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Control/RX Loss Mid Flight

Snarls

Gravity Tester
Mentor
#1
Had a few instances today where I would lose control mid flight. One time there was a visible RX Loss warning in the OSD as I loss control. Two other times losing control resulted in a slow flip, but there was no RX Loss warning. Luckily all times nothing was damaged because I was low to the ground.

Strangely, looking at the DVR footage, when the RX Loss warning pops up, the rssi on my osd still says 90+dbi. Here are a couple theories of what is going on. I am flying the HQ durable 6x4.5 props on Cobra 2204s. These props are actually really durable (haven't broke one yet), but they bend. I suspect one or two props are bent out of alignment and are causing bad vibes. Either the vibes or the FC trying to filter out the vibes is causing the CPU to lock up and me to lose control. Another idea is that with the out of balance props, one motor is drawing too many amps and an ESC is going into protection mode. That doesn't explain why somethings the loss of control leaves the quad still in level flight. The RX is built into the FC (FrSky XSRF3O) so its not a receiver wire coming loose.

Worth noting that last weekend I was flying a different quad at the same location and it lost receiver connection once during a flight. There are 4+ of us flying FrSky in the same spot, but I think the protocol is good enough to avoid any interference. There is also a radio tower just up the hill from out flying spot, but it has not been an issue before.

So to summarize I think it is the FC CPU locking up from bad vibes, or an ESC shutting down.

Let me know what you guys think it is. I have flown this quad dozens of times without issue.
 

PsyBorg

Wake up! Time to fly!
Mentor
#2
Unless the quad is visibly shaking by eye I doubt the bent props are effecting it. I crash and bend my Dal Cyclones 90 degrees and flex em back into reasonably straightness leaving only a slight kink and never have issues. It sounds like a failsafe if its rolling over and playing dead. since RSSI is still high when it happens I would suspect brown outs due to current draw. I would check for a weak solder connection somewhere in the chain or a damaged wire hiding somewhere.

Have you checked motor temps when this happens? Is any part of the carbon frame warm along any of the current paths to the motors?
 

Snarls

Gravity Tester
Mentor
#4
Thanks guys, I will take a closer look at the wiring. One other thing I forgot to report was that frequently after a crash, while either upside down or right side up, the quad would not arm. I would have to wait several seconds and try arming multiple times before it would agree to fly again. Sometimes it would not even arm/get in turtle mode and I would have to walk out and get it. I wonder if the arming problems are related. The crashes were not from the loss of control, just normal crashes.
 

PsyBorg

Wake up! Time to fly!
Mentor
#5
Is this one of your Kiss rigs or a beta flight set up? If it is beta flight that was common a while back with the arming issues. It has something to go with the acccelerometers and gyros. When I first started using betaflight on my Gremlin it was horrible for that. There were times I would have to up plug power and reboot it.

As far as turtle mode have you set the angle to 180 or left it set at stock 25 degrees? If its beta flight I suggest you grab the latest firmware AND Gui as I have not heard of that arming issue in a while.
 

kpixels

Antigravity or bust...
#6
Hi Snarls, I'm not familiar with the FrSky but I had very similar issues (everything you describe) after I tried to upgrade my cheap FlySky 6 ch to the FS-I6S 10 ch. It was so intermittent that it was hard to pin down what was causing the "loopy" behavior. After a while I noticed that these crisis never happened with my other controllers. By then I had bought the FS-I6S which was a 10 ch version of the cheap controller. Threw $80 away when I quit using the FS-I6S but I haven't had a similar instance since. Probably something else but throwing that out there just in case it might help. Good luck,
Ken
 

Snarls

Gravity Tester
Mentor
#7
Psyborg this is on the Betaflight quad. It is running the latest version as of January. Turtle mode angle is probably still the stock 25. I'm going to reflash the latest version on the board just to rule out any firmware corruption or whatever. Should be able to find some time in the next couple days to try it out.

Thanks for sharing your solution kpixels. I'm really hoping it is not a transmitter issue. My rssi seems fine so I think the transmitter is doing what it is suppose to.

Luckily I have a built in black box on this FC so if it happens again hopefully I can record it and try to see what it going on.
 

PsyBorg

Wake up! Time to fly!
Mentor
#8
Cool mate good luck. Grab some video and pics if you still have issues. Maybe someone can spot a behavior specific to a particular issue.
 

Snarls

Gravity Tester
Mentor
#9
Currently looking at the settings in betaflight and the CPU load is just over 50% with the quad just sitting on my desk. From what I've found that is high for idle. I'll try lowering it and see what happens. Also looks like I'm running betaflight 3.2.2 from November which is older than I thought. I'll upgrade the firmware to the latest (February) update.
 

Snarls

Gravity Tester
Mentor
#10
So I disabled accelerometer and got the idle CPU usage down to 30%. I am also running 4k gyro and PID loop times, which I could lower, but Ill try just turning off the accelerometer first.

Unfortunately a snow storm has come out of nowhere and it looks like I might not be able to test this quad this weekend.
 

PsyBorg

Wake up! Time to fly!
Mentor
#11
Does your yard look like this now too? Can't sit at my various benches on the propriety to fly for a while it seems.

Nor'easter.jpg
 

Snarls

Gravity Tester
Mentor
#12
Yep it looks like that, maybe even worse. Looks like it is melting fairly quickly though. Today I just flew my micro inside. I put some conformal coat on it so I might even chance flying it outside in the snow.