# Octorotor EKF errors

**URL:** <https://discuss.px4.io/t/octorotor-ekf-errors/9401>\
**Category:** Flight Testing & Log Analysis\
**Created:** [January 30, 2019, 12:08am UTC](https://discuss.px4.io/t/octorotor-ekf-errors/9401 "2019-01-30T00:08:59Z")\
**Posts on this page:** 1\
**Showing post:** 8

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**Author:** ![tumbili](https://discuss.px4.io/user_avatar/discuss.px4.io/tumbili/32/3779_2.png) [@tumbili](https://discuss.px4.io/u/tumbili)\
**Post date:** [February 1, 2019, 8:52am UTC](https://discuss.px4.io/t/octorotor-ekf-errors/9401/8 "2019-02-01T08:52:06Z")

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@Jeremy_Zanzig Yes, I had some time to look at it. The ekf reports a pre-flight fail at the beginning of your log (pre\_flt\_fail flag in estimator\_status message)

 ![](https://discuss.px4.io/uploads/default/original/2X/4/4de4dda352e981e1326da09d96878b03728f8270.png)

The conditions for that flag to trigger can be found [here](https://github.com/PX4/Firmware/blob/master/src/modules/ekf2/ekf2_main.cpp#L1733)

You can basically see that this can happen if the estimator innovations are too large. We check innovations for velocity, position, height and heading. In your case it looks like it might the heading innovation that triggers these failure.  
I can see some spikes in the heading innovation when the vehicle is on the ground, probably you should check out your compass data.

 ![](https://discuss.px4.io/uploads/default/original/2X/9/941a1309943610898d394b5c46268d745e6727bf.png)

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