Bad stability on vind

Hi all folks.

Despite autotune and low vibrations, my 650 drone is very unstable even in light winds. Autotune worked well when there was no wind at all, but then flying even in light winds, it becomes unstable.
This is my first build with the batteries on the top, is this a problem?
Tarot Ironman 650, 500KV engines and 1550 propellers
two parallel 6000mAh lipos and total weight of 3kg.

Hi yrjobjorkqvist,
Have you compared the stability if battery is under the frame?? I am really curious about this battery placement issue. I am also building similar frame with battery under the frame, and it is flying well, but vibration is a bit high. So I need to lower the vibe. first before comparing this battery placement issue.

I don’t think the top placement is a problem. I have built them both ways and even tried top and bottom mounting on the same craft and you can tune it fine either way. The Auto Tuned values don’t look great. The rate pitch and roll PID’s are pretty low as are Accel P/R max. . Perhaps increase the Autotune aggression closer to default (0.1) and try again.

The notch filter looks like it’s doing a good job.

Thanks Dave.
I have rebuilt the battery placement from the bottom to the top placement in order to harmonize CT and CG to the same line.
Placing the batteries on top also facilitates the placement of the camera.
Hope it’s flying weather tomorrow so I can change the parameter for Autotune aggression and test again.

The placement of the batteries seems to have some effect on vibrations. The Z component of vibration was halved when the batteries were placed from bottom to top. Balancing propellers and vibration damping of the autopilot is important.

This because the mass of the batteries are acting to damp the top plate that the FC is also mounted to. Very effective if you can do it that way.

Yes, both of you are correct about this, that battery on top will reduce Z vibration. Actually I also saw this phenomena… I think this is a simple way to reduce Z vibration. But I still have questions regarding auto tune:

  1. Is it ok to do auto tune while the copter in Loiter mode? (According to document we should do in Alt. hold). What is the impact if we do it in Loiter mode (by switching ch. 7 to do auto tune)?

  2. What is the main difference if we set auto tune as one of the flight mode within Ch.5 (I use ch.5 to change flight mode)… I mean that when we are in Loiter mode, then switch flight mode to Auto Tune directly (no need to use ch. 7). Actually it also will do Auto Tune. But I am curious why people recommend to be in Alt.hold mode before doing Auto Tune instead of Loiter mode. What is the logic behind it ?
    Thank you @dkemxr Dave

I switch from Position Hold when performing Auto Tune never tried Loiter.

It doesn’t matter if you have Auto Tune as a Chan 5 Flight mode or a Chan Option. I find the later to be more practical.

I always take off on Loiter mode and then switch to Autotune. When it’s done, I go back to Lpiter, fly back to the landing site and go down, then switch back to autotune and disarm. The gains vill be saved.

The autotune documentation clearly states that both loiter and alt hold are possible. Where are you getting your information from?

In our tests alt hold performs better. But you can use both.