MD80 crew had rapid cabin depressurization in ZLC class a airspace.

Attributes
ACN	477057
Time
Date	200006
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : bil.airport
State Reference	MT
Altitude	msl bound lower : 14000 msl bound upper : 31000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zlc.artcc
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Route In Use	enroute : on vectors enroute airway : ns.airway
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial pilot : atp pilot : multi engine
Experience	controller military : 4 controller non radar : 9 controller radar : 8 flight time last 90 days : 250 flight time total : 3300 flight time type : 500
ASRS Report	477057
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : instrument pilot : multi engine pilot : atp pilot : commercial
Experience	flight time last 90 days : 225 flight time total : 13000 flight time type : 1300
ASRS Report	477056
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : landed in emergency condition flight crew : diverted to another airport flight crew : declared emergency
Consequence	other other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

At FL310, 50 mi from billings, mt, experienced rapid decompression. Captain was flying. He executed a rapid descent after both of us donned oxygen masks. I declared emergency and manually dropped passenger oxygen masks. Descended to MSA. All checklists were run at that time, and evaluated medical condition of passenger. Medical condition of passenger was ok and proceeded to den at 10000 ft. Had medical personnel meet us at airport 'just in case.' no passenger complained of any effects. Supplemental information from acn 477056: checked cabin, found masks not yet deployed (cabin pressure was approximately 12000 ft at the time). Aircraft was at approximately FL270 in 3500-4000 FPM descent idle, boards just below v-limit needle. Had first officer deploy masks to 'beat the system' -- check that masks did deploy and made announcement to cabin to don oxygen masks. At 10000 ft, aircraft and cabin altitude cleared passenger off oxygen. Had flight attendant check (speak to) each passenger to check their status -- found all on board ok. Diverted to den for normal approach and landing.

Original NASA ASRS Text

Title: MD80 CREW HAD RAPID CABIN DEPRESSURIZATION IN ZLC CLASS A AIRSPACE.

Narrative: AT FL310, 50 MI FROM BILLINGS, MT, EXPERIENCED RAPID DECOMPRESSION. CAPT WAS FLYING. HE EXECUTED A RAPID DSCNT AFTER BOTH OF US DONNED OXYGEN MASKS. I DECLARED EMER AND MANUALLY DROPPED PAX OXYGEN MASKS. DSNDED TO MSA. ALL CHKLISTS WERE RUN AT THAT TIME, AND EVALUATED MEDICAL CONDITION OF PAX. MEDICAL CONDITION OF PAX WAS OK AND PROCEEDED TO DEN AT 10000 FT. HAD MEDICAL PERSONNEL MEET US AT ARPT 'JUST IN CASE.' NO PAX COMPLAINED OF ANY EFFECTS. SUPPLEMENTAL INFO FROM ACN 477056: CHKED CABIN, FOUND MASKS NOT YET DEPLOYED (CABIN PRESSURE WAS APPROX 12000 FT AT THE TIME). ACFT WAS AT APPROX FL270 IN 3500-4000 FPM DSCNT IDLE, BOARDS JUST BELOW V-LIMIT NEEDLE. HAD FO DEPLOY MASKS TO 'BEAT THE SYS' -- CHK THAT MASKS DID DEPLOY AND MADE ANNOUNCEMENT TO CABIN TO DON OXYGEN MASKS. AT 10000 FT, ACFT AND CABIN ALT CLRED PAX OFF OXYGEN. HAD FLT ATTENDANT CHK (SPEAK TO) EACH PAX TO CHK THEIR STATUS -- FOUND ALL ON BOARD OK. DIVERTED TO DEN FOR NORMAL APCH AND LNDG.

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.