B737 FMC N1 difference Takeoff Ref - Engine Bleeds Off T/O
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Join Date: Mar 2001
Location: Left seat of a Boeing... mostly!
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B737 FMC N1 difference Takeoff Ref - Engine Bleeds Off T/O
B737 Classic (Update 10.6)
Anyone know why you see might a difference in the FMC calculated N1(TAKE OFF REF PAGE, say 89.6/90.6) for left and right engines during an engine bleeds off takeoff? The A/T set the higher N1 setting (correct for the Bleed Off Config).
I can understand why you see a difference on stand with only one pack running, does the FMC not look at the Engine Bleed switch position (Both Engine Bleeds Off – Pack Switches On – Isolation Valve Closed) after configuration for an engine bleeds off take-off?
Engine Bleed valve position seems to be a discreet input into the FMC so why the difference?
Anyone know why you see might a difference in the FMC calculated N1(TAKE OFF REF PAGE, say 89.6/90.6) for left and right engines during an engine bleeds off takeoff? The A/T set the higher N1 setting (correct for the Bleed Off Config).
I can understand why you see a difference on stand with only one pack running, does the FMC not look at the Engine Bleed switch position (Both Engine Bleeds Off – Pack Switches On – Isolation Valve Closed) after configuration for an engine bleeds off take-off?
Engine Bleed valve position seems to be a discreet input into the FMC so why the difference?
Join Date: Nov 2005
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i can't fully answer the question, but to me it seems it depends on the ACTUAL pressure in the duct. when on stand and putting in the T/O-calc-data just give it a try and play around with the bleed panel. close the isolation valve, see what happens to the N1 on thje TO-page, than switch the apu-bleed OFF, see what happens ....
