An air carrier MD82 flight crew made a rapid descent when the cabin altitude started to increase.

Attributes
ACN	433230
Time
Date	199904
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : jfk.airport
State Reference	NY
Altitude	msl single value : 33000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zny.artcc
Operator	common carrier : air carrier
Make Model Name	MD-82
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	433230
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial pilot : multi engine
ASRS Report	433231
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : exited adverse environment
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

In new york airspace at FL330, experienced cabin climb of 800 FPM with corresponding loss of differential pressure both pack pressures indicated normal. First officer executed rapid descent to 10000 ft where cabin pressure returned to normal. Continued to bos. Callback conversation with reporter revealed the following information: the captain said that they had reviewed the MD82's maintenance log and noted a previous write-up about low air flow from the right pack. Initially, the pack worked normally, but just as they were preparing for descent they noted that the air conditioning and pressurization flow light was illuminated and the cabin altitude gauge was indicating an increase in altitude of 800 FPM. The flight crew requested a lower altitude and told the controller that they were having a pressurization problem and that they needed to get to 10000 ft when he could accommodate them. The captain said that at no time did he feel that the cabin altitude was going to increase to the point that the warning system were going to sound or the masks deploy. After arriving at 10000 ft, the rest of the flight was normal and maintenance personnel were waiting when they parked at the gate.

Original NASA ASRS Text

Title: AN ACR MD82 FLC MADE A RAPID DSCNT WHEN THE CABIN ALT STARTED TO INCREASE.

Narrative: IN NEW YORK AIRSPACE AT FL330, EXPERIENCED CABIN CLB OF 800 FPM WITH CORRESPONDING LOSS OF DIFFERENTIAL PRESSURE BOTH PACK PRESSURES INDICATED NORMAL. FO EXECUTED RAPID DSCNT TO 10000 FT WHERE CABIN PRESSURE RETURNED TO NORMAL. CONTINUED TO BOS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE CAPT SAID THAT THEY HAD REVIEWED THE MD82'S MAINT LOG AND NOTED A PREVIOUS WRITE-UP ABOUT LOW AIR FLOW FROM THE R PACK. INITIALLY, THE PACK WORKED NORMALLY, BUT JUST AS THEY WERE PREPARING FOR DSCNT THEY NOTED THAT THE AIR CONDITIONING AND PRESSURIZATION FLOW LIGHT WAS ILLUMINATED AND THE CABIN ALT GAUGE WAS INDICATING AN INCREASE IN ALT OF 800 FPM. THE FLC REQUESTED A LOWER ALT AND TOLD THE CTLR THAT THEY WERE HAVING A PRESSURIZATION PROB AND THAT THEY NEEDED TO GET TO 10000 FT WHEN HE COULD ACCOMMODATE THEM. THE CAPT SAID THAT AT NO TIME DID HE FEEL THAT THE CABIN ALT WAS GOING TO INCREASE TO THE POINT THAT THE WARNING SYS WERE GOING TO SOUND OR THE MASKS DEPLOY. AFTER ARRIVING AT 10000 FT, THE REST OF THE FLT WAS NORMAL AND MAINT PERSONNEL WERE WAITING WHEN THEY PARKED AT THE GATE.

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.