My buddy and I were flying drones this weekend and he decided to fly his drone from Vancouver island over to another island to view a lighthouse. The island is about  1.7kms away using "Tap and Fly" to do the bulk of the journey at 85m elevation, at approx 1km away the DJI Go 4 app gave video warnings, losing signal (I forget the wording) he kept flying briefly (about to turn around) then the app crashed?? A bit panicked he decided after a few seconds to push the return to home button on the controller. Tried and tried and tried again for about 1 minute to re-open DJI Go. When it finally opened and connected again it was still flying toward the lighthouse!Scary stuff as he was over the open ocean but eventually using the app he was able to command it home again. What the heck happened?
Specs
Phantom 4 advanced
Samsung galaxy note 4
DJI Go 4


Shouldn't the phantom return to home in the event the app crashes? And shouldn't the RTH button on the controller function in this situation?

Input appreciated so this doesn't happen again

Thanks!

How was the RTH configured? Was Smart Return To Home set?

There are so many variables.

Have your friend Post the flight LOG from that flight...
www.phantomhelp.com/LogViewer/Upload


RedHotPoker

It seems that the APP crash but the RC signal remains. You can check the RC indicator whether it switched to red or not.

Well i had my buddy send screen shots of his warning indicator screen for that flight. I don't believe he ever waited for return to home to initialize. Then starting early on in the flight and for the next 4 minutes he was getting warnings such as...
Cannot use this function without taking off
Intelligent flight modes are disabled in attitude mode
Strong wireless interference. Please fly with caution
Ambient light too weak
Forward obstacle sensors not working
Satellite positioning off fly with caution

One thing that is odd is seeing as how never acquired a strong GPS signal and took off anyways it would seem realistic to assume that he would be unable to fly in "tap and fly" mode which he was definitely using.

Still concerning the fact that the app crashed and it never automatically returned home, or more reasonably just stopped flying. And how the return to home button on the remote made no changes to its flight path

I was looking over his shoulder during flight not paying attention to these warnings I guess he wasn't either. Lucky day for him. Live and learn. Wait for return to home to initialize and don't keep flying with all these warnings popping up!!

Susan may have the basic answer...RTH will not occur automatically just because the app crashed.  It is only when the UAV looses contact with the RC that RTH is triggered automatically.  However, if no RTH is recorded before takeoff then all bets are off as to what will happen when that connection is lost bt RC & bird.  It may go to a previous Home Pt or just fly off.  I'd say all in all your bud was very lucky in how it turned out.  Last note, drone will still fly under RC control without the app once airborne.  DJI may require signing in to app to get started but it's not required after that, and even that seems to be up for debate as I've read others who say not so.  They can fly straight off without signing in, but I believe that ends up restricting the bird to a distance and height beyond where this bird was.

Return to home is more about the RC signal. Probably lost visual signal but not RC. Please be aware that when you fly out over the water that there are more challenges on this point.