An air carrier DC10 flight crew loses pressurization during climb, makes an emergency descent and re...

Attributes
ACN	395076
Time
Date	199802
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : hnl
State Reference	HI
Altitude	msl bound lower : 34000 msl bound upper : 34000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa
Operator	common carrier : air carrier
Make Model Name	DC-10 10
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : other oceanic enroute : pacific
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : atp
ASRS Report	395076
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 16000 flight time type : 2000
ASRS Report	396822
Events
Anomaly	aircraft equipment problem : critical non adherence : published procedure other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : declared emergency none taken : detected after the fact other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance

Narrative:

Declared emergency due to rapid depressurization, descended to 10000 ft. Was instructed by sfo commercial radio to squawk XXXX as per oak oceanic. Returned to hnl. Callback conversation with reporter revealed the following information: this so was hesitant about revealing his total time and experience level on the DC10-10. He did admit to getting impatient with the automatic pressurization controller when it did not show a rise in cabin altitude during the early climb out. The so said that he switched to the standby pressurization system to get the aircraft back on schedule. The standby system allows the operator to manually select a position for the outflow valve. This selection process is similar to the manual pressurization system except that the standby system drives the outflow valve much faster (an AC electrical drive versus a dc electrical drive). The faster drive can promote an overshoot situation unless it is carefully monitored, however. The reporter said that he realized that he had a pressurization problem when the cabin altitude warning sounded. He said that they accomplished the 'loss of pressurization checklist' without recovering control of the outflow valve. The crew decided to return to hnl where maintenance determined that the standby controller had failed. The next day the flight crew ferried the aircraft back to the mainland using the automatic system which worked normally. Callback conversation with reporter acn 395076 revealed the following information: reporter stated the cause of the cabin depressurization was the failure of the standby pressure controller.

Original NASA ASRS Text

Title: AN ACR DC10 FLC LOSES PRESSURIZATION DURING CLB, MAKES AN EMER DSCNT AND RETURNS TO HNL. MAINT PERSONNEL DETERMINE THAT THE STANDBY PRESSURIZATION CTLR HAD FAILED.

Narrative: DECLARED EMER DUE TO RAPID DEPRESSURIZATION, DSNDED TO 10000 FT. WAS INSTRUCTED BY SFO COMMERCIAL RADIO TO SQUAWK XXXX AS PER OAK OCEANIC. RETURNED TO HNL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THIS SO WAS HESITANT ABOUT REVEALING HIS TOTAL TIME AND EXPERIENCE LEVEL ON THE DC10-10. HE DID ADMIT TO GETTING IMPATIENT WITH THE AUTO PRESSURIZATION CTLR WHEN IT DID NOT SHOW A RISE IN CABIN ALT DURING THE EARLY CLBOUT. THE SO SAID THAT HE SWITCHED TO THE STANDBY PRESSURIZATION SYS TO GET THE ACFT BACK ON SCHEDULE. THE STANDBY SYS ALLOWS THE OPERATOR TO MANUALLY SELECT A POS FOR THE OUTFLOW VALVE. THIS SELECTION PROCESS IS SIMILAR TO THE MANUAL PRESSURIZATION SYS EXCEPT THAT THE STANDBY SYS DRIVES THE OUTFLOW VALVE MUCH FASTER (AN AC ELECTRICAL DRIVE VERSUS A DC ELECTRICAL DRIVE). THE FASTER DRIVE CAN PROMOTE AN OVERSHOOT SIT UNLESS IT IS CAREFULLY MONITORED, HOWEVER. THE RPTR SAID THAT HE REALIZED THAT HE HAD A PRESSURIZATION PROB WHEN THE CABIN ALT WARNING SOUNDED. HE SAID THAT THEY ACCOMPLISHED THE 'LOSS OF PRESSURIZATION CHKLIST' WITHOUT RECOVERING CTL OF THE OUTFLOW VALVE. THE CREW DECIDED TO RETURN TO HNL WHERE MAINT DETERMINED THAT THE STANDBY CTLR HAD FAILED. THE NEXT DAY THE FLC FERRIED THE ACFT BACK TO THE MAINLAND USING THE AUTO SYS WHICH WORKED NORMALLY. CALLBACK CONVERSATION WITH RPTR ACN 395076 REVEALED THE FOLLOWING INFO: RPTR STATED THE CAUSE OF THE CABIN DEPRESSURIZATION WAS THE FAILURE OF THE STANDBY PRESSURE CONTROLLER.

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.

An air carrier DC10 flight crew loses pressurization during climb, makes an emergency descent and returns to hnl. Maintenance personnel determine that the standby pressurization controller had failed.