Pressurization question
02-12-2013 | 08:43 PM
#1
Thread Starter
Line Holder
Joined: Jan 2012
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Pressurization question
How is pressurization controlled on the ground? I know the squat switch dumps some of the pressurization after landing and then decreases. But doesnt the cabin pressure controller play in it as welll? Lets say your're sitting on the ground waiting ot take off. The outflow valve is apart of the cabin pressure controller as well i guess.
Also i have a slight understanding of isobaridc and pressure differential mode
isobaric tries to remain constant cabin altitude right right?
Im just making sure i understand it before i move on
Also i have a slight understanding of isobaridc and pressure differential mode
isobaric tries to remain constant cabin altitude right right?
Im just making sure i understand it before i move on
Last edited by Hawker445; 02-12-2013 at 09:27 PM.
02-12-2013 | 11:29 PM
#2
Day puke
Joined: Feb 2006
Posts: 3,865
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From: Out.
Depends on the system. Fancy ones do that on their own. But older ones are controlled manually: set field elevation and barometer/altimeter setting and the box dumps at a set altitude.
400 series Cessnas I have flown say set the cabin alt to 500 feet above landing field elevation. The Saab was supposed to be at field elevation when landing if set correctly (HAH!). Both dumped with weight on wheels switches if improperly set.
400 series Cessnas I have flown say set the cabin alt to 500 feet above landing field elevation. The Saab was supposed to be at field elevation when landing if set correctly (HAH!). Both dumped with weight on wheels switches if improperly set.
02-13-2013 | 02:51 AM
#3
Gets Weekends Off
Joined: Oct 2007
Posts: 2,741
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From: Sr. VP of button pushing
Baby Nines aren't pressurized on the ground, the outflow valve control (wheel or lollipop) goes crazy at rotation. The F/E drives the cabin down 200 feet on 72s with pneumatic controlled systems during taxi out or flips the flight/ground switch on electronic systems. 744 - "system logic."
02-14-2013 | 01:18 AM
#4
Gets Weekends Off
Joined: Feb 2008
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From: On the Rock
The automatic system in a G-V works out the cabin altitude schedule by pressurizing to max diff at your programmed cruised altitude and bottoming out at 500+landing PA. Works great unless you are landing at a mid or high altitude airport. If you are flying to C Springs, it will set the cabin altitude at 6,500 ish in cruise instead of 4,500 ish for max diff at FL450 (normal mid weight cruise altitude). If you are flying to La Paz Bolivia or Leadville Colorado, you'd switch to semi-auto mode and keep the cabin altitue down until you started your descent and then slowly bring it up to 500+landing PA.
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