main engines, provide electrical power to aircraft  electronics, and to power the onboa rd air  conditioning (heating and cooling) systems.  Again, the computation and data inputs of APU fuel usage for computing GHGs is similar to that  uses for computing APU criteria pollutants (see  Appendix A2 ,  Auxiliary Power Units Emissions  Inventory for Criteria Pollutant ). As discussed, EDMS/AEDT contains a database of aircraft and  APU assignments as well as fuel flow rates  (typically ranging from 50 to 860 pounds per hour)  for the designated APU. However, EDMS/AEDT does not report this fuel usage.  Therefore, APU fuel usage should be estimated based on the APU assignment, the fuel flow rate,  the operating time, the number of operations, and fuel density. APU operating times (arrival plus  departure) typically range from 7 to 26 minutes depending on gate infrastructure and airport  operations.  Table C-2  ( APU Fuel Usage Rates ) presents the APU fuel flow rates for the 38 units  within EDMS/AEDT.  Table C-2. APU Fuel Usage Rates  Description  Fuel Usage  (pounds/hour)  APU 131-9  255  APU GTC 85  235  APU GTC85-72 (200HP)  210  APU GTCP 331 (143 HP)  268  APU GTCP 331-350  453  APU GTCP 36 (80HP)  221  APU GTCP 36-100  146  APU GTCP 36-150[]  149  APU GTCP 36-150[RR]  183  APU GTCP 36-300 (80HP)  221  APU GTCP 36-4A  134  APU GTCP 660 (300 HP)  767  APU GTCP 85 (200 HP)  235  APU GTCP100-544 (400 HP)  413  APU GTCP30-300  282  APU GTCP30-54  69.0  APU GTCP331-200ER (143 HP)  268  APU GTCP331-500 (143 HP)  536  APU GTCP85 (200 HP)  235  APU GTCP85-129 (200 HP)  235  APU GTCP85-98 (200 HP)  235  APU GTCP95-2 (300 HP)  293  APPENDIX C$_{ }$ 66$_{ }$