A340 Question
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A340 Question
When taking off with the packs supplied by the APU bleed, what happens if the APU failed on T/O, I understand that the thrust would be the same at the expence of increased EGT.What happened to the packs , will they be supplied by the engines immediately or will they be locked out till climb thrust is selected and packs recycled?. Refrences to the correct manual is appreciated.
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Johnman, if the APU (bleed) fails during take off, the eng bleed configuration will not change from closed until the thrust levers are moved to CLB. The Bleed warning is inhibited from T/O thrust selection until 1500ft so the only warning you will have in the cockpit getting quieter and warmer...So you can do a take off with the bleeds on APU without fear of losing performance should it fail. At least that is what I understand to be the case, I don't have the manuals on hand so no reference sorry...
This question is not directly answered by reference to the FCOMs. Enquiries to Airbus reveal that the FADEC "memorises" the bleed configuration at “brakes release” [flight phase 3?]. Therefore, as Max AB correctly states, there is no change to bleed config and no reduction to TO thrust until the thrust levers are moved to CLB. To ensure availability of the APU, Automatic shut down of the APU is inhibited, except for overspeed and “certain critical ECB internal failures”, in flight phases 2 to 9. Sorry I can’t be more helpful. As the old song goes: Don't blame it on the moonlight - blame it on the FADEC!
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APU bleed with Packs on
I was reading an A340 instructor support dated Dec 2000 , it says "in case of APU auto shutdown during T/O , the eng thrust is frozen , till the thrust is manually reduced;the packs revert to eng bleed which causes an increase of EGT to keep the N1 target". Please let me know if your information is updated differently.
