Duct pressure problem 744...please help

[Qavion 19]

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>

[Qavion 19]

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>

[Chaos81 110]

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.

[Guest SKireyev]

>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

[Guest KevinS13]

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

[Chaos81 110]

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.

[Guest KevinS13]

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

[cowpatz 243]

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

[Guest KevinS13]

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

[cowpatz 243]

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