Narrative:

Maintenance logbook stated that the previous crew experienced an over-pressurization passing FL230 and had diverted to lax. Our flight was dispatched with MEL 21-14A automatic pressurization inoperative. We read the MEL and familiarized ourselves with operation of the pressurization system in standby mode. We noticed passing FL225 that the aircraft differential pressure was in the yellow arc; so we leveled off at FL230. At FL230 the differential pressure went into the red arc; so we descended to 10000 ft MSL and all pressurization indications returned to normal. We returned to lax to have maintenance inspect the aircraft. After landing; we discovered that we had mis-applied the supplemental procedure for (400) standby pressurization operations. We were supposed to have set the cabin altitude to the placard altitude corresponding to our planned flight altitude after takeoff. We still had field elevation 200 ft set. No matter what the threats were (late; runway and departure changes; terrible WX; busy ATC departure; tired/circadian rhythm 180 degrees out of sync) I should have remembered to set the standby pressurization properly on the after takeoff checklist. Anticipation error: because the pressurization indications approaching FL230 happened to be the same as the previous crew's discrepancy; we were 'spring-loaded' into thinking that we had the same problem. Negative training: every yr in our recurrent simulations we get in the habit of switching to standby pressurization mode as a quick way to clear the 'off scheduled descent' caution light. We then run the simulation in standby without ever running the supplemental procedure. If we are going to 'train like we're going to fight;' then we should require crews to set up the standby mode properly prior to landing the simulator in order to preclude negative habit patterns from developing. MEL 21-14A flight crew procedures: it would be helpful to refer the crew to review both the (400) standby mode operations and the manual mode operation supplemental procedures. Circadian rhythm: I am a reserve captain. I had just flown 2 mex and 1 gdl all-night flts. I was assigned to fly this trip with the minimum 12 hours advance notice. I was not very well rested when I reported for the trip. I actually felt more rested at the end of our 1 hour duty day than I did at the start because that was where my body clock was used to (if that makes sense). Scheduling with safety: pilot scheduling built this 3 day 'special' pairing and assigned it to me (legally) in order to get the maximum utilization out of the limited pilot resources. If we truly want to lead in safety and compliance; then we should put out a scheduling policy that prohibits 'back-side-of-the-clock' reserve assignments without at least 24 hours notice. It is my experience (12 yrs on reserve) that 12 hours is not sufficient to turn around my 'body clock.'

Related reports:

Google
 

Original NASA ASRS Text

Title: A B737-400 CREW OPERATING WITH STANDBY PRESSURIZATION CTL FORGOT TO RESET THE CRUISE ALT SELECTION AND OVER PRESSURIZED THE ACFT CAUSING A DIVERSION.

Narrative: MAINT LOGBOOK STATED THAT THE PREVIOUS CREW EXPERIENCED AN OVER-PRESSURIZATION PASSING FL230 AND HAD DIVERTED TO LAX. OUR FLT WAS DISPATCHED WITH MEL 21-14A AUTO PRESSURIZATION INOP. WE READ THE MEL AND FAMILIARIZED OURSELVES WITH OP OF THE PRESSURIZATION SYS IN STANDBY MODE. WE NOTICED PASSING FL225 THAT THE ACFT DIFFERENTIAL PRESSURE WAS IN THE YELLOW ARC; SO WE LEVELED OFF AT FL230. AT FL230 THE DIFFERENTIAL PRESSURE WENT INTO THE RED ARC; SO WE DSNDED TO 10000 FT MSL AND ALL PRESSURIZATION INDICATIONS RETURNED TO NORMAL. WE RETURNED TO LAX TO HAVE MAINT INSPECT THE ACFT. AFTER LNDG; WE DISCOVERED THAT WE HAD MIS-APPLIED THE SUPPLEMENTAL PROC FOR (400) STANDBY PRESSURIZATION OPS. WE WERE SUPPOSED TO HAVE SET THE CABIN ALT TO THE PLACARD ALT CORRESPONDING TO OUR PLANNED FLT ALT AFTER TKOF. WE STILL HAD FIELD ELEVATION 200 FT SET. NO MATTER WHAT THE THREATS WERE (LATE; RWY AND DEP CHANGES; TERRIBLE WX; BUSY ATC DEP; TIRED/CIRCADIAN RHYTHM 180 DEGS OUT OF SYNC) I SHOULD HAVE REMEMBERED TO SET THE STANDBY PRESSURIZATION PROPERLY ON THE AFTER TKOF CHKLIST. ANTICIPATION ERROR: BECAUSE THE PRESSURIZATION INDICATIONS APCHING FL230 HAPPENED TO BE THE SAME AS THE PREVIOUS CREW'S DISCREPANCY; WE WERE 'SPRING-LOADED' INTO THINKING THAT WE HAD THE SAME PROB. NEGATIVE TRAINING: EVERY YR IN OUR RECURRENT SIMULATIONS WE GET IN THE HABIT OF SWITCHING TO STANDBY PRESSURIZATION MODE AS A QUICK WAY TO CLR THE 'OFF SCHEDULED DSCNT' CAUTION LIGHT. WE THEN RUN THE SIMULATION IN STANDBY WITHOUT EVER RUNNING THE SUPPLEMENTAL PROC. IF WE ARE GOING TO 'TRAIN LIKE WE'RE GOING TO FIGHT;' THEN WE SHOULD REQUIRE CREWS TO SET UP THE STANDBY MODE PROPERLY PRIOR TO LNDG THE SIMULATOR IN ORDER TO PRECLUDE NEGATIVE HABIT PATTERNS FROM DEVELOPING. MEL 21-14A FLT CREW PROCS: IT WOULD BE HELPFUL TO REFER THE CREW TO REVIEW BOTH THE (400) STANDBY MODE OPS AND THE MANUAL MODE OP SUPPLEMENTAL PROCS. CIRCADIAN RHYTHM: I AM A RESERVE CAPT. I HAD JUST FLOWN 2 MEX AND 1 GDL ALL-NIGHT FLTS. I WAS ASSIGNED TO FLY THIS TRIP WITH THE MINIMUM 12 HRS ADVANCE NOTICE. I WAS NOT VERY WELL RESTED WHEN I RPTED FOR THE TRIP. I ACTUALLY FELT MORE RESTED AT THE END OF OUR 1 HR DUTY DAY THAN I DID AT THE START BECAUSE THAT WAS WHERE MY BODY CLOCK WAS USED TO (IF THAT MAKES SENSE). SCHEDULING WITH SAFETY: PLT SCHEDULING BUILT THIS 3 DAY 'SPECIAL' PAIRING AND ASSIGNED IT TO ME (LEGALLY) IN ORDER TO GET THE MAX UTILIZATION OUT OF THE LIMITED PLT RESOURCES. IF WE TRULY WANT TO LEAD IN SAFETY AND COMPLIANCE; THEN WE SHOULD PUT OUT A SCHEDULING POLICY THAT PROHIBITS 'BACK-SIDE-OF-THE-CLOCK' RESERVE ASSIGNMENTS WITHOUT AT LEAST 24 HRS NOTICE. IT IS MY EXPERIENCE (12 YRS ON RESERVE) THAT 12 HRS IS NOT SUFFICIENT TO TURN AROUND MY 'BODY CLOCK.'

Data retrieved from NASA's ASRS site as of January 2009 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.