What are the three possible sources of air to the pneumatic system?
gsa,a,e
Ground source air, APU, Engines
APU can be used for Bleed Air up to what Altitude?
Approximately 22,000’
Which engine sections can engine bleed air be supplied from?
High Stage or low stage
When is low stage engine air used?
High thrust settings- T/O, climb and cruise.
When is high stage engine air used for?
During low thrust settings such as in the desent it will supplement low stage air
What are the two possible settings for the isolation switches
OFF and AUTO
How are engine Bleed Air valves controlled? Operated?
Electrically
Pneumatically
When you select the engine bleeds on do they automatically open all the time? Is there a scenario when they wouldn’t? Why?
Not always. They are pneumatically operated so if there’s no bleed air, they won’t necessarily open when selected on.
What might you see on the bleed air buttons before engine start? What lights would be on?
When would this change
You might see both the on light and the off light.
After engine start when the engines are producing air, the valves would be automatically opened
Do you need to turn off the packs before engine start?
No, they are automatically shut off during engine start
What is the normal position of all three isolation valves in normal operations in flight?
The left and right isolation valves are normally open, the center. Isolation valve is normally closed.
In the event of a bleed air overheat or over pressure what indications would you get?
E-V-O
First, you would get a bleed off EICAS. Simultaneously the associated bleed valve closes and the associated amber OFF light would illuminate on the BLEED AIR panel. You cannot use bleed air from that source again.
If an isolation valve fails closed, why would the switch show Auto and closed
Because it has failed closed but is the switch is commanded open when in the Auto position
If a bleed leak is isolated by closing the appropriate valves what EICAS message would you see after the area has cooled?
bleed LOSS___(to the associated area)
The APU supplies Bleed Air and electricical, which has priority?
Electrical
What is the maximum altitude to start the APU?
Max operating altitude.
What is the maximum altitude to use electricity from the APU?
Maximum operating altitude, it is available through the entire operating envelope.
To what altitude is bleed air available?
At and below 22,000 feet
Where is the APU selector?
On the electrical portion of the overhead panel.
What three things could cause the “APU fall” light to illuminate?
Fault
Fire
Momentarily during the self test
What are two ways to start the APU?
Electric Start Motor
Air turbine starter
What powers the APU starter?
The APU Battery
What provides fire detection for the APU?
Main aircraft battery
What air does the air turbine starter use to start the APU?
Bleed air or Ground Air
