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Guest KevinS13

Duct pressure problem 744...please help

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Hello,I think I may be having a problem with the duct pressure during startup on the 744 PAX version and I'm not sure if it's me or something else. I start cold and dark and go thru all the checklists, start the apu, apu bleed air on. At this point, with the packs off I am only getting 23 psi for the duct pressure. I have tried all combos of packs all on, all off, one on two off, etc. I have also tried the isolation switches on and off and I never get more that 23 psi on the duct pressure.Based on this psi value the autostart system does not work, although I can eventually get it started using a manual start.Anyone have and tips or suggestions to help out? Thanks,Kevin Shea

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I believe this question was answered yesterday, Kevin ;)Cheers.Q>

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Well, sort of....(if I'm thinking of the same thread) that guy could actually get started using autostart, and had 27 psi, mine is 23 psi and autostart failsAny other ideas?Kevin

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Hi Kevin,I can autostart with either 27psi (one pack off) or 19psi (two packs off).Did you the engines breed air on?Sincerely,Kan-ichiro Fushihara

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Kan-ichiro,I have tried all combos of bleed air, etc and can't seem to get more than 23 psi at all. Thanks for the reply, I guess it's manual starting for me:-( Kevin

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Kevin, by chance could you take a picture of the overhead when you are trying to do an autostart? That way we could see how you have everything set up, and it would help us figure out what you are doing wrong. :)If you do take a shot, make sure it's big enough so we can see it. ;)

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Hum,I can start engines with either auto or manual.Sincerely,Kan-ichiro Fushihara

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Do you also have Nacelle Anti-Ice selected? Or perhaps are using Ext air? (which might not have a variable output to compensate for increased load).Cheers.Q>

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Thanks for the replies, I will try to get a picture of my setup, however I just follow all the checklist items from the cold and dark setup at Everett field using the PMDG select a flight option. I know for sure I'm not using nacelle anti ice and I don't think I am using Ext air, I'll have to check that one.Thanks again,Kevin

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Here are shots of the overhead config I have and a shot of the panel showing the duct pressure at 23psi. I can't even get the duct pressure to change at all when I turn all the packs on, one on and two off, two on and one off, etc. If I turn off one isolation switch the pressure on that side drops to zero, but I can never get anything above 23 psi period. BTW, autostart will not function in this setup I have, when I pull the start knob the white light does not illuminate.Here are the shots. Hopefully you can see the overhead shot well enough, I had to edit it a bit to get it under the size limit.Thanks,Kevinhttp://forums.avsim.net/user_files/146059.jpghttp://forums.avsim.net/user_files/146061.jpg

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What happens when you turn the fuel pumps on? What I see different from what I do, is that also, the 4th Hyd Demand Pump should be in auxilary position (AUX). Packs don't matter as I recall, since Autostart configures them for start-up.

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As Sergey mentioned you need fuel to start the engines. :-)Turn the pumps on and they should fire.

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well folks,I tried to start up engines with exactly same config as shown on screens and it worked wellp.s. even with all fuel pumps off, engines will start and before you ask, no its not a bug, its boeing!

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So what was your psi value on the duct pressure? In my screen shots I didn't have the fuel pumps on because I was just showing the duct pressure problem I am having which is only 23 psi. When trying an autostart I obviouly turn on the fuel pumps. I am just trying to figure out why my duct pressure just sits at 23 psi regardless of what I do to anything in the air system.Kevin

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ЗДравствуйте, Sergey, packs do not automatically reconfigure, no matter what position the autostart switch is in (at least not in PMDG or any of the 744's I've worked on).The APU controlling system will, however, sense that the packs are on and the start system has been activated and it will command the APU to (attempt to) supply an appropriate amount of bleed air.The APU bleed system has various modes. The modes can be seen on one of the CMC Maintenance pages, but unfortunately, this cannot be seen in the sim.The pack supply valves will close automatically and shut down the packs if the duct pressure drops really low (but the pressure will have to be so low to do this, the bleed duct values on the ECS Synoptic will be amber).I'm not 100% sure if these bleed demand pressure changes are modelled in the PAX version of the 744 (My memory is a little fuzzy at the moment). Perhaps those without the Freighter update can check this for me.Thanks.Cheers.Q>

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Here's some real world duct pressures I recorded earlier...Healthy, new aircraft... CF6-powered TAT 23degC 0 packs = 21-22 psi1 pack = 19 psi2 packs = 26/27 psi3 packs = 28 psi P&W-powered aircraft (age unknown) 0 packs = 17 psi1 pack = 15/16psi2 packs = 22/23 psi3 packs = 23/24 psiI don't have any start values.As you can see, the pressure rise is not consistent with demand (in the case of one pack), but no explanation is given for this in the Maintenance Manual.Don't expect consistency in the real world ;)Cheers.Q>

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Kevin, not sure what the problem is with your plane. I set it up the exact same as your screen and was able to start the engines no problem.Did some testing with my non F version of the Queen. GE engines, although I don't think it matters without the F.0 packs on - 221 pack on - 192 packs on - 273 packs on - 28I'm impressed with how close, which to say, exact, the PMDG numbers are to your real world numbers Qavion.

