Narrative:

The flight was a scheduled air carrier flight between cos-den with 22 mins planned en route. The departure was a right turn to 010 degrees and climb to 9000 ft MSL (cos field elevation is 6180 ft). As the aircraft was leveling at 9000 ft, warning lights indicated a failure of electronic cabin pressurization control (ie, automatic fail). The pressurization control was placed to a backup mode (standby), and the cabin rate of climb was observed leveling. Clearance to 14000 ft (planned cruise altitude) was given and climb initiated. At this time the EFIS display lost color and went to black and white, and the crew turned their attention to this problem. As the aircraft approached 14000 ft, the captain heard the 1ST flight attendant instructing the passenger to don their oxygen masks which had begun deploying. As the crew donned their own oxygen masks, the first officer asked for and received descent clearance to 10000 ft. The captain made an announcement that the aircraft had lost cabin pressure and reiterated the need to don masks. Shortly after descent was initiated, the captain noticed both air conditioning/pressurization switches in the off position. The packs were turned on and pressurization returned to normal as did the EFIS color display (they require cooling air). A normal approach and landing were made at den. There were no reported injuries or complaints from the passenger. 1 flight attendant was admitted to hospital for observation after complaining of headaches. The following factors were involved in this incident. The first officer was new to the company and aircraft with a little over 100 hours in type. He was distracted in his after start SOP and failed to turn on the packs. Checking pack switches is not included in any before takeoff verbal checklist. It was a cool morning and the absence of air conditioning was not noticed. Cos airport elevation is 6180 ft and there was no perceived absence of pressurization. The initial climb heading was toward the sun and the captain had difficulty seeing the position of the switches. They are normally always on in-flight. They are 3 position switches and the off and on position can be confused. Checking packs and bleeds is after takeoff SOP. The crew misinterpreted the effects of switching the pressure controller from automatic to standby as having fixed the problem. The aircraft was level. The crew did not make the correct correlation between the lack of pressurization control and the loss of color on the EFIS displays. The aircraft altitude warning system failed and did not sound at 10000 ft, thereby depriving the crew of backup warning.

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Original NASA ASRS Text

Title: ACFT EQUIP OPERATING PROC -- ACR FLC FORGOT TO TURN ON THE PRESSURIZATION SYS SO THEY GOT A MASK DROP.

Narrative: THE FLT WAS A SCHEDULED ACR FLT BTWN COS-DEN WITH 22 MINS PLANNED ENRTE. THE DEP WAS A R TURN TO 010 DEGS AND CLB TO 9000 FT MSL (COS FIELD ELEVATION IS 6180 FT). AS THE ACFT WAS LEVELING AT 9000 FT, WARNING LIGHTS INDICATED A FAILURE OF ELECTRONIC CABIN PRESSURIZATION CTL (IE, AUTO FAIL). THE PRESSURIZATION CTL WAS PLACED TO A BACKUP MODE (STANDBY), AND THE CABIN RATE OF CLB WAS OBSERVED LEVELING. CLRNC TO 14000 FT (PLANNED CRUISE ALT) WAS GIVEN AND CLB INITIATED. AT THIS TIME THE EFIS DISPLAY LOST COLOR AND WENT TO BLACK AND WHITE, AND THE CREW TURNED THEIR ATTN TO THIS PROB. AS THE ACFT APCHED 14000 FT, THE CAPT HEARD THE 1ST FLT ATTENDANT INSTRUCTING THE PAX TO DON THEIR OXYGEN MASKS WHICH HAD BEGUN DEPLOYING. AS THE CREW DONNED THEIR OWN OXYGEN MASKS, THE FO ASKED FOR AND RECEIVED DSCNT CLRNC TO 10000 FT. THE CAPT MADE AN ANNOUNCEMENT THAT THE ACFT HAD LOST CABIN PRESSURE AND REITERATED THE NEED TO DON MASKS. SHORTLY AFTER DSCNT WAS INITIATED, THE CAPT NOTICED BOTH AIR CONDITIONING/PRESSURIZATION SWITCHES IN THE OFF POS. THE PACKS WERE TURNED ON AND PRESSURIZATION RETURNED TO NORMAL AS DID THE EFIS COLOR DISPLAY (THEY REQUIRE COOLING AIR). A NORMAL APCH AND LNDG WERE MADE AT DEN. THERE WERE NO RPTED INJURIES OR COMPLAINTS FROM THE PAX. 1 FLT ATTENDANT WAS ADMITTED TO HOSPITAL FOR OBSERVATION AFTER COMPLAINING OF HEADACHES. THE FOLLOWING FACTORS WERE INVOLVED IN THIS INCIDENT. THE FO WAS NEW TO THE COMPANY AND ACFT WITH A LITTLE OVER 100 HRS IN TYPE. HE WAS DISTRACTED IN HIS AFTER START SOP AND FAILED TO TURN ON THE PACKS. CHKING PACK SWITCHES IS NOT INCLUDED IN ANY BEFORE TKOF VERBAL CHKLIST. IT WAS A COOL MORNING AND THE ABSENCE OF AIR CONDITIONING WAS NOT NOTICED. COS ARPT ELEVATION IS 6180 FT AND THERE WAS NO PERCEIVED ABSENCE OF PRESSURIZATION. THE INITIAL CLB HDG WAS TOWARD THE SUN AND THE CAPT HAD DIFFICULTY SEEING THE POS OF THE SWITCHES. THEY ARE NORMALLY ALWAYS ON INFLT. THEY ARE 3 POS SWITCHES AND THE OFF AND ON POS CAN BE CONFUSED. CHKING PACKS AND BLEEDS IS AFTER TKOF SOP. THE CREW MISINTERPRETED THE EFFECTS OF SWITCHING THE PRESSURE CTLR FROM AUTO TO STANDBY AS HAVING FIXED THE PROB. THE ACFT WAS LEVEL. THE CREW DID NOT MAKE THE CORRECT CORRELATION BTWN THE LACK OF PRESSURIZATION CTL AND THE LOSS OF COLOR ON THE EFIS DISPLAYS. THE ACFT ALT WARNING SYS FAILED AND DID NOT SOUND AT 10000 FT, THEREBY DEPRIVING THE CREW OF BACKUP WARNING.

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.