Narrative:

On oct/xa/99, my crew chief sent me out on trip xyz for an inadvertent passenger mask deployment. I went out and found all the masks deployed, with the flight crew (both pilots and flight attendants) on board along with the cabin cleaners. I called back to the crew chief and told him I was going to need help 'because all the masks were deployed and it would take some time to repack them.' abc XXX was the mechanic who came out. After surveying the situation (a walk-through of the cabin) we noticed that row 20DEF's masks were hanging very low. Once we lowered the psu we discovered that the oxygen generator did not fire. Not that they were supposed to during deployment but because they had been (or at least appeared to be) pulled. This raised my suspicion, as to the appearance of the system in that row. We pulled down row 19DEF to look at it to compare the 2 rows. We noticed somewhat slack in 20DEF compared to 19DEF. I called the crew chief and asked him to pull up a history. He said there was no history. I told him what we had and to pull up paperwork. He said ok. The paperwork came out. With that, the supervisor left and we continued with row 20DEF. Once we got the paperwork, we still were unsure why the masks hung low. So we fired row 19DEF to see how the oxygen system actuates. The B737 system is quite different from the other fleets that I have worked on. We fired row 19. We noticed that there were cams that connected to the device that connected to the firing pin. In row 20, the cable and lanyards were connected but had slack. One of the cables came loose from the cam. Actually the cam came loose putting slack on the release cable which caused the mask to droop. If the masks were pulled, I believe the oxygen would have flowed due to the pin coming out because of the release cable on the other end picking up the slack. We then put the cable on, tighten the cam, and repacked the masks. We changed the canister in row 19DEF and repacked that and the rest of the masks in the aircraft including flight attendants. We tested the system per maintenance manual. I then made a maintenance entry to cover the removal and replacement of the oxygen generator we fired in row 19DEF to aid us in finding out why the masks dropped lower in 20DEF than the rest. We thought about making an entry for 20DEF and we figured the log would cover the discrepancy and the repack was covered by the signoff of the original PIREP. In retrospect, I should have made an entry for 20DEF, but we thought that would be covered by the mrr and corrective action was by the original PIREP. As this incident escalates realized this could have been avoided by the following actions: 1) perform my own history check. 2) understand what a manufacturer's maintenance recovery is really for. 3) be more precise in my maintenance entry as to why the canister fired (for troubleshooting purposes). I guess it led everybody to believe that the canister fired due to the deployment of the masks. 4) we failed to use enough maintenance manual references in the original signoff. We only used 35-22-00-5. We should have documented the use of 35-22-31-2, 35-22-11-2 and 35-22-11-4, which guides us for packing of the masks, psu oxygen installation respectfully. Document row 20DEF as a discrepancy as per general procedures manual in spite of whatever other forms are used.

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Original NASA ASRS Text

Title: AN MD80 HAD THE PAX EMER OXYGEN MASKS INADVERTENTLY DEPLOYED AND WHEN THE TECHNICIANS REPACKED THE MASKS SEAT ROW 20DEF CANISTER LANYARD WAS FOUND DISCONNECTED AND INOP.

