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In A320 Standard Operation Procedure (Parking procedure), the order of parking procedure is anti- ice off then APU bleed as required. Is there any meaning for this order? Can’t we switch the order instead? If there is any relation based on system relationship, I would like to know.

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  • $\begingroup$ Is A320 anti-ice electric - if so, then this'd be to reduce the load at switch over to ground power / APU off ...? Covered at page 41 of the A320 normal procedures $\endgroup$
    – Mr R
    Commented Apr 8, 2022 at 5:27
  • $\begingroup$ @MrR No, it's not electric. I think the 787 is the only jet airliner that uses electric thermal anti-ice. All others use bleed air. $\endgroup$
    – Bianfable
    Commented Apr 8, 2022 at 6:11
  • $\begingroup$ The "dupe" question is about Wing A/I; this question sounds like it's about Engine A/I. Is that not correct? $\endgroup$
    – Ralph J
    Commented Apr 8, 2022 at 7:02
  • $\begingroup$ @RalphJ I thought Engine A/I is separate from the rest of the bleed system, but I can't find a diagram to prove it. Anyway, OP should probably clarify which anti ice system they mean. $\endgroup$
    – Bianfable
    Commented Apr 8, 2022 at 7:20
  • $\begingroup$ @RalphJ: nope, engine AI on the 320 can only be supplied by the engine itself (dedicated bleed stage) $\endgroup$
    – user14897
    Commented Apr 8, 2022 at 9:17

1 Answer 1

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The SOP calls for

ANTI-ICE ... OFF
APU BLEED pb-sw ... ON

the former covers both wing and engine anti-ice.

It is not allowed to use APU bleed for wing anti-icing, as defined in FCOM Limitations. (FCOM-LIM-APU-OPERATIONAL ENVELOPE)

As APU bleed has priority over engine bleeds the wing anti-ice valves have to be closed before APU bleed valve is opened.

For engine anti-icing the order does not really matter. Each engine uses its' own closed system for anti-icing with dedicated bleed valves.

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  • $\begingroup$ Since each engine’s anti-ice is a local system, does that mean that if the engine shuts down for any reason and could be restarted later, there’ll be no anti-icing for that engine in the meantime? Has this ever caused a problem? (I doubt but curious) $\endgroup$ Commented Apr 8, 2022 at 17:59
  • $\begingroup$ Yes, since each engine anti-ices its own nacelle. Never heard it being a problem, but should engine fail in severe icing (especially if it flames out due ice) it is likely that it will not start again. $\endgroup$
    – busdriver
    Commented Apr 8, 2022 at 18:02

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