A partial loss of cabin pressurization led an air carrier flight crew to divert.

Attributes
ACN	293358
Time
Date	199501
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : ave
State Reference	CA
Altitude	msl bound lower : 26000 msl bound upper : 26000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa tracon : dal
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : atp pilot : instrument
Experience	flight time last 90 days : 235 flight time total : 18000 flight time type : 15000
ASRS Report	293358
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	none taken : unable other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	other

Narrative:

Air carrier flight from sjc to sna. Cleared to depart runway 12, moony 1 departure to ave, maintain FL230. Departure WX 5 scattered, 32 overcast 7R - destination WX W2 overcast 3F. Out of 10000 ft cleared to maintain 15000 ft, due to higher traffic following us (confirmed with TCASII). Subsequently step climbed in 1000- 3000 ft increments. Encountered heavy precipitation in climb, however, no icing. Approaching ave we were rerted over fim to maintain FL290. Out of FL260 noted cabin altitude warning light. Leveloff requested and noted 11000 ft cabin altitude. Requested lower altitude and was cleared to FL200. Cabin altitude did not respond to corrective procedures and cabin altitude slowly increased. Requested further descent. As descent initiated to 11000 ft oxygen masks deployed. Flight attendants assisted those passenger having discomfort to don masks. No panic. Attempts to contact arinc on 130.8 several times throughout preceding events were negative. Notified ATC of request to divert to lax. Approach and landing at lax uneventful and no passenger complications noted. Did not declare an emergency due to gradual loss of pressure during controled descent.

Original NASA ASRS Text

Title: A PARTIAL LOSS OF CABIN PRESSURIZATION LED AN ACR FLC TO DIVERT.

Narrative: ACR FLT FROM SJC TO SNA. CLRED TO DEPART RWY 12, MOONY 1 DEP TO AVE, MAINTAIN FL230. DEP WX 5 SCATTERED, 32 OVCST 7R - DEST WX W2 OVCST 3F. OUT OF 10000 FT CLRED TO MAINTAIN 15000 FT, DUE TO HIGHER TFC FOLLOWING US (CONFIRMED WITH TCASII). SUBSEQUENTLY STEP CLBED IN 1000- 3000 FT INCREMENTS. ENCOUNTERED HVY PRECIPITATION IN CLB, HOWEVER, NO ICING. APCHING AVE WE WERE RERTED OVER FIM TO MAINTAIN FL290. OUT OF FL260 NOTED CABIN ALT WARNING LIGHT. LEVELOFF REQUESTED AND NOTED 11000 FT CABIN ALT. REQUESTED LOWER ALT AND WAS CLRED TO FL200. CABIN ALT DID NOT RESPOND TO CORRECTIVE PROCS AND CABIN ALT SLOWLY INCREASED. REQUESTED FURTHER DSCNT. AS DSCNT INITIATED TO 11000 FT OXYGEN MASKS DEPLOYED. FLT ATTENDANTS ASSISTED THOSE PAX HAVING DISCOMFORT TO DON MASKS. NO PANIC. ATTEMPTS TO CONTACT ARINC ON 130.8 SEVERAL TIMES THROUGHOUT PRECEDING EVENTS WERE NEGATIVE. NOTIFIED ATC OF REQUEST TO DIVERT TO LAX. APCH AND LNDG AT LAX UNEVENTFUL AND NO PAX COMPLICATIONS NOTED. DID NOT DECLARE AN EMER DUE TO GRADUAL LOSS OF PRESSURE DURING CTLED DSCNT.

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.