C650 crew had cabin depressurization in ZLC class a airspace.

Attributes
ACN	476153
Time
Date	200006
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : boi.airport
State Reference	ID
Altitude	msl bound lower : 37000 msl bound upper : 37300
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zlc.artcc tower : mci.tower
Operator	common carrier : charter
Make Model Name	Citation III, VI, VII
Operating Under FAR Part	Part 135
Navigation In Use	other
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : charter
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 140 flight time total : 8700 flight time type : 700
ASRS Report	476153
Person 2
Affiliation	company : charter
Function	flight crew : first officer
Qualification	pilot : commercial pilot : cfi pilot : atp
Experience	controller non radar : 11 controller radar : 11 flight time last 90 days : 158 flight time total : 2960 flight time type : 141
ASRS Report	475580
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	other controllera other flight crewa other flight crewb
Resolutory Action	controller : issued alert controller : issued new clearance controller : provided flight assist flight crew : diverted to another airport flight crew : landed as precaution
Consequence	other
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Flight Crew Human Performance

Narrative:

On an IFR from north bend, or, to chicago midway, the cabin altitude alert light and warning horn caused immediate concern in the cockpit. While donning my oxygen mask, I inadvertently disengaged the autoplt, but re-engaged it as soon as I could. While dealing with what could have been a potential serious emergency, the 300 ft high altitude was initially unnoticed. I heard ATC calling about the atl alert, but was more concerned about the pressurization problem. Descent was requested and approved for FL240 so the alert was ended. I elected to make a precautionary landing at boi to determine the problem with the pressurization system. Supplemental information from acn 475580: aircraft was cruising on autoplt at FL370. A pressurization controller malfunctioned causing a rapid decompression. While reaching for his oxygen mask, the pilot inadvertently disconnected the autoplt causing a +300 ft altitude alert at center. Once the error was discovered, the pilot asked for a descent where a safe landing was made at boi.

Original NASA ASRS Text

Title: C650 CREW HAD CABIN DEPRESSURIZATION IN ZLC CLASS A AIRSPACE.

Narrative: ON AN IFR FROM NORTH BEND, OR, TO CHICAGO MIDWAY, THE CABIN ALT ALERT LIGHT AND WARNING HORN CAUSED IMMEDIATE CONCERN IN THE COCKPIT. WHILE DONNING MY OXYGEN MASK, I INADVERTENTLY DISENGAGED THE AUTOPLT, BUT RE-ENGAGED IT AS SOON AS I COULD. WHILE DEALING WITH WHAT COULD HAVE BEEN A POTENTIAL SERIOUS EMER, THE 300 FT HIGH ALT WAS INITIALLY UNNOTICED. I HEARD ATC CALLING ABOUT THE ATL ALERT, BUT WAS MORE CONCERNED ABOUT THE PRESSURIZATION PROB. DSCNT WAS REQUESTED AND APPROVED FOR FL240 SO THE ALERT WAS ENDED. I ELECTED TO MAKE A PRECAUTIONARY LNDG AT BOI TO DETERMINE THE PROB WITH THE PRESSURIZATION SYS. SUPPLEMENTAL INFO FROM ACN 475580: ACFT WAS CRUISING ON AUTOPLT AT FL370. A PRESSURIZATION CONTROLLER MALFUNCTIONED CAUSING A RAPID DECOMPRESSION. WHILE REACHING FOR HIS OXYGEN MASK, THE PLT INADVERTENTLY DISCONNECTED THE AUTOPLT CAUSING A +300 FT ALT ALERT AT CTR. ONCE THE ERROR WAS DISCOVERED, THE PLT ASKED FOR A DSCNT WHERE A SAFE LNDG WAS MADE AT BOI.

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.