Reading the P4 manual re Failsafe RTH I see this:

"Aircraft will stop ascending and immediately return to the home point if you move the throttle stick if the aircrafdt reaches 20 meters altitude or beyond during Failsafe."
Then I see:

"User cannot control the aircraft while it is ascending to it's failsafe altitude."


Trying to figure out what that means....

It means that:
....  if failsafe RTH is activated and your Phantom is ascending to the RTH height that you set, and it is already above 20 metres high and you move the control sticks ....
... the Phantom will stop climbing toward RTH height and come straight home.

Take your Phantom to a large, open area and experiment and you will see what they mean.

The first stage of RTH is: if the aircraft is below 20m, it ascends to 20m. During this ascent you have no control at all other than the ability to cancel RTH via the button on the RC.  After it reaches 20m it will rotate to face the home point, then continue ascending to the RTH altitude you set in the app.  During this ascent (from 20m to RTH height), if you touch the throttle stick, the aircraft will stop ascending & fly towards the home point.
Unnecessarily complicated IMO.

OK, thanks for both replies.  Sounds like it does exactly what it says.  I was re-reading the RTH info and had not caught this particular item before.
I can see that being a potential "gotcha" if you think you have a safe RTH altitude set but for whatever reason hit the throttle during the ascent.

I'm not sure why that feature would be useful.

ok, so the bottom line is: if you are below 20 meters, and press RTH u got no control, but once you exceed 20m but say your RTH definition is set for 50m, u can abort climb by moving the throttle stick?
Also, they do say "you have no control while ascending".. well - can you cancel RTH oir not, during that time?

Now, also... as soon as you are ABOVE 20 meters, and press RTH, the radius of 20 meters does not matter, it will still return to the exact RTH position and land, or will it land over the spot it is, because the radius is still below 20 meters?

Phantomski Posted at 2016-5-20 15:37
Now, also... as soon as you are ABOVE 20 meters, and press RTH, the radius of 20 meters does not mat ...

If your Phantom is within 20 metres, on RTH it wil just land.
No matter what height it is at.

Beyond 20 metres, it will RTH and land pretty close to home.

If you have activated rth and you can't see the drone and accidentally touch the throttle stick it will hover if above 20m you still can't see drone, can you re activate the rth and it will resume rth ?

mstevens1@btint Posted at 2016-5-20 02:28
If you have activated rth and you can't see the drone and accidentally touch the throttle stick it w ...

I do not think it will hover, i think it will continue RTH at whatever the altitude, which is what the danger is....