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MD80 encounters gradual loss of cabin pressure. Descend in stages to 10000 MSL and continue to destination.
| Attributes | |
| ACN | 736703 |
| Time | |
| Date | 200704 |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : sat.airport |
| State Reference | TX |
| Altitude | msl single value : 37000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Dawn |
| Aircraft 1 | |
| Controlling Facilities | artcc : zhu.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | MD-88 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Experience | flight time last 90 days : 240 flight time total : 11500 flight time type : 1500 |
| ASRS Report | 736703 |
| Events | |
| Anomaly | aircraft equipment problem : critical |
| Independent Detector | aircraft equipment other aircraft equipment : press wing system |
| Resolutory Action | aircraft : equipment problem dissipated flight crew : overcame equipment problem other |
| Consequence | other |
| Supplementary | |
| Problem Areas | Aircraft |
| Primary Problem | Aircraft |
Narrative:
Leveled off at FL370; having just avoided a line of WX east of sat; en route to atl. Noticed 'flow' light illuminated on overhead panel; along with a small climb rate on cabin vsi. Turned off engine anti-ice and got small improvement; but cabin continued to climb slowly. Descended to FL330; and cabin began much greater climb when power reduced for descent. Level at FL330; still slow cabin climb. Ran through loss of cabin pressurization memory items and then checklist; which included donning oxygen masks. Thought we may have a pack fail; so descended to FL250. Cabin continued to climb and was approaching 10000 ft. Got clearance down to 11000 ft; then 10000 ft and initiated emergency descent profile. Got to 10000 ft quickly and uneventfully; with maximum cabin altitude approximately 11500 ft. Passenger masks did not deploy. At 10000 ft; small differential pressure was maintained and cabin was comfortable at about 4000 ft MSL. Made sure no structural damage was evident; conferred with dispatch and maintenance control. Thankfully; we had a lot of fuel and were able to continue to atl with legal fuel reserves. On checking with maintenance afterwards; seemed like a duct had partially ruptured downstream of 1 AC pack.
Original NASA ASRS Text
Title: MD80 ENCOUNTERS GRADUAL LOSS OF CABIN PRESSURE. DESCEND IN STAGES TO 10000 MSL AND CONTINUE TO DESTINATION.
Narrative: LEVELED OFF AT FL370; HAVING JUST AVOIDED A LINE OF WX E OF SAT; ENRTE TO ATL. NOTICED 'FLOW' LIGHT ILLUMINATED ON OVERHEAD PANEL; ALONG WITH A SMALL CLB RATE ON CABIN VSI. TURNED OFF ENG ANTI-ICE AND GOT SMALL IMPROVEMENT; BUT CABIN CONTINUED TO CLB SLOWLY. DSNDED TO FL330; AND CABIN BEGAN MUCH GREATER CLB WHEN PWR REDUCED FOR DSCNT. LEVEL AT FL330; STILL SLOW CABIN CLB. RAN THROUGH LOSS OF CABIN PRESSURIZATION MEMORY ITEMS AND THEN CHKLIST; WHICH INCLUDED DONNING OXYGEN MASKS. THOUGHT WE MAY HAVE A PACK FAIL; SO DSNDED TO FL250. CABIN CONTINUED TO CLB AND WAS APCHING 10000 FT. GOT CLRNC DOWN TO 11000 FT; THEN 10000 FT AND INITIATED EMER DSCNT PROFILE. GOT TO 10000 FT QUICKLY AND UNEVENTFULLY; WITH MAX CABIN ALT APPROX 11500 FT. PAX MASKS DID NOT DEPLOY. AT 10000 FT; SMALL DIFFERENTIAL PRESSURE WAS MAINTAINED AND CABIN WAS COMFORTABLE AT ABOUT 4000 FT MSL. MADE SURE NO STRUCTURAL DAMAGE WAS EVIDENT; CONFERRED WITH DISPATCH AND MAINT CTL. THANKFULLY; WE HAD A LOT OF FUEL AND WERE ABLE TO CONTINUE TO ATL WITH LEGAL FUEL RESERVES. ON CHKING WITH MAINT AFTERWARDS; SEEMED LIKE A DUCT HAD PARTIALLY RUPTURED DOWNSTREAM OF 1 AC PACK.
Data retrieved from NASA's ASRS site as of January 2009 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.