Gulfstream IV / G350 / G450
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical
Flight Crew Diverted; General Declared Emergency
Aircraft
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.
[No additional information]
A GLF4 flight crew initiated an emergency descent; declared an emergency and diverted to a nearby airport following a loss of cabin pressurization.