A B737-300 cabin altitude warning horn sounded at 10000 ft. The crew began an emergency descent and ...

Narrative:

In cruise at FL350 cabin pressure warning horn sounded. First officer and I both confirmed that cabin altitude was just above 10000 ft and donned oxygen masks. We established communications and first officer ran loss of cabin pressure checklist. As he was working the problem; I notified ATC of our situation. As cabin pressure climbed to 12000 ft; we both agreed that a descent was in order. Coordinated with ATC for a rapid descent. ATC cleared us to descend to 14000 ft. Set throttles idle; speed brakes; speed 300 KT descent. We did not use the emergency descent procedure at this time because the first officer was still trying to control the cabin. At 20000 ft we had the cabin under control and cabin altitude decreasing using manual pressurization. We then reviewed the emergency descent QRH to ensure northing was left out. The time from cabin warning to repressurization was approximately 5 mins. Prior to reaching 20000 ft the purser called informing us an elderly gentleman was having trouble breathing and the doctor was with him. As I was talking to dispatch and maintenance; purser called again and said the doctor felt the gentleman should get to medical help as soon as possible. We declared a medical emergency and made an uneventful landing.supplemental information from acn 707016: flight attendant then called and said that since the passenger had a history of congestive heart failure and an irregular heartbeat; the doctor recommended that we divert to ZZZ1 to get the man further medical attention. Captain coordinated with center and we diverted into ZZZ1 with no further difficulties.callback conversation with reporter 707016 revealed the following information: reporter stated that his and the captain's initial response to the horn's sounding was 'what the heck is that;' but within about 5-10 seconds; they recognized the cabin altitude and had started a descent. He believed the reason they recognized the horn so quickly was that every ground school and simulator period the instructors are reminding the pilots of the horn's only cause in flight.

Original NASA ASRS Text

Title: A B737-300 CABIN ALT WARNING HORN SOUNDED AT 10000 FT. THE CREW BEGAN AN EMER DSCNT AND REGAINED PRESSURIZATION CTL AT FL200 WITH A PAX NEEDING MEDICAL ATTENTION.

Narrative: IN CRUISE AT FL350 CABIN PRESSURE WARNING HORN SOUNDED. FO AND I BOTH CONFIRMED THAT CABIN ALT WAS JUST ABOVE 10000 FT AND DONNED OXYGEN MASKS. WE ESTABLISHED COMS AND FO RAN LOSS OF CABIN PRESSURE CHKLIST. AS HE WAS WORKING THE PROB; I NOTIFIED ATC OF OUR SITUATION. AS CABIN PRESSURE CLBED TO 12000 FT; WE BOTH AGREED THAT A DSCNT WAS IN ORDER. COORDINATED WITH ATC FOR A RAPID DSCNT. ATC CLRED US TO DSND TO 14000 FT. SET THROTTLES IDLE; SPD BRAKES; SPD 300 KT DSCNT. WE DID NOT USE THE EMER DSCNT PROC AT THIS TIME BECAUSE THE FO WAS STILL TRYING TO CTL THE CABIN. AT 20000 FT WE HAD THE CABIN UNDER CTL AND CABIN ALT DECREASING USING MANUAL PRESSURIZATION. WE THEN REVIEWED THE EMER DSCNT QRH TO ENSURE NORTHING WAS LEFT OUT. THE TIME FROM CABIN WARNING TO REPRESSURIZATION WAS APPROX 5 MINS. PRIOR TO REACHING 20000 FT THE PURSER CALLED INFORMING US AN ELDERLY GENTLEMAN WAS HAVING TROUBLE BREATHING AND THE DOCTOR WAS WITH HIM. AS I WAS TALKING TO DISPATCH AND MAINT; PURSER CALLED AGAIN AND SAID THE DOCTOR FELT THE GENTLEMAN SHOULD GET TO MEDICAL HELP AS SOON AS POSSIBLE. WE DECLARED A MEDICAL EMER AND MADE AN UNEVENTFUL LNDG.SUPPLEMENTAL INFO FROM ACN 707016: FLT ATTENDANT THEN CALLED AND SAID THAT SINCE THE PAX HAD A HISTORY OF CONGESTIVE HEART FAILURE AND AN IRREGULAR HEARTBEAT; THE DOCTOR RECOMMENDED THAT WE DIVERT TO ZZZ1 TO GET THE MAN FURTHER MEDICAL ATTENTION. CAPT COORDINATED WITH CTR AND WE DIVERTED INTO ZZZ1 WITH NO FURTHER DIFFICULTIES.CALLBACK CONVERSATION WITH RPTR 707016 REVEALED THE FOLLOWING INFO: RPTR STATED THAT HIS AND THE CAPT'S INITIAL RESPONSE TO THE HORN'S SOUNDING WAS 'WHAT THE HECK IS THAT;' BUT WITHIN ABOUT 5-10 SECONDS; THEY RECOGNIZED THE CABIN ALT AND HAD STARTED A DSCNT. HE BELIEVED THE REASON THEY RECOGNIZED THE HORN SO QUICKLY WAS THAT EVERY GND SCHOOL AND SIMULATOR PERIOD THE INSTRUCTORS ARE REMINDING THE PLTS OF THE HORN'S ONLY CAUSE IN FLT.

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.

Attributes
ACN	707012
Time
Date	200608
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : zzz1.airport
State Reference	US
Altitude	msl single value : 35000
Environment
Flight Conditions	IMC
Aircraft 1
Controlling Facilities	artcc : zzz.artcc
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
ASRS Report	707012
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
ASRS Report	707016
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 : declared emergency flight crew : exited adverse environment
Consequence	other Other
Supplementary
Problem Areas	Aircraft Passenger Human Performance
Primary Problem	Aircraft

A B737-300 cabin altitude warning horn sounded at 10000 ft. The crew began an emergency descent and regained pressurization control at FL200 with a passenger needing medical attention.