slow tilting on ground during high RPM ground tests

[sansone]

before maiden flight of my 1st FBL 600 class electric, I've been running it on the ground @ high RPM zero pitch to check vibration, tail thrust, etc.

noticed after a few seconds of this high RPM sitting on the ground the heli begins to slowly tilt (on its skids) and immediately I cut power, she settles down, me shaking.

There are no vibrations, nothing coming loose, everything appears normal. Question is why is she slowly tilting to one side? Maybe I should give pich and hover? I'm expecting trim requirements since the heli is newly completed, am I just being too cautious?

[comatosed]

Tilting to the left?

[Thalios]

Swash not level?

[sansone]

Originally Posted by comatosed

Tilting to the left?

YES

[sansone]

Originally Posted by Thalios

Swash not level?

Swash is level

[Inverse]

You have a vibe somewhere, take the main blades off, spool it up and see if you can see the swash tilt.

[Heli.Maniac]

Its because of other factors like wind, tail thrust etc. The heli picks up the wind and tries to compensate, but on the ground it cant move that easily so the FBL system tries to move it even more resulting in what you describe. That is something I get on my 400 BeastX. The general rule of FBL is to take off quickly to prevent such behaviour.
But, to be safe I would check for vibrations take of the main and tail blades and spool up the heli but not on full throttle, just 65-75% and observe the swash. If it tilts then you have a vibe problem for sure. Is it a 3Gx that came with the kit?

[sansone]

ok.. I'll check all blade balance again, I didn't balance the tail blades (often neglected)

[sansone]

Originally Posted by anmatheextreme

Its because of other factors like wind, tail thrust etc. The heli picks up the wind and tries to compensate, but on the ground it cant move that easily so the FBL system tries to move it even more resulting in what you describe. That is something I get on my 400 BeastX. The general rule of FBL is to take off quickly to prevent such behaviour.
But, to be safe I would check for vibrations take of the main and tail blades and spool up the heli but not on full throttle, just 65-75% and observe the swash. If it tilts then you have a vibe problem for sure. Is it a 3Gx that came with the kit?

thanks for reply,
beastx in use, I don't think it's vibration but I'm going to check the tail blades because I didn't balance them.. I'm NOT seeing any vibrations, but checking anyway

[mkovalcson]

Originally Posted by sansone

thanks for reply,
beastx in use, I don't think it's vibration but I'm going to check the tail blades because I didn't balance them.. I'm NOT seeing any vibrations, but checking anyway

I didn't "SEE" any vibrations on my 550E when the main shaft bearings were SHOT and I mean very grindy. This was enough to make my FBL controller roll the heli right into the ground.

Taking off quickly can help, but if it is pulling hard there is most likely a problem somewhere.

[Mr.Andersen]

Just by setting my mcpx on the ground spinning it will if not stopped or taking off end up at full cyclic one direction ore the other.
Thats just how FBL systems behave on the ground.

[sansone]

Originally Posted by Mr.Andersen

Just by setting my mcpx on the ground spinning it will if not stopped or taking off end up at full cyclic one direction ore the other.
Thats just how FBL systems behave on the ground.

these responses make sense because I "see" no vibrations watching the usual points of reference, and the "tilting" I refer to is very slow, gradual

I just finished balancing the tail blades, they were VERY close in weight.
gonna try again

[TheBum]

I'd vote for ground resonance causing vibrations that are causing the gyros to drift.

[Mr.Andersen]

Do a test again but these time 1 meter off the ground.
You will se its alot easier to testing in the air then on the ground and if you dont feal safe of having a heli hovering at neck level take it just a litle higher so if the heli throw a blade it wil go above you.

[GB ian]

lift off and see what happens!

[belcom]

Which FBL unit? What mounting tape?

Generally it shouldn't be doing that when there are no vibrations. I've used Beastx and Vbar, on electrics and nitro. Even on nitro sitting on the ground at full RPM it never tilted on me. Try a different mounting tape. 3M 4011 (grey and stiff) or 4010 (clear gel)

[JCLs]

Almost any small thing can cause FBL system to initiate a slight change that then amplifies itself with Heli sitting on ground. It sounded like it was sitting for extended times. I have seen with all sorts of FBL units. Get it up in the air. If you did decent setup no trim will be needed. I have no trim on any of my FBL helies.


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[sansone]

got the lipo charging and instead of keeping the heli grounded at 80% power (no pitch)
I'll hover about 3-5 feet off the ground. need to grow some hair on my b***s

[rcflier1]

yep, vibration. i had the same issue with my beastx. changing from the supplied tape to te 3m tape solved all the issues

[Santini]

In the interest of clarity, I wanna say no way I would be spinning it up a FBL w main blades on it and keeping it on the deck looking for vibes etc. Recipe for disaster.

If you want to test things, spin it up w the main blades off, and if all is ok, then add the (balanced) main blades. Then, do a preflight to check that the FBL unit is reacting/compensating as it should as you tilt the armed machine (checking swash movements, tail). Then, spin it up and get it right off the deck as soon as you have adequate lift. Assuming every bolt and screw is snug and barring some freak unforeseeable failure, you should be fine. I would refrain from getting crazy on shake down flight(s) as you wanna get the FBL settings dialed as you listen and look for anything that seems not right. Good luck.