Hi, I am reasonably new at this and had a mishap with my quad plane yesterday. I am not at all proficient in the log analysis and would appreciate it highly if somebody with experience could look at the log and maybe advise me on what went wrong.

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.

The parameter file is attached and the log file is available at: 

https://login.filesanywhere.com/Login.aspx

Log in Name:   mp@cointech.co.za

Password:        Cointech1

Best Regards,
Marthinus

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AUW = 5200g
Will send some picture of mounts later.
Have a good day!

1mm Carbon sheet machined and the bottom side sanded to be course. The wing area also sanded level and straight. Glued with epoxy resin.

Machined 16mm clamps from alu and a m3 threaded strip from steel. The steel strip was glued to the bottom of the carbon sheet before I glued the sheet to the wing.


Motor mount same clamps but with a 2mm and 4mm carbon plate.

The 16mm tubes are slightly flexible and next time I will use 20mm, very little difference in weight. The wings flex alot so I put a brace from the left front motor attached to the right front motor supported on the nose of the fuzz and that stopped all flexing.

This was after the crash, actually very little damage. I think the major problem that happened is that if I calculate the max amps that all 5 motors draw it is about 180amps and the power board can only handle 60 amps. If you add the VCC 5 volt supply to the Pixhawk to the graph you will see there was a serious dip in the 5 volt and I believe that the processor reset.
Luc Maximilien said:

Glad you did it !

What is your AUW ?  4300 grams ?

I'm curious about how you attach the carbon tube with  motors , can you show a photo ?



Marthinus said:

Marthinus said: I think the major problem that happened is that if I calculate the max amps that all 5 motors draw it is about 180amps and the power board can only handle 60 amps. If you add the VCC 5 volt supply to the Pixhawk to the graph you will see there was a serious dip in the 5 volt and I believe that the processor reset.

Nice job for motors mounting !
Your quad motors have a good efficiency .

During QLoiter hover, your motors required 33,4 A , 728 Watts , while taking altitude in QLoiter 39 A , 833 Watts.
The plane motor with that propeller should use just 6,2 A to fly at 67 km/h - 18,1 m/s
So in theory 45,2 A would be enough to make the transition , 40A if you are in hovering.
Roughly even with full throttle at plane motor you should have , according to E-Calc, a total of  39+81 = 120 A .

At transition  to gain speed from 5 m/s while your plane was in Qloiter, still taking some altitude , the Auto Pilot when the transition start  add 20 A because of  full throttle at RcOu.C3 so you reach 59A .
That is an interesting point , in theory your plane motor should have draw much more Ampères at full throttle but it did not.
The reason was that the  plane Esc  was starting to limit current because of low battery voltage ?

My suggestion is to replace the battery with one with higher C rating and if you can start the transition to FBWA gaining some speed while in Quad plane mode to reach 10 m/s , it should help a lot to reduce current drawn.

I do not think that the processor reset since you have no "holes" in dataflash log recording.

5,2 Kg is quite a lot for the Talon even with wings extensions, it would be interesting to see how it flies when in FBWA mode and how much drag add the quad stuff.

I've built a couple of quadplanes now and the issue of current draw during transition to forward flight seems to be an issue that requires careful planning. In one of my builds I went as far as separating the vertical lift motors off to their own circuit and use a 6S high C battery to keep the current draw down. I run the forward flight motor off a 4S battery. I've just finished helping a friend build an X6 where we used a single circuit and 4S. We are testing with a Nanotech battery which has a very high C rating. Here's some info on my older builds if interested 

A Tale of Two Quadplanes

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