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B757 Zone/Duct Temp Indication  
User currently offlineCdfmxtech From United States of America, joined Jul 2000, 1341 posts, RR: 24
Posted (14 years 10 months 5 days 9 hours ago) and read 1897 times:

The Maintenance Manual states that the Zone temp Bulbs send a signal to the EICAS computers. I am going back to work tomorrow and I will check myself, but I was wondering if someone knew off the head if this is true. I always thought it was only duct temperature. And I can't find anything in the wiring diagrams that support the zone temp being displayed on EICAS. I know Duct temp is there, but don't remember Zone temp being there. Maybe it's an option on some aircraft.

My Maintenance training manual also makes no mention of the Zone Temp indicated on EICAS.


5 replies: All unread, jump to last
User currently offlineFDXmech From United States of America, joined Mar 2000, 3251 posts, RR: 30
Reply 1, posted (14 years 10 months 4 days 14 hours ago) and read 1857 times:

You're correct. The zone duct temp bulb feeds the EICAS computer. The zone compartment temp bulb feeds the digital readout on the air conditioning panel.

I researched my old AA 757 manuals and saw where you might have thought that the compartment temp bulb might have fed the EICAS (poor wording in the studyguide). Truth is after reading it, that was the same conclusion I drew. But after rereading and rerereading and studying the simplified schematic in the study guide, I came to the shaky conclusion that the compartment temp bulb didn't feed the EICAS.
Then I checked my 757 schematic manual (interesting story how I got my hands on this beauty, maybe another time) which definitelt shows compartment temp bulb does not go to EICAS.
When you go to work, check out 757 schematics 21-65-01 and 21-65-02.

You're only as good as your last departure.
User currently offlineCdfmxtech From United States of America, joined Jul 2000, 1341 posts, RR: 24
Reply 2, posted (14 years 10 months 4 days 12 hours ago) and read 1849 times:

Thanx...I thought I was going nuts!!!

Both manuals ( 2 different airlines)that I have at home says the following:

"(5)Three zone temperature bulbs send electrical signals to the compartment temperature indicator. The three zone temperature bulbs also send electrical signals to the EICAS computer. The resistance-type temperature bulbs send a signal to the indicator and the EICAS computer. The strength of the signal changes because of changes in the temperature."

Both wiring diagrams (the ones you referenced) that I have with these manuals don't show any Zone Temp Bulb wiring to the EICAS. So I'll check with the ones at work. I think we're right..but maybe the ones at work MIGHT tell me something different.


User currently offlineAir2gxs From , joined Dec 1969, posts, RR:
Reply 3, posted (14 years 10 months 4 days 9 hours ago) and read 1844 times:

I'll check tonight but I thought some operators had compartment temp displayed on the ECS/MSG page. MAybe some operators have it displayed on status also. Can't have the drivers looking up all the time to decide whether its too hot or cold.

I'll look tonight on one of our B757s.

User currently offlineCdfmxtech From United States of America, joined Jul 2000, 1341 posts, RR: 24
Reply 4, posted (14 years 10 months 3 days 19 hours ago) and read 1840 times:

OK...I checked our B757s and we don't have Zone/Compartment Temp indicated on EICAS on eitehr the ECS/MSG page or the status page. I sent out a letter to our pubs dept. Air2gxs...lemme know about yours.

FDX - the wiring prints don't show Zone temp bulbs with outputs to EICAS on our WDM.


User currently offlineAir2gxs From , joined Dec 1969, posts, RR:
Reply 5, posted (14 years 10 months 7 hours ago) and read 1831 times:

Sorry it took so long to get back to you. We had an air turnback for a failed 2040 (turbine seperation) and I never got back to the computer. Then I went on my days off. Precious days off.

We have no compartment twmp readout anywhere on EICAS. The only place to see compt. temp is the overhead panel. If I get a chance I'll break out the schematics and check if we have a leg from the bulbs to EICAS.

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