There have been lots of comments on forums on how much more worse Alaska Airlines would have been if the cabin door plug had blown out at cruise altitude. Looking at tables for the 747-400, the differential pressure at 16,000 feet would have already beeen around 2/3rds of the cruise value.
What are the typical pressures for an NG at 16,000 feet? I couldn't find any useful charts/diagrams in the NG Maintenance Manual or online.
Thanks!
KaraokeMan
13th Jan 2024, 19:21
There have been lots of comments on forums on how much more worse Alaska Airlines would have been if the cabin door plug had blown out at cruise altitude. Looking at tables for the 747-400, the differential pressure at 16,000 feet would have already beeen around 2/3rds of the cruise value.
What are the typical pressures for an NG at 16,000 feet? I couldn't find any useful charts/diagrams in the NG Maintenance Manual or online.
Thanks!
The placard on the pressurization control panel reads CAB ALT is LAND ALT at a FLT ALT of <FL160. Between FL160 and FL220 it shows CAB ALT of 2000, CAB ALT of 4000 between 220 and 260, 6000 between 260 and 320, and 8000 between 320 and max operating alt 410.
The max differential pressure limit (causing AUTO FAIL) is >8.75 psi, and the controller tries to set the lowest possible cabin altitude based on a schedule of 7.45psid max differential at or below 28,000’, 7.80 between 280 to 370, and 8.35 above 370.
so at 16000 it would been trying to keep sea level pressure in the cabin up to max differential of 7.45psid. Hypothetical max cruise of FL410 would be a cabin alt of 8000 and 8.35psid, which is over 2x the altitude difference between MSL and 16000. It would probably have been much worse to happen at cruise, in my opinion, but I’m just the guy pushing the buttons.