I think one thing we should all agree on is that the manual is both poorly written and inadequate. The writer(s) has interchanged terminology and failed to fully explain important features and safeguards. There are some very smart people in these forums, and even they can't agree on what's what.
So I'm working through all of this in my head, based on what I've read here and what I've read in the manual. Without yet testing everything myself, this is my understanding based on just a few weeks with my Phantom:
FAILSAFE - This one seems the most straight-forwarded. If the aircraft loses connection for more than a few seconds, it will by default automatically return to the home point. However, the user can OVERRIDE this by changing the setting labeled "Remote Controller Signal Lost" in the DJI Go app. There are three settings for this:
- Return to Home - Aircraft will return to home if RC signal lost
- Hover - Aircraft will hover if RC signal lost
- Land - Aircraft will land if RC signal lost
* Presumably, if you set it to the "Hover" setting, the aircraft will still land automatically if battery level becomes critical.
MANUAL Return to Home (RTH) - I'm refraining from using the "Smart" moniker because I think that's much of the confusion. MANUAL Return to Home should mean one of the following scenarios:
- Go-app initiated - Pilot initiated RTH by touching RTH icon and sliding. Aircraft returns to the home point (can be cancelled in-app or with S1 switch)
- Switch initiated - Pilot toggles the S2 switch (manual states to toggle at least two times). Aircraft returns to home point (can be cancelled in-app or by toggling S1 switch)
LOW-BATTERY Return to Home (RTH) - Aircraft returns to home point when battery level is low. THIS is where all of the confusion comes in. I see two possible scenarios, based on the pilots user setting for "Low Battery Warning":
- If the "Smart Return-to-home" setting is toggled to the ON position, the aircraft will continuously calculate the approximate time remaining to safely make it back to home based on distance and battery percentage. At the point it determines it needs to start returning to home, it will display a pop-up in the app asking the pilot to accept the setting. If there is no user input, the aircraft will automatically return to home after 10 seconds. Alternatively, the user may cancel the function.
- If the "Smart Return-to-home" setting is toggled to the OFF position, the aircraft will NOT calculate the time to return to home based on distance away, but will only initiate return-to-home based on the pilots "Low Battery Warning" setting. By default, this is set to 30%, and thus at 30% battery life, the aircraft will display a pop-up to return to home. EDIT: Does it even initiate a RTH if this setting is OFF or does it just pop up with a low battery warning?
* These are my assumptions and are likely either wrong or incomplete. I am assuming that the only difference between #1 and #2 above is that the "Smart" setting allow the aircraft to initiate RTH *before* your "Low Battery Warning" setting if it knows by calculation that it needs more than that to return home from its current location. To me, that is what makes it "Smart" - the fact that it is continuously monitoring distance and will initiate RTH before the low battery warning setting if it knows it needs to start returning home sooner. What I'm not entirely sure of is whether it will indeed initiate a RTH if you turn OFF the "Smart return-to-home" setting, or will it just give you a pop-up about low battery (but do nothing)? I have not tried turning off the "Smart return-to-home setting" - does it stop calculating the projected time based on distance and just show the battery percentage?
In my mind, here are the key things to remember as a Phantom pilot:
- You can always use the S2 switch to manually RTH (and cancel it with S1). The manual states toggling it at least twice, but I think it usually works with one full toggle down and up.
- You can change the failsafe behavior if you don't want it to RTH on disconnect (if you want it to hover or land in place). By default, it will RTH if disconnected for more than 3 seconds.
- You can adjust the Low Battery and Critical Battery settings, but know that at Critical battery level, the aircraft WILL land (though you can control pitch, yaw and roll).
- Always check that your home point is recorded properly before leaving your takeoff point.
- Always choose a home point that is free from obstructions in a decent radius (I would recommend at least a 6m/20ft radius).
- Always set a RTH altitude that is higher than any obstacles in your path home (trees, power lines, buildings, towers, etc).
- Never completely trust the "Smart" RTH calculations - get closer to home sooner than the app calculates, or before low battery warning.
- Never panic when you FPV or controller connection. If you lose the former, check to see if the controller light is green (if it is, you still have control). If you lose controller connection, aircraft will initiate your disconnect procedure (either RTH, hover, or land).
- If in doubt, gain altitude to avoid a crash. Immediately flying above obstacles is usually better than trying to manually fly around obstacles lower to the ground.
I hope we can come to some consensus on these issues. I will have to do some testing myself when I get a chance, but this is my current understanding. Thanks everyone!
