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Need Help with Diagnosis Log- Quad Plane Mishap

Firmware: Arduplane 3.8.4
Airframe: XUAV Talon 1718mm with 150mm wing extension each side
Power: Tattu, 10000mah, 6Cell, 22.2V, 25C
Pusher Motor: Maytech 3548-790-S, 790Rpm/V, 717watt
Pusher Prop: 11 x 8.5
Pusher Esc: Castle Creation Edge Lite 75
Quad Motors: 4 x KDE Direct 4012XF
Quad Props: 4 x KDE 15.5 x 3.5
Quad Esc: 4 x Castle Creation Lite 50.
Auto Pilot: Pixhawk with Power Block.
GPS & Compass: 3DR UBlox
Servo Rail Power: Separate 5 volt, 20 Amp Ubec

I took off in QLoiter and climbed to approximately 30 meters. Switched to FBWA and applied throttle. The transition was extremely smooth but soon afterwards almost seemed that when the quad motors stopped the rear pusher motor also stopped. Switch back to QLoiter and the quad motors started up and she stopped for a moment but then became completely unstable and gravity was declared the winner.

I would really appreciate it if somebody with experience please look at the log file and give me some explanation and advice.

Best Regards,
Marthinus

The log file is uploaded in: https://login.filesanywhere.com/Login.aspx

Log in Name: mp@cointech.co.za
Password: Cointech1

Talon 23042018.param (16.1 KB)

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You have severe power problems in this plane. When you transition the voltage per cell drops to 2.9V, which is probably below the cutout voltage for your ESCs. You don’t have enough current capacity to support the amount of power you are trying to draw in transition (that is a common problem in quadplanes).
Also check how you are powering the flight controller. Your POWR.Vcc varies by 0.6V (it shouldn’t vary by more than 0.1V or so) and your POWR.VServo varies a lot too.
I don’t know what your power setup is, but it just isn’t enough for what you are trying to draw. Use batteries with a higher C rating, and also ensure all current carrying wires are thick enough. I suspect you used wires that are too thin. Do a (careful!) ground test with the plane held down and the motors running for one minute, then switch off and immediately feel all components. See if any are getting warm. You may like to reverse the motors for that test, so it pulls down instead of up.
Your airspeed sensor is also not well positioned - it looks extremely noisy.
Cheers, Tridge

Dear Tridge,

Thank you very much for the response. I was not aware that the standard current/voltage sense PCB has a 60amp limitation, could that have caused the voltage surge because my demand is 180amps. I have ordered a high power board from Belgium.

Best Regards,

Marthinus

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Hello, I saw your post Need Help with Diagnosis Log- Quad Plane Mishap.
honestly I have had the same problem, could you help me how you have distributed your electronic, and how you came to solve your problem.

Hi, Sorry for the late reply. Mainly I changed two things. I upgraded the current sensing board from a standard PH board to a 200amp board and used much thicker power cables to my speed controllers. It resolved the problem.

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