<< >> NASA ASRS Report 309013, June 1995

Diversion to alternate mandated by a ruptured air conditioning duct in an air carrier medium large transport. Aircraft equipment malfunction problem.

Attributes
ACN	309013
Time
Date	199506
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : mco
State Reference	FL
Altitude	msl bound lower : 30000 msl bound upper : 30000
Environment
Flight Conditions	Marginal
Light	Dawn
Aircraft 1
Controlling Facilities	artcc : zma tower : cvg
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	climbout : intermediate altitude other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time type : 2500
ASRS Report	309013
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 other
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

On climb out from mia to atl we noticed that the flow light on the pressurization control panel came on indicating that the outflow valve was going full closed and the system was having trouble pressurizing the aircraft. We followed the normal procedure and monitored the cabin altitude. It appeared that it would be able to maintain pressurization. Approaching FL300 we realized that the system was not going to be able to hold the cabin within limits. Requested and received a lower altitude. We started an expeditious descent to 8000 ft. The cabin altitude reached 11500 ft maximum. The cabin altitude horn went off at 10000 ft, the oxygen masks did not drop. We were about overhead mco and decided to divert into mco. The approach and landing was uneventful. Maintenance found a blown air conditioning duct. They fixed it in a relatively short period and we continued on. There were no reports of passenger discomfort due to the higher than normal cabin altitude.

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Original NASA ASRS Text

Title: DIVERSION TO ALTERNATE MANDATED BY A RUPTURED AIR CONDITIONING DUCT IN AN ACR MLG. ACFT EQUIP MALFUNCTION PROB.

Narrative: ON CLBOUT FROM MIA TO ATL WE NOTICED THAT THE FLOW LIGHT ON THE PRESSURIZATION CTL PANEL CAME ON INDICATING THAT THE OUTFLOW VALVE WAS GOING FULL CLOSED AND THE SYS WAS HAVING TROUBLE PRESSURIZING THE ACFT. WE FOLLOWED THE NORMAL PROC AND MONITORED THE CABIN ALT. IT APPEARED THAT IT WOULD BE ABLE TO MAINTAIN PRESSURIZATION. APCHING FL300 WE REALIZED THAT THE SYS WAS NOT GOING TO BE ABLE TO HOLD THE CABIN WITHIN LIMITS. REQUESTED AND RECEIVED A LOWER ALT. WE STARTED AN EXPEDITIOUS DSCNT TO 8000 FT. THE CABIN ALT REACHED 11500 FT MAX. THE CABIN ALT HORN WENT OFF AT 10000 FT, THE OXYGEN MASKS DID NOT DROP. WE WERE ABOUT OVERHEAD MCO AND DECIDED TO DIVERT INTO MCO. THE APCH AND LNDG WAS UNEVENTFUL. MAINT FOUND A BLOWN AIR CONDITIONING DUCT. THEY FIXED IT IN A RELATIVELY SHORT PERIOD AND WE CONTINUED ON. THERE WERE NO RPTS OF PAX DISCOMFORT DUE TO THE HIGHER THAN NORMAL CABIN ALT.

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.