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Guest pooleycrp1

PMDG 747 400 APU Start

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Guest pooleycrp1

I am trying to start the APU from the 'cold and dark' Panel.I read that after refuelling (using the PMDG option), the fuel selector switches automatically set to the correct configuration.They momentarily iluminate then go out.Is this normal?If not, what am I doing wrong?Help please

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"They momentarily iluminate then go out. Is this normal?"Crossfeed valve VALVE lights will illuminate whenever the cockpit switch position disagrees with the actual valve position. Since valves are driven by electric motors and gearboxes, the valves don't instantaneously move from open to closed (or vice versa). This will cause the VALVE lights to momentarily illuminate. Colours on the EICAS FUEL Synoptic will also reflect this. However, EICAS messages for VALVE failures should not appear (even momentarily), because of time delays in the software. Fuel pump PRESS lights, in theory, will also not disappear instantaneously, as the pumps will take a few moments to build up enough pressure to activate the fuel pressure sensing switches located at the outputs of the pumps (to extinguish the PRESS lights).Hope this makes sense.Cheers.Q>

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Guest pooleycrp1

Thank you for the reply. No, the battery switch is not the problem, i set that to 'ON' at an earlier stagecheers>I am not real sure. I'm still new to all this myself, but if>I remember correctly you have to turn on your battery first.>Then once you have the APU started you click the buttons for>APU power.>>>>http://www.precisionmanuals.com/images/forum/747400.jpg

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Guest pooleycrp1

Thank you for the explanation of the way in which the fuel lights are illluminated. What you say is logical. However, am I to expect the lights to come on again when the valves and solenoids have switched in ?(completed the desired setting).I would apreciate help on this, thanks

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Guest LAzerxxx

After you push the buttons for your crossfeeds the valve lights will come on only as the valves are openig/closing. If you are opening them, there will be a lightly shaded bar running across the button, showing that they are open. If you are closing them the bar will not be there.Hope this help and that my information is correct.Also, could you please sign your name to your posts as it is a forum rule and also nice to know who we are addressing. I only say this cause I made the same mistake myself. I am in no way trying to sound rude or bossy, just trying to help you out so someone who is that way doesn't say it to you rudely :-DHappy Flying, Hayden Lee Laffoonhttp://www.precisionmanuals.com/images/forum/747400.jpg http://www.captainsim.com/user/dl/c130/c130_captain.gifhttp://www.captainsim.com/user/dl/b722/727_01.JPG

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"However, am I to expect the lights to come on again when the valves and solenoids have switched in ?(completed the desired setting)."The lights should illuminate momentarily at any time during the flight (or on the ground) during valve transit... or permanently illuminate if there is no power to open/close them (and the valves can't move to their selected positions). However, the fuel crossfeed valves are controlled by the Battery Bus, and it's not likely that the Battery Bus will fail completely.Hope this helps.Cheers.Q>

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Guest pilotbrian0

Just to add to what was said. Crossfeed valves should light momentarily and then go out. This says that they are where they belong. Pump Press lights are supposed to stay out until you have sufficient power supply to power all the utility busses (If you iso one bus at a time after applying APU power, you can see which pumps are on which buses).Typically, when doing an APU start with no Ground Power, I see all the press lights on except the #2 Fore Override pump (has a connection to the APU battery bus so that the APU can run since the APU uses that pump for its gas).The squence that I follow for APU start is as follows:Battery switch......................................OnStandby Power switch................................Battery--> Check PFD/ND/Primary EICAS screens on, Secondary EICAS screen offStandby Power switch................................Normal (This last 3 steps was to make sure that the battery standby bus is working correctly, and is real world procedure)APU.................................................Start--> Check that PFD/ND went black, Primary EICAS screen should still be on--> When the PFD/ND come back on, watch for the APU running on the Primary EICASAPU 1...............................................OnNOW I FUEL: WHY? Well, the fueling system actually requires power (this is not modeled in the PMDG because of limitations). The idea is that either the GPU at the airport is connected and providing sufficient power to fuel (but then why use the APU) or the APU is running providing that power.If I remember correctly, the Fueling system is on the Ground Service bus which requires A) EXT 1 or APU 1 to be selected ON or :( EXT 1 or APU 1 to be AVAIL and the switch at the Flight Attendents station near the 5L Door set to tie (has Tie/Isolate and allows tieing of the Ground Service bus to the Ground Handling bus. Allows flight attendants to get power in the cabin without the pilots having powered up the flight deck)-Brian

