Pneumatics Flashcards
Describe how the Environmental Control System controls the Bleed Air System.
The ECS is managed by an ECU which has two digital and two analog channels to control the cabin environment.
Which bleed valves can the digital and analog channels of the ECS ECU modulate?
The digital channels control the HP and LP bleed ports of their respective engines to control temperature.
The analog channels are backups that are only able to control the LP ports as the HP SOV is closed when operating on the analog channel.
If the engine bleeds switches are on is APU bleed air available?
No, regardless of if the engines are operating any time the engine bleed switch(es) are on the APU bleed is inhibited.
What valves are modulated by the Engine Bleed Selector rotary switch?
The engine Nacelle Shut Off Valves (NSOV) are modulated.
Describe the Bleed Air Precoolers.
There are two precoolers.
The High Stage Precooler uses P2.2 bleed air to reduce the temperature of P3.0 air at higher engine power settings.
The Deice Precooler uses P2.2 air to reduce the temperature of both P2.7 and P3.0 bleed air before it is routed to the deice system.
Both types of precoolers vent P2.2 air overboard after it has passed through the precoolers.
What steps does the ECS ECU take if a Bleed Air overtemp, Nacelle Duct Leak Overtemp or Bleed Overpressure is detected?
The ECU will shut the associated NSOV.
For Bleed Air overtemps the system will reopen the NSOV when the temperature returns to normal.
What is P2.2, P2.7 and P3.0 bleed air used for and when?
P2.2 Bleed Air is used to cool P2.7 and P3.0 air and provide pressure to the inflatable door seal system.
P2.7 Bleed Air is used for the De-ice and ECS systems at higher power settings. Also actuates exterior oil cooler door.
P3.0 Bleed Air is used for the De-ice and ECS systems at lower power settings.
