Narrative:

Automatic pressurization controller 2 failed. ZZZ maintenance MEL'ed it under 21-7. The proviso requires tests to be accomplished prior to engine start. The test checking the manual pressure controller authority on some valve failed. Maintenance operations center directed ZZZ maintenance to assess the possibility to MEL under 21-8. At this point, I helped local maintenance with these tests mainly because they were not in possession of the emergency checklists which are described in the proviso test. Once again the test failed because the manual pressure controller did not have authority on some of the valves. No relieve is offered by the MEL for a failure of all or part of the manual pressure controller. I believe MEL 21-8 does not include the manual pressure controller. It is only for the 2 automatic controllers. Even for an unpressurized flight the manual controller has to operate since other valves still have to be actuated like the ground valve and the emergency depressurization. All these valves are electrical motors rather than vacuum operated like other airplanes in the fleet. Callback conversation with reporter revealed the following information: the reporter said the crew assisted the local technician with the test to confirm operation of the manual pressurization system. The reporter said when deferring the automatic pressure system, the MEL special procedures requires a test of the manual pressurization system. The reporter stated the test failed as the outflow valve could not be controlled in manual mode. The reporter said it was the intent of maintenance operations to defer the manual mode pressurization system using the MEL 21-8. The reporter stated the airplane was refused as there was no way to control cabin pressure.

Google
 

Original NASA ASRS Text

Title: A CRJ-700 FAILED AUTO AND MANUAL PRESSURIZATION SYSTEM CHECKS DURING A MEL DEFERRAL TEST. MAINT'S INTENT WAS TO DEFER THE MANUAL SYSTEM. CAPT REFUSED AIRPLANE.

Narrative: AUTO PRESSURIZATION CTLR 2 FAILED. ZZZ MAINT MEL'ED IT UNDER 21-7. THE PROVISO REQUIRES TESTS TO BE ACCOMPLISHED PRIOR TO ENG START. THE TEST CHECKING THE MANUAL PRESSURE CONTROLLER AUTHORITY ON SOME VALVE FAILED. MAINT OPERATIONS CENTER DIRECTED ZZZ MAINT TO ASSESS THE POSSIBILITY TO MEL UNDER 21-8. AT THIS POINT, I HELPED LOCAL MAINT WITH THESE TESTS MAINLY BECAUSE THEY WERE NOT IN POSSESSION OF THE EMER CHECKLISTS WHICH ARE DESCRIBED IN THE PROVISO TEST. ONCE AGAIN THE TEST FAILED BECAUSE THE MANUAL PRESSURE CONTROLLER DID NOT HAVE AUTHORITY ON SOME OF THE VALVES. NO RELIEVE IS OFFERED BY THE MEL FOR A FAILURE OF ALL OR PART OF THE MANUAL PRESSURE CONTROLLER. I BELIEVE MEL 21-8 DOES NOT INCLUDE THE MANUAL PRESSURE CONTROLLER. IT IS ONLY FOR THE 2 AUTO CONTROLLERS. EVEN FOR AN UNPRESSURIZED FLT THE MANUAL CONTROLLER HAS TO OPERATE SINCE OTHER VALVES STILL HAVE TO BE ACTUATED LIKE THE GND VALVE AND THE EMER DEPRESSURIZATION. ALL THESE VALVES ARE ELECTRICAL MOTORS RATHER THAN VACUUM OPERATED LIKE OTHER AIRPLANES IN THE FLEET. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR SAID THE CREW ASSISTED THE LOCAL TECHNICIAN WITH THE TEST TO CONFIRM OPERATION OF THE MANUAL PRESSURIZATION SYSTEM. THE RPTR SAID WHEN DEFERRING THE AUTO PRESSURE SYSTEM, THE MEL SPECIAL PROCS REQUIRES A TEST OF THE MANUAL PRESSURIZATION SYSTEM. THE RPTR STATED THE TEST FAILED AS THE OUTFLOW VALVE COULD NOT BE CONTROLLED IN MANUAL MODE. THE RPTR SAID IT WAS THE INTENT OF MAINT OPS TO DEFER THE MANUAL MODE PRESSURIZATION SYSTEM USING THE MEL 21-8. THE RPTR STATED THE AIRPLANE WAS REFUSED AS THERE WAS NO WAY TO CONTROL CABIN PRESSURE.

Data retrieved from NASA's ASRS site as of July 2007 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.