A captain reports a B737 aircraft had an erratic and recurring cabin pressurization problem which co...

Narrative:

We had the airplane on the flight from ZZZ-ZZZ1 operating under MEL with auto pressure controller inoperative. The stby (standby) pressure controller worked normally. The airplane routine overnighted (ron'ed) in ZZZ1. The next morning we got the same airplane. Maintenance had replaced the pressure controller and removed the MEL. The first flight ZZZ1-ZZZ was normal. On the second flight; ZZZ-ZZZ2; we had a problem with the auto pressure controller again; so we switched to the stby controller and continued to ZZZ2. We wrote up the problem after landing in ZZZ2. Maintenance again placed the automatic controller on MEL. The next flight ZZZ2-ZZZ3 was normal until descending below approximately FL270 when the cabin pressure began to climb uncontrollably. We regained control using the man (manual) position of the system and continued the remainder of the flight using that system. We landed in ZZZ3 and wrote up the problem for maintenance.

Original NASA ASRS Text

Title: A Captain reports a B737 aircraft had an erratic and recurring cabin pressurization problem which continued even after two replacements of the Auto Pressure Controller.

Narrative: We had the airplane on the flight from ZZZ-ZZZ1 operating under MEL with Auto Pressure Controller inoperative. The STBY (Standby) Pressure Controller worked normally. The airplane Routine Overnighted (RON'ed) in ZZZ1. The next morning we got the same airplane. Maintenance had replaced the pressure controller and removed the MEL. The first flight ZZZ1-ZZZ was normal. On the second flight; ZZZ-ZZZ2; we had a problem with the Auto Pressure Controller again; so we switched to the STBY Controller and continued to ZZZ2. We wrote up the problem after landing in ZZZ2. Maintenance again placed the AUTO controller on MEL. The next flight ZZZ2-ZZZ3 was normal until descending below approximately FL270 when the cabin pressure began to climb uncontrollably. We regained control using the MAN (Manual) position of the system and continued the remainder of the flight using that system. We landed in ZZZ3 and wrote up the problem for Maintenance.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	981144
Time
Date	201111
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Dusk
Aircraft 1
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Descent
Flight Plan	IFR
Component
Aircraft Component	Pressurization Control System
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Critical

A captain reports a B737 aircraft had an erratic and recurring cabin pressurization problem which continued even after two replacements of the auto pressure controller.