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Erratic Flight
Helicopter holds heading and altitude in a hover but oscillates in a counterclockwise circle
Tags: Syma X9
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Face
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Guests
January 11, 2015 - 11:38 am

I am looking for assistance trouble shooting a flight stability problem.  I bought 2 S36s for my sons, I know this is a 107 forum but the rotor system seems very similar and there is no S36 forum I could find.  

Both aircraft flew remarkably well for the first couple weeks.  One is now hovering erratically.  It holds altitude and heading just fine but oscillates in a counter clockwise circle.  This is not a heading trim issue...heading hold is solid, the aircraft flies a 2-3 foot circle while maintaining a constant heading.  

I have inspected the top rotor system. The blades have minor nicks but seem fine. The spindle seat lugs and blade grips are good, I have seen the excellent video on that issue.  The pitch links (dog bones) are also good.  I do not see any issue with the balance bar either...I swapped balance bars with my the other aircraft and did not see a change in performance.  I have held the aircraft still while the rotor is spinning and can see the balance bar oscillating.  Additionally, the aircraft's oscillations are lessened if I fly with only 1 dog bone attached.  Any thoughts on what could be causing this?  

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Syma Freak
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January 11, 2015 - 12:12 pm
Member Since: November 26, 2010
Forum Posts: 1432
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hey_mate-4138Welcome to the forum. It sounds like TBA "Toilet bowl effect" it is like the heli is caught in a whirl pool or being flushed down a toilet. The heli behaves as if you are making rotating commands as it traces out a circle in flight, but with the nose of the helicopter not turning. 

The main reasons are bent main shaft after a crash or gears chipped or bent flybar not responding correctly , usual on a coaxial heli the lower rotor is not the problem, I have noted if the the Flybar is stiff and binding on the pivot points in the head or on the ball links going from the flybar to the rotors causes this.Try disconnecting the flybar linkage and push flybar up and down to see if easy movement just tap it to see it bounces up and down freely.You could try a little silicone spray on it not oil or Wd40.

Here is a link to a video that might help middle of page Syma repairs
Shows about gears causing spinning. Now having said all this it could be something completely different, keep us posted, did you have a bad crash?

"Fly like a butterfly sting like a Syma" http://syma107.com

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Face
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Guests
January 11, 2015 - 7:30 pm

Thanks.  Yes the aircraft have had a rough go of it with 3 new pilots, multiple hard landings, and impacts with walls, chairs, etc.

I took a look at the items you mentioned. I disassembled the top rotor head to lubricate and discovered a cracked lug on the spindle seat.  It looked solid but moved easily...likely the culprit.  I have some parts on order and let you know how it does with those installed.

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Tailwind
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Guests
January 20, 2015 - 9:58 am

We have this "Toilet Bowl" problem around here too.  I say that because me and a co-worker here at the office got into the Syma S107Gs at the same time and both our copters started exhibiting these symptoms.  Of course these were our first RC Copters so keep in mind the learning curve and not knowing there limitations (like dog fighting over landing zone and suspended nose down take off).

6 months later we have a little grave yard of S107g's that have been retired due to "the toilet bowl effect".  We thought they were just shot, but now we are excited to troubleshoot according to your suggestions here.  Thanks for your help!

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Tailwind
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Guests
January 27, 2015 - 7:20 am

Im not stopping the T.B. symptom so easily as Face.  Please lets keep this thread going.  I would be interested in other feedback and suggestions.  

I swapped the main (inner) shaft out and it did not stop the T.B action.

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