Vtol crazy after Switching to FBWA, Pixhawk damaged? help me to understand

Hello folks,

Need help to understand this crash.

The Vtol plain was performing the 3rd flight since rebuilding after ending up on a tree due to extreme wind (my fault)

1st flight was few weeks ago just performed Qhold and QLoiter to test vertical part (windy day, didn’t want risk)
2nd flight was the first of yesterday. Normal take off, performed full flight without issues. Just a bit of trimming.
3rd flight was planning to re-check trim. Vtol take off, transition to fw flight, a bit of manual flight and once I was going to land ( manual to FBWA to aligh with runaway) the plane started to roll on one side then the other and endedup on a tree again. Minor damages this time.
Considering the behaviour I was quite sure that one servo failed but “of course” they all works fine (2x aileron, 2x A tail)

I checked the logs and I find out that:

  • I had bad gyro health while in flight
  • 20-30 sec before switching to FBWA the compass went crazy
  • when I tried to convert I had gyro and accel bad health and EKF is all over the place

the flight controller is a pixhawk with 2mb of flash
GNSS unit is a matek F3 with full external baro (use as secondary)

I guess I will need to put in the bin the FC and replace is but I would like to have a second opinion.




Nobody can help me understand?

Have you calibrated all your compasses after the crash?

I am on my iphone so can’t review your logs at this point but compass re calibration is a must.

Also all your pre arm checks are enabled?

Yes of course to both

I have limited knowledge on VTOLS at this point.

Go to this thread. Someone in this thread can help you.

@GregCovey is our VTOL expert in this group. See if you can get his attention.

Did you have any luck? Just checking on you.

No reply from him on the forum

Thats too bad. I wish I can help, I am far behind in VTOLS.

Looks like all the old timers like me taking a break lately. Maybe due to holiday season.

Anyway, I will try to review your log on the plane on Tuesday. Maybe look at the last active people on that thread and send them an email.

I will be working on this giant soon then I will have more knowledge to share, however I stick with Pixhawk or Cube FC’s. No experience with Maytek. I stick with Here2 or 3 GPS.

Post some pics of your plane and hardware setup.

Greg has passed away … see here: In memory of Greg Covey. RIP - General - ArduPilot Discourse

Oh no…that is so sad :frowning: I missed that post. He was amazing. Now I am heart broken. I was trying to meet him in person but we couldn’t find the time to do it. He will be missed.

I quickly checked few things. I have a flight to catch…

Why your plane was disarmed in the middle of the flight or was it on the ground?

Do you have left stick down disabled in your parameters so you can avoid accidental disarming the plane while in flight?

Also, AHRS settings seems wrong. tons of errors coming up.

Also, your GRYO not healthy at all. keep saying GYRO bad, in consistent by 26 degree.

Also keep saying EXCEL not healthy prior to arming it.

Are you using any SIK radio to get telemetry back from the plane inside mission planner before arming it and taking off?

Also, have you disabled Pixhawk internal compasses and just using external compass in your GPS?

Do you have 1MB Pixhawk or 2MB Pixhawk?

Please post pics…

And have you re done the MAG calibration after last crash?

The disarm that you see is because I landed, change some setting for the servo (trim) and then flew again.

I have rudder as arm/disarm as all my systems so I’m aware what I can and can’t do. And no. I didn’t disarm in flight.

If you see during the second flight, while in manual mode, the compass suddenly rotates almost 90 degrees CCW while plane is keep moving forward. within 30 sec the correct heading is restored.
The “crash” starts as soon I switch back to fbwa when sensor need to provide assistance.

I could be wrong but bad gyro and inconsistent by 26 degrees are not related as gyro can’t tell you a degree error. This is referred to the compass.
I noticed the issue as well with gyro and then with accelerometer.

I got a telemetry module connected all the time during the flight

yes of course, internal compass is disable because it is very close to power cables, only use the external one

my pixhawk has 2mb of flash so full features.

Are you familiar with Yaapu telemetry? Its a life saver gives real time Data via voice on any FrySky radio about any anomalies while in the air.

I would still remove dis arm feature. Just my 2 cents.

Going back to your problem, without thoroughly analyzing data I am just doing simple guess work. Sorry.

Only thing I can think of your GPS has damaged due to previous crashes??

Honestly not sure…

Currently I’m on futaba si no telemetry on radio. I ordered last week some frsky Rx to move all UAv to frsky on purpose :slight_smile:

Let’s waiting for the other to reply

I have the same problem, please help