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Guest Bjorn Ghezzi

737 NG engine start and packs

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Hello all,I had a question....a couple of times it happened that in the haste of getting underway, I forgot to turn the packs off before engine start as stated in the checklist and standard procedures for the 737. At least as far as the sim goes, the engines started anyway with no problem. I don't know if this is a limitation of FS9 as to the extent of system simulation. So the question is: in real life, having packs ON during engine start, would it preclude the possibilities of achieving enough N2 fan speed because the bleed air is being used by the A/C system, or would it not affect so much the start procedure as it happens in the sim?Are there any other eventual dangers associated with leaving the packs on during eng. start?Thanks for any info on this. :-)Regards,Bjorn

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The issue would be (like you said) the air lost to the packs. On a hot day in Denver, Salt Lake, Reno, etc, it could make the difference between the engine starting and a hung start. Otherwise, they should start ok with the pack(s) on. The reason you always turn them off is to improve start performance and reduce peak EGTs for the engines and the APU (thereby reducing wear and improving service life).

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Thanks Eric for the simple and informative answer. Appreciate your time.Regards,Bjorn

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