Precomp.... DO IT!!!

[stunks]

Have a read at this

Precomp.... DO IT!!! - HeliFreak



Hi,

the gyro doesn't know when the tail will start to turn. It has to measure the sensor data and wait until the tail starts to drift. So it always lags behind a little bit. Now when you give a very quick collective stick input or when collective changes from a very low to a very high amount in a very short time then the change will be so drastically that the gyro will have a lot work to do. By using RevoMix you can help the gyro as you simply add a small amount of rudder input against the rotor torque. This doesn't has to be very much and you cannot define exactly how much this has to be, as the amount of rudder stick input to be given is depending on a huge number of factors like wind speed, rotor, rpm, ... but it will help the gyro a lot as you tell it that it should get ready for work and you additionaly bridge the gap between occurence of torque and counteraction of gyro.
This also applies to a cyclic stick input as this also produces torque but on collective load changes are much stronger and more abrupt due to the larger pitch range. So usually you only need half (or even less) of the amount of revomix for cyclic than for collective and it is much harder to see a need for RevoMix. But on collective this can help very much and can give you a much better rocksolid tail. Anyway the need for it depends very much on the tail performance of the heli. If you have a lot of tail thrust available you should need RevoMix at all. But most people use to small tail blades, like to fly their heli with low headspeed, ... and then you can typically see that the tail shortly kicks to the right (nose to the left) with the rotor torque when they tuck in collective. So Revomix can help here out as raising gain won't and which usually is already maxed out.

[Paulice]

All gyros that work in heading hold advise against using Revo mixing, If your going to use Rate mode then yes you need to activate it.

[Guest]

It's a misnomer.. not really revo mixing, but "pre-compensation". I suppose it's like the throttle feed-forward in the PID algorithm on the V-bar, this is collective feed-forward for the yaw control.

[moyesboy]

This is not revo mix in the Tx, but an internal setting the BeastX for which you need the USB lead (the helifreak link is in the beastX section).
Revo mix in the Tx applies some rudder when you aplly collective - this would change the heading of the head lock gyro. You shoudln't use that with heading hold - only with a rate gyro.

Imagine you had another servo that moved the tail pitch directly, independant of the gro. On a trex 600n for example it moved the hinge point of the tail bellcrank forwards and backwards.
Waht the pre-compensation does is apply a bit of tail pitch when you apply collective (and also cyclic a little too). The Gyro doesn't know - it just tries to keep the heli pointign the same way becuase there was no change in your rudder stick.
The result is that when you apply collective instead of the gyro having to make a big correction, some of the correction was made automatically - tihs is called active control - or feedforward. The gyro just has less to do.

Using cyclic throttle mixing with am active governor is the same principle.
What you see is less tail swing when you boot the collective.

Flybarless 3 axis gyros know about the collective and also control the tail - so this feedforward is possible. On the beastX you have to switch it on - but its beleived it is always active on the V bar.

The downside is the mix still happens during an auto (bacause the BeastX doesn't know what the throttle is doing) - so then it is a disturbance the gyro has to correct. I was trying this yesterday and it didn't seem to matter. When you bale out of an auto the tail swing is actually less - becuase it applies the tail correction even before the motor gets going.

If you go back into the history of this forum a year or two you might find a post where I suggested it might be possible to link a CL1 cyclock and the CSM720 to provide this feed forward mix.

The other thing a 3 axis gyro could do is link ccpm phase and rudder so you could fly a piroetting heli as if it was not piroetting (making all those revolving manoevres pointless in terms of pilot skill). Maybe the top pilots already have secret software that does that - becuase those manoevres do seem to be impossible

[Planehazza]

Hmm I'm going to mess with this setting when I'm next out, as the tail is kicking on mine when I give it collective punches. It's a v2 only feature though right?