Originally Posted by
Pin Head
Should rate of change react reasonably quickly? If so how long would you give it?
It depends on what is causing the issue largely, and also the thrust setting to a smaller degree.
It is important to take your time.
Basically, your only avenues to control it are, switching to Alternate mode and seeing if the computer can have a second go at it, or Standby mode and controlling the outflow valve yourself.
If you have an Unscheduled Pressurization Change, take the time to look at the Cab Alt, Diff and cabin VSI, but also take note of the Outflow Valve position.
If the valve is wide open due to a controller fault, then Alternate or Manual mode may gain control.
If the valve is already been driven fully closed by the controller, then you have a leak in the airplane, and you probably will not gain control of it.
If you hear a bang and the diff needle is racing towards zero, there is not much chance you are going to control it by closing the outflow valve.... but you still need to take the time to analyse it fully. Once you have gone to manual mode and confirmed that the outflow valve is fully closed, but the diff needle is still falling toward zero rapidly, it’s safe to say you don’t have control of it.
If you go to Manual mode, close the outflow valve and the diff needle slows or stops, then you may have control of it. If the needle starts going back the other way then you are pressurising the airplane.
With the outflow valve fully closed at cruise or climb thrust, you will pump the airplane up fairly quickly, remember to MAINTAIN control of the cabin.
It becomes a full time job for the RHS pilot....
Long story short, take your time....