airborne portion of the ascent up to cutback during which the aircraft operates  at  maximum thrust; and  • Climb Out : The portion from engine cutback to the end of the flight profile or the mixing  height. 