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Guest pilotbrian0

OOPS: TYPOS!Crossfeed valves should light momentarily and then go out. This says that they are where they belong. Pump Press lights are supposed to stay out until you have sufficient power supply to power all the utility busses (If you iso one bus at a time after applying APU power, you can see which pumps are on which buses).What that is SUPPOSED TO SAY (SORRY!) is:Crossfeed valve lights should light momentarily to show that they are moving, then go out. If they are out, it means they are where the switch is set to (AKA, if the switch is set to closed but the valve is open, the valve light will be on, and will always be on when it's in transit, THIS IS NORMAL and lets the pilot know what the valve is doing.) Also note that the light is Yellow because it is an advisory indicator. That means that if its on, its telling you something is different than what you have set or is different than what is required for normal operation.Pump Press lights are also yellow (also advisory, rather than simply informative) and should stay ON until the APU 1 switch is set to On powering the Utility Buses. The exception is the #2 Fore Override pump which operates to provide fuel to the APU. Other than that, what I said above is correct.-Brian

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Brian.. You seem to be guessing at what powers the fuelling system and pumps(?)According to my manuals, the refuelling system can be powered by the main busses, the Ground Handling Bus or the HOT Battery Bus. Unless you are down to battery power and battery is flat, you will still be able refuel the aircraft. There is a Battery switch at the wing fuelling station to activate the HOT Battery powered fuelling system. PMDG may have taken this into account.Utility Busses only power certain pumps. These pumps are loadshed when the elec power system is being overloaded. The pumps are powered by various busses for safety reasons. PMDG have programmed this correctly as far as I can recall.The #2 AFT BOOST pump is activated automatically with the APU running, NOT the FWD Override Pump. Optionally in the real world, the #3 AFT Boost pump can also provide fuel to the APU.Hope this helps.Cheers.Q>

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Guest pilotbrian0

ok, got the Aft/Fore backwards (I knew I should have actually run the procedure while typing.)I also have to wonder why you say I seem to be guessing at what powers the pumps as you appeared to agree with me.However, I find I have to disagree with the availability of the Fueling system. According to the manual(page 11-45):"Electrical power for fueling operations must be provided by the APU, aircraft battery, or an external power source."In short, the Fueling system can use the battery as a backup, but cannot run off of a main bus, it has to run off either the main Hot bus or the Ground Handling Bus. Which is logical, I missed the part about battery power when I first reviewed the manual. However, it is not advisable to rely heavily on the battery before start of the APU, if it's going to be needed for power at the gate. If there is a GPU available and the APU is only going to be used to start the engines after pushback, then yes, go ahead and use the battery to fuel the plane.-Brian

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Guest pilotbrian0

Brian :(Bored College Student-Brian

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Guest LAzerxxx

LOL, I hear ya Brian, I love all things flight but until recently just haven't had any extra time to sit down and study flight manuals or aicraft manuals. Sure do hope I get a job soon though, going stir crazy just sittin around and not makin any moneyHappy Flying, Hayden Lee Laffoonhttp://www.precisionmanuals.com/images/forum/747400.jpg

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"ok, got the Aft/Fore backwards (I knew I should have actually run the procedure while typing.)"And the pump is not an override pump as you suggested ;)"I also have to wonder why you say I seem to be guessing at what powers the pumps as you appeared to agree with me."You seem to be saying that ALL the pumps are powered by Utility Busses. Switch off the Util Busses and you will see that this is not the case. Note: Since the power supplies to the PRESS light lamps is also modelled, you may not get all the PRESS lamps lighting up (so you may have trouble identifying which pumps are actually working by depowering various busses)The FQIS is the brains of the refuelling system. The FQIS is normally powered by Main Busses 3 and 4, but I will look into the matter further.Cheers.Q>

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