Yesterday I went out to a nearby canal and took the Mavic along for a fly.  I'd read about issues with the quad getting thrown by the Visual Positioning System, so I turned it off.  When I brought it in to land, when it made contact with the ground it started spinning around from the back and the motors wouldn't turn off, despite having the left stick full down. I then tried a CSC, but no joy. I alternated between both procedures and (finally) the engines cut. The aftermath was a broken prop.
The only setting I could think of having changed was disengaging the VPS.  Has anyone else had this happen?

Yes I did. Crashed mine twice indoors with a similar result, a drone upside down spinning out of control and destroying a prop and unable to stop the motors. It was literally on the ground but I couldn't get the motors to stop. Sliced my finger open as I grabbed it to flip it over and hit the power on the battery.

I looked closer at my flights and realized that 3 seconds is a really long time and I never truly held the stick in the position long enough (2.9 seconds is not 3). You have to hold the sticks in those positions for AT LEAST 3 seconds otherwise it will not shut it down. After that realization I took the drone and took off and landed multiple times until I was more comfortable with what the Mavic 3 seconds is. This also applies if you are doing a hand catch as you need to hold on for a while. Also it is 3 seconds in the exact 100% left down or emergency motor shutoff position without any change in stick position otherwise the timer resets.

Just as mentioned above. Please make sure you pull the left stick full down for 3 seconds.

I may've not held it for the 3 secs (as mentioned, when the a/c is flipping around, 3 secs feels like a looooong time).  That doesn't explain why, when I've landed it with full stick down, why it would still have the engines spinning fast enough for it to start spinning the quad around, out of control.  Any idea why that happened?  Does turning off the VPS mean that the Mavic doesn't realise that its now on the ground and therefore the motors are still rotating at a speed meant to keep it aloft?

GMG Posted at 2016-12-13 22:48
I may've not held it for the 3 secs (as mentioned, when the a/c is flipping around, 3 secs feels like a looooong time).  That doesn't explain why, when I've landed it with full stick down, why it would still have the engines spinning fast enough for it to start spinning the quad around.  Any idea why that happened?  Does turning off the VPS mean that the Mavic doesn't realised that its now on the ground and therefore the motors are still rotating at a speed meant to keep it aloft?

I have sometimes switched VPS off in order to do a hand catch, and the Mavic would eventually stop the motors when I held the stick full down. I'm pretty sure I've also landed on the ground without VPS at least once. I've never had it keep spinning while on the ground. That doesn't sound right.

ps. I no longer bother switching VPS off to hand catch, since I saw the tip about grabbing towards the front, avoiding the sensors.

left stick down for 3 second works in all mode? (1,2 and custom)

GMG Posted at 2016-12-13 06:48
I may've not held it for the 3 secs (as mentioned, when the a/c is flipping around, 3 secs feels like a looooong time).  That doesn't explain why, when I've landed it with full stick down, why it would still have the engines spinning fast enough for it to start spinning the quad around, out of control.  Any idea why that happened?  Does turning off the VPS mean that the Mavic doesn't realise that its now on the ground and therefore the motors are still rotating at a speed meant to keep it aloft?

Without VPS of course it has no idea where the ground is so of course it will continue to try and keep itself stable. That low to the ground you also have Ground Effect that is in full swing while almost sitting on the ground which aggravates the whole situation if you can't get the motors off. The Mavic responded for you exactly as designed and if you just practice the 3 seconds a few times with VPS off you will understand the parameters of the design and intent of the system.

I understand them, I think and, as a former pilot, have an appreciation for the impact of things like ground effect.  I was looking for confirmation that it was VPS turned off that was the origin of the problem, to know what to expect in the future.  Thanks for the feedback.

Is there any reason to turn the VPS off? I am trying to think of an advantage to having it off and can not but I am sure I am missing something.

Thanks

Mentioned in the first post - a number of users have found that flying over water presents challenges for VPS, as that can present a uniform surface, making it hard for the system to interpret position.  As a result the a/c may crash.

GMG Posted at 2016-12-14 17:17
Mentioned in the first post - a number of users have found that flying over water presents challenges for VPS, as that can present a uniform surface, making it hard for the system to interpret position.  As a result the a/c may crash.

Flying over snow must do the same you could fly right to the ground if you wanted.

Blade Breaker 0 Posted at 2016-12-14 21:37
Flying over snow must do the same you could fly right to the ground if you wanted.

Or, more to the point, if you didn't want to! {:4_142:} Yes.  Same deal with snow.

Blade Breaker 0 Posted at 2016-12-13 15:08
Is there any reason to turn the VPS off? I am trying to think of an advantage to having it off and can not but I am sure I am missing something.

Thanks

To fly indoors.

GrizzlyAdams Posted at 2016-12-14 15:07
To fly indoors.

Isn't VPS beneficial indoors, since you likely lose GPS?

GrizzlyAdams Posted at 2016-12-14 15:07
To fly indoors.

Flying indoors VPS is a great advantage!

BuzzCut Posted at 2016-12-14 17:36
Isn't VPS beneficial indoors, since you likely lose GPS?

What I have found, is that with the forward on, majority of the time, it will not let me move forward or side ways. If I am getting drift from the prop wash in small rooms, I then have to rotate and back in the direction I want to go.  With the forward off, I can move around in very tight quarters. But I now leave the downward on or I can drop right into things and crash. I may play with turning downward  off for a few specific shot, where I want it to closely clear something and not have pull up on me, ruining the shot.