APU TO PACK

[MarkW 1,490]

Does anyone here know what does APU to PACK mean in terms of configuration and why is it used ?   thanks.

[skelsey 765]

It is what it says -- running the packs off the APU (instead of the engine bleed air).

Used if you want to run the packs during takeoff (e.g. passenger comfort) but you need or desire to reduce the bleed demand on the engines (e.g. for takeoff performance reasons or to reduce EGT and thus preserve engine life).

[MarkW 1,490]

Thanks for the explanation.

[Budbud 227]

Hi,

The way to achieve that is described in the FCOM page SP.2.1 (supplementary procedures).

[berts 97]

Mark,

APU to Pack take-offs are normally used on the B744 as a standard operating procedure whenever the planned take-off weight (TOW) is greater than 300,00kgs. The aircraft is configured shortly before take-off so that the APU bleed air is fed to the No.2 (centre) Pack only.  Turning off the Nos 1 & 3 packs and selecting both Isolation Valves off reduces the number of air bleeds from the engines and this helps to keep the EGT's lower for a given power.  There is also a performance weight gain of about 1,900kgs using this procedure (after allowing for a 100kgs penalty due to the drag from the open APU door!).  During the initial climb and with climb power set the Nos 1 & 3 Packs are turned back on and the Isolation Valves are opened before the APU is selected to off. The non handling pilot will normally do this during the Flap retraction schedule.  However, if an engine fails then the APU to Pack configuration is not changed until the Flaps are UP and Vref +100 is achieved or 1500ft AGL; whichever is later.   

This procedure is not used whenever the TOW is within 15,000kgs of RTOW; or if the APU is U/S (for obvious reasons).

Bertie Goddard.

[MarkW 1,490]

Great info.  I am beta testing FS2Crew and this is an option but I did not know when it was used. 

[Patco Lch 1,463]

On 5/13/2017 at 10:06 PM, MarkW said:

Great info.  I am beta testing FS2Crew and this is an option but I did not know when it was used. 

Good for you! Get with it! Getting tired of waiting, and getting so use to single pilot operation I'm beginning to feel like I don't need the crew.