737 Pack Control - Zone Temp Control
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Joined: Jan 2006
Aviation Qualifications: CPL
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From: Between a rock and a hard place
737 Pack Control - Zone Temp Control
For the Boeing techs out there,
Is the Pack Controller and Temp Controller one and the same electronic unit? Different books (FCOM, MEL) talk about pack controller, temperature controller, electronic controller? I understand that pack temperature output is to accommodate the zone demanding coolest air. Trim air is added to the other zones to achieve selected temperature.
What I don't understand, if it's the same 'unit', then what determines if you get a Pack light or a Zone Temp light for failure of an electronic controller? (Assuming no overheat caused the Pack/Zone Temp)
Recently we dispatched with a Pack Controller inoperative (i.e. Pack Light on Recall). The MEL (O) procedure was to verify operation of remaining controller. It instructs you to press Recall and verify Master Caution, AIR COND annunciator, Pack and Zone Temp illuminates. Then to reset and verify all lights go out. In our case the Pack illuminated but not the Zone temp. Ok, fair enough. We departed. Thought it was strange the DDPG said Zone Temp should illuminate as well but it didn't.
Is there an easy way to describe the relationship between Pack and Zone Temp?
Is the Pack Controller and Temp Controller one and the same electronic unit? Different books (FCOM, MEL) talk about pack controller, temperature controller, electronic controller? I understand that pack temperature output is to accommodate the zone demanding coolest air. Trim air is added to the other zones to achieve selected temperature.
What I don't understand, if it's the same 'unit', then what determines if you get a Pack light or a Zone Temp light for failure of an electronic controller? (Assuming no overheat caused the Pack/Zone Temp)
Recently we dispatched with a Pack Controller inoperative (i.e. Pack Light on Recall). The MEL (O) procedure was to verify operation of remaining controller. It instructs you to press Recall and verify Master Caution, AIR COND annunciator, Pack and Zone Temp illuminates. Then to reset and verify all lights go out. In our case the Pack illuminated but not the Zone temp. Ok, fair enough. We departed. Thought it was strange the DDPG said Zone Temp should illuminate as well but it didn't.
Is there an easy way to describe the relationship between Pack and Zone Temp?
