MD80 flight crew reports flow light at FL330. Emergency is declared after QRH provides no relief.

Attributes
ACN	792838
Time
Date	200806
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl single value : 33000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zzz.artcc tower : iah.tower
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
ASRS Report	792838
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
ASRS Report	792653
Events
Anomaly	aircraft equipment problem : critical inflight encounter : weather
Independent Detector	aircraft equipment other aircraft equipment : flow light other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : declared emergency
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

Cruising at FL330 in visible moisture; with engine and airfoil anti-ice on. Pressurization flow caution light illuminated. Cabin was climbing 400-500 FPM. Accomplished QRH procedure; cabin continued climbing. We asked for lower altitude and were cleared to FL290; then FL270. Cabin continued to climb; now in the 1500 FPM range. We asked for lower and were cleared to FL200. Cabin altitude warning illuminated at 10000 ft cabin altitude. We declared an emergency; told center that we were descending to 10000 ft; accomplished the QRH items -- no change. Cabin continued to climb until below 14000 ft MSL; then began to repressurize. Level at 10000 ft we returned to automatic pressurization and system operation appeared to be normal the rest of the way to ZZZ.

Original NASA ASRS Text

Title: MD80 FLT CREW REPORTS FLOW LIGHT AT FL330. EMERGENCY IS DECLARED AFTER QRH PROVIDES NO RELIEF.

Narrative: CRUISING AT FL330 IN VISIBLE MOISTURE; WITH ENG AND AIRFOIL ANTI-ICE ON. PRESSURIZATION FLOW CAUTION LIGHT ILLUMINATED. CABIN WAS CLBING 400-500 FPM. ACCOMPLISHED QRH PROC; CABIN CONTINUED CLBING. WE ASKED FOR LOWER ALT AND WERE CLRED TO FL290; THEN FL270. CABIN CONTINUED TO CLB; NOW IN THE 1500 FPM RANGE. WE ASKED FOR LOWER AND WERE CLRED TO FL200. CABIN ALT WARNING ILLUMINATED AT 10000 FT CABIN ALT. WE DECLARED AN EMER; TOLD CTR THAT WE WERE DSNDING TO 10000 FT; ACCOMPLISHED THE QRH ITEMS -- NO CHANGE. CABIN CONTINUED TO CLB UNTIL BELOW 14000 FT MSL; THEN BEGAN TO REPRESSURIZE. LEVEL AT 10000 FT WE RETURNED TO AUTO PRESSURIZATION AND SYS OP APPEARED TO BE NORMAL THE REST OF THE WAY TO ZZZ.

Data retrieved from NASA's ASRS site as of May 2009 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.