Narrative: ON OCT/XA/99, MY CREW CHIEF SENT ME OUT ON TRIP XYZ FOR AN INADVERTENT PAX MASK DEPLOYMENT. I WENT OUT AND FOUND ALL THE MASKS DEPLOYED, WITH THE FLC (BOTH PLTS AND FLT ATTENDANTS) ON BOARD ALONG WITH THE CABIN CLEANERS. I CALLED BACK TO THE CREW CHIEF AND TOLD HIM I WAS GOING TO NEED HELP 'BECAUSE ALL THE MASKS WERE DEPLOYED AND IT WOULD TAKE SOME TIME TO REPACK THEM.' ABC XXX WAS THE MECH WHO CAME OUT. AFTER SURVEYING THE SIT (A WALK-THROUGH OF THE CABIN) WE NOTICED THAT ROW 20DEF'S MASKS WERE HANGING VERY LOW. ONCE WE LOWERED THE PSU WE DISCOVERED THAT THE OXYGEN GENERATOR DID NOT FIRE. NOT THAT THEY WERE SUPPOSED TO DURING DEPLOYMENT BUT BECAUSE THEY HAD BEEN (OR AT LEAST APPEARED TO BE) PULLED. THIS RAISED MY SUSPICION, AS TO THE APPEARANCE OF THE SYS IN THAT ROW. WE PULLED DOWN ROW 19DEF TO LOOK AT IT TO COMPARE THE 2 ROWS. WE NOTICED SOMEWHAT SLACK IN 20DEF COMPARED TO 19DEF. I CALLED THE CREW CHIEF AND ASKED HIM TO PULL UP A HISTORY. HE SAID THERE WAS NO HISTORY. I TOLD HIM WHAT WE HAD AND TO PULL UP PAPERWORK. HE SAID OK. THE PAPERWORK CAME OUT. WITH THAT, THE SUPVR LEFT AND WE CONTINUED WITH ROW 20DEF. ONCE WE GOT THE PAPERWORK, WE STILL WERE UNSURE WHY THE MASKS HUNG LOW. SO WE FIRED ROW 19DEF TO SEE HOW THE OXYGEN SYS ACTUATES. THE B737 SYS IS QUITE DIFFERENT FROM THE OTHER FLEETS THAT I HAVE WORKED ON. WE FIRED ROW 19. WE NOTICED THAT THERE WERE CAMS THAT CONNECTED TO THE DEVICE THAT CONNECTED TO THE FIRING PIN. IN ROW 20, THE CABLE AND LANYARDS WERE CONNECTED BUT HAD SLACK. ONE OF THE CABLES CAME LOOSE FROM THE CAM. ACTUALLY THE CAM CAME LOOSE PUTTING SLACK ON THE RELEASE CABLE WHICH CAUSED THE MASK TO DROOP. IF THE MASKS WERE PULLED, I BELIEVE THE OXYGEN WOULD HAVE FLOWED DUE TO THE PIN COMING OUT BECAUSE OF THE RELEASE CABLE ON THE OTHER END PICKING UP THE SLACK. WE THEN PUT THE CABLE ON, TIGHTEN THE CAM, AND REPACKED THE MASKS. WE CHANGED THE CANISTER IN ROW 19DEF AND REPACKED THAT AND THE REST OF THE MASKS IN THE ACFT INCLUDING FLT ATTENDANTS. WE TESTED THE SYS PER MAINT MANUAL. I THEN MADE A MAINT ENTRY TO COVER THE REMOVAL AND REPLACEMENT OF THE OXYGEN GENERATOR WE FIRED IN ROW 19DEF TO AID US IN FINDING OUT WHY THE MASKS DROPPED LOWER IN 20DEF THAN THE REST. WE THOUGHT ABOUT MAKING AN ENTRY FOR 20DEF AND WE FIGURED THE LOG WOULD COVER THE DISCREPANCY AND THE REPACK WAS COVERED BY THE SIGNOFF OF THE ORIGINAL PIREP. IN RETROSPECT, I SHOULD HAVE MADE AN ENTRY FOR 20DEF, BUT WE THOUGHT THAT WOULD BE COVERED BY THE MRR AND CORRECTIVE ACTION WAS BY THE ORIGINAL PIREP. AS THIS INCIDENT ESCALATES REALIZED THIS COULD HAVE BEEN AVOIDED BY THE FOLLOWING ACTIONS: 1) PERFORM MY OWN HISTORY CHK. 2) UNDERSTAND WHAT A MANUFACTURER'S MAINT RECOVERY IS REALLY FOR. 3) BE MORE PRECISE IN MY MAINT ENTRY AS TO WHY THE CANISTER FIRED (FOR TROUBLESHOOTING PURPOSES). I GUESS IT LED EVERYBODY TO BELIEVE THAT THE CANISTER FIRED DUE TO THE DEPLOYMENT OF THE MASKS. 4) WE FAILED TO USE ENOUGH MAINT MANUAL REFS IN THE ORIGINAL SIGNOFF. WE ONLY USED 35-22-00-5. WE SHOULD HAVE DOCUMENTED THE USE OF 35-22-31-2, 35-22-11-2 AND 35-22-11-4, WHICH GUIDES US FOR PACKING OF THE MASKS, PSU OXYGEN INSTALLATION RESPECTFULLY. DOCUMENT ROW 20DEF AS A DISCREPANCY AS PER GENERAL PROCS MANUAL IN SPITE OF WHATEVER OTHER FORMS ARE USED.

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.