Pneumatics Flashcards
Which stage of compression normally supplies bleed air from the engines?
The 8th stage.
Which stage of compression augments the primary source of bleed air?
The 13th stage.
How are the pneumatic crossfeed valves operated?
With cables attached to the handles in the cockpit.
Are the crossfeed valves designed to be air tight?
No, there may be a little bit of leakage.
Which bus powers the pneumatic pressure start gauge?
The AC emergency bus.
How much PSI is required to operate the airfoil anti ice system?
A minimum of 20 PSI.
Which bleed air supply stage has a check valve?
The 8th stage.
Which bus powers the 13th stage augmentation valves?
Respective DC bus.
To what position will the 13th stage augmentation valves move if DC power fails?
They will fail to the close position.
In which two modes can the 13th stage augmentation valves operate?
Either pressure sensitive or temperature sensitive.
When will the 13th stage augmentation valves be temperature sensitive? Will air still be supplied to the air conditioning units?
With the anti ice on. Yes, air will still be supplied but temperature regulation has priority.
Can APU air be turned on in flight?
No.
What is the power source for the engine starters?
APU pneumatic air.
Can the APU start an engine while supplying air conditioning?
No.
When will the red TAIL COMPT TEMP HI light come on? How many sensors are in the tail cone?
When temperature in the tail compartment rises to 180 F. There are 2 sensors.
Where does the air from the L ACM and the R ACM first ‘go’ after leaving each machine?
To a mixing chamber.
Are there separate ducts from the air mixing chamber to the cockpit and the cabin?
Yes.
If one ACM system fails enroute are you required to descend?
No, you may stay at altitude provided that the sole ACM can maintain cabin pressure.
Can you be dispatched with one ACM inoperative?
Yes, maximum operating altitude is FL250.
How are the heat exchangers cooled in flight?
By ram air from a duct at the base of the vertical stabilizer.
Where does the heat exchanger ram air exit the aircraft?
On either side of the tail compartment through rectangular exits.
How are the heat exchangers cooled inflight?
By ground blower fans.
Where do the ground blower fans exhaust?
Through louvers on either side of the aircraft.
Which bus is the source of power for the ground blower fans?
The respective AC generator bus.
Which bus is the source of power for the HP bleed supply switches?
The emergency DC bus.
With the HP bleed supply switches off what is the function of various fans and valves?
The flow control valve, pressure regulator, and shutoff valve are all closed preventing any pressurized air from entering the ACM. The ground blower fan is also turned off.
Which bus is the source of power for the temperature control valves when in the auto position?
Respective AC bus.
Which bus is the source of power for the temperature control valves when in the manual mode?
The emergency AC bus.
What causes the air conditioning system to automatically shut down?
The system will automatically shut down when compressor discharge increases excessively, and excessive temperatures occur in either the outlet duct or the turbine inlet.
