I had a crash today where my 3D6 RTF Y6 seemed to be a glide slope type landing with no control from my end

Today I was doing a manual flight using my DX8 radio for the 3DR Y6. I was trying to get some video while flying a remote area over a near by river. At about 6 1/2 minutes into the flight and with a reported 50% remaining in my readymaderc 8000mah battery. The Y6 seemed to switch into a fail safe or unknown mode where it wanted to land while in motion and would not take commands from the remote. When this occurred, I was flying in loiter mode at 15mph with a 1.2ghz video transmitter and I witnessed the whole event live. I tried to override the thrust by going to stability mode and it still would not increase thrust or follow the movement commands I was giving it. I was very lucky today because the Y6 missed the water completely and didn't even break a blade. Here is a link to the video of the whole flight. https://vimeo.com/84828838 At about 6:33 "end of video" you will notice the copter starts the oscillate more than the camera gimbal and take out and the motors sound erratic. Now I still have to adjust the PID's which I'm in the process of doing. Here is what is strange is this doesn't seem to occur when on a autopiloted mission or when in stability mode. I've flown it in stability mode over 55mph ground speed. The only time I've seen it happen is at low attitude under 150ft and under or around 15mph. Is there some sort of adjustment or PID change I need to make to correct this issue? Am I just losing radio signal and the Y6 is doing some sort of auto land fail safe?

Additional information:

Radio DX8

APM 2.6

3DR telemetry with Mission Planner 1.2.92 ground station active during flight

1.2ghz video transmitter on for FPV viewing

Crashes have occurred from 281 to 558 yards away through forested areas while in moving loiter mode.

 This was going to be a great flight until the obvious happened. I'm just thankful it landed out of the water.

 

 

Drone Crash - barely missed the river from West Fork Armory on Vimeo.

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OK first off, from the sound of your motors and the quality of the video,, I see that you have a very good blg and a very poorly tuned copter. Other than that you will have to supply a dataflash log for any real proof. We don't know what mode it thought it was in for sure unless we see the log file. Excellent video though!

Definitely poorly tuned. That's a work in progress. I'll try to get a log down loaded tomorrow so you guys can see what's up. I can tell you that the 3DR factory PIDs don't account for a lot.
before bashing "3DR factory PID's" - you need to understand that they cannot provide good PID's for all cell counts, payloads, and battery capacity (weight) - this is before I mention weight distribution.
So.. it's smart to be a bit humble until you are an expert, and even then...

Re: LAND event.

What was the failure code? In log browser, filtering on ERR. That will tell you what called the land event. I get random LAND events too...and they appear as Battery voltage spike, which trigger the land. However, I've never actually seen the voltage value which causes the spike...I had one last weekend. My landing was also a glide slope version, but mine was to the left. I was too close to the ground to save it in stabilize (yes, you are "locked" out when LAND or RTL occurs, unless you mode change). Idle Volts were 4.01-4.02 on all cells. Coincidence? What is your C rating of the battery btw, and did you just do snap action on the throttle, maybe?

 

Re: PID's.

If I understand the situation correctly (probably not!), Michael is wondering why the factory PID's on a RTF (?) supplied airframe were less than optimal. Im assuming it flies ok with the approved battery and no gimbal Michael?  If someone buys a RTF Y6, surely the standard Y6 PID's will already be set by 3DR before it leaves the factory? I find it unlikely 3DR would ship it without the Y6 PID's pre-loaded. And even with a gimbal it shouldn't be out by too much.

 

However, I see the RTF is supplied with a 4200 3S...Michael is flying on 8000. That will definitely require a "PID retune".

Very true. It did have the oscillations during flight with the factory batteries as well, but the auto land never engaged. Did have a the upper starboard side prop fly off once during a auto mission. It had a very similar affect as seen in the video, it just did a gliding type landing but a little hard in my opinion. I've since used blue threadlock on the nuts and it hasn't happened since. Overall, I am very satisfied with the 3DR RTF Y6, and when you get into this hobby, it's all about tuning in the end.

 

I've tried to switch to stabilize when this issue occurs and I'm still locked out with no control. The last time it happened it was only about 250 yards away with some trees in between me and the copter and started to auto land again and none of the mode changes would let me override it. I'm downloading the logs right now. Also the battery is a 35C (280.0A) Continuous, 70C (Max burst) 8000mAH 3S1P. I also don't remember doing and throttle changes before the autoland crashes occur, only the "what the hell?" give it more throttle action that occurs when it's crashing.

This should be the log for the flight

Attachments:

your desired climb rate increases in negative desired crate as you sink - APM does have a reason to sink.

There is no proof of mode change. (no RTL or other failsafe)

Also, during your critical part of descend,  your throttle in flatlined, (no throttle)  - this is a sign of typical reciever failsafe - except you did not configure failsafe properly in APM,  So APM just kept last input, which had a desired pitch and sink rate.

your FS_THR_VALUE is set to <=975  - I bet this was NOT what your reciever output was.

please, next time, use the new ardupilot.com forum for support :)

So are you saying I should increase the failsafe throttle value or set it to RTL when a loss of radio signal occurs?
No, you should decrease failsafe rx output to a very low pwm, lower that it ever gets while it have connection. Check the url I sent for documentation.
What url?

You can manually test your failsafe setup using MP. Set your throttle failsafe low threshhold, set it to switch to RTL, connect to MP, switch to the first screen and watch that it changes flight mode to RTL when you turn off your TX.

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