A C550 lost cabin pressure and executed an emergency descent.

Attributes
ACN	794414
Time
Date	200807
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl single value : 41000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zzz.artcc
Operator	common carrier : air taxi
Make Model Name	Citation II S2/Bravo
Operating Under FAR Part	Part 135
Flight Phase	cruise : level ground : maintenance
Flight Plan	IFR
Person 1
Affiliation	company : air taxi
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : cfi pilot : atp pilot : multi engine pilot : instrument
Experience	flight time last 90 days : 90 flight time total : 7500 flight time type : 200
ASRS Report	794414
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude
Independent Detector	other flight crewa
Resolutory Action	flight crew : exited adverse environment
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

We were at FL410 when the emergency pressurization automatically activated. The cabin altitude was rising rapidly so I; the PIC and PF; initiated a descent and told the PNF to coordinate a descent with ATC. The center controller coordinated a descent to FL230 and then later to FL140. I am filing this report because we might have had an altitude violation prior to coordination of a new altitude. The reason for the delay is because of the loud noise in the cockpit due to the emergency pressurization airflow and inadequate oxygen mask mikes which caused poor communication with ATC. I believe that new oxygen mask mikes would correct the situation.

Original NASA ASRS Text

Title: A C550 LOST CABIN PRESSURE AND EXECUTED AN EMERGENCY DESCENT.

Narrative: WE WERE AT FL410 WHEN THE EMER PRESSURIZATION AUTOMATICALLY ACTIVATED. THE CABIN ALT WAS RISING RAPIDLY SO I; THE PIC AND PF; INITIATED A DSCNT AND TOLD THE PNF TO COORDINATE A DSCNT WITH ATC. THE CTR CTLR COORDINATED A DSCNT TO FL230 AND THEN LATER TO FL140. I AM FILING THIS RPT BECAUSE WE MIGHT HAVE HAD AN ALT VIOLATION PRIOR TO COORD OF A NEW ALT. THE REASON FOR THE DELAY IS BECAUSE OF THE LOUD NOISE IN THE COCKPIT DUE TO THE EMER PRESSURIZATION AIRFLOW AND INADEQUATE OXYGEN MASK MIKES WHICH CAUSED POOR COM WITH ATC. I BELIEVE THAT NEW OXYGEN MASK MIKES WOULD CORRECT THE SIT.

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.