Skywalker X8 Crash

It is very sad to say that my Skywalker X8 flight got crashed.

Incident:

Hand Launched. Used only Throttle stick.
Plane started to glide and suddenly it rolled left and crashed.

After crash I checked my Control surfaces and it’s perfectly configured.
I used FBWA mode and it worked.

After checking the logs I found that both Compass and Magnetometer got failed.
I’ve successfully did all the calibration and the plane got Armed after all.
My CG and weight balance was fine.

My analysis:
I’ve enabled EKF in mission planner parameter and I did my Mag calibration successfully. But I don’t know what happened really.

I attached my log file links (https://drive.google.com/open?id=1LZyPhObXW30uKauDdFdQc6oHD91hzYSa) https://drive.google.com/open?id=18hPlAPL9uKtd4jqApMaDsiBtLAvjKSY5. Hope someone can understand and can help me out of this problem.

Hi,

Sorry to hear about your crash. On the initial flights, I launch with Manual Mode and then only switch to FBWA once the plane is trimmed and flying well. In this manner, you can switch back to Manual Mode as your emergency bailout if something goes wrong with the APM setup while high in the air.

Good luck on your repairs!

Ok.
Next time I’ll launch with Manual mode.

Can somebody figure out the problem??

My log bin file link is below.

https://drive.google.com/open?id=1LZyPhObXW30uKauDdFdQc6oHD91hzYSa

looks like your RC1 OUT is configured incorrectly: (had similar issue when upgraded 3.9.1 to 3.9.2 )
red desired roll, green actual roll.

I upgraded from 3.8 to 3.9.2.
How to correct this problem? Should I reverse the RC1 out?

As per Ardupilot wiki, my FWBA is working properly. (I’m using a Elevon setup with Skywalker X8).

Since because I’m not from aero background, the flight dynamic always confusing me.

At manual mode - both elevon go up for takeoff and go down for landing.

Using transmitter stick down from center for takeoff and up from center for landing. (please correct me if I’m wrong)

Also please attach a link to aerodynamics for proper control surface movements and transmitter stick movements.

I know these all are very basics. But it’s confusing me a lot.

Thanks in advance.

One easy method to remember how the control surfaces should respond to the sticks is the “High Five” method, which I personally use: https://www.flitetest.com/articles/high-five-control-surfaces-flite-tip

When in manual mode, if you move your aileron stick right, you should see the right aileron moving up, making a “high five” with your stick. Same goes for rolling left.

Likewise, moving your elevator stick down should make your aircraft elevator (or both elevons, in your case) move up to make a “high five”, and vice versa.

The only exception to this is the rudder: Move your rudder stick and the rudder should respond in the same direction, not the opposite direction (unlike the aileron and elevator).

Once you are more familiar with the aerodynamics you will be able to understand why the control surfaces respond as such. But this method is a quick and easy way to remember things.

Hope this helps!

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Hello Rijun,
Sorry for your crash, I did the same thing with an expensive Quad copter by having two motor inputs reversed. The control servos can move correctly in Manual mode, but be reversed in FBWA or anything other than manual. You need to test this before flight. Test the response of the servos not with the Tx(Manual mode) but let the flight controller do it. Just take the prop off for safety and engage the servos. Hold the plane and tilt it up/down, left/right and see that the surfaces move in the correct direction. From the wiki:
Here is how to fix the problem.

Check servo movements

BEFORE EVERY FLIGHT : before take off, hold the aircraft in your hands and switch to FBWA mode, then pitch and tilt the plane it to confirm that the control surfaces move the correct way to return it to level flight. (The ailerons and elevators will move; the rudder only coordinates turns with the ailerons in flight, so it won’t move much on the ground). This will ensure that you haven’t accidentally reversed a channel.

You should do this before every flight, just as you move your control surfaces with your RC transmitter to ensure that nothing’s reversed. Failing to do this is the #1 cause of crashes.