PIxhawk log help

Hey guys, so I finally got new ESC Hobbywing xrotor 40a. I can finally get my quad in the air but I am now having new issues. Once it gets in the air if I leave the throttle stick at a fixed position, the throttle oscillates quad goes up and then down and repeats. It is barely flyable at this point. I have included the log from the flight as well as my config file for mission planner. Thanks for any help.2017-04-29 18-00-46.log (1.9 MB)
x650f.param (10.1 KB)

Did you tune or run autotune?

I didnt even try a different flight mode other than stabilized. Should I? I figured if it wasnt holding throttle like it should it wouldnt hold it in another mode.

In stabilize never hold altitude, but your log looks that you need more tunning too. I have a Hitec Aurora rc and it´s very difficult mantain altitude with de cri cri throtle in stab.

Yes I have alot more tuning to do, my issue is I am not sure where to start. I will try out loiter tomorrow and see if I get a different result, I feel like throttle PID’s need to be adjusted but I have never played with throttle PID’s. I will need to look at wiki for a rundown of what value does what.

And while I know it is difficult to maintain altitude in stab mode its not like my other quads. This thing will will just go shooting off into the sky so I will lower throttle and you can hear it take a second to react to the throttle change. Once it changes it will come down and I will be able to get it somewhat stable then throttle will just drop all the sudden almost to nothing and down it will go. A video would show better what is going on, I will break out my gorpo tomorrow and get a video of it.

Perhaps that is your vibration level consecuence, your vibration levels doesn´t looks so good, check that too; check the FLAGS in Mission planner Hud when you are flying and looks flag levels to check.

According to this


My vibes are good till the end of the flight the spikes you see at the end are the quad hitting the ground kind of hard. Other than those spikes my vibes are below 30

Hi Jonathan,

I’ve experienced many of the same issues you’re describing (e.g. instability in stabilize mode, delayed throttle response) and I found that performing an AutoTune for each axis helped to resolve them. (http://ardupilot.org/copter/docs/autotune.html)

Before conducting an AutoTune however, it’s important that you’re able to achieve relatively stable flight in AltHold mode. From your log it looks like you’re experiencing the most vibration on the Y-axis (IMU > AccY; VIBE > VibeY), so you may want to keep an eye on it. Vibrations can contribute to much of the behaviour you’re experiencing. What size propellers are you running?


15 inch of the folding variety.

Okay, I’d highly suggest, if you haven’t done so already, to do point 6 of the AutoTune article:

For large copters (with props at least 13inch or 33cm diameter) set the Rate Roll and Pitch filters to 10hz (in Copter-3.3 these are RATE_RLL_FILT_HZ and RATE_PIT_FILT_HZ, in Copter-3.4 they are ATC_RAT_RLL_FILT, ATC_RAT_PIT_FILT)

I noticed a massive improvement in stability once I decreased the filters to 10 Hz.


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Yeah not sure how I missed that. I have been through the documentation several times now. Thanks for pointing that out. I am going to go back through the documentation one more time. I have changed the filters to 10hz. Will try it out when weather gets nice

So another issue I am noticing and I am not sure if it is an issue or not. I have my motors set to not spin when armed but when I start increasing throttle slowly all the motors will not spin the same speed one will even totally stop.

Hi Jonathan,

I’ve found that I can often achieve the same behaviour of having a single motor stall by slowly increasing roll or pitch while the aircraft is on the ground. It could just be a matter of how your craft is stabilizing itself at any given time. Is this occurring with a high throttle input? Taking off in stabilize can be nerve-wracking, especially before performing an AutoTune, and sometimes it’s best to be aggressive with the throttle.


No not occuring with high throttle. I understand what you are saying as well. What other modes can I take off in? Or would I want to take off in? GPS modes are new to me sort of. I came from Libre Pilot where I could not get GPS working 100% due to 3d mag issues. So when I decided to go pixhawk and purchased all new equipment minus frame. Weather has been horrible here the past few days nothing but ran and bad wind. So I am waiting for a decent day to get her outside and up in the air to see if changes made affect in a positive way.

Hey Jonathan,

Here in Canada we’ve had some of the same horrible weather as well recently. Its certainly not very conducive to getting out to fly!

With respect to flight modes, I usually stick to taking off in either Stabilize or AltHold mode. You’ll want to make sure your throttle is setup properly with AltHold, but it’s a good mode because it tends to commit the craft to a swift takeoff once you’ve reached a certain throttle input.

As for GPS based modes, I’d take a look at this list here if you haven’t already: http://ardupilot.org/copter/docs/flight-modes.html It’ll give you a good sense of which flight modes will be reliant on first obtaining a GPS lock.

Another good suggestion is to program a simple takeoff mission (e.g. Takeoff to 4 m) and activate it using Auto. I almost always let my aircraft takeoff automatically now, and then I can just switch from Auto to AltHold (make sure throttle is mid position). This was a hard learnt lesson after having my aircraft tip over on me due to a payload imbalances.


Hey thanks for the information. I am used to taking off in a non GPS mode then switching to a GPS mode. At least that is how I used my REVO FC’s at least. I will re-read what you linked just in case I missed something. I should be having a day here soon that I can see if the changes made have improved the quad. Stay Tuned

So update for you, Today was nice enough to get my quad in the air. I kept it in stabilized mode and it lifted off perfect. All the problems that were there are no longer there now.

Changing the filters to 10hz was the ticket!! Now just gotta get an autotune done. The wiki says as little wind as possible so it might be a while until an autotune gets done. Excited to finally have it flying though after almost a year!


Great to hear, Jonathan!

I remember that change to 10Hz really making a big difference for me, too. For the AutoTune I’d definitely recommend doing one axis at a time, and even if it’s a little windy you can still conduct the tuning, as long as you are flying perpendicular to the direction of the wind.