A B757-200 had previous reports of cold cockpit and the trim air was deferred per the MEL. In-flight...

Attributes
ACN	693159
Time
Date	200604
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	agl single value : 0
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
ASRS Report	693159
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical maintenance problem : non compliance with mel maintenance problem : improper documentation maintenance problem : improper maintenance non adherence : far non adherence : published procedure
Independent Detector	aircraft equipment other aircraft equipment : cockpit temp indicator other flight crewa other flight crewb
Resolutory Action	other
Consequence	other other
Factors
Maintenance	contributing factor : schedule pressure performance deficiency : testing performance deficiency : repair performance deficiency : logbook entry performance deficiency : non compliance with legal requirements performance deficiency : fault isolation
Supplementary
Problem Areas	Flight Crew Human Performance Environmental Factor Maintenance Human Performance Aircraft Chart Or Publication
Primary Problem	Maintenance Human Performance
Situations
Publication	Maint Manual Chap 21

Narrative:

I picked up aircraft for a transcontinental. Inbound crew advised that the trim air was placarded inoperative; and they had trouble controling the temperature in all cabins and were pretty cold up front. They also advised that the previous crew reported we froze our buttocks off. The first placard was for the flight deck temperature being inoperative. Maintenance changed the placard to the trim air after a second write-up. Following takeoff; we had the same problem -- excessive cold air in the flight deck and forward cabin; thus having problems controling the temperature in any cabin. I feel that maintenance is pressured to placard items without troubleshooting just to keep the airline flying. I was preparing to divert the aircraft for operational necessity. Flying for a 5+ hour flight in 65 degree or colder flight deck temperature would have been unsafe and subject the crew to hypothermia. Reviewing the system and from experience; I decided to turn the left pack off; which supplies 75% of the air to the cockpit. This solved the extreme temperature problem and the system then operated normally on one pack. Upon arrival I wrote up the left pack. It is my opinion that a simple operational check of the air conditioning system on the ground by maintenance would have found the left pack failed to the cold side. But doing so would have caused the flight to be delayed; thus subjecting the flight crew to possible complications in-flight and causing an air interruption.

Original NASA ASRS Text

Title: A B757-200 HAD PREVIOUS RPTS OF COLD COCKPIT AND THE TRIM AIR WAS DEFERRED PER THE MEL. INFLT CREW EXPERIENCED COLD COCKPIT. SWITCHED OFF L PACK AND COCKPIT TEMP BECAME NORMAL.

Narrative: I PICKED UP ACFT FOR A TRANSCONTINENTAL. INBOUND CREW ADVISED THAT THE TRIM AIR WAS PLACARDED INOP; AND THEY HAD TROUBLE CTLING THE TEMP IN ALL CABINS AND WERE PRETTY COLD UP FRONT. THEY ALSO ADVISED THAT THE PREVIOUS CREW RPTED WE FROZE OUR BUTTOCKS OFF. THE FIRST PLACARD WAS FOR THE FLT DECK TEMP BEING INOP. MAINT CHANGED THE PLACARD TO THE TRIM AIR AFTER A SECOND WRITE-UP. FOLLOWING TKOF; WE HAD THE SAME PROB -- EXCESSIVE COLD AIR IN THE FLT DECK AND FORWARD CABIN; THUS HAVING PROBS CTLING THE TEMP IN ANY CABIN. I FEEL THAT MAINT IS PRESSURED TO PLACARD ITEMS WITHOUT TROUBLESHOOTING JUST TO KEEP THE AIRLINE FLYING. I WAS PREPARING TO DIVERT THE ACFT FOR OPERATIONAL NECESSITY. FLYING FOR A 5+ HR FLT IN 65 DEG OR COLDER FLT DECK TEMP WOULD HAVE BEEN UNSAFE AND SUBJECT THE CREW TO HYPOTHERMIA. REVIEWING THE SYS AND FROM EXPERIENCE; I DECIDED TO TURN THE L PACK OFF; WHICH SUPPLIES 75% OF THE AIR TO THE COCKPIT. THIS SOLVED THE EXTREME TEMP PROB AND THE SYS THEN OPERATED NORMALLY ON ONE PACK. UPON ARR I WROTE UP THE L PACK. IT IS MY OPINION THAT A SIMPLE OPERATIONAL CHK OF THE AIR CONDITIONING SYS ON THE GND BY MAINT WOULD HAVE FOUND THE L PACK FAILED TO THE COLD SIDE. BUT DOING SO WOULD HAVE CAUSED THE FLT TO BE DELAYED; THUS SUBJECTING THE FLT CREW TO POSSIBLE COMPLICATIONS INFLT AND CAUSING AN AIR INTERRUPTION.

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.

A B757-200 had previous reports of cold cockpit and the trim air was deferred per the MEL. In-flight crew experienced cold cockpit. Switched off left pack and cockpit temperature became normal.