B737-300 suffers pressurization failure at FL360. Performance of emergency descent procedure is flaw...

Attributes
ACN	802732
Time
Date	200809
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : zzz.artcc
State Reference	US
Altitude	msl single value : 36000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zzz.artcc tower : cle.tower
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 240 flight time total : 10000 flight time type : 4000
ASRS Report	802732
Events
Anomaly	aircraft equipment problem : critical non adherence : published procedure
Independent Detector	aircraft equipment other aircraft equipment : cabin alt warning
Resolutory Action	flight crew : landed in emergency condition flight crew : declared emergency
Supplementary
Problem Areas	Environmental Factor Flight Crew Human Performance Aircraft
Primary Problem	Aircraft

Narrative:

Level at FL360 during cruise and some 40-50 mins of flight; the intermittent warning horn for cabin above 10000 ft went off. My first officer thought we might have a gear horn; but he noticed me performing emergency action items for loss of pressure and during which I showed him the cabin altitude; he then quickly followed suit. QRH procedures were started; ATC was informed that we needed emergency descent for a pressurization problem. I'm doing the QRH and taking the packs to high; I showed and physically touched my first officer to look at my actions. QRH to the line we noted the cabin coming back and below 10000 ft then 9000 ft. I suggested to the first officer to stow speed brakes so as not to alarm passenger and showed him the cabin ok. During the continued descent; a master caution for overhead went off. Looking up; we noticed passenger oxygen deployed. Prior to the master caution and during descent; I was re-doing my QRH steps and noticed I had put the packs to off and not high. Finding this problem; they were put to the correct position as per QRH. It was both our recollections that we caught the error prior to passenger oxygen masks deploying. We then re-commenced our full emergency descent. ATC did not move traffic for us; we were given up to 3 heading changes; and small altitude changes until area was clear for our descent. Around 12000-10000 ft; massive cabin pressure bumps and ears popping; I noticed cabin at 24 and differential at 8.65. I stated to the first officer 'we got to get this aircraft lower' and I took my attention to aircraft and QRH. My first officer took this literally and got us 6000 ft then 5000 ft approved by ATC. Level at 5000 ft; ears and pressure normal. We decided MEA; MOCA all ok; aircraft working good; let's stay here (don't change what works). Problems getting company and maintenance; then solved; returned to ZZZ. After landing; aircraft still pressurized for safety; went to an area well clear of terminal. Briefed flight attendant not to touch doors to keep all safe; parked; used maintenance and depressurized aircraft. All ok. Took passenger to gate.

Original NASA ASRS Text

Title: B737-300 SUFFERS PRESSURIZATION FAILURE AT FL360. PERFORMANCE OF EMERGENCY DESCENT PROCEDURE IS FLAWED WHEN CAPT TURNS PACKS OFF VICE HIGH AS DIRECTED BY QRH. SUBSEQUENTLY OVER PRESSURIZE THE CABIN AND; AFTER LNDG; MUST PARK AND BLEED OFF PRESSURE PRIOR TO OPENING DOORS.

Narrative: LEVEL AT FL360 DURING CRUISE AND SOME 40-50 MINS OF FLT; THE INTERMITTENT WARNING HORN FOR CABIN ABOVE 10000 FT WENT OFF. MY FO THOUGHT WE MIGHT HAVE A GEAR HORN; BUT HE NOTICED ME PERFORMING EMER ACTION ITEMS FOR LOSS OF PRESSURE AND DURING WHICH I SHOWED HIM THE CABIN ALT; HE THEN QUICKLY FOLLOWED SUIT. QRH PROCS WERE STARTED; ATC WAS INFORMED THAT WE NEEDED EMER DSCNT FOR A PRESSURIZATION PROB. I'M DOING THE QRH AND TAKING THE PACKS TO HIGH; I SHOWED AND PHYSICALLY TOUCHED MY FO TO LOOK AT MY ACTIONS. QRH TO THE LINE WE NOTED THE CABIN COMING BACK AND BELOW 10000 FT THEN 9000 FT. I SUGGESTED TO THE FO TO STOW SPD BRAKES SO AS NOT TO ALARM PAX AND SHOWED HIM THE CABIN OK. DURING THE CONTINUED DSCNT; A MASTER CAUTION FOR OVERHEAD WENT OFF. LOOKING UP; WE NOTICED PAX OXYGEN DEPLOYED. PRIOR TO THE MASTER CAUTION AND DURING DSCNT; I WAS RE-DOING MY QRH STEPS AND NOTICED I HAD PUT THE PACKS TO OFF AND NOT HIGH. FINDING THIS PROB; THEY WERE PUT TO THE CORRECT POS AS PER QRH. IT WAS BOTH OUR RECOLLECTIONS THAT WE CAUGHT THE ERROR PRIOR TO PAX OXYGEN MASKS DEPLOYING. WE THEN RE-COMMENCED OUR FULL EMER DSCNT. ATC DID NOT MOVE TFC FOR US; WE WERE GIVEN UP TO 3 HDG CHANGES; AND SMALL ALT CHANGES UNTIL AREA WAS CLR FOR OUR DSCNT. AROUND 12000-10000 FT; MASSIVE CABIN PRESSURE BUMPS AND EARS POPPING; I NOTICED CABIN AT 24 AND DIFFERENTIAL AT 8.65. I STATED TO THE FO 'WE GOT TO GET THIS ACFT LOWER' AND I TOOK MY ATTN TO ACFT AND QRH. MY FO TOOK THIS LITERALLY AND GOT US 6000 FT THEN 5000 FT APPROVED BY ATC. LEVEL AT 5000 FT; EARS AND PRESSURE NORMAL. WE DECIDED MEA; MOCA ALL OK; ACFT WORKING GOOD; LET'S STAY HERE (DON'T CHANGE WHAT WORKS). PROBS GETTING COMPANY AND MAINT; THEN SOLVED; RETURNED TO ZZZ. AFTER LNDG; ACFT STILL PRESSURIZED FOR SAFETY; WENT TO AN AREA WELL CLR OF TERMINAL. BRIEFED FLT ATTENDANT NOT TO TOUCH DOORS TO KEEP ALL SAFE; PARKED; USED MAINT AND DEPRESSURIZED ACFT. ALL OK. TOOK PAX TO GATE.

Data retrieved from NASA's ASRS site as of May 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.

B737-300 suffers pressurization failure at FL360. Performance of emergency descent procedure is flawed when captain turns packs off vice high as directed by QRH. Subsequently over pressurize the cabin and; after landing; must park and bleed off pressure prior to opening doors.