Pressurization Flashcards
When do you pressurize?
Thrust levers moved into the takeoff range
(this moves outflow valve closed during takeoff)
Captains Altimeter ONLY- lets system know when you’re at standard and not at standard
What part does the FMC play in pressurization of your airplane?
No part in pressurization
How many controllers are part of the pressurization system?
3 (2 AC, 1 DC) It’s on the knob
Auto 1- AC Powered Automatic Control
Auto 2-AC Powered Automatic Control
MAN- DC motor that lets me control the cabin manually
What Systems are inputs of my pressurization system
Main Gear Air Ground Logic
Air Data Computer- As temp and pressure change it knows this to place inputs in
Captains Altimeter
What is crew required to do with the Pressurization Controller?
- Set Landing Field Elevation
- Select Auto 1 or Auto 2 (whoever is flying CA or FO)
- Verify AUTO RATE is in index position (climb 500fpm descent 300 fpm)
Land after 8 hour flight, what is target cabin altitude to select?
200’ lower than the elevation of where you are landing. But never to exceed .125 inches if differential pressure
When I land what does main gear air logic do?
Allows the outflow valve to go wide open to depressurize.
200’ equals what?
.125 PSI
How does the cabin climb?
Relative to the airplane climb.
Airplane Logic of Climb Cruise Descent
Climb, Cruise, Descent
Level off in 1 minute Climb will change to Cruise-
1000’ dictates climb back to cruise
Boeing when you go into cruise has programmed into pressurization system to look at final cruise altitude and cabin altitude you’re at and your landing altitude. Will take the higher of the landing altitude and cabin altitude to calculate new PSI differential. Will climb the cabin to this!
I.e. Denver example from class-
Target of this pressurization system FL35 or greater should be what?
8.6 PSI
(if it is higher- tell Captain- maybe outflow valve stuck or not working properly)
The system will do it’s best to maintain 8.6 all the way up to Flight Level 350 and higher
Max Differential Pressure where Overpressure Relief Valve is starting to kick in is ___ PSI. Doors will open up and let pressure decrease to a safe PSI.
9.1 PSI
Coming into Denver, I put in my arrival- Last altitude on arrival is 4000’. Power off descent all the way down the STAR. What does the controller do?
More than 1000’ fpm CRUISE mode changes to DESCENT mode
Goal is to have cabin altitude stop 200’ below LFE .125
Flying in AUTO 1- lose AUTO 1, what happens?
AUTO 1 will automatically switch to AUTO 2
What if I move Mode Select to Auto 1 to Manual with everything powered normally?
Nothing will happen to outflow valve it’ll freeze and it will just show AUTO INOP light above the knob. Same as if there is a failure- the outflow valve will stop and not move!
When would you see AUTO INOP light on Mode Select Panel
AC failure of AUTO 1 or AUTO 2
Moving the controller to MAN
How many Negative Pressure Relief Valves?
Where are they?
5 Negative Pressure Relief Valves
1 on left side of airplane forward of positive pressure relief doors AIRCRAFT LEFT
2 on fwd cargo door AIRCRAFT RIGHT
2 on aft cargo door AIRCRAFT RIGHT
How many Over Pressure Relief Valves?
2 Forward of left wing root
CABIN ALT light comes on when?
10000’
Warning system is our ears!
PUT YOUR MASK ON and call for Immediate Action Item Checklist
“CABIN ALT”
“RAPID DECOMPRESSION”
I need to tell ATC “i’m losing my cabin, I need to descend what heading do you want me on to avoid traffic.”
Cabin altitude continues to climb and reaches 11,000’ what happens? What is it called?
CABIN RATE LIMITING!
Separate signal sent to outflow valve by DC power to command it CLOSED.
“If you reach 11000 feet with DC power closing the outflow valve it is called Cabin Rate Limiting”
Cabin Altitude reaches 14,000’ what happens?
Rubber Jungle Deployment Automatically (12 mins supply)
Once cabin goes back below 8,500’ what happens?
Warning resets in case it re climbs above 10,000’
At 11,000 feet cabin altitude what happens?
“CABIN RATE LIMITING”
Outflow valve is closed by DC power
Flying Denver (field elevation 5430) to Tulsa at sea level, how would you set up the panel?
Go to AUTO __ depending on who is flying
Landing elevation will be at 0
Rate will turn to the diamond index
Climb up to FL 290,
