Warning ! Do not try this.

It has been a couple of weeks now and I'm getting more comfortable with my STABALIZE and LOITER set up on my 3DR quad. Still having some yaw issues but yesterday morning I was enjoying the fruits of my labor out at my local RC field.

In one of my last few flights I was testing the high decent stability oscillation I noticed from way up high about 150-200ft  the props would almost stop while decending very rapidly and I applied power and it would keep level and stop the decent.

I did the stupid phrase with my friends cheering me on and said "hold my beer, and watch this!"

Well, I didn't have a beer. but I'm sure you all know what happens next..........

Took it up to about 200ft and cut the throttle all the way off. It never recovered and hit the ground quite hard.

Not too bright.

I'm up late collecting damage costs to repair and the DIY Drones store should see a nice order monday morning ;>)

Would a log file help?

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Permalink Reply by Helldesk on April 8, 2012 at 12:28am

Stopping the motors is the problem; hobby grade ESCs may not be able to re-spin the motors again, since at worst they may be spinning backwards from the descent. They have no tachometers and rely on the back-emf from the three wires to time their pulses to get the motor started, and that job gets too hard if they get stopped in mid-air in a multicopter. In a plane a prop would almost certainly always spin the right way, actually helping with the re-start; not so in a multicopter. There have been some videos posted about accidents similar to this, if you want to hit YouTube for some peer support. My condolences. :)

Permalink Reply by Keith S on April 8, 2012 at 12:36am

I had lots of fun yesterday. I’m not complaining at all or asking for help,  just thought I’d share a learning experience.


DistributorPermalink Reply by Martint BuildYourOwnDrone.co.uk on April 8, 2012 at 1:07am

Hello Keith,

 

I did this last year, as I just had to know! I was out with a buddy of mine, and I always crash with him..... I think it has to do with pushing a little to hard, or reaching a little to far.... As you say lesion learnt, I did not think to share as I did not know there would be others that would do "silly" things like me! So welcome to the club of "motors off", two members now, any others care to join us? :)

 

Regards

 

Martin.

www.buildyourowndrone.co.uk

Permalink Reply by Keith S on April 8, 2012 at 1:16am

Thanks!

I from time to time still get the "crowd courage". Just as long as no body gets hurt.......

 

Motors-Off  Member #2

Keith

Permalink Reply by Marc Puig Pasarrius on April 14, 2012 at 4:11am

I join the group, member #3 :)

Permalink Reply by Keith S on April 14, 2012 at 5:31am
You're in, but you need to share the story ;-)
Permalink Reply by Marc Puig Pasarrius on April 14, 2012 at 7:03am

More or less the same history, I was pushing it to its limits, I wanted to descend as fast as possible, one second after cutting the throttle it started to rotate in all directions like crazy and it finally... crashed :| 

Permalink Reply by James Y. on April 8, 2012 at 1:59am

Matter of fact, it's almost a definite the motors would be turning the wrong way.  When you cut the throttle entirely, the motors would have stopped, and auto-rotated the wrong direction during descent.  When doing that, the ESC won't be able to start the motor again, and will probably cut out.  When an ESC does that, it usually won't start up again until power is taken away.

In this case you piled into the ground before you got to restart the ESC :D

Permalink Reply by Jan Schermer on April 8, 2012 at 3:49am

What ESCs are you using? I did this many times with Plush on my hexa and it always recovered... (so far ;))

Permalink Reply by Keith S on April 8, 2012 at 4:28am
It did it one time, but I pushed it too far the second and final time. 
;>)
Permalink Reply by Helldesk on April 8, 2012 at 4:43am

I've done very short, fast descends but I don't think I reduced throttle all the way to zero. That is, keeping the props still spinning but too slowly to produce lift while not quite stopping or arresting any of the momentum. The "backwards" air stream produced from the falling won't have enough authority to override a little throttle, since the motor and ESC ought to fight it to keep up the commanded turning speed (unless I'm mistaken and the ESC doesn't actually care about the motor speed as such).

Permalink Reply by Keith S on April 8, 2012 at 7:38am

Damage wasn't too bad. Flew it again the next morning, Happy Easter

 

 

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