Trex 600E rudder servo moves with +/- pitch

[Br0tz34]

Title says it all, when i hit pos. or neg. pitch the rudder servo is moving a tiny bit causing the heli to spin right on take off, what could this be? I did recently move from a top rudder servo to the lower mount, just dont know why the rudder is moving! thanks guys

[nabl74]

One reason why your tail servo is moving when you apply pitch (positive or negative) is pitch precompensation.

You can check this by turning pitch precompensation down on the bench (without blades). With it turned down, tail slider wont move.

What you are seeing is normal re pitch precompensation settings and the amount is dependant on that setting.

You didn't mention if your tail continued spinning or whether it was just an initial spin movement during spool up. Its normal for your tail to drift during spool up a little if you apply pos pitch too early as tail doesn't have as high an authority at low head speed.

[Epoweredrc]

Are you sure your not hitting a little bit of rudder when moving throttle?
try adding some expo to the rudder might help

[Smoggie]

It's normal on many FBL controllers. As already noted, it's called 'pre-compensation' and it's to compensate for the increased torque from the main rotor when you add collective pitch. You may also have cyclic pre-comp which makes the tail servo move when you add cyclic.

This wont cause the heli to spin, in fact it's there specifically to stop the tail 'kicking' when you add collective and/or cyclic.

[nabl74]

Originally Posted by Grumpy_Old_Man

It's normal on many FBL controllers. As already noted, it's called 'pre-compensation' and it's to compensate for the increased torque from the main rotor when you add collective pitch. You may also have cyclic pre-comp which makes the tail servo move when you add cyclic.

This wont cause the heli to spin, in fact it's there specifically to stop the tail 'kicking' when you add collective and/or cyclic.

+1 to cyclic comments

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[Br0tz34]

i know its normal but its a pretty swift kick out, almost 180 degrees. how would i turn the precomp off? i have an ikon fbl

[Smoggie]

I'm not familiar with the iKon but 'pre-comp' will be in the setup somewhere, If you think it's set too high then find the setting and reduce it. However it would be highly unusual for the default setting to cause a kick as big as you describe, the gyro would catch it before it got anywhere near 180 deg rotation..

Which way does the heli rotate when it kicks CW or CCW?

[HELI_FUN]

more dead band needed? expo? maybe there is a pre comp set up?

[nabl74]

I have the brain installed. Works well.

I would strongly suggest 2 things initially.

Reset your gyro to default for your bird size.

Make sure you have some deadband for tail maybe 5 for test purposes to eliminate thumb error

If this doesnt improve things would strongly suggest servo or tail hub investigation.

Default setting has never caused a kick while taking off or spooling up. But as said previously you can turn it down further from default value via the advanced menu.

Another thing to consider is that your tail is setup correctly in brain and your nuetral setting and tail end point settings are calibrated correctly. Ie tail blade tips are aligned when folded back and tail slider is centred and servo horn at 90 degrees to control rod.

If correct - when you spool up make sure your tail blades are at nuetral position. If they are not your tail will kick until the gyro compensates


Pre-comp is located under advanced menu and tail section. Its a slider. You can set it there. You dont want to turn it off. You just need it set right. Default settings shouldnt be far off being right

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[Br0tz34]

Originally Posted by Grumpy_Old_Man

I'm not familiar with the iKon but 'pre-comp' will be in the setup somewhere, If you think it's set too high then find the setting and reduce it. However it would be highly unusual for the default setting to cause a kick as big as you describe, the gyro would catch it before it got anywhere near 180 deg rotation..

Which way does the heli rotate when it kicks CW or CCW?

CCW and ok im going to check it out in the ikon again and see what i can come up with!

[nabl74]

Originally Posted by Br0tz34

CCW and ok im going to check it out in the ikon again and see what i can come up with!

Apart from recommendation to check tail settings described above, what you mention = Right kick would indicate not enough pre-comp is set or precomp value is set wrong way.


As a guide, when you increase pitch, tail slider should move in a direction to counter torque, not add to it. This is the fundemantal thing to check for.


I suspect tail setting is off more so than pre -comp

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[Br0tz34]

the precomp was high i guess i didnt know i even messed with it? hmm anyway its good, she lifted off without any kick either direction! Thanks guys! yall are awesome!

[nabl74]

Originally Posted by Br0tz34

the precomp was high i guess i didnt know i even messed with it? hmm anyway its good, she lifted off without any kick either direction! Thanks guys! yall are awesome!

Hoooray!

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[Br0tz34]

i know this might not have anything to do with this but would a headspeed thats too low cause the tail to blow out or no?! i dont have a way to see whats going on in the esc and i think the head speed is too low and excessive pitch causes the tail to blow out (right)

[nabl74]

Originally Posted by Br0tz34

i know this might not have anything to do with this but would a headspeed thats too low cause the tail to blow out or no?! i dont have a way to see whats going on in the esc and i think the head speed is too low and excessive pitch causes the tail to blow out (right)

If your headspeed is lower than recommended and tail ratio is low ( dependent on your tail transmission gears used- stock??? 600 pro or 600e?) Then more collective management is typically requiredm . Tail blowouts do occur on the 600 pro / L with lower headspeed as the tail ratio is only 3.85 so other users including myself run headspeeds around 2400 + to get good tail holding

Having said that aggressive pitch pumps can be too much for hard collective jabs on low headspeed low tail ratio setups.

You can limit this to some extent with gains ( only so far you can go with this) and pitch precomp increases but personally dont like adding too much precomp as the gyro starts to fight against u in other manouvres

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[Br0tz34]

ok awesome, i think i need to get into my castle esc and fix somethings cause the headspeed isnt going up anymore on the ikon, do you know if there is a way to turn the gov off on the castle with out the castlelink

[nabl74]

Originally Posted by Br0tz34

ok awesome, i think i need to get into my castle esc and fix somethings cause the headspeed isnt going up anymore on the ikon, do you know if there is a way to turn the gov off on the castle with out the castlelink

Not that i am aware of.
You dont want to exceed the max recommended headspeed. Im not familiar with 600e and its tail gear. But if its greater than 3.85 you prob dont want to go as high as 2400.

Others might be able advise



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[Smoggie]

Originally Posted by Br0tz34

CCW and ok im going to check it out in the ikon again and see what i can come up with!

The fuselage rotating CCW means that the pre-comp is if anything too low.

It could also be too low headspeed as you suggested. too low headspead will lead to poor tail hold resulting in fuselage rotating CCW under torque.. generally that's what pre-comp is there for, especially at low headspeed it should be INCREASED not reduced.

If the rotation only happens during initial spoolup then it's probably just the spoolup being too fast.