A DC9 flight crew lost pressurization and descended near cmh.

Attributes
ACN	451877
Time
Date	199908
Day	Thu
Local Time Of Day	0601 To 1200
Place
State Reference	OH
Altitude	msl single value : 29000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob.artcc tower : dfw.tower
Operator	common carrier : air carrier
Make Model Name	DC-9 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 6000 flight time type : 1500
ASRS Report	451877
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : exited adverse environment
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

At FL290, we had a pressurization problem. Our cabin altitude started to spin. Maintenance had change gauge day prior I thought it was only an indication problem. Decided to take precaution and descend below FL250 just in case. When first officer reduced power to start descent 'cabin pressure' light illuminated -- told first officer to request descent to 10000 ft. I was already on SELCAL with company to notify them about gauge so they could fix in myr. The oxygen mask then deployed while in our descent. We found that if we pushed the power up we got our differential back. I never declared an emergency even though I should have. I also did not descend as quickly as we should have. Reasons for this is, because we still had differential and I knew there was a problem with the gauge the day before I did not really believe there was a true total depressurization. Also there were a lot of thunderstorms in the area and my flight attendants were in the aisle still. I should have done a high dive anyway, but I did not. In the future, if I encountered the same situation I would declare the emergency and do a high dive and not second guess the aircraft.

Original NASA ASRS Text

Title: A DC9 FLC LOST PRESSURIZATION AND DSNDED NEAR CMH.

Narrative: AT FL290, WE HAD A PRESSURIZATION PROB. OUR CABIN ALT STARTED TO SPIN. MAINT HAD CHANGE GAUGE DAY PRIOR I THOUGHT IT WAS ONLY AN INDICATION PROB. DECIDED TO TAKE PRECAUTION AND DSND BELOW FL250 JUST IN CASE. WHEN FO REDUCED PWR TO START DSCNT 'CABIN PRESSURE' LIGHT ILLUMINATED -- TOLD FO TO REQUEST DSCNT TO 10000 FT. I WAS ALREADY ON SELCAL WITH COMPANY TO NOTIFY THEM ABOUT GAUGE SO THEY COULD FIX IN MYR. THE OXYGEN MASK THEN DEPLOYED WHILE IN OUR DSCNT. WE FOUND THAT IF WE PUSHED THE PWR UP WE GOT OUR DIFFERENTIAL BACK. I NEVER DECLARED AN EMER EVEN THOUGH I SHOULD HAVE. I ALSO DID NOT DSND AS QUICKLY AS WE SHOULD HAVE. REASONS FOR THIS IS, BECAUSE WE STILL HAD DIFFERENTIAL AND I KNEW THERE WAS A PROB WITH THE GAUGE THE DAY BEFORE I DID NOT REALLY BELIEVE THERE WAS A TRUE TOTAL DEPRESSURIZATION. ALSO THERE WERE A LOT OF TSTMS IN THE AREA AND MY FLT ATTENDANTS WERE IN THE AISLE STILL. I SHOULD HAVE DONE A HIGH DIVE ANYWAY, BUT I DID NOT. IN THE FUTURE, IF I ENCOUNTERED THE SAME SIT I WOULD DECLARE THE EMER AND DO A HIGH DIVE AND NOT SECOND GUESS THE ACFT.

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.