I had built a 10inch drone, took a flight yesterday and it did 1.5km flight and RTL worked fine. Did the same today and when tried RTL, it initially starting coming and then suddenly fell from the sky.
I know the tuning and settings are not all at best, but want to know the exact reason for it flying yesterday and crashing today.
Parts:-
Mark4 10inch
Microair H743 V2 + Am32 70A Stack
3115 MAD Motors
Crossfire module on TX16s
Caddx GT VTX
My Analysis: Since I built this last week, it flew fine on the first day, but when I was testing its hovering at 2m height, it used to fall after a few min. Had made changes based on some suggestions by @Allister as I was already having mid-air falls. And suspecting of ESCs shutting off, the AM32’s temp and low volt cutoffs had been disabled.
Have been beating my head since this was built, so any help is appreciated.
NOTE: I’m learning how to diagnose issues. Someone please speak up if I got something wrong!
I think you had an electrical failure.
Here is a plot of the 4 thrust commands, one per motor. And also a plot of the RPM from the ESC(s). Notice the general correlation for the first half of the RTL mode (before fall started). Then, the ESCs report suspiciously constant RPM. The copter probably begins to descend. The control system rapidly requests additional thrust from all 4 motors… but it never happens. From this I conclude that you experienced some sort of 4 motor failure, which the autopilot did not expect/command.
Yes, shouldn’t have but the gps interreference wasn’t allowing arming to test. Even when I had initially tested with disabling GPS,(in stabilize) it kept on falling after a few min of hover every time . Unable to solve this , I just tried giving more altitude and it somehow flew fine.
Yesterday, with gps it did 1.5km fine with RTL too, today finally it gave up.
What ever caused the ESCs to shut down, the FC responded after the fact with the full power command. By the time the FC was sending the command, the current had already dropped to nothing so the motors were already stopped/stopping.
I would agree it’s suspicious. That is likely erroneous data because the RPM is never that level, even when everything is working perfectly.
The fact motors were so clean in stabilised mode, but then everything went down hill when switched to RTL says there’s some tuning issues here. I can see the quad isn’t tuned fully yet so this may have stressed things out. I’d be curious to see the previous flight and RTL to see if there’s any signs of stress there.
Does the esc temp need any calibration? How come it is so hot during start itself.
Also is the tuning or para so bad that it can cause such a failure, or could the esc be faulty.
I’ve had ESCs that have suffered damage before and then still “worked” but they also got incredibly hot afterwards. I replaced them before in-flight failure, but I think that may be a consideration here. The ESC was damaged from before and now it just gave up. I don’t know too many electronic parts that will continually withstand 120c temps.
The data points for the temperatures aren’t recorded in the logs at a very high rate, so you’re only seeing the temperature at a moment in time. The log holds that value until it’s refreshed giving it that stepped look in the graphs. But even if those fluctuations are a bit wild, the fact is their average is much higher than normal.
The question is more where is temperature measured inside the ESC and what kind of compents are used inside the ESC. One second is really are long time in modern fast switching digital systems.
I assume you are using a relative low cost 4 in 1 module. Does it have any heatsinks directly mounted on the MOSFET’s. These kind of components have a maximum junction temperature of 150°C.
Mostly the values on the productsheet like 70A continous current a optimistic meaning under idle conditions. Like all four channel work constant with the same load not switching up and down. Not one more and the other lower and working in a good airflow.
There is no way a 10” quad should overload a 70A ESC when flying a mission, especially if you are running 6S - unless you are using motors with a too high KV rating. I find that for 10”, 6 Cell 900KV is a good option. For 4 cell, I would use a 1250KV motor.
There are multiple ways for that to happen, the most common are incorrectly configured parameters that lead to high noise levels at the motor outputs, causing the ESCs and motors to heat.
