EX900 FLT CREW LOSES CABIN PRESSURE AT FL430; EMER DECLARED; EMER DSCNT EXECUTED.

Narrative

SLOW LOSS OF CABIN PRESSURE AFTER LEVELING AT FL430. ROUTINE TKOF AND CLB TO ALT. INITIALLY FL400. DUE TO LIGHT CHOP; WE REQUESTED A CLB TO FL430. AFTER LEVELING; WE NOTICED A CABIN RATE OF CLB AT 600 FPM AND PASSING 6000 FT CABIN ALT. WE REQUESTED A DSCNT TO FL380 AND TRIED SEVERAL OTHER MODES; INCLUDING MANUAL; TO STOP THE CLB BUT NOTHING WORKED. CTR GAVE US FL290 BUT WE HAD TO DECLARE AN EMER TO EXPEDITE THE DSCNT BEFORE THE CABIN EXCEEDED 10000 FT. WE DSNDED VIA EMER DSCNT CHKLIST TO 10000 FT MSL AND THEN TO 8000 FT. CABIN ALT REACHED 11000 FT. MASKS DEPLOYED FOR PAX; BUT WENT BACK TO 8000 FT AND STABILIZED. NO OTHER INCIDENTS OCCURRED. NO PAX PROBS WERE EXPERIENCED. FULL TIME FLT ATTENDANT WAS PART OF CREW AND WAS ESSENTIAL IN HANDLING CABIN. GREAT ASSET FOR CALMING PAX CONCERNS AND COVERING SAFETY ITEMS. IT'S COMPANY POLICY TO HAVE THEM ON BOARD FOR ALL FLTS. STILL AWAITING RESULTS FROM MAINT INSPECTION AND TROUBLESHOOTING. CABIN PRESSURE REMAINED AT 8.5 BUT WE COULD NEVER GET CTL IN ANY MODE TO DRIVE OUTFLOW VALVES CLOSED AND DRIVE CABIN ALT DOWN. CPR AVIATION CONSTANTLY FIGHTS TO JUSTIFY FLT ATTENDANTS BUT THIS CASE WILL CERTAINLY HELP OUR CAUSE -- HER EFFORTS AND COORD ALLOWED US TO CONCENTRATE ON GETTING DOWN QUICKLY AND NOT ALLOWING FEAR OR DOUBT TO ENTER THE PAX THOUGHTS. OVERALL; I THINK IT WAS HANDLED WELL BUT WE WILL REVIEW ENTIRE INCIDENT AND GET PAX FEEDBACK WITHIN THE NEXT BUSINESS WK.