Aardvark Posted at 2017-5-15 09:32
" went into RTH briefly and was canceled again when signal was regained. "

The RTH will not cancel when signal regained unless you cancel it. As you say above, in this case the left stick operation appeared to stop the aircraft climbing to its pre-set RTH height (it did not stop RTH), at which point it flew straight into the hill while attempting to returning to home.

Thanks, I meant that when I lost video, It still had RC signal. I should have just pressed RTH then instead of trying to increase altitude. The craft didn't enter RTH until RC signal was lost as I was ascending (to which I had 0.5 seconds to respond (i.e. stop trying to ascend). The best thing for me to have done in that situation was to press RTH when I first lost video signal but still had RC signal (before I tried to ascend).

DroneX4 Posted at 2017-5-15 08:13
Yes I understand what happened here. However I had no indication that RC signal was lost as video signal was already gone. My instinct was to increase my altitude and was working fine, but the craft briefly lost RC signal during my ascension and went into RTH briefly and was canceled again when signal was regained. Again I had no idea RC signal was lost as it was only lost for 7 or 8 seconds. I was looking out for signs of the craft rising above the hill, not at the little red/green light on the controller during those 7 seconds. I didn't interfere with RTH (intentionally) as I had no indication RTH was even happening until it regained RC and video signal for 0.5 seconds. Basically it let me know it was in RTH mode at the same time it canceled the return to home height.

I wasn't faulting anything, just helping to explain what happened according to the video.

DroneX4 Posted at 2017-5-15 14:58
I'm confused as to what you think I should have done after loss of video? Just don't touch the sticks and let it hover until it lands itself in the water? Press RTH? I let off on the sticks as soon as video was lost. You can see in my google earth diagram how far the craft went after I let off on the sticks (the purple line). I still had radio signal. It was only as I was ascending that I lost RC signal and it went in to RTH, but I only had 0.5 seconds to respond (let off on the throttle).

If you lose signal, one thing you can do which should be pretty safe is do nothing (let go of the sticks) and wait to see if you get signal when it starts to climb in RTH. If nothing happens after say 30 seconds, you can shut off the remote to force a RTH without pressing the button (just in case you still have spotty signals such as in your case). That way you do not inadvertently cancel RTH, or cancel the climbing during RTH.  After another 30 seconds (15 would probably be enough), power the RC back on and see if you reestablish connection.

Another thing you can do instead of powering off 'if' you are using an aftermarket gain antenna is to just turn around 180 degrees from the AC which should be enough to make a spotty signal go completely dead.

KM5RG-Robert Posted at 2017-5-15 15:26
If you lose signal, one thing you can do which should be pretty safe is do nothing (let go of the sticks) and wait to see if you get signal when it starts to climb in RTH. If nothing happens after say 30 seconds, you can shut off the remote to force a RTH without pressing the button (just in case you still have spotty signals such as in your case). That way you do not inadvertently cancel RTH, or cancel the climbing during RTH.  After another 30 seconds (15 would probably be enough), power the RC back on and see if you reestablish connection.

I never thought of just shutting off the remote. That is a great tip. Thanks!

It takes 3 secs for the AC to RTH.  When you lost FPV, you must not touch the sticks because if the craft is in RTH or goes to RTH and needs to rise to RTH height, what happened will happen.  This is especially dangerous because as it rises, the chance of the AC regaining the control signal increases with elevation.  And all this happens while the pilot has no clue what's going on due to the lack of FPV/telemetry.
This is a bit of a unique flight because most pilots don't fly so low and then around objects.  In a normal LOS flight, even a long LOS flight (for many miles), this kind of thing wouldn't be a problem.

Why do you say you only had .5 secs to respond?  Besides, as Aardvark mentioned, often the best response is no response.  

Edit:  Yes, as Robert says, shutting off the remote is foolproof.  It guarantees RTH.  It's old school and still works great.  On the P2 series, it's the only way a pilot can purposely invoke a guaranteed RTH (we have no RTH button).  And yes, turning the controller around (with a directional antenna or using your body to block with an omni) is a cool trick because it can invoke RTH without interrupting the log being kept on the mobile device although if you do that you're still not positive that you broke the connection.  

Great news that you have recovered it.

None of this would have happened if you had kept the aircraft in VLOS. I know the laws there suck but that one is quite sensible.

Mark The Droner Posted at 2017-5-15 16:17
It takes 3 secs for the AC to RTH.  When you lost FPV, you must not touch the sticks because if the craft is in RTH or goes to RTH and needs to rise to RTH height, what happened will happen.  

Why do you say you only had .5 secs to respond?

My understanding of the craft is that it does not initialize RTH when video signal is lost, only when RC signal is lost. Please correct me if I am wrong. I still had RC control after video was lost. If I did not touch the sticks after video loss, the craft would just hover in place until battery RTH kicked in.

I still had RC control, and tried to ascend. The craft was not in RTH mode. During the ascend, the RC lost signal as well. There was no way for me to know it was in RTH mode as all (video and RC) signal had been lost at that point. I was still under the impression I was bringing the craft upwards as I did not know RC was lost during my ascend as I was looking for the craft to rise up over the hill.

The craft briefly regained both video and RC signal during RTH (long enough to broadcast that it was in RTH and pick up my throttle input again (which canceled the RTH height) after 0.4 secs the craft lost all signal again. I did not have time to know the craft was in RTH mode so I could let off on the throttle and allow it to do it's thing. It broadcast RTH and within 0.4 secs of that broadcast, RTH height was canceled and all signal lost again.

