737NG Stuck PRSOV?
 

Need some help here:
Flying in the NG -700, and noticed upon descent a major decrease in airflow in the cabin. This correlated with engine thrust, low airflow until we got a level off. Power was increased and consequently cabin airflow increased. I could not see if it was a duct split as i was in the cabin. I do know of the 5th to 9th stage changeover at 40% N1. But this was not a regular event in that the cabin flow rate was not consistent with this. I wonder if it was a stuck PRSOV, do not know if it was an MEL issue.

Looking for your wisdom...

Jason S.

If when you are doing the external check, with the APU running and delivering air to the packs, can you hear air hissing if/when you stick your head in the intake of either engine?

If so, a good clue to the ground engineers that something is wrong in the PRSOV dept, IIRC?