Narrative:

Climbing through FL400 to cruising altitude of FL430 cabin pressurization became erratic. Red cas message illuminated (cabin pressure) cabin altitude was 10;500 and climbing at 1;500 ft a minute. Stopped climb and donned the oxygen masks and turned on the seatbelt and no smoking signs. A quick assessment was done and an emergency descent was initiated. [We] followed the emergency descent checklist with a left turn to clear the airway. Contacted ATC and declared an emergency and requested 10;000 ft altitude. Once level at 10;000 ft checked the aircraft; the flight attendant; and passengers. We then diverted to a suitable airport.

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Original NASA ASRS Text

Title: A GLF4 flight crew initiated an emergency descent; declared an emergency and diverted to a nearby airport following a loss of cabin pressurization.

Narrative: Climbing through FL400 to cruising altitude of FL430 cabin pressurization became erratic. Red CAS message illuminated (cabin pressure) cabin altitude was 10;500 and climbing at 1;500 FT a minute. Stopped climb and donned the oxygen masks and turned on the seatbelt and no smoking signs. A quick assessment was done and an emergency descent was initiated. [We] followed the emergency descent checklist with a left turn to clear the airway. Contacted ATC and declared an emergency and requested 10;000 FT altitude. Once level at 10;000 FT checked the aircraft; the flight attendant; and passengers. We then diverted to a suitable airport.

Data retrieved from NASA's ASRS site as of July 2013 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.