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Mar 31, 2016, 06:13 PM
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Analog Pilot trying to go Digital


It has been a few year since I was involved in helis. All of my previous equipment involved flybars, Blade CP, Trex 450SA, and a few others. I recently purchased a Blade 450X from a buddy of mine and have been having a blast with it! I have gotten to the point where I am comfortable to start doing rolls and loops. Herein starts my troubles...

When I switch into idle up, my helicopter goes crazy during forward flight. It develops an incredible oscillation on the roll axis. Pitch is fine. The moment that I switch it back to normal mode the oscillations go away. This only occurs in forward flight though, I experimented with doing a couple loops from a hover and had no issue. There is a noticeable increase in head speed when I switch into idle up though.

The thing that really gets me is that there is no hint of it wanting to oscillate in the normal setting, I can fly it as fast as it will go with out a problem.

I am afraid to move the dials on the AR7200BX, although I have read the manual I am not quite sure what each one does and this type of reaction does not seem to be covered under any of them in the manual.

My throttle and pitch curves setup below.

Norm
Throttle 0, 30, 60, 60, 65
Pitch 30, 40, 50, 75, 100

Idle Up 1
Throttle 100, 70, 70, 70, 100
Pitch 0, 25, 50, 75, 100

Has anyone encountered this before or have any insight into what is causing this?

Thanks!
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Mar 31, 2016, 08:32 PM
Use the flybar young Padawan
jombo's Avatar
Your throttle curve is low in normal and pitch are just percentages of what??? You need to put a pitch gauge and see what you are getting . I thought you done this before ...??
For a 450 , a normal pitch would be -3 to +12with 0 in the middle . Idle up -12to+12 with 0 in the middle . Throttle curve , normal 0-100 , idle up 80-80-80-80-80, or whatever your pitch curve and head speed allows . Check out mr Mel's head speed calc and figure what your head speed should be for the pitch your getting . More pitch more ossilation at speed .
Start there and get back to us .
Apr 01, 2016, 03:06 PM
Registered User
I dont have a fbl bird but i have read so much that i think you should try to turn aileron gyro gain down a bit, when you hit that idle up you head speed go up and then you gain is too high.
Apr 12, 2016, 07:17 AM
ChrisG does 3D!
RCvehicleGuy's Avatar
There is a whole setup process for the BeastX system. Which is what you have. There are no gains on the BeastX, I forget what the dials do but they are for finer tuning than getting rid of aileron oscillations.
You should grab your BeastX manual and a good digital pitch gauge and setup the helicopter again. There is a part where you tell it what 6 degrees of cyclic is, I believe here is where the BeastX decides on a cyclic gain.
If it still oscillates after a proper setup then the issue is mechanical, head dampeners or vibrations? Too low headspeed? I remember my Trex 450 having a flat 100% throttle curve.
Apr 12, 2016, 08:56 AM
rc user
pdooley's Avatar
Quote:
Originally Posted by rsiaviation
There is a noticeable increase in head speed when I switch into idle up though.
do you see any increase in vibration? most FBL controllers don't like increased vibrations.
Apr 16, 2016, 09:58 AM
Registered User
Pot #1 *IS* the cyclic gain control (aileron+elev) and is not just a fine adjustment..
You should be good/safe starting with all pots at mid-way (50% setting).
If you are shaking on idle-up you have either too much gain or something off balance
causing a vibration or a bent shaft (main,feathering/tailand) which is worse at the higher frequency in idle-up.
Also check that the BeastX (AR7200BX) is isolated from the frame with a good thick layer of sticky pad
and that it's not coming loose or anything. Stock one is ok.
Wires should have some slack and not be pulled tight against anything.
If the gain is too high you should get/see oscillations when you give the aileron control
quick sudden 'jabs' while hovering.


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