737-800 APU Fuel Consuption
Join Date: Apr 2003
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As / big turbine engine performance it depends on environmental conditions / systems selections etc.
Select maint on FMC and APU (think these are the correct prompts) and it will give you the fuel flow for the specific condition you have at that point in time.
Select maint on FMC and APU (think these are the correct prompts) and it will give you the fuel flow for the specific condition you have at that point in time.
Join Date: Jul 2008
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nicoals is about right.But it does vary widely depending on the load.use th APU bite via the CDU to see real time rate, temps etc.
Join Date: Feb 2006
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I am retired now, but I seem to recall that the MEL says to increase fuel consumption by 50 kg per hour if dispatched with APU running. This would typically be with APU bleed off and generator supplying the bus. The figure presumably takes into account the increased efficiency of the APU at altitude.
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On a related note - anyone know why the APU burn is higher with one pack than it is with 2? I always thought it was because one pack in auto defaults to high if the other is off. Someone was telling me that is not the reason though - I didn't understand what he was getting at though - something about fans...
Join Date: Jul 2008
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ng apu has a separate compressor for air unlike the classic that pulls air out of the engine.
so the engine needs to run the compressor anyway so unloading it by turning on bleed and the packs unloads the apu.
My terminology maybe dodgy but I think its close enough.
so the engine needs to run the compressor anyway so unloading it by turning on bleed and the packs unloads the apu.
My terminology maybe dodgy but I think its close enough.
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The pressure demand of one pack running in high is higher than the demand for two packs running in normal configuration to deliver the same airflow - hence the APU has to work harder (the EEC cleverly adjusts VBVs and fuel flow) to deliver it.
