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Return land mandated for the flight crew of a B737-300 when they are unable to pressurize the aircraft through normal and alternate procedures after takeoff from anc, ak.
| Attributes | |
| ACN | 611577 |
| Time | |
| Date | 200403 |
| Day | Wed |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : anc.airport |
| State Reference | AK |
| Altitude | agl bound lower : 0 agl bound upper : 10000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : a11.tracon |
| Operator | common carrier : air carrier |
| Make Model Name | B737-700 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | climbout : intermediate altitude |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 180 flight time total : 25000 |
| ASRS Report | 611577 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | controller military : 10 controller non radar : 8 controller radar : 24 flight time last 90 days : 240 flight time total : 5000 flight time type : 1600 |
| ASRS Report | 611570 |
| Events | |
| Anomaly | aircraft equipment problem : critical maintenance problem : improper maintenance non adherence : published procedure non adherence : company policies other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : alt warn horn |
| Resolutory Action | flight crew : diverted to another airport flight crew : landed as precaution other |
| Consequence | other other |
| Factors | |
| Maintenance | contributing factor : lighting contributing factor : weather performance deficiency : inspection |
| Supplementary | |
| Problem Areas | Weather Maintenance Human Performance Aircraft Environmental Factor Flight Crew Human Performance |
| Primary Problem | Maintenance Human Performance |
Narrative:
Climbing through 10000 ft, the altitude warning horn sounded. First officer leveled off and immediately noticed that the pressurization controller was in 'manual.' he selected 'automatic' and we observed outflow valve while contacting ATC of our leveloff. Outflow valve remained in full open position in both 'automatic' and 'alternate.' after getting 180 degree vector, it became obvious that cabin would not pressurize. We requested a long slow descent for passenger comfort and landed anc uneventfully. Maintenance was able to cycle the valve and system was checked and released. Overweight landing inspection completed. Redispatched flight uneventful. The manual switch position was missed during both our preflts, however the outflow valve did malfunction, as normal cabin pressurization should have been available upon selection of 'automatic.' the significance of this event lies in a seemingly inconsequential oversight. Preflight was done in early dawn light with the cockpit light selector in 'dim.' with the rising sun in our eyes, we did not select 'bright.' this prevented me from 'trapping and mitigating' the original mistake during my after takeoff check of bleeds and packs, by not noticing the green 'manual' light on the AC panel. We confirmed that in 'dim,' the light is invisible in a brightly lit cockpit. I will be more cognizant of the AC panel during preflight and certainly be more careful of the light position switch as conditions change. Supplemental information from acn 611570: during preflight on a B737-700, I noticed the pressurization outflow door was open. The OAT was about -7 degrees C, so I assumed maintenance had not closed the door as they usually do when the aircraft remains out overnight. I was informed, later, their procedure is to leave it open when warm air is supplied to the aircraft (my only question would be: why they did not re-select automatic). When doing the cockpit preflight, I missed the pressurization control rotary switch was in 'manual,' rather than 'automatic.' it was missed during the before start check and on the after takeoff check. Also, neither the automatic fail light nor the alternate would come on when selected.
Original NASA ASRS Text
Title: RETURN LAND MANDATED FOR THE FLT CREW OF A B737-300 WHEN THEY ARE UNABLE TO PRESSURIZE THE ACFT THROUGH NORMAL AND ALTERNATE PROCS AFTER TKOF FROM ANC, AK.
Narrative: CLBING THROUGH 10000 FT, THE ALT WARNING HORN SOUNDED. FO LEVELED OFF AND IMMEDIATELY NOTICED THAT THE PRESSURIZATION CTLR WAS IN 'MANUAL.' HE SELECTED 'AUTO' AND WE OBSERVED OUTFLOW VALVE WHILE CONTACTING ATC OF OUR LEVELOFF. OUTFLOW VALVE REMAINED IN FULL OPEN POS IN BOTH 'AUTO' AND 'ALTERNATE.' AFTER GETTING 180 DEG VECTOR, IT BECAME OBVIOUS THAT CABIN WOULD NOT PRESSURIZE. WE REQUESTED A LONG SLOW DSCNT FOR PAX COMFORT AND LANDED ANC UNEVENTFULLY. MAINT WAS ABLE TO CYCLE THE VALVE AND SYS WAS CHKED AND RELEASED. OVERWT LNDG INSPECTION COMPLETED. REDISPATCHED FLT UNEVENTFUL. THE MANUAL SWITCH POS WAS MISSED DURING BOTH OUR PREFLTS, HOWEVER THE OUTFLOW VALVE DID MALFUNCTION, AS NORMAL CABIN PRESSURIZATION SHOULD HAVE BEEN AVAILABLE UPON SELECTION OF 'AUTO.' THE SIGNIFICANCE OF THIS EVENT LIES IN A SEEMINGLY INCONSEQUENTIAL OVERSIGHT. PREFLT WAS DONE IN EARLY DAWN LIGHT WITH THE COCKPIT LIGHT SELECTOR IN 'DIM.' WITH THE RISING SUN IN OUR EYES, WE DID NOT SELECT 'BRIGHT.' THIS PREVENTED ME FROM 'TRAPPING AND MITIGATING' THE ORIGINAL MISTAKE DURING MY AFTER TKOF CHK OF BLEEDS AND PACKS, BY NOT NOTICING THE GREEN 'MANUAL' LIGHT ON THE AC PANEL. WE CONFIRMED THAT IN 'DIM,' THE LIGHT IS INVISIBLE IN A BRIGHTLY LIT COCKPIT. I WILL BE MORE COGNIZANT OF THE AC PANEL DURING PREFLT AND CERTAINLY BE MORE CAREFUL OF THE LIGHT POS SWITCH AS CONDITIONS CHANGE. SUPPLEMENTAL INFO FROM ACN 611570: DURING PREFLT ON A B737-700, I NOTICED THE PRESSURIZATION OUTFLOW DOOR WAS OPEN. THE OAT WAS ABOUT -7 DEGS C, SO I ASSUMED MAINT HAD NOT CLOSED THE DOOR AS THEY USUALLY DO WHEN THE ACFT REMAINS OUT OVERNIGHT. I WAS INFORMED, LATER, THEIR PROC IS TO LEAVE IT OPEN WHEN WARM AIR IS SUPPLIED TO THE ACFT (MY ONLY QUESTION WOULD BE: WHY THEY DID NOT RE-SELECT AUTO). WHEN DOING THE COCKPIT PREFLT, I MISSED THE PRESSURIZATION CTL ROTARY SWITCH WAS IN 'MANUAL,' RATHER THAN 'AUTO.' IT WAS MISSED DURING THE BEFORE START CHK AND ON THE AFTER TKOF CHK. ALSO, NEITHER THE AUTO FAIL LIGHT NOR THE ALTERNATE WOULD COME ON WHEN SELECTED.
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.