Robin DR400 Regent Roll Stability



  • I just purchased the Robin DR400 Regent, and I noticed that it is not at all stable in the roll axis. I would think that an aircraft with the wing dihedral that the DR400 has would be very stable. I especially noticed that the aircraft seems to like to roll to the left. Is there any way to trim he aircraft so that it simply flies in a straight line without having to continuously compensate for this left roll?



  • Hi,

    I think you may be suffering from a combination of problems:

    1. weather / realistic coefficients as detailed in the following thread - http://forum.justflight.com/forum_posts.asp?TID=31751&KW=weather&title=hunter-instability-question

    2. Any required adjustments to make the aircraft fly straight in real life are done when the aircraft is rigged. The sim cannot cope with this, so you have to use a touch of aileron trim.

    Cheers,
    Paul.



  • Does the aileron trim work with the Robin? i assigned some keyboard buttons but they dont appear to have any effect .

    cheers
    Rich



  • It should do, Rich - I haven't taken anything out that would affect it as far as I remember.



  • @Delta558
    Hi Paul,

    Did you see my issue with the rudder trim?
    https://community.justflight.com/topic/571/rudder-trim



  • @Eric-Bakker I hadn't, I have now - that's really odd. Simple to remove it - open the aircraft.cfg file in notepad, scroll roughly 3/4 of the way down to where it says 'rudder trim effectiveness = 1.00' in the [flight_tuning] section and change it to = 0.00. Save, reload your aircraft and it should be gone! I'll make a note to try and ensure that's updated here so will be included automatically in any future update.

    Cheers,
    Paul.



  • @Delta558 said in Robin DR400 Regent Roll Stability:

    It should do, Rich - I haven't taken anything out that would affect it as far as I remember.

    Hi Just tried it again .... zero wind ... took off .. straight and level then applied some left aileron trim... nothing happened sadly...i used keys on the keyboard and also some spare buttons on my joystick
    Rich



  • So I did finally figure out why my Robin wanted to keep rolling to the left....
    In the aircraft fuel and weight and balance screen, I had set the Pilot weight to my own weight. But then I set the Co-pilot and passengers weight to zero, and the baggage weight to zero. This made the CG move to the left quite a ways (the pilot sits on the left)
    When I finally noticed this, I set the pilot and co-pilot weight to the same value, and the CG re-centered. I also enabled auto fuel selector so the fuel tanks will remain balanced throughout the flight.
    Now the aircraft no longer has the tendency to bank left, and I don’t have any problem flying it straight and level.



  • Hi,

    mine is also not Roll stable.

    CG is in the middle, should not affect it.
    I'd follow the instructions from Delta558 but it didn't work.

    My exact Problem is that the Plane rolls slowly to the left or right hand side when it is trimmed.
    I turned off the Wind, the effect is still there.
    If I use some rudder to the right the Plane starts rolling to the left side.

    is that an issue or is this Plane like that ?

    Best regards

    Karim



  • Aah, I think I remember something like this with the original PA28 Arrow - the sim load manager creates an excessive rolling moment based on weight added, and I think I centralised the payload / passenger positions on that. Looks like I may have to do the same here.

    Meanwhile, try flying it with equal passenger numbers left and right, see if that improves the situation which would also confirm my thoughts.



  • @Delta558
    I have equal passenger number, CG is in the middle.



  • @Nougatschnitte I took it up again last night and, with equal loadings, couldn't replicate what you are seeing in calm conditions. Engine-associated movement is a possibility but it is really minimal so should not be causing you a problem. Without any further info, all I can suggest at the moment is to check the calibration of your controls.



  • clean weather
    fuel payload CG in the middle
    controlls are calibrated

    Okay I made some Photos.
    I use FSX Steam Edition with the Logitek Saitek x52 H.O.T.A.S controller.

    1. Weather is calm
    2. CG is in the middle.
    3. controls are calibrated.

    I uploaded this Video:
    https://youtu.be/8VSOMPKmrqo

    1. maneuver: centered Plane then it starts rolling it self.(sometimes left, sometimes right)
    2. same thing
    3. apply full left rudder
    4. apply full right rudder

    But i have watched that the effect is bigger when the plane is heavier
    also tested vanilla Cessna it flew straight



  • you have some other ideas what can cause this?



  • I just noticed you are using FSX rather than P3D, it could be to do with the extra flight dynamics tables available to the more modern sim possibly as it certainly doesn't behave like that in P3D. I'll do some digging.



  • Did you find something out ?



  • Hi Karim,

    Apologies, thought I'd got back on this already - In a word, no: The airfile is only using the FSX tables, so that suspicion was unfounded. I'm at a loss as to what could be causing it. Everything should be balanced, I cannot see the problem myself and really don't know what to suggest.

    Sorry that it's not better news,
    Paul.



  • Hello,
    I have the same issue. It seems to me it comes from the left aileron which is not perfectly centered (slightly up) while the right is. On mine at least, I have this none symmetric design. I asked the support, so hopefully we will have a feedback and update soon.