Captain of air carrier mdt aircraft declared emergency due to a pressurization problem.

Attributes
ACN	219154
Time
Date	199208
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : rbv
State Reference	NJ
Altitude	msl bound lower : 12500 msl bound upper : 12509
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Medium Transport, High Wing, 2 Turboprop Eng
Navigation In Use	Other
Flight Phase	climbout : intermediate altitude
Route In Use	enroute airway : zny
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : cfi
Experience	flight time last 90 days : 180 flight time total : 5000 flight time type : 2000
ASRS Report	219154
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	aircraft : equipment problem dissipated flight crew : declared emergency flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

Approximately 10 mi east of rbv, climbing through 12500, the master caution light and crc came on with the 'excess cabin altitude' on cap. Cabin altitude gauge showed 10500 ft and climbing. Pressure differential was about .5 psi. I requested an immediate descent from ZNY, explaining we had a pressurization problem. The request was denied so I declared an emergency and told ATC we were descending to 10000 ft. Checklist procedures were followed. After selecting pressurization manual mode, system then functioned normally. I then contacted system control and maintenance and told them the situation. After discussing the problem with maintenance they suggested we try automatic mode briefly to see if we still had a problem with that part of the system. I selected automatic mode and the system worked perfectly again. The flight continued to iad.

Original NASA ASRS Text

Title: CAPT OF ACR MDT ACFT DECLARED EMER DUE TO A PRESSURIZATION PROBLEM.

Narrative: APPROX 10 MI E OF RBV, CLBING THROUGH 12500, THE MASTER CAUTION LIGHT AND CRC CAME ON WITH THE 'EXCESS CABIN ALT' ON CAP. CABIN ALT GAUGE SHOWED 10500 FT AND CLBING. PRESSURE DIFFERENTIAL WAS ABOUT .5 PSI. I REQUESTED AN IMMEDIATE DSCNT FROM ZNY, EXPLAINING WE HAD A PRESSURIZATION PROBLEM. THE REQUEST WAS DENIED SO I DECLARED AN EMER AND TOLD ATC WE WERE DSNDING TO 10000 FT. CHKLIST PROCS WERE FOLLOWED. AFTER SELECTING PRESSURIZATION MANUAL MODE, SYS THEN FUNCTIONED NORMALLY. I THEN CONTACTED SYS CTL AND MAINT AND TOLD THEM THE SITUATION. AFTER DISCUSSING THE PROBLEM WITH MAINT THEY SUGGESTED WE TRY AUTO MODE BRIEFLY TO SEE IF WE STILL HAD A PROBLEM WITH THAT PART OF THE SYS. I SELECTED AUTO MODE AND THE SYS WORKED PERFECTLY AGAIN. THE FLT CONTINUED TO IAD.

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.