Pressurization / BAECS Flashcards
Normal bleed air pressure
40-50 psi
Bleed air pressure check, 30 to 15 psi
Not less than 22 seconds
What systems use bleed air?
engine starting AC cabin pressurization leading edge ice protection ABSLATS
Where does the cross ship manifold extend across?
the wing front beams btwn engines 1 and 4
A bleed air duct that extends along the right side of the fuselage delivers bleed air for what?
the cargo compartment refrigeration unit and floor heat
What do bleed air compensators do? Where are they installed?
allow for expansion and contraction of the ducts caused by heating and cooling. in the longer sections of the bleed air ducts
If you close an isolation valve, are both refrigeration units lost?
No. the opposite pair of engines will drive both units.
Where are the isolation valves located?
on each wing just before the cross ship manifold enters the cargo compartment
If you close the divider valve, are both refrigeration units lost?
Allows at least one AC system to continue to operate.
Where is the divider valve located?
in the cross ship manifold between the two wing isolation valves.
What do the check valves in the bleed air system do?
Permit air flow in one direction only. Prevents air flow into an inoperative engine or the APU and loss of system pressure to the atmosphere
What do augmenter valves in the bleed air system do?
Regulate 14th-stage bleed air from the engine compressor
What does the BA/ECS do? What valves does it control?
regulates air temperature and pressure in the bleed air system augmenter valves and nacelle SOVs
Normal pressurization can be maintained with one AC, provided what else is on?
cargo underfloor heat
What does the outflow valve do in flight? on the ground?
in flight - exhausts air from the cabin at a controlled rate to maintain the desired level of pressurization on ground - allows avionics cooling discharge air to escape overboard
Where is the outflow valve located?
aft right hand corner of the flight station, behind the ACS.
What does the safety valve do?
relieves excessive positive or negative pressure to prevent damage to the aircraft or injury to personnel
What does the MANUAL VALVE CONTROL ROCKER SWITCH do?
controls the electric actuator of the outflow valve. Functional only when the pressurization mode select switch is in MAN
AUTO RATE SELECTOR What does NORM do? MIN? MAX?
NORM - provides a nominal climb rate of 500 fpm and a nominal descent rate of 300 fpm MIN - zero fpm rate MAX - 3000 fpm rate
What does NO PRESS do?
opens the outflow and safety valves and depressurizes the cabin at the rate set by the AUTO RATE selector
What does AUX VENT do?
opens the AUX VENT valves and closes the AC flow control valves and floor heat shutoff valves
What does the LDG/CONST ALT selector do?
sets the altitude of the selected landing field or the desired altitude when in the CONST ALT mode
What does the DIF PRESS indicator display?
the cabin-to-atmosphere differential pressure in inches of mercury
What does the EMER DEPRESSURE handle release?
releases the emergency depressurization door in the center overhead escape hatch
Which cabin pressurization system switch controls the electric actuator of the outflow valve when the pressurization mode switch is in the MAN position?
MANUAL VALVE CONTROL switch
Basically, how is pressurization achieved?
with air supplied from the bleed air system and ducted through the air conditioning system
What event would have to occur to force the safety valve to work?
combination of the cabin pressure controller and outflow valve fails to regulate the cabin pressure within structural limits
At what differential pressures does the safety valve open?
14.96 in Hg or -0.76 in Hg
What are the 6 sub modes within the AUTO mode of the cabin pressurization system?
GROUND - provides an unpressurized cabin by opening the outflow and safety valves PREPRESSURIZATION - as power levers are advanced above FLT IDLE for takeoff, cabin altitude begins a descent to 300 ft below field elevation CLIMB - occurs at liftoff. Either with WOW or gear is retracted and IAS is greater than 100 kts CRUISE - cabin altitude will increase to the auto schedule value and hold that value after the aircraft altitude remains constant within 200 feet for 10 minutes DESCENT - initiated when aircraft altitude decreases 1,000 ft or more from the highest altitude achieved during flight LANDING - WOW or landing gear extended and IAS is less than 60 kts
When will you get the CAB PRESSURIZED ACAWS?
differential pressure exceeds 0.2 in Hg with WOW and power levers below FLT IDLE
What is the duty cycle of the outflow valve manual control motor?
3 mins on, 17 mins off
When will you get the CAB ALT HIGH ACAWS?
when cabin altitude is greater than 10,000 ft
The constant altitude pressurization mode uses what as an altitude reference?
pilot barometric setting
What is the rate of depressurization when the EMER DEPRESS switch is in the DUMP position?
an uncontrolled rate independent of cabin altitude
What 3 valves close when the EMER DEPRESS switch is in the DUMP position?
floor heat shutoff valve flight station AC control valve cargo compartment AC control valve
How long does it take to gain control of the outflow valve in manual pressurization mode?
40 seconds
What does the cross flow valve in the AC system do?
connects the flight station and cargo compartment distribution ducts so that one system can provide AC to both the flight station and cargo compartment
What are the two stages of the refrigeration unit in the AC system?
air-to-air heat exchanger cooling turbine
Under what conditions might the ECS produce small chunks of ice and expel them at high speed from the air conditioning outlets?
high humidity
How much water is removed from the refrigerated air by the water separators?
70-85 percent
In which position is the pressurization mode select switch placed when using an external air conditioning unit?
AUX VENT
