APU fuel burn with apu bleed ON and both packs OFF

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APU fuel burn with apu bleed ON and both packs OFF

Postby Electron » 07 Jul 2019, 21:14

Hi all

I’m trying to find the reference that says that whilst on the ground, leaving apu bleed on with packs off causes 40% unnecessary fuel burn. Can anyone remember where it is?

I could’ve sworn it was in a service letter
Electron
 
Posts: 12
Joined: 21 Mar 2015, 14:17

Re: APU fuel burn with apu bleed ON and both packs OFF

Postby motortek » 08 Jul 2019, 16:15

737-SL-49-060
motortek
 
Posts: 96
Joined: 16 Dec 2011, 02:05

Re: APU fuel burn with apu bleed ON and both packs OFF

Postby Electron » 09 Jul 2019, 16:16

Not quite brother. I appreciate the attempt to help though

There is or WAS written SOMEWHERE, that there is specifically 40% loss of efficiency with packs off and apu bleed on, on gnd without eng’s running.

With my boeingfleet changes, i don’t know how to search for historical inactive stuff :(
Electron
 
Posts: 12
Joined: 21 Mar 2015, 14:17

Re: APU fuel burn with apu bleed ON and both packs OFF

Postby motortek » 05 Aug 2019, 19:05

Electron wrote:Not quite brother. I appreciate the attempt to help though

There is or WAS written SOMEWHERE, that there is specifically 40% loss of efficiency with packs off and apu bleed on, on gnd without eng’s running.

With my boeingfleet changes, i don’t know how to search for historical inactive stuff :(


It is recommended that you operate the APU with the two air conditioning
packs when maximum cabin cooling is necessary. Use the two air
conditioning packs as an alternative to the one air conditioning pack
operation. The results of the operation of two air conditioning packs will be
cooler cabin temperatures, lower APU fuel burn, better APU hot section life
and lower APU noise. Refer to Service Letter 737-SL-49-060 for more data
on these results.

SDS 49-50 PAGE 12
motortek
 
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