A B737-700 experienced a cabin altitude warning horn and excessive cabin altitude. They declared an ...

Attributes
ACN	786891
Time
Date	200805
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : flw.vortac
State Reference	CA
Altitude	msl single value : 40500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zla.artcc tower : zzz.tower
Operator	common carrier : air carrier
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 216 flight time type : 5000
ASRS Report	786891
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Experience	flight time last 90 days : 218 flight time type : 5000
ASRS Report	786894
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	aircraft equipment other aircraft equipment : cabin alt warning horn other flight crewa other flight crewb
Resolutory Action	flight crew : exited adverse environment flight crew : declared emergency
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

We had just begun a descent out of FL410 when we received a cabin altitude warning horn. We donned the oxygen masks and established communication between us. My first officer declared an emergency. Next we began an emergency descent. I was flying and my first officer ran the checklist. We received a clearance to descend to 10000 ft so we continued to that altitude. After running the checklists we decided to continue to ZZZ; which we felt was the best choice of landing airports considering our altitude and location. The approach and landing were uneventful. The only indication that we had a problem was the intermittent warning horn and the cabin altitude needle. There were no caution lights or other indications of this event. During the descent I noted the cabin altitude slightly above 11000 ft. The passenger oxygen masks did not deploy. No injuries were noted among the passenger or crew. Supplemental information from acn 786894: we ran the cabin altitude warning horn checklist as well as the emergency descent checklists. The frequency was congested so I squawked 7700. The controller then called us and asked the nature of our emergency; number of souls on board and amount of fuel we had. I requested a descent to 10000 ft and we were given that limit.

Original NASA ASRS Text

Title: A B737-700 EXPERIENCED A CABIN ALT WARNING HORN AND EXCESSIVE CABIN ALT. THEY DECLARED AN EMERGENCY AND EXECUTED AN EMERGENCY DESCENT.

Narrative: WE HAD JUST BEGUN A DSCNT OUT OF FL410 WHEN WE RECEIVED A CABIN ALT WARNING HORN. WE DONNED THE OXYGEN MASKS AND ESTABLISHED COM BTWN US. MY FO DECLARED AN EMER. NEXT WE BEGAN AN EMER DSCNT. I WAS FLYING AND MY FO RAN THE CHKLIST. WE RECEIVED A CLRNC TO DSND TO 10000 FT SO WE CONTINUED TO THAT ALT. AFTER RUNNING THE CHKLISTS WE DECIDED TO CONTINUE TO ZZZ; WHICH WE FELT WAS THE BEST CHOICE OF LNDG ARPTS CONSIDERING OUR ALT AND LOCATION. THE APCH AND LNDG WERE UNEVENTFUL. THE ONLY INDICATION THAT WE HAD A PROB WAS THE INTERMITTENT WARNING HORN AND THE CABIN ALT NEEDLE. THERE WERE NO CAUTION LIGHTS OR OTHER INDICATIONS OF THIS EVENT. DURING THE DSCNT I NOTED THE CABIN ALT SLIGHTLY ABOVE 11000 FT. THE PAX OXYGEN MASKS DID NOT DEPLOY. NO INJURIES WERE NOTED AMONG THE PAX OR CREW. SUPPLEMENTAL INFO FROM ACN 786894: WE RAN THE CABIN ALT WARNING HORN CHKLIST AS WELL AS THE EMER DSCNT CHKLISTS. THE FREQ WAS CONGESTED SO I SQUAWKED 7700. THE CTLR THEN CALLED US AND ASKED THE NATURE OF OUR EMER; NUMBER OF SOULS ON BOARD AND AMOUNT OF FUEL WE HAD. I REQUESTED A DSCNT TO 10000 FT AND WE WERE GIVEN THAT LIMIT.

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.

A B737-700 experienced a cabin altitude warning horn and excessive cabin altitude. They declared an emergency and executed an emergency descent.