First Skyfun Flight - I need some tuning Help ....

First Skyfun flight today.

It was a bit tricky because it was windy / gusty and the stock setup is very weak...   but all went well.

I switched a couple times from normal to stabilize mode and every time the plane immediately started diving.

I am not sure where to start trouble shooting the issue.

I was replaying the session but can not find the time-slot when I tried stabalize mode.

I assume to analyze the issue I'd need to find that spot. Is there a trick to it?

What else can I do to figure out what the problem is?

Here is what I have:

Skyfun Stock motor, Elevons upgraded to balsa, wings covered with Monocoat

APM 2 with Gps on board

2200 MAH lipo

Dx7s & Spectrum 8100 Receiver

DR3 900 mHZ Radios ( Yes the work now :))

Current Sensor ( Sparfun)

Air speed sensor will be installed tonight...

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  • I broke my motor mount yesterday on takeoff.

    I was using a new setup  E-Flite bl450 870 KV and a 9/6 prop.

    The plane went into a steep climb and lost airspeed.

    I chickened out and and pulled the throttle back and landed flat. with the big prop attached that broke the mount.(not the prop)

    I suspect the added thrust from this motor caused the step climb.

    I will use a washer as a shim to angle trust a degree to 2 down.

    Has anybody seen the behavior after a motor upgrade on the Skyfun?

  • I was able to replicate the behavior on the ground.

    Plane is mounted stationary (CAN NOT PITCH ROLL OR YAW)

    I start with the plane pitched down at -10 degree

    At 21:22:55 I go to full throttle - watch the artificial horizon, it keeps dropping.

    At 21:24:00 pitch is at -35 degrees I cut throttle and within 4 sec it is back at -10.

    I repeated the same test with the plane mounted at +10 degree and the artificial horizon pitched up to +40 at full throttle.

    I improved the vibration isolation and upgraded to 2.34

    I did a very short test (to late too loud) and did not observe this behavior. (Horizon was still shaking a bit)

    More testing tomorrow!  The logs are included.

    Comments welcome……


    2012-05-17 21-22-07 ground test stationary.rlog

    2012-05-17 21-22-07 ground test stationary.tlog
  • James,

    That is an excellent idea, I'll try to find time for a " ground test" tonight.

    If any body could take a quick look at my logs and tell me if the out put is "normal' that would be very helpful!

  • Sorry this took so long, work is keeping me pretty busy….

    Having not seen any output from an Ardupilot before I have no reference, but the output ( logfile replay)seems much more nervous than what I observed flying the plane.
    I flew 4 batteries 16 min each and tried to switch to stabilize mode several times. Most of the time, the plane would go into a 45-60 Degree dive. If I countered with ruder the plane would still be nervous around the roll axis. Once during these four flights I managed to put the system in stabilize mode and I it worked for about 3-5 minutes as anticipated. The Plane flew stable in one direction responded to control inputs and would level roll and pitch axis as soon as I let the controls go. Then - suddenly the plane went into a steep dive again and I had to switch back to manual. Despite several attempts I was not able to get the plane to behave normal in stabilize mode again L. I have no idea how to explain this behavior. The Ardupilot is mounted with double sided tape to the plane and has no play at all.

     At 15:16:34 you can see a example when I switched to stabilize mode. Ardupilot “ thinks” the plane is pitched 24d upward (while it was really flying straight) as a result Ardupilot applies down rudder and the plane goes into a dive….

    On the ground, in stabilize mode the elevon action is exactly as expected.

    Could it be a problem with vibration?
    The prop is balanced but the motor runs a bit uneven.

    Bad output from the ESC(bec)?

    I attached the log file and would greatly appreciate some feedback

    Aloha Matthias

    PS: not sure what the difference between T and Rlog, or which one is needed so I am uploading both...

    2012-05-13 15-01-49.tlog

    2012-05-13 15-01-49.rlog

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