My X8

Posted by Brian S on February 24, 2014 at 2:45pm


I had my first maiden X8 flight the other day. It flew great off the bungee launcher and in Manual Mode, straight and level. But when I witched to FBWA, it headed down at a downward angle, Had to put it in Manual MODE to recover. I had it a Bixler 2 before and it flow well.
I’m running AruPlane v2.78b inX8. Bixler2 was on V2.76. The only other difference is the APM was level in the Bixler but not in the X8. I thought buy going threw the setup it won’t matter. I have since leveled the APM in the X8 but hadn’t had time to test.
It also did the same when I put it in a Auto MODE

My question is: Does the APM have to be level in the plane?

Any input will be appreciated.
Thx, Brian

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Replies

  • Josh Welsh February 24, 2014 at 3:14pm

    Another thing with the X8 and APM... those magnets that hold the canopy on can wreak havoc on your mag depending on where you have placed it, so many folks are removing them and using something else to keep the lid secured.

    Like the others are saying, you definitely don't have to have the APM level in the plane, but the APM needs to know what level is, and that is typically a little bit of nose-up on the X8, so re-level as suggested and that will hopefully solve your problem.

    • Brian S > Josh Welsh February 24, 2014 at 8:19pm

      Josh,

      Thx for the info. At this time I'm not using the magnets and will not use they. Just taping the hatch down for now.

      I'll level the APM and calibrate a little nose high.

      Thx, Brian

  • Icarus February 24, 2014 at 3:06pm

    Hi Brian,

    I had exactly the same issue when first running an APM in x8s. It was solved by levelling the airframe to be in a slightly nose up attitude. If you sit the airframe on a flat surface and lift the nose so the "chin" lump is about 5cm up, then tell the APM that is it's new level. It should fly nice after that. Also check your CofG, mine is like this http://im13.gulfup.com/2012-02-11/1328957218161.jpg

    The apm does not need to be level inside the plane, but it does need to be told what is normal flight attitude, which is quite nose high for the x8.

    • Brian S > Icarus February 24, 2014 at 8:15pm

      Icarus,

      Looks like our CoG are the same... in line with the holes in the wing. Mine flys level in manual MODE, no trimming.

      I'll level the APM inside the plane, Then calibrate the APM.... correct????  by MP/Initial Setup/Accel Calibrate.. then do a "Calibrate Accel" and then do a "Calibrate Level" ??? And once that is done I don't have re-level or re-calibrate the plane on each startup at the field???

      Thx, Brian

    • Icarus > Brian S February 24, 2014 at 8:18pm

      yes, that's all correct. good luck with it. remember not to move the airframe for a minute or so after powering up the APM at the field. 

  • Lockhart February 24, 2014 at 3:04pm

    Hopefully more people will comment, as I am not (yet) terribly experienced (building my APM equipped X8 now). Three things:

    1. The APM does need to be level with respect to the fuselage waterline axis. You can set different orientations (rotated 90 degrees, upside down, etc), but not anything off orthonormal.
    2. Are you sure you set up the elevon mixing correctly? This would not have been an issue in the Bixler. I had to mess with mine for a while before getting my transmitter, wiring, and software in sync. For example, MANUAL would work, but STABILIZE would be backwards. I found it easier to get things to work in STABILIZE, and then modify my 9x mixing to be congruent. Remember, too, that the APM should do the "opposite" (in a sense) as your radio would command (eg. stick left should yield a bank to the left, but rotating the X8 in a left bank in STABILIZE mode should yield elevons that yield a right bank).
    3. Perhaps APM did what it was supposed to do, but the gains are too high? Do you have the telemetry file? Everyone seems to say that the default (mostly only proportional) gains work fairly well on an X8.

     

    Hope this helps!

    • Brian S > Lockhart February 24, 2014 at 7:57pm

      Lockhart,

      Thx for your replays

      1, Ok, I'll level the APM to center line

      2, Yes my elevons are setup correctly, they were tricky. Pitch the nose up calls for the elevons (both) to go down. Bank right, left wing elevon goes up...right wing elevon goes down. I even check the HUD on MP.... pitch up the horizon goes down.

      3, No t-logs files. I had flown many launches without resetting, so the whole time is on one log. I am flying default settings

      Thx again

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