Pressurization problem.

Attributes
ACN	288327
Time
Date	199411
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : hvq
State Reference	WV
Altitude	msl bound lower : 11000 msl bound upper : 29000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : ztl
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise other other
Route In Use	enroute airway : ztl
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : commercial pilot : atp pilot : instrument
Experience	flight time last 90 days : 240 flight time total : 11000 flight time type : 1640
ASRS Report	288327
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 4500 flight time type : 1000
ASRS Report	287952
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude altitude deviation : overshoot non adherence : clearance
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	controller : issued new clearance flight crew : overcame equipment problem flight crew : exited adverse environment flight crew : declared emergency
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

At level off FL290, experienced cabin press light and requested lower altitude. Received clearance to FL270. Initiated checklist to restore cabin pressure. Requested further clearance to 11000 ft. Received clearance. In short order to 11000 ft may have exceeded initial clearance to FL270 prior to receiving clearance to 11000 ft. Did not declare emergency. Autoplt inoperative, copilot was manually controling cabin. PF was hand flying aircraft and communications. Altitude control may have been less than desired or assigned. Supplemental information from acn 287952: autoplt made a rather abrupt, uncommanded pitch- up so the captain hand flew the aircraft to level off. Icing conditions had been encountered, wing and engine anti-ice equipment had been turned on and then turned off after exiting icing conditions. Shortly after level off, the master warning lights and cabin pressure annunciator light came on. We noted the cabin pressure climbing through 11000 ft and continuing to rise, so we donned our oxygen masks. Atlanta asked how low we needed to go. The captain replied '11000 ft.' the passenger oxygen masks deployed at about 13000 ft cabin altitude. I accomplished emergency checklist procedures. We determined that the right airconditioning unit had overheated (possibly associated with earlier use of anti- ice equipment) and automatically shut off during the descent, we regained control of the pressurization through manual control. The flight continued to destination after the airconditioning unit and pressurization were determined to be operating normally.

Original NASA ASRS Text

Title: PRESSURIZATION PROB.

Narrative: AT LEVEL OFF FL290, EXPERIENCED CABIN PRESS LIGHT AND REQUESTED LOWER ALT. RECEIVED CLRNC TO FL270. INITIATED CHKLIST TO RESTORE CABIN PRESSURE. REQUESTED FURTHER CLRNC TO 11000 FT. RECEIVED CLRNC. IN SHORT ORDER TO 11000 FT MAY HAVE EXCEEDED INITIAL CLRNC TO FL270 PRIOR TO RECEIVING CLRNC TO 11000 FT. DID NOT DECLARE EMER. AUTOPLT INOP, COPLT WAS MANUALLY CTLING CABIN. PF WAS HAND FLYING ACFT AND COMS. ALT CTL MAY HAVE BEEN LESS THAN DESIRED OR ASSIGNED. SUPPLEMENTAL INFO FROM ACN 287952: AUTOPLT MADE A RATHER ABRUPT, UNCOMMANDED PITCH- UP SO THE CAPT HAND FLEW THE ACFT TO LEVEL OFF. ICING CONDITIONS HAD BEEN ENCOUNTERED, WING AND ENG ANTI-ICE EQUIP HAD BEEN TURNED ON AND THEN TURNED OFF AFTER EXITING ICING CONDITIONS. SHORTLY AFTER LEVEL OFF, THE MASTER WARNING LIGHTS AND CABIN PRESSURE ANNUNCIATOR LIGHT CAME ON. WE NOTED THE CABIN PRESSURE CLBING THROUGH 11000 FT AND CONTINUING TO RISE, SO WE DONNED OUR OXYGEN MASKS. ATLANTA ASKED HOW LOW WE NEEDED TO GO. THE CAPT REPLIED '11000 FT.' THE PAX OXYGEN MASKS DEPLOYED AT ABOUT 13000 FT CABIN ALT. I ACCOMPLISHED EMER CHKLIST PROCS. WE DETERMINED THAT THE R AIRCONDITIONING UNIT HAD OVERHEATED (POSSIBLY ASSOCIATED WITH EARLIER USE OF ANTI- ICE EQUIP) AND AUTOMATICALLY SHUT OFF DURING THE DSCNT, WE REGAINED CTL OF THE PRESSURIZATION THROUGH MANUAL CTL. THE FLT CONTINUED TO DEST AFTER THE AIRCONDITIONING UNIT AND PRESSURIZATION WERE DETERMINED TO BE OPERATING NORMALLY.

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.