An air carrier B737 flight crew operating with one air-conditioning and pressurization system found ...

Attributes
ACN	377083
Time
Date	199708
Day	Tue
Local Time Of Day	0001 To 0600
Place
Locale Reference	atc facility : den
State Reference	CO
Altitude	msl bound lower : 24000 msl bound upper : 24000
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	tower : zdv tower : bfi
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	cruise other other other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : atp
Experience	flight time last 90 days : 180 flight time total : 10600 flight time type : 6500
ASRS Report	377083
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	controller : issued new clearance flight crew : declared emergency other
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

Level in cruise flight at FL240. IMC in thunderstorms. Autoplt and autothrottles engaged. Engine and wing anti-ice on due to icing conditions. Flight being operated at lower than normal altitude due to left air-conditioning pack inoperative. At approximately XA20Z, (aircraft position approximately den 060 degree radial, 150 NM) cabin altitude horn sounded. Cabin altitude at 10000 ft and climbing slow. No warning or master caution lights at this time. Placed pressurization in standby mode and set appropriate altitude in standby window. Cabin altitude continued to climb. Contacted ZDV and initiated descent to 10000 ft. Received current altimeter setting from ZDV. During descent, cabin altitude reached 13000 ft. Burning smell prevailed in aircraft. Declared emergency and obtained WX for den from center (1/4 mi visibility, ceiling 100 ft overcast fog). Checked with flight attendants, passenger oxygen mask had deployed (oxygen generators active). Master caution illuminated for passenger oxygen light on overhead panel. Unable to communicate with company dispatch or maintenance despite several attempts through company network and company frequency. This was probably due to aircraft altitude, location, and thunderstorms. Radio communication with ZDV also poor. Diverted to den. Radio contact made with company dispatch approaching den. Executed ILS runway 35L approach to minimums (RVR approximately 3000 ft which had improved). No emergency equipment on ground necessary. Landed den approximately XH00 am local. Parked aircraft and deplaned passenger. Switched aircraft and continued flight to las at XD00Z. Contributing factors: aircraft being operated with air-conditioning pack inoperative due to poor maintenance, lack of spare parts and spare aircraft. (500 mechanics fired and aircraft maintenance out-sourced). Reoccurring problems with inoperative air-conditioning pack (prolonged flight operations due to loss or revenue). Weak pack (remaining operational one). In-flight icing conditions contributing to pack failure or possible outflow valve ice.

Original NASA ASRS Text

Title: AN ACR B737 FLC OPERATING WITH ONE AIR-CONDITIONING AND PRESSURIZATION SYS FOUND THAT THEY WERE UNABLE TO MAINTAIN THE CABIN ALT WHEN THEY TURNED ON THE AIR BLEED ANTI-ICE SYS. THE ALERT SYS AND STANDBY OXYGEN SYS WORKED WELL AND THE FLC DIVERTED AND LANDED. THE FLC FEELS THAT THE OUTSIDE MAINT PERSONNEL ARE UNABLE TO ADEQUATELY SVC THE ACFT.

Narrative: LEVEL IN CRUISE FLT AT FL240. IMC IN TSTMS. AUTOPLT AND AUTOTHROTTLES ENGAGED. ENG AND WING ANTI-ICE ON DUE TO ICING CONDITIONS. FLT BEING OPERATED AT LOWER THAN NORMAL ALT DUE TO L AIR-CONDITIONING PACK INOP. AT APPROX XA20Z, (ACFT POS APPROX DEN 060 DEG RADIAL, 150 NM) CABIN ALT HORN SOUNDED. CABIN ALT AT 10000 FT AND CLBING SLOW. NO WARNING OR MASTER CAUTION LIGHTS AT THIS TIME. PLACED PRESSURIZATION IN STANDBY MODE AND SET APPROPRIATE ALT IN STANDBY WINDOW. CABIN ALT CONTINUED TO CLB. CONTACTED ZDV AND INITIATED DSCNT TO 10000 FT. RECEIVED CURRENT ALTIMETER SETTING FROM ZDV. DURING DSCNT, CABIN ALT REACHED 13000 FT. BURNING SMELL PREVAILED IN ACFT. DECLARED EMER AND OBTAINED WX FOR DEN FROM CTR (1/4 MI VISIBILITY, CEILING 100 FT OVCST FOG). CHKED WITH FLT ATTENDANTS, PAX OXYGEN MASK HAD DEPLOYED (OXYGEN GENERATORS ACTIVE). MASTER CAUTION ILLUMINATED FOR PAX OXYGEN LIGHT ON OVERHEAD PANEL. UNABLE TO COMMUNICATE WITH COMPANY DISPATCH OR MAINT DESPITE SEVERAL ATTEMPTS THROUGH COMPANY NETWORK AND COMPANY FREQ. THIS WAS PROBABLY DUE TO ACFT ALT, LOCATION, AND TSTMS. RADIO COM WITH ZDV ALSO POOR. DIVERTED TO DEN. RADIO CONTACT MADE WITH COMPANY DISPATCH APCHING DEN. EXECUTED ILS RWY 35L APCH TO MINIMUMS (RVR APPROX 3000 FT WHICH HAD IMPROVED). NO EMER EQUIP ON GND NECESSARY. LANDED DEN APPROX XH00 AM LCL. PARKED ACFT AND DEPLANED PAX. SWITCHED ACFT AND CONTINUED FLT TO LAS AT XD00Z. CONTRIBUTING FACTORS: ACFT BEING OPERATED WITH AIR-CONDITIONING PACK INOP DUE TO POOR MAINT, LACK OF SPARE PARTS AND SPARE ACFT. (500 MECHS FIRED AND ACFT MAINT OUT-SOURCED). REOCCURRING PROBS WITH INOP AIR-CONDITIONING PACK (PROLONGED FLT OPS DUE TO LOSS OR REVENUE). WEAK PACK (REMAINING OPERATIONAL ONE). INFLT ICING CONDITIONS CONTRIBUTING TO PACK FAILURE OR POSSIBLE OUTFLOW VALVE ICE.

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.