Narrative:

Approximately XA00 on jun/tue/02 flight abc, ZZZ-ZZZ1. Ambient temperature approximately 90 degrees, ramp temperature +90 degrees. At around 10 mins to scheduled departure, I received a gate call for aircraft X with an EICAS status message 'equipment cooling flow' accompanied by an equipment overheat light. Troubleshooting the system revealed that the forward exhaust flow sensor was the source of the EICAS message and overheat light procedure was to perform airflow checks by feel at the equipment cooling overboard exhaust valve and east&east racks. These checks were performed and it as determined that east&east air flow was normal. Removing the electrical connector from the forward equipment cooling low flow detector extinguished the equipment cooling EICAS low flow message and overheat light. Since the aircraft was loaded, already on delay, was the last flight of the day and the aircraft was to remain overnight at a maintenance station, it was determined by maintenance control and myself to MEL the equipment cooling warning system. MEL procedures require the connector on the low flow detector to be removed and stowed, which I did. As a result of removing this connector, other EICAS maintenance messages can be generated which are also addressed in the MEL special procedures. These procedures require the following airflow checks through the equipment cooling system: 1) exhaust vent -- which I checked while troubleshooting the system. 2) E6 rack -- also checked with troubleshooting. 3) remove copilot's HSI CRT and verify that airflow can be felt with a hand located against the first officer's control column, which I accomplished and reinstalled the HSI. I completed the MEL and signed the logbook stating the MEL special procedures were accomplished. The aircraft was dispatched and I felt rather good about saving the flight and getting 150 people to their destination without too much inconvenience. The problem, which was pointed out to me several days later by a member of air carrier X flight safety committee, was that it did not occur to me to downgrade the CAT status of the aircraft due to the HSI removal and reinstallation. I certainly do accept that it was/is my responsibility to enter the CAT statement. However, I do feel that the somewhat lengthy and complicated special procedures and the use of a CAT item (HSI) to perform the airflow check is a setup for just such an error. A statement or caution in the MEL procedure noting the CAT situation would be helpful.

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Original NASA ASRS Text

Title: A B757 WAS DISPATCHED IN NON COMPLIANCE AFTER A FLOW SENSOR WAS DEFERRED PER THE MEL. SPECIAL PROCS DID NOT STATE REMOVAL OF ACFT FROM AUTOLAND STATUS.

Narrative: APPROX XA00 ON JUN/TUE/02 FLT ABC, ZZZ-ZZZ1. AMBIENT TEMP APPROX 90 DEGS, RAMP TEMP +90 DEGS. AT AROUND 10 MINS TO SCHEDULED DEP, I RECEIVED A GATE CALL FOR ACFT X WITH AN EICAS STATUS MESSAGE 'EQUIP COOLING FLOW' ACCOMPANIED BY AN EQUIP OVERHEAT LIGHT. TROUBLESHOOTING THE SYS REVEALED THAT THE FORWARD EXHAUST FLOW SENSOR WAS THE SOURCE OF THE EICAS MESSAGE AND OVERHEAT LIGHT PROC WAS TO PERFORM AIRFLOW CHKS BY FEEL AT THE EQUIP COOLING OVERBOARD EXHAUST VALVE AND E&E RACKS. THESE CHKS WERE PERFORMED AND IT AS DETERMINED THAT E&E AIR FLOW WAS NORMAL. REMOVING THE ELECTRICAL CONNECTOR FROM THE FORWARD EQUIP COOLING LOW FLOW DETECTOR EXTINGUISHED THE EQUIP COOLING EICAS LOW FLOW MESSAGE AND OVERHEAT LIGHT. SINCE THE ACFT WAS LOADED, ALREADY ON DELAY, WAS THE LAST FLT OF THE DAY AND THE ACFT WAS TO REMAIN OVERNIGHT AT A MAINT STATION, IT WAS DETERMINED BY MAINT CTL AND MYSELF TO MEL THE EQUIP COOLING WARNING SYS. MEL PROCS REQUIRE THE CONNECTOR ON THE LOW FLOW DETECTOR TO BE REMOVED AND STOWED, WHICH I DID. AS A RESULT OF REMOVING THIS CONNECTOR, OTHER EICAS MAINT MESSAGES CAN BE GENERATED WHICH ARE ALSO ADDRESSED IN THE MEL SPECIAL PROCS. THESE PROCS REQUIRE THE FOLLOWING AIRFLOW CHKS THROUGH THE EQUIP COOLING SYS: 1) EXHAUST VENT -- WHICH I CHKED WHILE TROUBLESHOOTING THE SYS. 2) E6 RACK -- ALSO CHKED WITH TROUBLESHOOTING. 3) REMOVE COPLT'S HSI CRT AND VERIFY THAT AIRFLOW CAN BE FELT WITH A HAND LOCATED AGAINST THE FO'S CTL COLUMN, WHICH I ACCOMPLISHED AND REINSTALLED THE HSI. I COMPLETED THE MEL AND SIGNED THE LOGBOOK STATING THE MEL SPECIAL PROCS WERE ACCOMPLISHED. THE ACFT WAS DISPATCHED AND I FELT RATHER GOOD ABOUT SAVING THE FLT AND GETTING 150 PEOPLE TO THEIR DEST WITHOUT TOO MUCH INCONVENIENCE. THE PROB, WHICH WAS POINTED OUT TO ME SEVERAL DAYS LATER BY A MEMBER OF ACR X FLT SAFETY COMMITTEE, WAS THAT IT DID NOT OCCUR TO ME TO DOWNGRADE THE CAT STATUS OF THE ACFT DUE TO THE HSI REMOVAL AND REINSTALLATION. I CERTAINLY DO ACCEPT THAT IT WAS/IS MY RESPONSIBILITY TO ENTER THE CAT STATEMENT. HOWEVER, I DO FEEL THAT THE SOMEWHAT LENGTHY AND COMPLICATED SPECIAL PROCS AND THE USE OF A CAT ITEM (HSI) TO PERFORM THE AIRFLOW CHK IS A SETUP FOR JUST SUCH AN ERROR. A STATEMENT OR CAUTION IN THE MEL PROC NOTING THE CAT SIT WOULD BE HELPFUL.

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.