AQ with 3 GoPros almost ends up in the ocean

[chris24g]

Was flying at one of my usual beach locations today. Before heading over water, I will burn a pack over the beach to make sure there are no issues. First flight was fine and proceeded to have fun with the surfers. On the 3rd flight, at about 100ft, maybe 30 seconds into a fresh pack, the AQ felt like it was responding very late to stick input and/or it had difficulty self leveling. I do not know, it was happening quickly. I dropped altitude and fought to land it. My stick inputs by this time felt like they were at maximum endpoints just to keep it flying toward me. Once it got down to about 4 ft, I knew it was home safe. No damage, but the gremlin struck again. This happened to me once before, and the crash from 8 feet cracked the IR filter inside my nex5n. I seem to remember that after take off that time, I heard the motors making a pulsing sound as it hovered. Soon after, the controls were unresponsive and it went down at an angle.

Otherwise, it has flown many dozens of flights like it was on rails.

I'm running 6.6 on a rev1 board IIRC

Luckily I had a card in the AQ and got the log. I hope someone can take a look and shed some light on this.

[chschmid]

Good to hear you made it back to the beach.
I was not so lucky yesterday.

Maybe you can post your log.

Cheers
Chris

[chris24g]

here is the log
https://www.dropbox.com/sh/mh09llm58rmk ... 20-AQL.LOG

[JussiH]

There is a massive inbalance in that craft showing up in the motors plot. You can see that pitch, roll and yaw is out of balance, they should be more centered around 0 ina a craft that is well balanced.

It pushes the motors into saturation, which is a very good explanation for the loss of control:

Mainly 2 things can cause this: Bad balance of the craft itself, or thrust mismatch. Look for tilted motors, motors not working properly, bad propellors, range of ESC´s.

You need evenly distributed thrust and the COG as close to center of the frame as possible. If there is imbalance then the control uses a lot of effort in stabilizing an inherently unstable craft and that will mean that vital control overhead is lost.

[chris24g]

[kinderkram]

Woah, that sounds really bad.
Check your motors, especially the bearings - any play there?

[chris24g]

I don't think those are bearing noises. I'm running AXI 2814 motors so the bearings and construction are high quality.I believe it has something to do with motor timing. Could be a sign that the motors are working too hard due to the imbalance. I'm off to test some more today and see if I can reproduce the condition.

[bluuu]

check C-clip at the bottom of motors (on shaft), try to move up and down and try to felt the "gap"

[r0sewhite]

[chris24g]

i'm estimating the total weight of the ship (AUW) to be 6 lbs. it's about 660mm motor to motor with 11" props
gimbal with cameras about 700g
my current angle I val is .0005

thanks guys for your ideas