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bjratchf

Fwd Cargo Fire Loop B

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I was performing a flight and noticed after landing that due to service based failures, my FWD CARGO FIRE LOOP B had failed. It's ok, we can MEL it (with restrictions on ETOPS, etc). But other than looking at the FMC "failures page," how does one find out the loop has failed. It passes the Fire warning test, and there's not a message on the Status page after landing. So say I was the maintenance guy at the outstation and wanted to PDC check the plane for the ETOPS signoff- is there a way to "find failures" without cheating and looking at the FMC failures page?

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FCOM 8.20.9 describes how to do the cargo fire detection tests and It clearly says that all loops must be operating to pass the test.  Which specific test did you perform when you say it "passes the fire warning test?"

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23507130648_ec0a5a5022_b.jpgFMC fire by Violin Velocity, on Flickr

 

36649469404_85fd194fe8_z.jpgfire panel by Violin Velocity, on Flickr

 

23507130828_5d1079b2e4.jpgdisplay by Violin Velocity, on Flickr

 

Following this guidance... I'll have to check PMDGs version of the FCOM... 

 

23507182768_74f0d99abf.jpgVol1 by Violin Velocity, on Flickr

 

 

I could be that because one loop can be MEL'd- it will pass the test? I'm just trying to figure out, if it never shows a LOOP fault on the EICAS- and the fire test passes, how does the operator know to write it up in the aircraft logbook? 

 

I tested with both loops failed, and as expected, the fire test does not pass, which is indicated in the EICAS.  

 

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I recommend you check the FCOM section that I referenced.  And it's not a "PMDG version" rather it is a Boeing publication licensed for limited distribution by PMDG.  I prefer the Boeing documentation.

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Thanks Dan- I realize PMDG's version is a copy the boeing publication- whenever I have any questions I usually refer to my company's own manual which also comes from Boeing source material. 

///////////////

Cargo Compartment Smoke Detection
The forward and aft cargo compartments each have smoke detectors. Each compartment is divided into three detection zones. If smoke is detected in any zone, a fire warning occurs. Whenever cargo compartment smoke detection is inoperative, the EICAS advisory message DET FIRE CARGO (FWD or AFT) is displayed. 

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In any case both FCOM sections match for the most part, but as is typical with boeing manuals, they don't go into much depth to say what happens when one loop fails. In the engine fire paragraph it describes the result of a single loop fail as reconfiguring to single loop operation, and that the failure of both loops will yield a  DET FIRE ENG EICAS caution. It's probably the same with the cargo fire detection loop. 

 

It's no big deal, I was just curious how one would ascertain (from a pilot's seat) that a loop has failed- and initially I'd expect such a low level fault to be something that would pop up on the status page after landing, but it isn't. With modern aircraft its possible for maintenance staff to go into the FMC and pull faults that pilots cannot see, which is something that PMDG most likely doesn't simulate. 

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16 hours ago, bjratchf said:

I was performing a flight and noticed after landing that due to service based failures, my FWD CARGO FIRE LOOP B had failed. It's ok, we can MEL it (with restrictions on ETOPS, etc). But other than looking at the FMC "failures page," how does one find out the loop has failed. It passes the Fire warning test, and there's not a message on the Status page after landing. So say I was the maintenance guy at the outstation and wanted to PDC check the plane for the ETOPS signoff- is there a way to "find failures" without cheating and looking at the FMC failures page?

 

If you have a FWD cargo loop B failure, the STS page will show the relevant msg (likely to be DET CHAN 1 or 2 CARGo FWD in this case) prompting the captain to put an entry into the tech log to notify the engineer upon arrival. 

 

The engineer will then go to the MAT ( Maintenance access terminal) nearby the 4th observer's seat to check the nature of the msg and perform relevant software tests on the all of the systems in accordance their maintenance manual. 

 

The FMC on the real airplane does not hold any information with regard to the failure of any of the systems, it is the MAT which does the job.

However, you can access the Maintenance Screen using the FMC menu, there is a prompt MAINT, to check detail parameters of some of the systems  i.e IDG oil service requirements, output temperature of a pack, precise position of the outflow valve etc. you may also deactivate the electronic checklist in this section. 

 

this video show how the engineer used the MAT as well as the FMC -MAINT function. 

 

There are maintenance messages which is a level below STS message, in this case, the airplane manufacturer thinks that the pilots do not need to know about the such maintnenance message, therefore those messages only shown up in the MAT for the engineers to check. 

During every transition check, the engineers will check the MAT as well as the EICAS and STS message before they can release the airplane for flight. 

 

Any action taken will be recorded in the maintenance logbook of the airplane so that the next set of pilots will know what maintenance action had been done with the airplane. 

 

 

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Thank you so much- this is very insightful, I had an inkling that it would be a status message on the STS page- but this is probably out if the scope of the PMDG simulation. 

What's funny is that out of curiosity, I failed a single loop on an engine (not cargo), and the PMDG status page displays it (FIRE LOOP 1 ENG L). I'm guessing the cargo fire det single loop failure is either low enough priority to not be on the status page (instead, it is on a MAINT diagnostic page accessed as shown in your video). Failing both ENGINE loops gives the EICAS caution- DET FIRE ENG L/R, while as said a single loop is only a STS message. 

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System Tests
The smoke detectors have Built-in-test-equipment (BITE). The BITE does power-up and periodic tests of the system. Faults cause alert messages, status messages, or maintenance messages. You can also use the FIRE/OVERHEAT TEST switch to do a test of the system.

MAINTENANCE TIP
The CMCS shows status and maintenance messages for the smoke detectors. A fire protection maintenance page shows information about the system. The cargo smoke detectors keep fault data in memory. You can use the MAT to access this fault data. You can also use the MAT to access smoke detector hardware and software part numbers. Use the CMCS download function to load new software into the smoke detector.

 

23521092418_1e33581e0e_z.jpgfireprotMAT by Violin Velocity, on Flickr

 

23521092388_6b9b981051_b.jpgsystest by Violin Velocity, on Flickr

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