Hi, I've just maidened my 3DR Y6 into the ground, and I'm not sure why. (This is my first multirotor, I've flown a trad heli and fixed wing up until now.)
I got it light on the skids for a moment then carefully added a tiny bit more throttle when it suddenly shot to about 3m high before I could react. I panicked and cut the throttle to zero instinctively. I knew I'd have no control so I got it back to about 20% power but it was too late, it flipped and landed at my feet. It broke one prop, I'm happy that I got off so lightly.
The logs show it was light on the skids at 30% throttle, and I only ever got up to 36% when it took off. Surely that's not normal. Is there something I've missed?
(I know my choice of location was a mistake. I did it in a small yard. If I did it in a big park I'd have been standing further away and 3m high wouldn't have caused me to panic.)
It's a brand new 3DR Y6, with APM2.6 with v3.0.1 Tri firmware. All default PIDs
Log attached, I arm it at about 58%. Any pointers appreciated.
Replies
I flew today and it was a lot better. I used channel 6 to tune Rate Roll and Pitch P. I went right down to 0.03 and I think that was about the best. But that was very low compared to some of the suggestions I've had. I lowered the I down to 0.06.
It still wobbled a little, you can't see it as much as hear it in the new vid below. It is certainly 10x better.
I did a little auto course, at 5m/s and it worked really well. When it got the last WP it just loitered there nicely. So while it loitered I re-wrote the flight path by moving the WPs slightly further out and increased the speed to 7m/s. I uploaded the WP via telemetry (and the dialog box showed a few timeout errors, but seemed successful). When I clicked restart mission it announced "heading to way point home" and did just that but descended gently and hit the ground. It was as if it wanted to land at the home point, but it came in with horizontal speed and tipped over when it touched the ground.
But that was nothing compared to what happened next. I straightened it out, hit the restart mission key on Mission Planner and armed it again. I don't remember what I actually did because it was all so fast, but it took off backwards over my head at full speed. I ducked for cover and hit the mode switch. It came crashing down at high speed about 40m behind me. The tlog shows there was almost zero channel 3 in input (throttle) but channel 3 out went over 50% and that it went into RTL mode. It had a top speed of about 55km/h and altitude as low as -30m.
I don't know what happened with either of those crashes. Tlog attached, the excitement all happens towards the end of the file.
2013-11-16 08-24-16.tlog
It sounds, to me, like something is mechanically wrong on the vehicle.
That squeaking sound sounds like a bad bearing or something rubbing on the motor housings.
Can you detect any resistance (battery disconnected!) when slowly rotating each propellor? Magnet 'bumps' are normal. I am referring to a rotational drag spot or where it might feel tight while being rotated as compared to all the other motors.
I vote this is a motor/bearing/rotating issue.
-=Doug
I flew again today in a park with lots of space, but with much the same result.
I didn't have the telemetry running so I can't revisit the details, but basically it went from light on the skids, then with a little more throttle it took off to about 2 or 3m high, I reduced the throttle and it kept climbing to 4 or 5m. I reduced it some more and it didn't really descend until almost zero throttle when it started tipping over. I gave it a touch more throttle which leveled it, but it was too late and it hit the ground. The whole thing was over in less than 5 seconds.
There was nothing broken so I tried again, even more gently. The same thing happened but this time I broke a prop and the landing gear.
On the plus side it was nice and level both times until I reached minimum throttle.
It just feels like it's got too much power. I'll go through the Setting Throttle Mid instructions, and set 1/3 on the stick to mid throttle and hope for better results. Those instructions suggest adding weight which I'll do too. I'll start with adding 300gm.
Any other ideas?
If you are airborne at a low throttle setting that's a good thing. A Y6 for your first multirotor is a touch ambitious but with your heli time you should be ok. Multirotors can be a bit weird whilst in touch with the ground and enjoy getting to a meter or two and settling down. Sounds like more room is required. I notice you say Tri firmware, you mean Y6 of course a tricopter uses a servo for yaw. I have a feeling you have the right firmware or else it would not have made it to 3m