After lifting off, the helicopter almost always turns 90° to the right.
Why ?
What size is your helicopter?
From your 1750 RPM I’m guessing a 600 or 700?
Your ATC_ACC_Y_MAX is set very low at 270.
I would increase it to the suggested initial tuning value of 800 and see how that works.
Mike, be careful. He maybe using 4.7 which means the units were changed from centidegrees/sec/sec to degrees/sec/sec
Hi Bill!
Looks like he’s running 4.7.1.
I believe the old initial value was 80000 and became 800, correct?
Ok. Now I understand. Sorry I thought you were referring to an 800 size heli.
No worries, Bill.
I do happen to be using ATC_ACC_Y_MAX: 800 on my 800-sized helicopter. 
It’s a Trex 550 with 550 blades in a 600 scale fuselage.
I am running 4.7.1.
I will try ATC_ACC_Y_MAX 800 and post the result.
Here is the log file with ATC_ACC_Y_MAX 800.
I did some extra lift offs at the end.
I’m not sure if I notice any improvement.
The tail mostly broke out to the left, once to the right and once not at all.
To be honest, both of my machines (450 and 800) have mild yaw kick at takeoff but have excellent tail control in flight.
I’ve gotten accustomed to it over time and am instinctively ready to give a little input when lifting off.
Bill will know best, but raising ATC_ACC_Y_MAX more may help.
Do you have your tail rotor rigged to have flat pitch or some anti-torque at neutral? Biasing it one way or the other might correct some of the kick.
Adding some H_COL2YAW could possibly help too.
Yes, I have about 5° of anti-torque pitch.
What I don’t understand is this:
It’s normal for the tail to break out slightly at takeoff.
But that should be corrected automatically.
This is my only Ardupilot helicopter.
My other seven have “normal FBL systems”.
None of them exhibit this behavior.
@twistedwings It appears that you have all default values for the yaw axis. you should tune the yaw axis to get better performance. I know that you did not have much success with autotune. If you provide a SystemID run of the yaw axis. I could perform an analytic tune. For my 500, my yaw P gain was significantly higher, almost twice the default value. So there might be some room for improvement. If you want to try the autotune, I would recommend reducing the AUTOTUNE_VELXY_P to 0.05. On the smaller helis, the default value is a little too aggressive
thank you for the support.
Unfortunately I have no idea how to do a SystemID run.
Maybe I will retry autotune for the yaw axis with AUTOTUNE_VELXY_P set to 0.05
This thread will help you out with SystemID and analytic tuning, @twistedwings.
thank you, I will have a look…
Autotune failed with “Failed to level, please tune manually”.
Then I made a SystemID run of the yaw axis.
here’s the Log file
I had a chance to look over the log and used the analytic tune web tool. The coherence of the data was not great but I did an initial tune. Here are my suggested changes
ATC_ANG_YAW_FF 0
ATC_ANG_YAW_P 6
ATC_RAT_YAW_P 0.25
ATC_RAT_YAW_D 0.0035
I would like you to do another SystemID run. Here are some param changes I would like you to make before doing the flight.
SID_MAGNITUDE 10
SID_F_STOP_HZ 12
thank you Bill !
Parameters changed, log file to follow…
here is the new Log file
Here are the parameters I would suggest you change. I don’t know that I would raise the rate P and D gain much higher. You definitely want to make FF gain zero.
ATC_RAT_YAW_FF 0
ATC_RAT_YAW_P 0.28
ATC_RAT_YAW_D 0.004
Is it still yawing as you take off? I mean I can see that it is yawing but it looks like you are commanding the yaw.
Thank you !
I’ll change the parameters.
No, during the last flights there was no yawing at lift off.