Failsafe RTH is amazing, it makes it so that losing signal causes drone to fly backwards for 50 m on its original route and then ascend to RTH altitude and then starts to return home. In practice we get signal back during this process, interupt it and continue flying.
Low Battery RTH on the other hand is downright dangerous, and to make things worse saftey settings offer no way of making it less dangerous. Low Battery RTH almost crashed my drone a couple of times already, and here's how it happens even if you're being very safe and conservative with your flying:
I would be very close, mere 50 meters away from myself, flying in a park full of big trees. I would be flying in normal mode so I can safely and precisely navigate under the canopies. I'm flying around 2 meters above ground, and 2-15 meters below tree canopies, here's a screenshot of this situation:
Taken from this flight, at 10:58:
Keep watching for a few seconds longer and 8 seconds later my battery goes from 26% to 25%, triggering Low Battery RTH, causing the drone to immediately lock my controls and start ascending very quickly. It takes me around 2 seconds to realize what just happened, get my bearings and reach for the pause button, stopping the ascent into the canopy. Luckily I was under a bigger tree at the moment so drone ascending 3.6 meters into the air didn't cause a crash, but look at the video and consider what would have happened if RTH got triggered 5 seconds sooner: I would have been few meters in front of the location of the above screenshot with canopy less than 3.6 meters above me, and before I would have been able to react, drone would have crashed into the canopy.
I've had this situation happen multiple times already and it feels like it's only the matter of time until this saftey feature causes the drone to crash.
When I go to settings, only thing I could do there is change the RTH altitude to a minimum of 20m, but even that wouldn't have helped as 20m would still cause the drone to crash in this case, and multiple such prior cases I've experienced. And even if it was possible to set this 0m, I wouldn't really want to do that as it would strongly interfere with functionality of Failsafe RTH that I mentioned at the begining.
As a matter of safety, we should be able to disable Low Battery RTH. When low battery is detected, I would prefer for either nothing to happen instead or for drone to just pause as a reminder that I should start going towards home point and land, just don't fly directly up into an obstacle!
Or at the very least, have the drone pause for 5 secondsbefore starting to ascend, that way we would have enough time to cancel RTH ascend and prevent the crash.
Like I said in the other thread, safety features that remove or interrupt pilot control of the aircraft are generally extremely dangerous. That's the dark side of the otherwise great, automated RTH feature of DJI aircraft like the FPV drone. It's fantastic and will save your bacon, until it doesn't. There's no way to anticipate when and where an emergency will arise, so there will always be cases where the safety feature that takes over the aircraft creates more hazards than it solves.
The default action on a Betaflight quad in case of a failsafe is to simply disarm and drop out of the sky. I used to think that was really weird, until I came to realize that that's ultimately the safest thing to do as an overall, catch-all behavior. Reason being, what I said above: there is no way to anticipate all situations where a failsafe may happen. For example, the quad might be stuck in a tree, or somehow have wandered into an area in proximity with people. If it suddenly fires up to full power and tries to save itself in those situations, it's easy to see how that can be a really dangerous behavior. Just shutting down immediately and becoming completely inert is basically the best compromise. You lose the drone, but it's turned off and can't do anything bad but just sit wherever it landed and beep, etc.
So the automated RTH of the FPV drone is a good news/bad news kind of thing. It covers a lot of situations safely, but it can create really bad danger in others that we can't anticipate. So we have to fly with that in mind....
My FPV gives 10seconds warning prior to low battery RTH plenty of time to cancel it. Maybe check your firmware and go through your settings. In fact if I cancel it at 30% the first time it goes off it gives another 10 second warning at around 20% with time to again cancel it. when the battery is depleted the FPV lands itself pretty much right where it is but gives you partial control of the landing to guide it down safely. It does not ascend at all on the last critical battery it just lands. There are settings in the HUD for the RTH altitude etc. I generally fly untethered using phone only for updates prior to filight possibly this causes a difference.
@shadetail. Go into your settings and change the RTH logic. You can set one of three methods (RTH, Hover, Land). When flying inside, or in enclosed areas, it’s best to set hover or land. I believe this logic will then apply to low battery/Failsafe RTH and it definitely applies to lost comm RTH logic.
Buster1 Posted at 6-27 05:03
@shadetail. Go into your settings and change the RTH logic. You can set one of three methods (RTH, Hover, Land). When flying inside, or in enclosed areas, it’s best to set hover or land. I believe this logic will then apply to low battery/Failsafe RTH and it definitely applies to lost comm RTH logic.
As you can see in the image, this setting is called Aircraft Signal Lost Action and only affects what happens when signal is lost, and in that case the default behaviour is fantastic. It by default returns backwards for 50m on its original route and then ascends to RTH altitude and returns home (or at least that's what it should do according to manual, it's hard to confirm this since not only is the video feed inherently lost, but video recording to local SD card literally shuts off when this happens).
The problem I'm pointing out in this thread is only the low battery behaviour, which is not customizable in the settings. If it was, I would change it from RTH to hover same as the Aircraft Singla Lost Action setting can be changed.
I have a Mavic 2 Pro for over 2 years now and I've never used the RTH option. I prefer to check the battery and when the sound of low battery comes I just turn around and fly to home point. I know it doesn't give much freedom to fly very far and normally I still have about 15 min to fly but that's what I need to come home.
Is there any update about this? I got a DJI FPV just a week ago and almost crashed for this same situation.. I was following a car that I was in.. trees on the sides, and since I was located consideravely far away from the take off location, the drone entered in automatic RTH at 50% battery when I was under trees.. I pressed the pause button inmediately but it didnt respond for a few seconds.. Luckily for me it didn't go high enough to crash..
Yeah it's kind of dangerous if you are not expecting it, but like others said, you should get a warning beforehand.
Setting it to hover is actually a good idea if you fly in enclosed spaces.
In manual mode RTH doesn't kick in which is great.
I had exactly this happen to me today. Entire flight at under 2m, Drone decides to rise up into tree at low battery RTH despite me hitting cancel using the pause button.
Trying to post the video but can't seem to upload video files here.
Why would you fly in an enclosed area where RTH wouldn’t be safe? I always use RTH and watch the battery, so that as I get to the per cent age remaining that I know it’ll kick in I am already in an area free of obstacles and know that it will RTH safely.
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