Here's the excerpt from the "DJI Phantom Vision Summary Guide" which is way more readable than this flowchart. See "2 - Regain Control" ... pretty much explains it all.
BTW Geert is correct.
D- Failsafe (RTH)
You are flying and suddenly you get the “Control Signal Lost” warning followed by “Coming Home” (Meaning
you’ve lost the “First Channel - 5.8Ghz” connection). You’ve entered the Failsafe mode. Phantom tail lights turned
rapid Yellow flashing. Be sure to also check out the “Failsafe” section later in this guide, where you’ll find more
detailed information on what’s really happening during a Failsafe.
When will Failsafe activate?
1-
The Remote Control is Powered off (maybe because of dead batteries) or you have flipped the S1 to the bottom position by mistake or intentionally.
2-
The Phantom has flown out of effective Remote Control range (CE mode ~400 / FCC mode ~800m).
3-
The signal between the Remote Control and the Phantom has been blocked.
4-
There is interference causing a signal problem with the Remote Control.
Need to know: if you flip S1 to Failsafe by mistake, you have less than 3 sec to cancel it by flipping it back up
otherwise Failsafe is activated.
When it activates, you have 2 choices:
1- Let the Phantom do is thing and land by itself:
How it will land depends on GPS Status.
- If GPS is still Active: The Phantom will either stay at current elevation OR raise up 20m/66ft above your
pre-established (auto or manual) home point, whichever is highest, and then make a
straight-line course back to your "Home Point” (Return to home (RTH)), pausing for about
15 sec before descending, land and power itself off.
Need to know: If there are obstacles, buildings or trees in the way when flying at that
elevation on Return to Home, the aircraft WILL hit them on its way back...!
You cannot adjust the Return to Home elevation height, unless you reset your Home
Point. See the “IOC section” to learn how to manually reset the Home Point and why you
would want to do that. The main reason being to effectively avoid crashing into obstacle
higher than 20m/66ft in case failsafe is activated.
- If GPS signal is Lost or not Active: Phantoms simply land straight down. It may be drifting during the descent
and landing process (ATTI mode). I hope you’ve bought some spare props…
Need to Know: The Phantom cannot avoid obstacles during Failsafe. So it might be a good idea to try Regaining
Control as soon as you can.
Need to Know: In FAILSAFE mode, the aircraft speed is really slow and if you are low on battery it may
be an issue! Page 15
2- Regain Control:
This will depend on the position of the S1 switch (GPS or ATTI) when the Failsafe was triggered.
S1 was on ATTI: You will get back control as soon as signal is recovered.
S1 was on GPS: You WILL need to toggle the S1 switch to ATTI once to regain control. If the signal is
recovered, you will get back control; switch S1 back to GPS.
If you do not toggle the S1 switch, you won’t be able to control anything. Why? Because it’s the
“Phantom’s Flight Control System” that controls your aircraft now and land it automatically (it
will not exit the Failsafe mode by itself even if the signal is restored). So remember to switch
S1 from GPS (top) to ATTI (center) then back to top position after you regain control.
(The GPS > ATTI > GPS Flipping Sequences).
Need to know: What will happen if you have manually reset the Home Point way up in the air and Failsafe
activates; will it kill the motor when it reaches the Home Point and crash down?
Not to worry! The Phantom will just slowly descend until it cannot descend anymore. Once it feels
that the altitude is no longer changing for about 3-5 secs, it will turn off the motors.