pneumatics panel

[flyingmoose1]

erj 145, switching off apu after take off, what is the order of operation? I E select engine bleeds first then selector to open or what? And what would be the correct sequence for switching back to apu bleed?

 

[tarp]

Don't know Emb but do know CRJ.

Can't say that it is exactly the same but our little pnemonic is:

"Find a source, Lose a source"

That is - if going from APU to Engines, we select left engine bleed air (finding a source) and then deselect the "APU load control valve" (losing a source) - then select right engine bleed air (finding a source) and finally deselect the "isolation valve" (losing a source).

Going from Engine to APU - Select APU load control (find) and deselect Left engine bleed (lose). Select Isolation Valve (open)(find) and deselect right engine bleed (lose).

PS - APU Load Control Valve is the APU Bleed Shutoff Valve or the method that Bleed air is tapped off the APU. The Isolation Valve separates the left side bleed air supply from the right hand bleed supply. In the CRJ, the APU is tapped into the left side.

If this does it for you - stop reading.

If not try this:

Pnuematic Bleed "valves" are "Blown open". I know Beavis and Butthead laughs aplenty. But it serves a purpose on how you can think of any switch controlling a bleed air valve. For the valve to move open - it must be "blown" open by an active source. For example, let's say we try to "open" the left engine bleed valve on the ground with only the APU running. Won't happen! The valve has to be "blown" open. Springs will "close" the valve, but you need air pressure to open.

Thanks for letting me review this systems chapter - recurrent in 3 months.