While climbing through FL240 the cabin altitude horn sounded. The flight crew donned their oxygen and continued with the emergency checklist. At the same time the flight crew started a descent to a lower altitude. While performing the loss of pressurization checklist the so found that one of the packs had been left 'off.' the crew turned the pack on as per the checklist. The aircraft pressurized and they returned to altitude to continue the flight.

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Attributes
ACN	331892
Time
Date	199603
Day	Sun
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : zob
State Reference	OH
Altitude	msl bound lower : 11000 msl bound upper : 24000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zob
Operator	common carrier : air carrier
Make Model Name	B727 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 100 flight time total : 4000 flight time type : 600
ASRS Report	331892
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : commercial pilot : instrument
Experience	flight time last 90 days : 200 flight time total : 19000 flight time type : 727
ASRS Report	332088
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude non adherence : published procedure other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : overcame equipment problem flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

While climbing through FL240 en route from cvg to lga the cabin altitude horn sounded. We donned our oxygen mask and continued with the emergency checklist. At the same time we started a descent to a lower altitude. While performing the loss of pressurization checklist I found that one of the packs had been left 'off.' this was the cause of the cabin altitude to reach 10000 ft. Turning the pack 'on' caused the cabin altitude to return to normal. With oxygen mask on we had trouble communicating. The first officer continued descent to 11000 ft. At this time we took off the oxygen masks and discussed the situation. It was determined that failing to turn the pack on at 18000 ft (as directed to do in the climb checklist) allowed the cabin altitude to reach 10000 ft, and that there were no mechanical problems. We then climbed to our cruise altitude and continued to lga.

Original NASA ASRS Text

Title: WHILE CLBING THROUGH FL240 THE CABIN ALT HORN SOUNDED. THE FLC DONNED THEIR OXYGEN AND CONTINUED WITH THE EMER CHKLIST. AT THE SAME TIME THE FLC STARTED A DSCNT TO A LOWER ALT. WHILE PERFORMING THE LOSS OF PRESSURIZATION CHKLIST THE SO FOUND THAT ONE OF THE PACKS HAD BEEN LEFT 'OFF.' THE CREW TURNED THE PACK ON AS PER THE CHKLIST. THE ACFT PRESSURIZED AND THEY RETURNED TO ALT TO CONTINUE THE FLT.

Narrative: WHILE CLBING THROUGH FL240 ENRTE FROM CVG TO LGA THE CABIN ALT HORN SOUNDED. WE DONNED OUR OXYGEN MASK AND CONTINUED WITH THE EMER CHKLIST. AT THE SAME TIME WE STARTED A DSCNT TO A LOWER ALT. WHILE PERFORMING THE LOSS OF PRESSURIZATION CHKLIST I FOUND THAT ONE OF THE PACKS HAD BEEN LEFT 'OFF.' THIS WAS THE CAUSE OF THE CABIN ALT TO REACH 10000 FT. TURNING THE PACK 'ON' CAUSED THE CABIN ALT TO RETURN TO NORMAL. WITH OXYGEN MASK ON WE HAD TROUBLE COMMUNICATING. THE FO CONTINUED DSCNT TO 11000 FT. AT THIS TIME WE TOOK OFF THE OXYGEN MASKS AND DISCUSSED THE SIT. IT WAS DETERMINED THAT FAILING TO TURN THE PACK ON AT 18000 FT (AS DIRECTED TO DO IN THE CLB CHKLIST) ALLOWED THE CABIN ALT TO REACH 10000 FT, AND THAT THERE WERE NO MECHANICAL PROBS. WE THEN CLBED TO OUR CRUISE ALT AND CONTINUED TO LGA.

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.