Originally Posted by
Yaw String
Ian W,.....I meant to put !!! instead of ????..
Sure you can switch the CACs off, both of them, then you have no air coming in,but may already have a cabin full of smoke...
Point is,on the 787,the CAC intakes are much closer to each other,than with the separation achieved by using engine bleed supplied air.
So smoke entering the cabin via one intake,could also, be more likely to enter via the other,too...as would most certainly have been the case,in Vegas.
In the air the CAC has the advantage that an engine problem will
not cause the input cabin air to be contaminated.
If the aircraft is on the ground having just RTO with engine fire, both engines are shut down. So with bleed air all air input stops. With CAC air power down CAC all air input stops.
Sorry I do not see a significant difference apart from advantages in flight and in normal ops of no cabin air contamination.