Wednesday, 02 May 2012 16:48

Hydraulics - a bit more


We are just about done with our hydraulics simulation and our tech consultant Jan, recently completed a video on our IXEG YouTube channel demonstrating some of the features of our simulation. If you haven't seen it yet, we suggest you watch it. There are some other things in our simulation though that Jan did not have time to show in the video so we will just let you know about it here.

We simulated the hydraulic pumps, both engine driven and electrical pumps as well as the fluid quantity as the basis for providing hydraulic power. In addition though, we also simulated all the electro-mechanical valves necessary to manage and distribute the hydraulics. This means that if certain electrical busses go down, then the hydraulic valves will respond accordingly and affect the hydraulic flow. In the case of the engine pump shutoff valves, which opens in the absence of electricity, you can do something as crazy as shut down the left engine and also shut down all pumps with the gear down and then raise the gear with a windmilling left engine by disconnecting the respective DC bus allowing the hydraulics to flow through the shutoff valve. Of course in this case, the gear raises very slowly!

Now if you turn off both system A hydraulic pumps with the gear up and locked, then you need to unlatch the gear manually and let gravity extend the gear. We really do not let "gravity" extend the gear in this case though, we let a force extend the gear. It just so happens that when the plane is flying normally in a 1G situation, that gravity is the force extending the gear; however, if you were to fly the hump of a parabolic arch, with zero Gs, with the gear partially extended with no hydraulic power, then the gear will hold its position. If you manage any negative Gs, then the gear will actually move up towards the wheel wells. (If you were to fly upside down, the gear would not extend either :)) The rate of extension in this mode is based of the "downforce" acting on the gear, but only up to a limit because of hydraulic damping.

As Jan mentioned in our YouTube video, we model the relative work on each of the system pumps, so in the absence of engine driven pump power, electrical consumption increases on the remaining system electrical pump as it has to handle loads alone. Such increased electrical consumption causes an increase in heat dissipated from the respective engine generator. This increase in temperature can be seen on the generator temperature indicator on the overhead panel should the electrical load be sustained long enough to heat up the cooling fluid sufficiently to register on the needles.

Something else of note is that when you move the yoke rapidly from side to side, that such movement loads up both hydraulic system A and B (in normal operation) and you will see pressure fluctuations on both systems as you move the yoke. You will only see this during rapid movement though as the pump's ability to respond to rapid demand lags a bit. If you move the yoke slowly, the pumps can keep up with demand better and you will not see pressure fluctuations. Of course you see bigger pressure fluctuations when only the electrical pumps are powering the controls and even bigger fluctuations when only using one electrical pump and you will also see electrical current fluctuations on the ammeter in these cases.

Also simulated are the PTU, LGTU, autoslats, flap load relief and standby pump with electrical consumption and both manual and automatic actuation where different generators are loaded based on the actuation mode. We know we are on to something good when a beta tester reports the flaps will not go to "flaps 40" and he happens to be flying > 158 kias and the flap load relief function is in effect. Get studying!


  • Comment Link Sunday, 10 June 2012 20:12 posted by marco

    Very nice to hear, Jan. I really look forward to see your beautiful model in better resolution. It really is beautiful so to see it in HD really makes total sense.

    Something that would be interesting to see in the coming videos would be if you used the instruments so that those real to live looking movements could be showcased.

    Thanks again and great work, all of the team!

  • Comment Link Sunday, 10 June 2012 12:26 posted by Jan

    Hi marco,

    I will keep that in mind when doing the next one. So far the emphasis has been on showcasing the functionality of the systems - less so the visual fidelity (although we are VERY proud of the way the needles and lights animate ;-).

    The future videos will have increasing emphasis on showing the 3D and artwork. Higher resolution and video quality lends itself to that. File sizes do still matter though, try to create a 8-10 minute video in X-Plane with HD resolution and a decent (30+) framerate and you will see that size racks up incredibly fast... I am usually doing these videos and create narration to go along, then have one of our artists go over and process them for youtube uploading. I am not much of a video editor myself, so we have to ship the raw files back and forth...


  • Comment Link Sunday, 10 June 2012 11:43 posted by marco

    Thanks! Maybe we are lucky and can have 1080p videos to better showcase your excellent model. I sure hope so! Good work guys!

  • Comment Link Sunday, 10 June 2012 09:52 posted by Jan

    Oh, forget the link to our thread at x-pilot:


  • Comment Link Sunday, 10 June 2012 09:49 posted by Jan

    Hi guys - we answered Flo´s request with a post on the .org a few days ago. Go check the "Aircraft development" forum there...

    We will become a lot more active as release date draws closer. For now you can take the lack of regular updates as a reliable sign for us being too busy working on the 737!

    We will do another video preview soon - like in a month or so - but we want to wait for the 3D cockpit to be almost finished so we make a good impression.

    Feel free to post at the .org or "our" thread at x-pilot if you have any further questions. I read both frequently and answering there is easier and will have the benefit of allowing other readers to see the response, too.

    Best regards, Jan

  • Comment Link Saturday, 09 June 2012 11:37 posted by Josh

    I'm in with Flo. More regular updates on what is being done coupled with screenshots etc. It's sad to check out every two days just to see nothing has been written or updated.

    On the other hand, great job with the model. I'm truly amazed of the work you are doing. Now, if we just could get a bit more frequent updates...

  • Comment Link Sunday, 03 June 2012 13:59 posted by Flo

    What about a summarizing post about what is done and what is still to do to finish the project?
    Not talking about a release date, but an overview of the state of play.
    It´s somewhat confusing to see very advanced system simulations on the one hand, rare blog updates and very few "general information" on the other...

    How does this fit together? Any decisions about XP10 developement? Any progress in building the fuselage? What about a monthly post to keep people up to date?

    No rant, just trying to spur you on a little ;)

    All the best

  • Comment Link Sunday, 27 May 2012 11:34 posted by Maksim

    Yeah, requesting some more info! Too hard to wait and refresh this page n times a day;)

  • Comment Link Friday, 25 May 2012 13:44 posted by Stephéne

    Please post more videos (1080p) and info!

  • Comment Link Sunday, 06 May 2012 12:24 posted by Carsten

    I love what I can see - with your work X-Plane will get more attention.

    Thank you! I hope, that I can buy it soon.

  • Comment Link Thursday, 03 May 2012 15:31 posted by XAM

    really amazing!! guys, your product will burst XP with life, as a great number of virtpils will turn their attention from MS to it.......what XP deserves.

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