Large transport makes emergency descent when cabin pressurization problem develops.

Attributes
ACN	255944
Time
Date	199310
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : cmk
State Reference	NY
Altitude	msl bound lower : 10000 msl bound upper : 24000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zbw tracon : lub
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : instrument pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 150 flight time total : 20000 flight time type : 9000
ASRS Report	255944
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 150 flight time total : 6000 flight time type : 4000
ASRS Report	255941
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : declared emergency other
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

Level at FL240 cabin was losing pressure. Requested descent. Cleared to 10000 ft. Passing 17800 ATC requested we stop at 18000 then requested we climb back to FL220. A climb at this time would have been unsafe due to existing pressurization malfunction. Therefore, I declared an emergency and requested continued descent to 10000 ft. Request was approved and an uneventful landing was made at ewr. During the event, vectors were provided to avoid traffic and conflicting traffic was monitored on TCASII. TCASII issued TA but no RA. I believe the need to declare an emergency could have been avoided if I had advised ATC that any delay in descent to 10000 ft could adversely affect flight safety and might result in an emergency.

Original NASA ASRS Text

Title: LGT MAKES EMER DSCNT WHEN CABIN PRESSURIZATION PROB DEVELOPS.

Narrative: LEVEL AT FL240 CABIN WAS LOSING PRESSURE. REQUESTED DSCNT. CLRED TO 10000 FT. PASSING 17800 ATC REQUESTED WE STOP AT 18000 THEN REQUESTED WE CLB BACK TO FL220. A CLB AT THIS TIME WOULD HAVE BEEN UNSAFE DUE TO EXISTING PRESSURIZATION MALFUNCTION. THEREFORE, I DECLARED AN EMER AND REQUESTED CONTINUED DSCNT TO 10000 FT. REQUEST WAS APPROVED AND AN UNEVENTFUL LNDG WAS MADE AT EWR. DURING THE EVENT, VECTORS WERE PROVIDED TO AVOID TFC AND CONFLICTING TFC WAS MONITORED ON TCASII. TCASII ISSUED TA BUT NO RA. I BELIEVE THE NEED TO DECLARE AN EMER COULD HAVE BEEN AVOIDED IF I HAD ADVISED ATC THAT ANY DELAY IN DSCNT TO 10000 FT COULD ADVERSELY AFFECT FLT SAFETY AND MIGHT RESULT IN AN 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.