(and that is why I said: "Lets say you are at 35.000 ft, and cabin alt is 8.000 ft. The pressurisation system just kicks up a notch, and keeps the airpressure at a comfortable 8000ft. (The airpressure inside does not decrease further.) When the plane climbs further, the cabin altitude will not rise further. That assumption was wrong (at least in arliners). You have assumed that when flying higher the cabin altitude will rise as well. It seems you read somewhere a aircraft (f18) has a cabin pressure (/cabin altitude) of 8000ft when flying at 23.000 That means the pressure in the cabin is not sea level pressure, but the pressure you would have in ambient air at 8000 ft.Īt that pressure air is still perfectly breathable.Īirliners maintain this pressure during the climb when they pass 8000 ft, up to cruise at for example 37.000 ft. Most airliners maintain a cabin altitude of 8000 ft during cruise. Max_pressure_differential=10.700 = PSI at 6,000 ft - PSI at 60,000 ft, also = PSI at MSL - PSI at 32,000 ft. Concorde cabin alt 0 ft for flt alts from MSL to 32,000 ft, increasing to design cabin alt 6,000 ft at flt alt 60,000 ftĭesign_cabin_pressure=11.772405 = PSI at design cabin alt 6,000 ft (PSI = millibars * 0.0145) Max_pressure_differential=5.500 = PSI at 8,000 ft - PSI at 25,000 ft, also = PSI at MSL - PSI at 12,500 ftįlying the HS748 at flt alt 30,000 ft (5,000 ft above design flight alt 25,000 ft) the pressure differential read 5.500 and the cabin alt 13,000 ft (5,000 ft above design cabin alt 8,000 ft). HS748 cabin alt 0 ft for flt alts from MSL to 12,500 ft, increasing to design cabin alt 8,000 ft at flt alt 25,000 ft Max_pressure_differential=8.500 = PSI at 7,900 ft - PSI at 42,000 ft, also = PSI at MSL - PSI at 22,000 ftĪnd to the HS748 which does have working pressurization gauges on the panel (which worked fine before I added this section to the aircraft.cfg): B727 cabin alt 0 ft for flt alts from MSL to 22,000 ft, increasing to design cabin alt 7,900 ft at flt alt 42,000 ftĭesign_cabin_pressure=10.969350 = PSI at design cabin alt 7,900 ft (PSI = millibars * 0.0145) I thought I'd add the section to my B727 aircraft.cfg even though there are no working pressurization gauges on the 727 panels I use. At flight altitude 35,000 ft (12,000 ft above design flight alt 23,000 ft) the cabin altitude should be about 20,000 ft (12,000 ft above design cabin alt 8,000 ft). My calculations indicate that the FA-18 would reach the given max_pressure_differential of 4.960 and design cabin altitude of 8,000 ft at a flight altitude of about 23,000 feet, above which the pressure_differential should remain at 4.960 while the cabin altitude increases by 1,000 ft for each 1,000 ft of flight altitude above 23,000 ft. Max_pressure_differential=4.960 = PSI at 8,000 ft - PSI at 23,000 ft, also = PSI at MSL - PSI at 11,000 ft FA-18 cabin alt 0 ft for flt alts from MSL to 11,000 ft, increasing to design cabin alt 8,000 ft at flt alt 23,000 ftĭesign_cabin_pressure=10.908350 = PSI at design cabin alt 8,000 ft (PSI = millibars * 0.0145) I thought I'd try to figure out the mathematics of this section and came up with the following: I recently came across the section in the FSX FA-18 aircraft.cfg file even though the aircraft doesn't appear to have any pressurization gauges on the panel.
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