<< >> NASA ASRS Report 720800, December 2006

A B737-700 experienced cabin altitude warning horn; probably because the first officer failed to turn the right pack on.

Attributes
ACN	720800
Time
Date	200612
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : zzz.artcc
State Reference	US
Altitude	msl single value : 30000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zzz.artcc
Operator	common carrier : air carrier
Make Model Name	B737-600
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 207 flight time type : 15000
ASRS Report	720860
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Experience	flight time last 90 days : 180 flight time type : 3900
ASRS Report	720799
Events
Anomaly	aircraft equipment problem : critical non adherence : published procedure non adherence : company policies
Independent Detector	aircraft equipment other aircraft equipment : cabin altitude warning other flight crewa other flight crewb
Resolutory Action	other
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

On climb out at FL300; altitude warning horn went off. This aircraft had experienced the same problem the day before. I was the PF and the captain. I declared an emergency and requested a return. I possibly made 2 mistakes: first I started a descent as I was getting permission from ATC. Their response was quick and we only descended a few hundred ft from our climb before receiving clearance. I also may have missed the right pack switch in off on the climb check and if so; the cabin altitude would have been abnormal. We were unsure of this switch position as the first officer put the packs in high and thought the right pack may have been off. This event; if the pack switch was off; could have been prevented by slowing down on the climb check. Also; I overacted and started a descent 1 min too early.

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Original NASA ASRS Text

Title: A B737-700 EXPERIENCED CABIN ALT WARNING HORN; PROBABLY BECAUSE THE FO FAILED TO TURN THE R PACK ON.

Narrative: ON CLBOUT AT FL300; ALT WARNING HORN WENT OFF. THIS ACFT HAD EXPERIENCED THE SAME PROB THE DAY BEFORE. I WAS THE PF AND THE CAPT. I DECLARED AN EMER AND REQUESTED A RETURN. I POSSIBLY MADE 2 MISTAKES: FIRST I STARTED A DSCNT AS I WAS GETTING PERMISSION FROM ATC. THEIR RESPONSE WAS QUICK AND WE ONLY DSNDED A FEW HUNDRED FT FROM OUR CLB BEFORE RECEIVING CLRNC. I ALSO MAY HAVE MISSED THE R PACK SWITCH IN OFF ON THE CLB CHK AND IF SO; THE CABIN ALT WOULD HAVE BEEN ABNORMAL. WE WERE UNSURE OF THIS SWITCH POS AS THE FO PUT THE PACKS IN HIGH AND THOUGHT THE R PACK MAY HAVE BEEN OFF. THIS EVENT; IF THE PACK SWITCH WAS OFF; COULD HAVE BEEN PREVENTED BY SLOWING DOWN ON THE CLB CHK. ALSO; I OVERACTED AND STARTED A DSCNT 1 MIN TOO EARLY.

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.