I don't know how else to explain this to you. Look at the timestamps at the end of the log. Read what I have posted here, and watch the video. It confirms everything I have just said.

The video you provided tells the story.  Great video btw.  

I'm sorry, I didn't state what I meant correctly.  YOu're right, FPV signal has nothing to do with RTH.  So doing nothing at the first sign of FPV problems would not be best.  What I meant to say was when you lose FPV, unless you have a live 3G tracker or you can see it with your own eyes, it is probably best to RTH the AC one way or another.  The foolproof way is to turn off your controller.  You can also press the RTH button, of course, but it's not foolproof.  

When I'm flying and lose FPV, I'm in the habit of just continuting to blast ahead at full speed - but I have a live tracker so I am watching it on my second tablet.  I know where it's going, how fast, how high, battery voltage, etc.  I know my AC will lose the control signal eventually due to distance and turn around on its own - but I'll be watching it when it does.  Without a live tracker though, that would be kind of crazy.

As far as what actually happened with your flight, forget about the FPV connection and the log for a moment.  Let's just examine the control signal via the video.  

It started to coast to a stop at about 1:35 or so.  This is when the control signal became intermittent apparently.  We can presume the signal was intermittent because otherwise it would have RTH'd at around 1:38.  Or maybe you just let up on the forward throttle leaving the sticks centered.  Whichever.  So it hovered.  It began to rise at 1:42.  We know it was you elevating it via your left controller stick because it didn't turn towards home yet.  At 1:43 it stopped elevating because it lost the control signal again - because it's intermittent.  So it hovered for three seconds.  At 1:46 it turned towards home clearly indicating RTH.  Then it began to rise towards the RTH height.  It rose a bit more until it received the intermittent control signal once again.  This is at about 1:53.  This is where the rise to RTH height was interrupted.  So now it won't rise to RTH height because it is programmed to come directly home at the given height after it received any stick command.  So it went straight towards home and into the tree at 2:16.  But just before it hit the tree, you regained your telemetry signal which informed you that the AC was in RTH.  But it was actually in RTH mode for about 30 secs.

Mark The Droner Posted at 2017-5-15 19:06
The video you provided tells the story.  Great video btw.  

I'm sorry, I didn't state what I meant correctly.  YOu're right, FPV signal has nothing to do with RTH.  So doing nothing at the first sign of FPV problems would not be best.  What I meant to say was when you lose FPV, unless you have a live 3G tracker or you can see it with your own eyes, it is probably best to RTH the AC one way or another.  The foolproof way is to turn off your controller.  You can also press the RTH button, of course, but it's not foolproof.  

When the craft began to coast was when I lost video (I let off on both sticks immediately). Other than that everything else seems spot on. Now you have me wanting a 3G tracker sounds pretty awesome.

This all started as a favor for a friend. Their cabin is just around the point I flew around. They wanted to know if the ice was gone out of the cove their cabin is in and I was like, hey I could just fly the P3 out there and check... and the rest is history. Next time I am just going to shut off the remote and leave it in DJI's capable hands to get the craft back to the home point.

DroneX4 Posted at 2017-5-15 05:31
So a couple of lessons learned here:

1. Don't fly behind hills, fly over them. (I didn't realize how far behind the hill I had gone until video signal cut out)

Probably one of the most honest posts reflecting on your flight I have seen on these forums.

Glad we were all able to help you understand what happened and also what occurs if you lose signal.  
Thanks for changing the original thread title as well.

DroneX4 Posted at 2017-5-15 14:58
I'm confused as to what you think I should have done after loss of video? Just don't touch the sticks and let it hover until it lands itself in the water? Press RTH? I let off on the sticks as soon as video was lost. You can see in my google earth diagram how far the craft went after I let off on the sticks (the purple line). I still had radio signal. It was only as I was ascending that I lost RC signal and it went in to RTH, but I only had 0.5 seconds to respond (let off on the throttle).

When signal is lost there are a few things to do. First is just to wait for a few seconds to make sure signal really is lost. Then wait and do not touch the remote as sometimes you can go to RTH mode and signal can be re-acquired. By not touching the sticks your drone would have ascended to its RTH height.  In your case the RC link was restored.   By waiting you would have seen your drone come up over the hill before it started the return journey.

I had my DJI App crash with my drone 1 mile from home.  I was already in RTH mode but I then also shut off the power to my RC.   Dang you say shut down app and shut power to RC.  Well yes and my drone did what it is supposed to do.  It was already above it's RTH height at I was at 1300 feet plus, and secondly it flew to home point.   I re-started my RC then app when my drone was about a thousand foot above me.  I wrote about it on a thread.  

If all else fails shut off the App and remote control.  Your drone will do as it should and you won't be sending commands which could stop the drone climbing to RTH height.    Even on a test flight go out 200 yards and do that.  You will see your drone will simply come home and land itself.    

http://app.airdata.com/main?share=YkDcjd

DroneX4 Posted at 2017-5-15 20:01
When the craft began to coast was when I lost video (I let off on both sticks immediately). Other than that everything else seems spot on. Now you have me wanting a 3G tracker sounds pretty awesome.

This all started as a favor for a friend. Their cabin is just around the point I flew around. They wanted to know if the ice was gone out of the cove their cabin is in and I was like, hey I could just fly the P3 out there and check... and the rest is history. Next time I am just going to shut off the remote and leave it in DJI's capable hands to get the craft back to the home point.

Here's my lost signal thread

http://forum.dji.com/thread-86645-1-1.html