Narrative:

80 mi northwest of kansas city missouri we lost cabin pressure, followed company SOP's -- declared an emergency -- made a rapid descent and diverted to mci -- no injuries reported. We were at 35000 ft when we lost pressurization. Callback conversation with reporter revealed the following: pressurization loss was due to automatic-shutdown of air conditioning packs. Company engineering said that there had been similar cases in this aircraft due to the water separator icing which causes a lack of airflow across the heat exchanger. Also, the aircraft was in icing conditions and the wing anti-ice was in use, which could have contributed to the low airflow. This aircraft air conditioning/pressurization ducting must be maintained constantly or they develop air leaks which again precipitate this type of incident. Reporter captain's first notice of pressure. Problem was feeling it in his ears and when looking at the rate gauge, it was climbing the cabin at 2500 FPM. Both pilots donned 02 masks with no difficulty. The cabin did go above 10000 ft because the warning light came on, but the passenger 02 masks didn't deploy nor were they deployed manually. Flight crew made an emergency descent, declared emergency and diverted to kansas city. When aircraft descended through 16000 ft the packs came back on and the aircraft re-pressurized. Warmer air either melted the ice in the water separator or turning off the wing anti-ice provided improved flow of bleed air. On the ground maintenance changed the pressure regulator valve and flow controller valve and the reporter ferried the aircraft back to the home base. Before takeoff a deadheading pilot idented himself to the captain and volunteered his help if needed so during the emergency the flight crew had him come to the cockpit and he provided a lot of aid in the emergency.

Related reports:

Google
 

Original NASA ASRS Text

Title: ACFT EQUIP PROB -- PRESSURIZATION EMER DIVERSION.

Narrative: 80 MI NW OF KANSAS CITY MISSOURI WE LOST CABIN PRESSURE, FOLLOWED COMPANY SOP'S -- DECLARED AN EMER -- MADE A RAPID DSCNT AND DIVERTED TO MCI -- NO INJURIES RPTED. WE WERE AT 35000 FT WHEN WE LOST PRESSURIZATION. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: PRESSURIZATION LOSS WAS DUE TO AUTO-SHUTDOWN OF AIR CONDITIONING PACKS. COMPANY ENGINEERING SAID THAT THERE HAD BEEN SIMILAR CASES IN THIS ACFT DUE TO THE WATER SEPARATOR ICING WHICH CAUSES A LACK OF AIRFLOW ACROSS THE HEAT EXCHANGER. ALSO, THE ACFT WAS IN ICING CONDITIONS AND THE WING ANTI-ICE WAS IN USE, WHICH COULD HAVE CONTRIBUTED TO THE LOW AIRFLOW. THIS ACFT AIR CONDITIONING/PRESSURIZATION DUCTING MUST BE MAINTAINED CONSTANTLY OR THEY DEVELOP AIR LEAKS WHICH AGAIN PRECIPITATE THIS TYPE OF INCIDENT. RPTR CAPT'S FIRST NOTICE OF PRESSURE. PROB WAS FEELING IT IN HIS EARS AND WHEN LOOKING AT THE RATE GAUGE, IT WAS CLBING THE CABIN AT 2500 FPM. BOTH PLTS DONNED 02 MASKS WITH NO DIFFICULTY. THE CABIN DID GO ABOVE 10000 FT BECAUSE THE WARNING LIGHT CAME ON, BUT THE PAX 02 MASKS DIDN'T DEPLOY NOR WERE THEY DEPLOYED MANUALLY. FLC MADE AN EMER DSCNT, DECLARED EMER AND DIVERTED TO KANSAS CITY. WHEN ACFT DSNDED THROUGH 16000 FT THE PACKS CAME BACK ON AND THE ACFT RE-PRESSURIZED. WARMER AIR EITHER MELTED THE ICE IN THE WATER SEPARATOR OR TURNING OFF THE WING ANTI-ICE PROVIDED IMPROVED FLOW OF BLEED AIR. ON THE GND MAINT CHANGED THE PRESSURE REGULATOR VALVE AND FLOW CTLR VALVE AND THE RPTR FERRIED THE ACFT BACK TO THE HOME BASE. BEFORE TKOF A DEADHEADING PLT IDENTED HIMSELF TO THE CAPT AND VOLUNTEERED HIS HELP IF NEEDED SO DURING THE EMER THE FLC HAD HIM COME TO THE COCKPIT AND HE PROVIDED A LOT OF AID IN THE EMER.

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.