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>ЗДравствуйте,>Sergey, packs do not automatically reconfigure, no matter what>position the autostart switch is in (at least not in PMDG or>any of the 744's I've worked on).>>The APU controlling system will, however, sense that the packs>are on and the start system has been activated and it will>command the APU to (attempt to) supply an appropriate amount>of bleed air.>>The APU bleed system has various modes. The modes can be seen>on one of the CMC Maintenance pages, but unfortunately, this>cannot be seen in the sim.>>The pack supply valves will close automatically and shut down>the packs if the duct pressure drops really low (but the>pressure will have to be so low to do this, the bleed duct>values on the ECS Synoptic will be amber).>>I'm not 100% sure if these bleed demand pressure changes are>modelled in the PAX version of the 744 (My memory is a little>fuzzy at the moment). Perhaps those without the Freighter>update can check this for me.>>Thanks.>Cheers.>Q>What's up Q! (Like in James Bond movies -- Q) Good to have a person knowledgeable in 744 systems here.My highest duct pressure is 23, with all three packs on, and 19, with just one on. Everything starts just fine, but then again I never use autostart.Cheers,-----------------------------------------Sergey Kireyevhttp://www.precisionmanuals.com/images/for...argo_hauler.gif http://bav.vatools.com/pilotinfo.php?pid=0...b744&vid=958937

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Guys,Thanks for the replies. What are your thoughts about me not even having the duct pressure change at all when I turn on or off one or more of the packs. That pressure is stuck at 23 psi regardless of what I do unless I close (or open, can't remember) the isolation switches and then the psi just goes to zero.Kevin

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I meant to ask this earlier, but how are you loading the plane? Are you loading a saved flight?As for it getting stuck at 23psi, that makes me think something is wrong with the flight file. Which is why I asked what I did above.The only suggestions I have at this point are, one, make sure you load the plane by loading the default cessna, then switching to the 744, and two, reinstall. I know, I hate that word too. ;)Maybe someone else can chime in and help you. I've about exhasted all I can think of. Sorry man, wish I could be of more help.

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Mike,I don't like that re-install word either :-erks but it might come down to it. FYI, I am loading FS up in the following way.1) Start FS2) Go to the select a flight section and then to the PMDG section.3) Choose the 747 C&D at KPAE delivery flight option at dawn. (Can't remember exactly what it's called but it's close)Then at this point I either choose a new aircraft (like Air Canada or Northwest) and start through the checklists.I haven't tried loading the 744 by way of the default Cessna for a long time now, I use it all the time for the PMDG 737 loading so it makes sense that I should try it for the 744 as well.Thanks for the tip and I will let you know how it goes.Kevin

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Gidday Kevin,The engines will start with no fuel pumps on but that is not normal. Duct press at 23 psi before start is normal. Packs 2 and 3 should be off for the start. Hyd Demand pump in the aux position and then 1, 2 and 3 demand pumps to auto in that order (stops hyd fluid migration thru the park brake sys). I suspect you may not be doing the autostart correctly.1. Make sure that the autostart switch is selected on.2. Pull the start switches. Usually 3 and 4 first (starting engines two at a time is the norm). 3. Place the fuel cutoff switches to the run position straight away. Do not wait for any N2 rotation (I assume you are using the GE Eng version) . Nothing will happen until you do this. Once you have done this if you look at the overhead panel you will see the start switches illuminate. The start switches will cutout at 50% N2 as normal. The duct pressure will increase from 23 psi when you do the above as the APU supplies extra air for the start.When the start is complete turn off the APU and select the Hyd demand pump 4 to auto and then turn on packs 2 and 3.Hope this helps with your problem. No point kick starting a motorbike when you have an electric starter !!!!!!!!!!!!CheersSteve

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Steve,You did it!!!! It worked finally. I think my problem seemed to be the fuel cutoff switches, I left them off for a while when trying an autostart. I turned them to run before pulling the start knob and it worked right off the bat. Thanks for the help, now off to fly.Kevin

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Glad it worked Kevin,The correct line procedure is to pull the starter switches first then select the fuel cutoff (switches)levers to run. After you do that you will see the start switch illuminate blue to show that the start valve has opened.CheersSteve

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