Heli keeps spinning on the ground..

[jacko83]

Hey guys need ur Help n Solution...
My Trex 450 Plus keep spinning on d ground even throttle almost to the max....anyone pls help....cheers

[Adrianli]

Reverse ur gyro direction

[VinCopter]

check the rotor blade pitch.

[blueangel]

if its a belt drive.. maybe belt is twisted / reversed.
Gyro or tail servo was reversed. Check setting in TX servo NOR or REV.
Otherwise .. buy new heli because it makes you happy

[Redtwilight]

If it's a TT maybe the gears might be stripped.

[ngkohwee]

I am also in a similar state and has exhausted all the possibilities that I know of. Hope to have anyone's help on what I am missing.

First let me described my problem. I have just completed building a Trex 450L Dominator and has done all the set up according to the manual. When I spooled up, the tail boom would drift counterclockwise. I have to hold the rudder stick slightly right to counteract the yaw.

I have check all of the following:

a. gyro setting on the 3GX FBL system is in the correct direction--tested this by jerking the tail in one direction and watch how the tail rotor pitch reacted in response.

b. gyro gain is already set at 80%

c. setting on the transmitter is not reversed. Checked this by moving the rudder stick left and right, and verified the tail blade pitch. This is also confirmed by the rudder stick being able to counteract the yawing action.

d. tail rotor is not turning the wrong way--this is not a belt driven but torque shaft driven

e. none of the trim on my transmitter is set--they are all in the centre mark.

I am running the 3GX FBL system with a satellite receiver and this is binded to a Spektrum DS6i.

What am I missing? Would appreciate anyone's help to correct this.

[blueangel]

Sorry i didnt have much flight time on my heli so may not give you the right advise..but your problem seems to also happened to me during my build.
Having own 2 heli myself i may offer you this inspection..

When you first power up your heli, let the fbl system initialize itself complete and then do this..
Flick your gyro from head holding to rate.
Your tail rudder should now center itself.
Now at this position you should be able identify that there is a slight pitch on the tail rudder such that it will be trying to push your tail in its clock wise direction ( if it were to be spinning, of course )
If it is completely zero pitch, or opposite pitch of what i had described above, then your tail servo mounting position on the tail boom, linkage length, or horn could be incorrect. Adjust if necessary, and it will be ok.

In neutral position on all your sticks, there should be a slight pitch on your tail rudder to counteract the anti clockwise rotation of a clockwise spinning main rotor.
About 7 degree...
Hope that helps.

I know this extra 7 degree pitch offset on the tail blade seems to be technically out and unbalance , or untidy, or wrong when you first built your first heli. I had the same feeling.
I kept adjusting everything mechanically to zero offset, flushed, balanced, squared, trued, straight.
But no.. Not on the tail rotor blade.. It has to have some pitch at neutral stick position.cheers

[ngkohwee]

Thanks. Will look into your suggestion of ensuring a slight pitch on the tail rotor this weekend. If I recall correctly, the tail rotor was on the middle of the slider when my transmitter stick is in neutral position I thought it wouldn't matter as the gyros was supposed to sense the tail movement and to compensate.

Will get back with what I get.

[Redtwilight]

Thanks. Will look into your suggestion of ensuring a slight pitch on the tail rotor this weekend. If I recall correctly, the tail rotor was on the middle of the slider when my transmitter stick is in neutral position I thought it wouldn't matter as the gyros was supposed to sense the tail movement and to compensate.

Will get back with what I get.

The gyro does compensate but if the tail blades need a bigger angle than the mechanical limit of the pitch slider or servo then the heli's tail will still drift, being unable to fully counter the torque of the main blades. The pitch angle at neutral position just adds a CCW torque offset while maintaining full servo throw.

[hallobaby]

The slight angle can be compensate during flight..
If the heli is spinning despite flyer compensate then it will be the direction of either the servo or the gyro
Do note that the gyro is behaving the opposite of the servo.

[ngkohwee]

Thanks for replying but I am not sure now I am understanding you.

The slight holding of the stick to the right does compensate for the tail spinning counterclockwise. So my conclusion here is that the servo is fitted right. Otherwise, if the servo is wrong, holding the stick slight right should worsen the spin?

I have also checked that the gyro is counteracting correctly by jerking the tail, say counterclockwise, and watching the reaction. The pitch on the tail blade does increase, ie the slider went left. So this looks correct to me too?

So, there is something I am not understanding. The gyro is not compensating sufficiently to hold the tail. That I can hold the stick right and steady the spin would suggest that the slider has not reached its limit--it is also what I observed too.

The slight angle can be compensate during flight..
If the heli is spinning despite flyer compensate then it will be the direction of either the servo or the gyro
Do note that the gyro is behaving the opposite of the servo.

[ngkohwee]

The gyro does compensate but if the tail blades need a bigger angle than the mechanical limit of the pitch slider or servo then the heli's tail will still drift, being unable to fully counter the torque of the main blades. The pitch angle at neutral position just adds a CCW torque offset while maintaining full servo throw.

Yes, noted this. But the pitch slider is still some distance from the limit when the slight stick right could steady the spinning, ie I still have more throw and can in fact spin the tail clockwise by increasing the stick throw to the right.

So the problem seems to be the gyro is not compensating enough to stop the tail spin. But let me adjust the length of the link so that I have slight pitch angle at neutral position to see if the problem goes away.

[jacko83]

Hi guys thankz for sharing all the errors...anyway for mine now no more spinning its only on the air tails sometime wagging now trying to find the errors....for the spinning try reverse the gyro mayb its works like mine...

[blueangel]

One more to take note.
If you are first timer building or flying heli, then there might be a possibility your headspeed is very low.
So with low headspeed, the tail has not enough authority to counter the rotation.
This is a common fear among new hobbist in real rc heli ..to reduce the motor speed too much...including myself.
Check to see if your heli is able to get light on the skids at mid stick.
If you need 3/4 or near full stick to lift off, then try changing pinion or check your throttle curve.

[ngkohwee]

I think I might have somewhat figured it out. Nothing to do with wrong setting up servo, gyro, transmitter etc.

The root lies in my using a 6-channel transmitter with the 3GX FBL connected directly to a satellite remote. In this configuration, Channel 5 is used for the governor while Channel 7 is where the gyro gain is located. Since there is no signal on Channel 7, the 3GX starts up in rate mode instead of HH.

I suppose I should have done a bit more research. This was posted in various way--see:

a. http://www.helifreak.com/showthread.php?t=318364
b. http://rc.runryder.com/helicopter/t674185p1/

So it looks like I have to get a proper receiver instead of using a satellite. Or get a 7-channel transmitter.