Loss of cabin pressure control causes flight crew to declare an emergency.

Attributes
ACN	174830
Time
Date	199104
Day	Sat
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : bgm
State Reference	NY
Altitude	msl bound lower : 8000 msl bound upper : 18000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zny
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 120 flight time total : 9000 flight time type : 100
ASRS Report	174830
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : declared emergency flight crew : exited adverse environment
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

While level at FL180 and cabin altitude of 850', the cabin altitude began to climb at a rate of 2000 FPM (pegged). The first officer attempted to regain control of the rate by use of the pressurization rate knob and cabin altitude selector knob on control panel, with no effect. The bleed system valves and pressure (45 psi) gave normal indications throughout the whole flight. When the cabin reached 3000', I requested an immediate descent to 10000' MSL and told the controller was a had a pressurization problem. He gave us 10000' immediately and asked if he could be of further assistance. I commenced a smooth expedited descent to 10000', and by the time I leveled at 10000', the cabin altitude had stabilized at about 5500' and the rate at 0. Cabin rate then began to go from full rate up to full rate down, so I requested and was given 8000' for cruise in case we lost pressurization completely. Later, after the first officer was able to get the cabin altitude back to syr plus 200' for landing, we returned to 10000' to complete flight to syr. Flight continued and landed uneventfully at syr, although the cabin pressure rate was erratic, climbing and descending 500-1000 FPM. Spoke with our maintenance the following day. They replaced the controller for the pressurization and found a pressure control line crimped that wasn't supposed to be. Crew was excellent and the controllers were very helpful and professional, as always, when an immediate request was made with a problem.

Original NASA ASRS Text

Title: LOSS OF CABIN PRESSURE CTL CAUSES FLT CREW TO DECLARE AN EMERGENCY.

Narrative: WHILE LEVEL AT FL180 AND CABIN ALT OF 850', THE CABIN ALT BEGAN TO CLB AT A RATE OF 2000 FPM (PEGGED). THE F/O ATTEMPTED TO REGAIN CTL OF THE RATE BY USE OF THE PRESSURIZATION RATE KNOB AND CABIN ALT SELECTOR KNOB ON CTL PANEL, WITH NO EFFECT. THE BLEED SYS VALVES AND PRESSURE (45 PSI) GAVE NORMAL INDICATIONS THROUGHOUT THE WHOLE FLT. WHEN THE CABIN REACHED 3000', I REQUESTED AN IMMEDIATE DSNT TO 10000' MSL AND TOLD THE CTLR WAS A HAD A PRESSURIZATION PROB. HE GAVE US 10000' IMMEDIATELY AND ASKED IF HE COULD BE OF FURTHER ASSISTANCE. I COMMENCED A SMOOTH EXPEDITED DSNT TO 10000', AND BY THE TIME I LEVELED AT 10000', THE CABIN ALT HAD STABILIZED AT ABOUT 5500' AND THE RATE AT 0. CABIN RATE THEN BEGAN TO GO FROM FULL RATE UP TO FULL RATE DOWN, SO I REQUESTED AND WAS GIVEN 8000' FOR CRUISE IN CASE WE LOST PRESSURIZATION COMPLETELY. LATER, AFTER THE F/O WAS ABLE TO GET THE CABIN ALT BACK TO SYR PLUS 200' FOR LNDG, WE RETURNED TO 10000' TO COMPLETE FLT TO SYR. FLT CONTINUED AND LANDED UNEVENTFULLY AT SYR, ALTHOUGH THE CABIN PRESSURE RATE WAS ERRATIC, CLBING AND DSNDING 500-1000 FPM. SPOKE WITH OUR MAINT THE FOLLOWING DAY. THEY REPLACED THE CTLR FOR THE PRESSURIZATION AND FOUND A PRESSURE CTL LINE CRIMPED THAT WASN'T SUPPOSED TO BE. CREW WAS EXCELLENT AND THE CTLRS WERE VERY HELPFUL AND PROFESSIONAL, AS ALWAYS, WHEN AN IMMEDIATE REQUEST WAS MADE WITH A PROB.

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.