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Quad Fell out of Sky

Hi Guys,new to the forum here.
Ive built myself a 450 Flamewheel copter but ive never gotten to fly it for more that 10 minutes without it skewing off in a random direction.

I put it into a shop to get it looked at and the guy there tuned the PID’s and calibrated everything so he said it was ready to go.

Flew it today and whilst in loiter mode which was working well, all power was cut to the motors and it fell approx 30m to break into many bits on the ground.

If someone could have a look at the log it would be much appreciated.

Cheers
2017-10-08 12-03-14.bin (822.9 KB)

In a word - vibration.And the electrical supply to the flight controller is suspect dipping below 4.6v on occasions.It was too heavy using over 3/4 throttle most of the time.

But mainly it was vibration wot dun it.

Hi Jagger, thanks for the reply.

Why would vibration cause the quad to kill throttle completely?

Cheers

As @Jagger pointed out vibrations is number one and also the large variations in Vcc to the flight controller.
Your logging is very minimal, with no RCout AHRS etc, so any conclusions are based on minimal information from you.

Start with sorting your vibrations, then fix the fluctuating voltage to the FC, and then try an Autotune.

Reducing vibration at the flight controller is the number one requirement for every one made.There are stipulated safe limits in the wiki of +/- 3 for the X/Y axes and -5/-15 for the Z axis.Safe maximums.The result of having big vibes is a reboot/freeze/confusion/erros in the flight controller and the result of that is usually a crash.Which is why we spend so much time getting the vibes as low as possible.So have another look at your graph bearing those wiki figures in mind and wonder how it managed to stay in the air for quite so long.

The power supply to the flight controller is required to be 4.1V to 5.7V with a variation of less than 0.3v and preferably less than 0.15v.Yours dropped to 4.2v with a variation of 0.59v.The result of a voltage drop to the flight controller can be remarkably similar to the result of excessive vibration.Flight controller confusion or reboot leading to a brownout and a very sudden and undignified end to that flight.As the log ends abruptly at alitude,and your VCC (power feed) is dodgy,there’s a great chance this was a brownout which would appear to be a throttle cut on the ground as the flight controller shuts down.

Worth doing a lot of reading of the wiki for this sort of stuff.That copter was doomed.Time for a new frame and a Pixhawk. :smiley:

http://ardupilot.org/copter/docs/common-vibration-damping.html

Which flight controller are you using by the way ? No mention of specs but I’m thinking an APM 2.xsomething using 3.2.1 firmware…

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