Flight Rig Testing ( video )

I built a flight test rig for debugging the configuration of my flybarless system without worrying about trashing my 550E.  My first attempt at flying my heli ended badly because I had one of my servos reversed. Since then I have another issue I’ve been trying to diagnose and I’m hoping this rig will help me find the answer in a safe for my heli way.

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Clicking on the picture below will bring up a video showing my heli flying perfectly fine on the test rig.  ( IMPORTANT!!! Notice I didn’t hang around too long  before I gave it some positive collective. )

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However on a flight before this is just leaned over hard left with no TX stick input as shown below.  Notice the flexing in the landing  gear and the plywood.  Clicking on the picture below will show how that video.

(IMPORTANT! This time I spent too much time with the heli spooled up without getting it off the ground. The FBL system got confused and compensated where it shouldn’t have.)   A fly bar is very simple and is not confused, but the software in the electronic fly bars will behave this way. This is very similar behavior for all of the electronic fly bars from all the reports I have seen.    I’ve been told by Skookum that the heli should be able  to spool up on  the ground and not have this issue happen. The flight log I sent them indicated my main bearings were bad and they were. I’ve since replaced them with KDE Direct Thrusted Bearing Blocks and  the main shaft is spinning much more smoothly. I’ve also flown the heli without incident.

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So now that I’ve identified that my issue was pilot error and I just need to get the heli off the ground faster, its time to fly Smile

My tethered flight on this rig, has at least given me the confidence that everything is configured properly.

So all the configuration on the previous post is actually now a known good configuration for this particular helicopter with the SK-720 oriented with the servo bus forward and right-side up.  Obviously the sub trims and any travel limits would need to be adjusted appropriately if I were to build an exact replacement for it.

Addendum: 8/25/2011  I flew the heli for about 25 minutes total air time and nothing bad happened. I may dial back the collective gain a smidge, but all my  flights were very easy to control and the heli  operated exactly as I would have hoped it would. There was no tail wag, and it has a LOT more power than I can exploit at this point.

I’m going  retest on my test bed to see if I can reproduce the earlier problem now that my main bearings have been replaced, but I suspect that it has.

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2 Responses to “Flight Rig Testing ( video )”


  1. 1 Deep Patel February 7, 2016 at 12:44 pm

    can you please explain me the concept and working principle of test rig of rc helicopter?

    • 2 mkovalcson February 7, 2016 at 4:34 pm

      I built this after my very first build when RC Helis were very new to me. I had a tip over after my first flight attempt due to incorrect FBL setup (a channel was reversed) and I didn’t realize that the main bearings were shot after that accident. So I didn’t repair the heli properly after it flipped. The vibrations were so bad that once I got the FBL controller configured correctly, it was not behaving properly.

      The bottom line is that I built this to help me reproduce a problem and because I didn’t trust that I had things set up properly. I mostly fly 700’s these days and I wouldn’t ever use a testing rig like this again. I don’t think the landing gear on any of my 700’s would hold up.


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