I was thinking about the left stick's throttle down "sticky position" at the bottom.   I noticed myself doing somthing that seems wrong.

That is, to descend rapidly, I've been clicking the throttle to its full down position.  The motors are supposed to stop if it's held there for 3 seconds, but that's not what I've observed unless the craft is actually landed.

My question is: Does it even know if it's touching the ground?  Or have I just been lucky not to shut the motors down in midair while descending rapidly?  

(I know it's aware of altitude via GPS, but that's often inaccurate if there are hills, etc.)

The motors will only stop if it detects that it hasn't dropped for 2- 3 seconds

The risk is zero of the phantom shutting the motors off by holding the throttle down while in flight.
After landing, holding the throttle down will shut off the motors in 3 seconds.
So yes, the phantom does know when its landed as the IMU detects movement and changes in altitude.

johnwarr@live.c Posted at 2015-4-7 23:48
The risk is zero of the phantom shutting the motors off by holding the throttle down while in flight ...

"The risk is zero of the phantom shutting the motors off by holding the throttle down while in flight"

Nothing is absolute with a Phantom

jliddil Posted at 2015-4-7 23:50
"The risk is zero of the phantom shutting the motors off by holding the throttle down while in fli ...

If you do the regular shutdown with the throttle in the locked down position, as long as it is descending, it will not shutdown.  That is why the 3 second delay to detect no movement.  Only then will it shutdown upon landing.

Ah, so although it's not "precisely" aware that it's at zero altitude, it's "more or less precisely" aware that it's no longer descending.  

paul@westpointd Posted at 2015-4-8 00:13
Ah, so although it's not "precisely" aware that it's at zero altitude, it's "more or less precisely" ...

It senses movement, when it is "on the ground", then it will stop your motors after 3 seconds of no movement.

paul@westpointd Posted at 2015-4-8 00:13
Ah, so although it's not "precisely" aware that it's at zero altitude, it's "more or less precisely" ...

Not exactly. I doesn't matter at what altitude it is, if you pull the stick down for 3 seconds and it doesn't move (e.g you've just landed it on the top of a nearby hill) the motors will stop.  Like wise, if you lower into a nearby valley, below your home point, the motors won't stop until its been on the ground for 3 seconds (ish)

adrianjacobs@nt Posted at 2015-4-8 00:47
Not exactly. I doesn't matter at what altitude it is, if you pull the stick down for 3 seconds and ...

So far two people have corrected me but I'm pretty sure we're saying the same thing.  Lack of movement tells it that it's landed.  I get it.

It also works if you hand catch the drone. How does it know it is no longer descending? Is it air pressure alone that tells it the change in altitude? It must be a pretty precise measurement.

http://www.phantompilots.com/thr ... s-mid-flight.26928/

johnwarr@live.c Posted at 2015-4-7 23:48
The risk is zero of the phantom shutting the motors off by holding the throttle down while in flight ...

Well that is not 100% true,  it will shut down mid air with throttle down if motor cut-off type was changed from default intelligent to immediate.