Narrative:

After takeoff from iln to msy, first officer noticed the cabin was not pressurizing when climbing through about 5000 ft after departure. I noticed the differential was 'zero' psi and the cabin was climbing with the vsi. We requested from ATC a lower leveloff, so we stopped at 10000 ft. I then requested the cabin pressure (abnormal) uncontrollable, and the automatic pressurization inoperative checklist. We called flight control to see if they wanted us to continue unpressurized at 10000 ft. (Check on fuel, WX, etc) at which time we were told to return. After shutdown at the gate, I noticed both of the packs were off. I had turned them off on taxi out of iln when passing behind an aircraft that had been deiced and did not turn them back on. At the time of departure, iln had low visibility, strong winds and heavy snow. The ramps and the runway were all white, contributing to being preoccupied with braking conditions, abort, deice holdover times and general fatigue for that time in the morning. 1) I should have set some sort of reminder that the switches were off. 2) I should have done the checklists also to make sure nothing was missed. 3) an additional abnormal simple-like aircraft not pressurizing. Check outflow valve, check air conditioning packs both on.

Related reports:

Google
 

Original NASA ASRS Text

Title: RETURN LAND MANDATED IN A DC9 CARGO FLT WHEN FLT CREW IS UNABLE TO PRESSURIZE THE ACFT, FINDING OUT WHEN SHUTTING DOWN THAT BOTH PACK SWITCHES WERE IN THE 'OFF' POS AT ILN, OH.

Narrative: AFTER TKOF FROM ILN TO MSY, FO NOTICED THE CABIN WAS NOT PRESSURIZING WHEN CLBING THROUGH ABOUT 5000 FT AFTER DEP. I NOTICED THE DIFFERENTIAL WAS 'ZERO' PSI AND THE CABIN WAS CLBING WITH THE VSI. WE REQUESTED FROM ATC A LOWER LEVELOFF, SO WE STOPPED AT 10000 FT. I THEN REQUESTED THE CABIN PRESSURE (ABNORMAL) UNCONTROLLABLE, AND THE AUTO PRESSURIZATION INOP CHKLIST. WE CALLED FLT CTL TO SEE IF THEY WANTED US TO CONTINUE UNPRESSURIZED AT 10000 FT. (CHK ON FUEL, WX, ETC) AT WHICH TIME WE WERE TOLD TO RETURN. AFTER SHUTDOWN AT THE GATE, I NOTICED BOTH OF THE PACKS WERE OFF. I HAD TURNED THEM OFF ON TAXI OUT OF ILN WHEN PASSING BEHIND AN ACFT THAT HAD BEEN DEICED AND DID NOT TURN THEM BACK ON. AT THE TIME OF DEP, ILN HAD LOW VISIBILITY, STRONG WINDS AND HVY SNOW. THE RAMPS AND THE RWY WERE ALL WHITE, CONTRIBUTING TO BEING PREOCCUPIED WITH BRAKING CONDITIONS, ABORT, DEICE HOLDOVER TIMES AND GENERAL FATIGUE FOR THAT TIME IN THE MORNING. 1) I SHOULD HAVE SET SOME SORT OF REMINDER THAT THE SWITCHES WERE OFF. 2) I SHOULD HAVE DONE THE CHKLISTS ALSO TO MAKE SURE NOTHING WAS MISSED. 3) AN ADDITIONAL ABNORMAL SIMPLE-LIKE ACFT NOT PRESSURIZING. CHK OUTFLOW VALVE, CHK AIR CONDITIONING PACKS BOTH ON.

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.