A320 APU Bleed

[Black_Dawn]

Hello
Talking about the A320 apu bleed air indication.
On the right corner of the ECAM APU screen you've got the value (in psi) of bleed air: the system FCOM says that an amber "XX" replaces the indication when ADIRS2 is not available or selected off.

Can someone explain to me why it's so?

thanks B_D

[PEOPLESX]

The bleed pressure is measured upstream of the APU bleed valve by a total pressure sensor.
The indication on ECAM is relative to the ambient pressure, so the ambient pressure must taken into account and this information is provided by one of the ADIRU's as soon as they're switched on and the air data part is available.

Take a look at the PRESS-page of the lower ECAM, the differential pressure indication also works as soon as the first ADIRU is switched on, same principle here.

[planeboy_777]

i took a print out of this page....showed to my instructor ....and have observed this in the simulator but the thing about delta p isnt correct..

[Slasher]

Its about apparent and absolute pressure within the duct esp
in flight which is why an ADR input is required.