Pressurization problem. Md-80 with anti-ice system on.

Attributes
ACN	301584
Time
Date	199504
Day	Mon
Place
Locale Reference	atc facility : sgf
State Reference	MO
Altitude	msl bound lower : 23000 msl bound upper : 23000
Environment
Flight Conditions	IMC
Aircraft 1
Controlling Facilities	artcc : zkc
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	cruise other descent other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	cruise other descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	301584
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
ASRS Report	301585
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem other
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

In the vicinity of sgf VOR about XA00Z, the cabin flow light came on and after checking the cabin vsi, we could see the cabin rising at about 300 FPM. The airconditioning pack flow gauges were at or near '0' psi. Running the QRH procedure for flow at or near '0' psi we were able to initially regain control of the cabin, only to have it start to climb again within a min or so. We requested a lower altitude and descended to FL230 in order to keep the cabin under control. I did not panic and declare an emergency since this same problem has happened to me twice before -- the most recent in jan/95, and I knew that we could gain control of the cabin by getting out of the icing. However, ZKC, after the md-80 behind us had to do the same thing we did, got rather angry and said, 'I don't know what is going on with you guys today, but you are the 6TH md-80 - - all from your airline -- that have had to descend to get control of your pressurization. We at ATC have to declare an emergency for each of you, it really makes our job difficult having to clear out all of this airspace. So, you can just stay out of the higher altitudes for now.' I don't blame them for this at all. I sent you the same in jan of this yr regarding my feeling that the ram air scoop is icing up. Every time I write up this problem or see it in the logbook, the signoff is everything checks out normal. It sounds to me like the anti-icing system can't keep the ram air scoop clear, causing the packs to overheat and shut down, causing the cabin to climb 300-500 FPM. I personally am getting tired of dealing with this md-80 anomaly. Callback conversation with reporter revealed the following information: the reporter talked to the airline's fleet technical manager and the problem is apparently increasing. There have been numerous reports recently. The technical manager does not think that the air scoop is the problem since it is continuously deiced when the anti-ice system is on regardless of the selector switch position (wings or tail). The airline is working on this and they have been in contact with the manufacturer.

Original NASA ASRS Text

Title: PRESSURIZATION PROB. MD-80 WITH ANTI-ICE SYS ON.

Narrative: IN THE VICINITY OF SGF VOR ABOUT XA00Z, THE CABIN FLOW LIGHT CAME ON AND AFTER CHKING THE CABIN VSI, WE COULD SEE THE CABIN RISING AT ABOUT 300 FPM. THE AIRCONDITIONING PACK FLOW GAUGES WERE AT OR NEAR '0' PSI. RUNNING THE QRH PROC FOR FLOW AT OR NEAR '0' PSI WE WERE ABLE TO INITIALLY REGAIN CTL OF THE CABIN, ONLY TO HAVE IT START TO CLB AGAIN WITHIN A MIN OR SO. WE REQUESTED A LOWER ALT AND DSNDED TO FL230 IN ORDER TO KEEP THE CABIN UNDER CTL. I DID NOT PANIC AND DECLARE AN EMER SINCE THIS SAME PROB HAS HAPPENED TO ME TWICE BEFORE -- THE MOST RECENT IN JAN/95, AND I KNEW THAT WE COULD GAIN CTL OF THE CABIN BY GETTING OUT OF THE ICING. HOWEVER, ZKC, AFTER THE MD-80 BEHIND US HAD TO DO THE SAME THING WE DID, GOT RATHER ANGRY AND SAID, 'I DON'T KNOW WHAT IS GOING ON WITH YOU GUYS TODAY, BUT YOU ARE THE 6TH MD-80 - - ALL FROM YOUR AIRLINE -- THAT HAVE HAD TO DSND TO GET CTL OF YOUR PRESSURIZATION. WE AT ATC HAVE TO DECLARE AN EMER FOR EACH OF YOU, IT REALLY MAKES OUR JOB DIFFICULT HAVING TO CLR OUT ALL OF THIS AIRSPACE. SO, YOU CAN JUST STAY OUT OF THE HIGHER ALTS FOR NOW.' I DON'T BLAME THEM FOR THIS AT ALL. I SENT YOU THE SAME IN JAN OF THIS YR REGARDING MY FEELING THAT THE RAM AIR SCOOP IS ICING UP. EVERY TIME I WRITE UP THIS PROB OR SEE IT IN THE LOGBOOK, THE SIGNOFF IS EVERYTHING CHKS OUT NORMAL. IT SOUNDS TO ME LIKE THE ANTI-ICING SYS CAN'T KEEP THE RAM AIR SCOOP CLR, CAUSING THE PACKS TO OVERHEAT AND SHUT DOWN, CAUSING THE CABIN TO CLB 300-500 FPM. I PERSONALLY AM GETTING TIRED OF DEALING WITH THIS MD-80 ANOMALY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR TALKED TO THE AIRLINE'S FLEET TECHNICAL MGR AND THE PROB IS APPARENTLY INCREASING. THERE HAVE BEEN NUMEROUS RPTS RECENTLY. THE TECHNICAL MGR DOES NOT THINK THAT THE AIR SCOOP IS THE PROB SINCE IT IS CONTINUOUSLY DEICED WHEN THE ANTI-ICE SYS IS ON REGARDLESS OF THE SELECTOR SWITCH POS (WINGS OR TAIL). THE AIRLINE IS WORKING ON THIS AND THEY HAVE BEEN IN CONTACT WITH THE MANUFACTURER.

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.