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JumboJet

A proposal for the APU

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Hello
I want to say that I am not a pilot, I make a proposal, if I am wrong I hope to learn, so I repeat I can be wrong!!!!!

During the APU Start the PMDG AFT MAIN 2 and 3 PRESS light are extinguished, but I think that, during start only MAIN 2 AFT PRESS gotta be extinguished and when the APU is running the MAIN 2 and 3 AFT PRESS light is extinguished.

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Full names in the PMDG forums please.  You'd save the time for an answer by looking the in the FCOM..., it was pretty easy to find in the fuel systems description system for APU (FCOM 12.20.13).

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It says that if AC power is available main 3 pump operates, which is confirmation that what you see is correct.  Am I missing something?  An please, full names here.

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Do I have to share my identity all over the internet? If so, I do not want, I find it dangerous for me.

 

FCOM says :

Verify that the MAIN 2 aft pump PRESS light is extinguished
when APU is running.

Verify that the MAIN 2 and 3 aft pump PRESS lights are
extinguished when APU is running.

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Jean, what electrical power do you have on the aircraft prior to APU start?

During APU start with no power on the main AC Busses, the main tank AC-powered boost pumps cannot run. In this situation, a backup DC pump is used. There are no flight deck indications for DC pump pressure.

The fuel pressure produced by the DC pump cannot reach the AC-powered boost pump pressure sensors (because of one-way (check) valves in the fuel lines). This means that the Aft Boost Pump pressure lights will not respond to DC pump operation.

 

Hope this makes sense.

Cheers

JHW

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1 hour ago, JumboJet said:

Do I have to share my identity all over the internet? If so, I do not want, I find it dangerous for me.

 

Yes, to use this forum.  Billions of people have names, I didn't realize you were unique in that sense.  However, you are welcome to contact PMDG directly for support rather than using the user forum.  Open an account at PMDG Product Support and submit a trouble ticket.

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Thanks for the answer Qavion2, I was on EXT POWER.

 

downscc : Thanks for the info, I will now used PMDG ticket because you do not have the right to anonymity in this forum and you do not understand that some people can be afraid of the internet, facebook etc with real name.

PMDG had told me to put a signature not my name, sorry to have you deranged by not giving you the honor to know who I am in my private life.

 

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1 hour ago, JumboJet said:

 

PMDG had told me to put a signature not my name, sorry to have you deranged by not giving you the honor to know who I am in my private life.

 

The PMDG signature rules are posted here for your review. A signature means first and last name.

Since you feel uncomfortable signing your real name the ticket system will be your best course of action going forward as you mentioned.

Sean Campbell

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4 hours ago, JumboJet said:

FCOM says :

Verify that the MAIN 2 aft pump PRESS light is extinguished
when APU is running.

Verify that the MAIN 2 and 3 aft pump PRESS lights are
extinguished when APU is running.

 

7 hours ago, JumboJet said:

but I think that, during start only MAIN 2 AFT PRESS gotta be extinguished and when the APU is running the MAIN 2 and 3 AFT PRESS light is extinguished.

 

So you're saying that Main 3 Aft should stop running during start. Is this when the switch is held in START, or while the APU starter is engaged?

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Jean, unless I've overlooked something, looking at the 747-400 wiring diagrams, I can find no reason why the #3 Aft Boost Pump should stop working during APU start.

#2 and #3 Aft Boost pumps are energised whenever the APU Fuel Control Relay is energised. The APU Fuel Control Relay is energised when the APU selector is in the ON or START positions and the following is not true:

APU fire handle pulled

APU fire detected

APU fault not active

Aircraft in the air

(There may be airline variations, however.)

Even during loadshedding (or Utility Busses switched off), only the forward pumps are affected.

Cheers

JHW

 

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On the FCOM a sentence gives you reason and a sentence gives me reason it was to be revealed that it depends on the model of the plane. So PMDG were not wrong, but could add as an option if they want.

109 = PAX avec PW
570 = Freighter avec GE

So I will try with a 747-400ERF GE, he gotta start like you said

EDIT : This is the same with GE ERF but PW do not have to start like PMDG does ( some old models I think )

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I think Jean is asking whether Fuel Pump 3 Aft running automatically when the APU is running and AC power is available can be made an option, not according to aircraft version (as the FCOM implies). The good news is that it already is. Page 11 of the equipment options is FUEL & WT/BAL. The first item is FUEL SYSTEM and if you select UPDATED Pump 3 Aft will run together with Pump 2 Aft. If you select ORIGINAL, only Pump 2 Aft runs. Other things change too, such as center tank pump operation with low fuel quantities.

The Introduction Manual describes this option generally but not in full detail so the operation with APU is not specified. So reading the manual would not have helped.

The depth and complexity of this sim never ceases to amaze me.

  • Upvote 2

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Thanks you made my day I needed this option for Delta flights many times thank you!

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