First Flight & some issues with X8. Need help analysing logs!

Hi all,

I tested my X8 this morning. I originally planned to do a test flight, then AutoTune, but cancelled after the first one as I experienced some issues.


  • F2X8 Frame

  • T-Motor U5

  • 40A ESCs

  • 1655 props, lower ones have a broader airfoil

  • PixHack FC

  • X8R Receiver, X9D Transmitter

General summary:

  1. It took off in a relatively stable manner and was well-controllable.

  2. I noticed that one channel was reversed, probably Pitch. [I bought this one as an unfinished setup, so it’s possible that the FC orientation is reversed and it’s not Pitch, but Roll] I reversed it on the Taranis, but couldn’t try it out yet.

  3. After landing, when disarmed, what seems to be Motor 8 stopped immediately and not just after disarming.

  4. Trying to power up again, I noticed a strange noise roughly from the direction of Motor 8, so I called it a day. It sounded a bit like a prop hitting a wire, but there is absolutely none close, so it should come from the motor.

  5. The log analyzer tells me:
    Test: Motor Balance = FAIL - Motor channel averages = [1159, 1256, 1281, 1280, 1210, 1216, 1239, 1315] Average motor output = 1244 Difference between min and max motor averages = 156

Basically these are my questions:

  1. Does anyone have an idea what’s up with that motor? Should I recalibrate the ESCs?

  2. Will that also solve the Motor Balance issue? Or is Motor Balance generally difficult due to the X8 configuration?

  3. Is there anything else in the logs that jumps at you as being wrong / dangerous?

Here’s a video of the flight:

I uploaded the .tlog and the .bin, please tell me if you need more!

2017-04-30 06-25-08.bin (1.1 MB)

Hard to tell from the logs since it was not in the air very long. You need to fix how the flight controller is mounted. I see high vibrations when it was in the air. This can cause motor issues.


Thanks for the quick reply @iseries!

Strange, the PixHack should have a dampened IMU, also it’s mounted on a foam plate. What else could I do to keep it from vibrating without wobbling back and forth?

I also just did an (AIO) ESC calibration, maybe that’ll help, too.

Unfortunately, it’s become quite windy outside, so I can’t really test a lot. Or is there anything I could try inside?

UPDATE: I just armed it inside after the ESC calibration and powered it up to ~20% throttle. It seems a whole lot stronger now. When armed, the motors spin a lot faster, also at 20% throttle it was close to lifting (Thrust/Weight should be 4.5:1). When putting the throttle at 0%, all motors are still spinning, so the previous issue with that seems to be solved. Now I need to get that vibe fixed.

Test: Motor Balance = GOOD - Motor channel averages = [1072, 1073, 1072, 1072, 1073, 1072, 1072, 1072] Average motor output = 1072 Difference between min and max motor averages = 1

Well, do another test flight and try to leave it hover for while and I can take another look at the vibrations. Sometimes 4 small squares are better than one large square when it comes to vibrations.


Ok, I’ll do that as soon as the wind calms down and them report back. Thanks!

The motor sound should be straight forward to track down.

Spin the motors, any sound?
Pull and push the motors when spinning them.
When running the top motors pull up but the bottom motors push.
Check that the free play in the motor is not allowing one of the bottom motor shafts to touch the mount.

It is quite audible in the video.

Could there be anything else loose on the frame.

Remember, vibration is your enemy.

Definitely a mechanical issue there somewhere judging from the sound. I’d remove the props, then run the motor test in Mission Planner to spin up each motor independently. It should be obvious which one is the problem. Sometimes the magnets in the motors pick up metal fragments etc while building. Either that or a bearing is bad. Regardless it should be easy to find. From a safety point of view I’d recommend a bit more distance from the copter during a maiden flight.