At cruise altitudes at or below FL 280, the max differential is 7.45 PSI. which will result in a cabin altitude of 8000’ at FL280. At cruise altitudes above FL280 but below FL370, the max differential is 7.80 PSI. which will result in a cabin altitude of 8000’ at FL370. At cruise altitudes above FL 370, the max differential is 8.35 PSI. which will result in a cabin altitude of 8000’ at FL410
No.
The MAX cabin altitude the cpc will allow is 8000 ft.
At intermediate levels the cabin altitude will be dependent on the max psi as you mentionned above but also on the cabin altitude you have on top of your head when seated on the right seat.
At FL280 for example,the cabin would be about 5000ft.
If you want a lower cabin altitude,you can set in the FL a level which will make the CPC schedule a higher PsI therefore a lower cabin.
Example:if you set 375 and fly at 330 , the psi will be limited to 8.35 instead of 7.8,therefore a lower cabin,7000 ft instead of 8000ft.
The difference is not worth messing about,however on the planning ground stage,setting the highest level you can reach within your SOP,personal preference(wx/margin),will be benefitial in two ways.
First if you dont get your optimim level,you may keep a lower cabin altitude until you reset your CP Cruise level,again some sop are requesting it to be done when the final level is reached,ATC final FL 330,you level off and set the CP FL.
Or you can wait to reach before you descend(before descent checklist).
So in that case you may have a cabin altitude rise from lets say 6000 to 7000 ft.
Secondly if you forget to reset the CP fL during descent,you will simply get an off schedule descent.
Much better than setting 270 on the ground but climbing to 410 and not resetting the CP fl which will possibly get the pressure releief valves to operate.
I have set my Flight Altitude to L350. I climb to L330 and maintain L330, without resetting my cruise altitude. How does this help the life cycle of an airframe?
After a while I rest my my Flight Altitude to L330. Now the cabin starts to descent why?
The CPC may have scheduled at fl 350 the psi to be 7.8 and cabin of 7000f,at fl 330 psi of 7.8 and cabin of 6500.
When you reset the CP fl, the cabin will descend to the new calcualted cabin altitude.
The CPC knows your actual altitude via the alternate static and will readjust the cabin descent/climb rate depending on your actual rate of descent.
Now you have obviously never looked at your actual cabin altitude at various FL,which leads me to believe you are either not rated or doing your rating and havent been in the sim yet.
If you are not rated nor going to be on the NG,maybe changing screen name would help getting sensible answers to your type related questions.