- Select 27000' as Flight Altitude on Pressurisation panel.
The system is then programmed for 7.45 psid; that would correspond to 4500 feet cabin altitude.
Later you climb to 37000' [as per the new clearance]. But still 27000' is set as Flight altitude.
As a result,
1. Will cabin altitude increase to maintain 7.45 psid ? or
2. Will differential pressure increase to maintain 4500' Cabin altitude?
FCOM says, " Increase in flight altitude can cause the differential
pr. to increase" In other words 4500' CA will be maintained and diff.
pr. would increase beyond 8.45 psid leading to failure of AUTO at diff.
pr. of more than 8.75 psi!!!
Isn' it ridiculous?
In any other a/c, even in B737 classic. diff.
pr. would be maintained constant.
Has anyone come across this odd theory, earlier?