A320 temp and QNH

[squawkident.]

Hi,

Just a quick one.
I remember some time ago during my initial line training that in the Landing Perf. page, the only calculation the QNH and Temp is used for is to set a pressure altitude.

This is so that the airplane can work out its descent rate and cabin recompression from cabin alt. to pressure altitude on ground.

I've been trying to find a reference to this but to no avail. Does anybody have any input on this?

In summary, my question is simply: What calculations are the QNH and temp. variables used for in LDG page.

Thank you

[Goldenrivett]

What calculations are the QNH and temp. variables used for in LDG page.

If the temperature is changed in the LDG page during a managed descent, then the vertical profile often changes, and the AP attempts to regain the profile rather aggressively. I therefore suspect the top of descent point calculation uses that data (as well as the forecast descent winds).

The pressurisation controller will only need the QNH to calculate its diff pressure profile.

[I-2021]

Originally Posted by squawkident.

Hi,

Just a quick one.
I remember some time ago during my initial line training that in the Landing Perf. page, the only calculation the QNH and Temp is used for is to set a pressure altitude.

This is so that the airplane can work out its descent rate and cabin recompression from cabin alt. to pressure altitude on ground.

I've been trying to find a reference to this but to no avail. Does anybody have any input on this?

In summary, my question is simply: What calculations are the QNH and temp. variables used for in LDG page.

Thank you

Hi,

check DSC-22_20-50-10-25

Cheers.

[squawkident.]

Thanks very much for your comments.

Found it.

QNH is used for CPC pressurisation.
Temp. is used for descent profile