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Steve Keaton

RE: Apu usage from cold and dark scenario...

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Hi,

 

I'm sure the FCOM explains my forthcoming question in detail SOMEWHERE in it's cryptic volume, but for the life of me I can't seem to locate the answer I'm looking for.    Specifically, in a cold and dark scenario without external power usage, is the APU started without first doing a fire bottle/warning detect test beforehand?     When the battery master is turned on from a C and D scenario, the normal standby power mode is not active and the fire protection loops can't be tested until the APU is started and it's generator in on bus.      Does the 777 automatically do a fire protection loop test in the background before the APU starts is this condition?

 

It is possible to manually activate standby power via a guarded switch on the very top part of the overhead panel and commence a fire warning system check before starting the APU (without external power), but is this in fact normal procedure or is the automation doing all of this already in a normal cold and dark start up scenario?

 

Thank you,

 

Steven Keaton

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It should be in the Supplemental Procedures section of FCOM v1. SP 6.2 is the page on "my" FCOM, but I'm not completely sure whether the page will match on PMDG's FCOM.

In any case, the 777 is a highly automated beast. As far as I can see, no fire test is necessary before starting the APU.

 

As always, I could be wrong.

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I know on the CRJs, we ran a first test prior to starting it up. I know it's a different aircraft, but fire is fire and an APU is an APU.

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It is possible to manually activate standby power via a guarded switch on the very top part of the overhead panel and commence a fire warning system check before starting the APU (without external power), but is this in fact normal procedure or is the automation doing all of this already in a normal cold and dark start up scenario?

The Engine Battery Start Supplemental Procedure (FCOM v1, SP7) requires the Standby Power switch to be pushed to BAT then released to AUTO. Maybe that enables the APU fire test to be performed?

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Kyle:

 

I know. My company does a fire test on the 737 before starting anything too. However, in the 777 I can't find a mention of the APU needing a fire test before starting up. That makes me think this "automated beast" does the test itself.

Either that, or it's a maintenance responsibility.
In fact, the last option seems to be more and more feasible to me, come to think about it.

Kevin:

The checklist/flow you mention seems to be handling about an engine start straight from the batteries. (with a bleed source, of course.) You don't even need to start the APU to accomplish this flow if you have an external bleed source.
I'm not 100% sure, but I do think that's a different situation altogether.

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Thanks for the replies guys.    Digging into the FCOM a little more thoroughly, the section in volume 2, Chapter 8 on Fire Protection basically states that the fire detection and extinguisher systems for both the APU and engines do indeed have automatic fault detection systems associated with them.     If a fire is detected on the ground during APU start (without external power), the fire protection system will automatically both shut down the APU AND discharge the fire bottle.     Apparently, all the pilot has to do is run.....    :lol:

 

I decided to test this with the PMDG 777 and programmed an APU fire to occur 15 seconds after I started it on the ground.     APU fire warning activated and the fire bottle automatically discharged whilst the APU shut itself down.     Wow PMDG, fine details much?     This is good stuff!

 

-Steven Keaton

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Apparently, all the pilot has to do is run.....

 

That reminds me of a good book written by a B-52 navigator. His first flight in the real thing included smoke from an electrical fire and the AC yelling 'BAIL BAIL BAIL,' instructions during school were any possibility of fire on the ground in a fully loaded BUF were to run. One student asked how far they should run, and the instructor responded 'until you feel silly.' Still makes me giggle.

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I know. My company does a fire test on the 737 before starting anything too. However, in the 777 I can't find a mention of the APU needing a fire test before starting up. That makes me think this "automated beast" does the test itself.
Either that, or it's a maintenance responsibility.
In fact, the last option seems to be more and more feasible to me, come to think about it.

 

Yeah. Wasn't really questioning you, really. I was actually trying to make it more apparent that I was guessing, myself, instead of asserting that an RJ's procedures should be the same as 777 procedures.

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That reminds me of a good book written by a B-52 navigator. His first flight in the real thing included smoke from an electrical fire and the AC yelling 'BAIL BAIL BAIL,' instructions during school were any possibility of fire on the ground in a fully loaded BUF were to run. One student asked how far they should run, and the instructor responded 'until you feel silly.' Still makes me giggle.

 

George Costanza and I share the same outlook on self-preservation instincts in the event of a fire.     Perhaps this is why the airlines won't hire me...   :unsure:

 

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Kyle: I must've misread your post then, my bad. Considering the time of night when I answered yesterday, that might be the reason. :unsure:

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The checklist/flow you mention seems to be handling about an engine start straight from the batteries. (with a bleed source, of course.) You don't even need to start the APU to accomplish this flow if you have an external bleed source.

I'm not 100% sure, but I do think that's a different situation altogether.

It isn't the exact situation I agree, but it covers it essentially. It's a DC power only engine start which may also involve an APU start. Both would require fire system monitoring as for a start with AC power available.

 

Anyway, with the Standby Power switch in AUTO that should automatically power the standby busses from the battery with no AC available. So fire testing will be normal. Switching it to the BAT position forces it to work from battery power if it wasn't already in that mode,

 

edit: According to the FCOM, the APU fire detection system powered by the main battery, so this whole discussion may be moot. Without wiring schematics it's not possible to know exactly what powers what and when.

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