𝑬 𝒊𝒊 =  𝟏 𝟏𝟎𝟎𝟎 ×  𝑳 ×  𝑭𝑭 𝒊 ×  𝑬𝑭 𝒊𝒊 Where:  E$_{ij }$ = emissions of pollutant i, expressed in pounds, produced by the APU model installed on  aircraft type j for one LTO cycle  T = operating time per LTO cycle, expressed in minutes  FF$_{j }$= fuel flow, for each APU used on aircraft type j, expressed in pounds per minute  EF$_{ij }$= emission factor for pollutant i, expressed in pounds of pollutant per one thousand pounds  of fuel, for each APU used on aircraft type j  i = pollutant type (e.g., HC, CO, NO$_{x}$, SO$_{2, }$etc.)  j = aircraft type (e.g., B-737, MD-11, etc.)  Equation A2-1. APU Emissions from a Single LTO  Equation A2-2. Total APU Emissions  𝑬𝑳 𝒊 =  ෍ ൣ𝑬 𝒊𝒊 ×  𝑳𝑳𝑳 𝒊 ൧ 𝒊 Where:  ET$_{i }$ = total APU emissions of pollutant i, expressed in pounds, produced by all aircraft types in  question  E$_{ij }$ = emissions of pollutant i, expressed in pounds, produced by the APU model installed on  aircraft type j for one LTO cycle  LTO$_{j }$= number of landing and takeoff cycles for aircraft type j during the inventory period  The data inputs required to  estimate APU emissions and the likely sources of obtaining this  information are listed in  Table A2-1  ( Data Inputs for Estimating Emissions from APU ).  Total APU emissions are estimated by applying  Equation A2-2  ( Total APU Emissions ), which  multiples the APU emissions per LTO for a given aircraft type and operating time (determined  using  Equation A2-1 ,  APU Emissions from a Single LTO ) by the number of corresponding  LTOs, then sums the emissions over all aircraft types.  APPENDIX A2$_{ }$ A2.2.1  Data Inputs  Data Inputs  Description  Source  Model  The particular APU model that is  installed on an aircraft mus t be  determined to select the emiss ion  factors  used  in  calculating the  emissions.  Individual aircraft operators at airports are potential  sources of site-specific APU model information.  If site-specific information is not available, FAA’ EDMS/AEDT lists APU models commonly found on  Table A2-1. Data Inputs for Estimating Emissions from APU  11$_{ }$