RTH Altitude! Take it seriously!

[Chris Vedeler]

I was flying around a local mountain this morning and I wanted to pan nicely around the summit. Only I miscalculated my altitude and a ridge cut off my line of sight to my P3 (I was 2 miles away) and I abruptly lost signal. I had set the RTH altitude to 500 meters as the summit of the mountain is about 480 meters above were I took off.

I can't tell you how close I was to setting it to 250 meters or even lower since I wanted to avoid the annoying low battery warning on my return home since the Phantom calculates not only the distance to home, but also the time and energy to get to the RTH altitude.

Luckily I decided to keep it at 500 meters or my P3 would have kept below a ridge line (i.e. totally out of my control) and certainly crashed into the mountain.

You can see the video here:

 

[jryser]

WhoA!!!!


Sent from my PT beating heart

 

[Wibble]

I always worry about this when I am flying down valleys - when the drone is below me. I assume when RTH is initiated it just takes a straight line back - is that correct?

 

[Chris Vedeler]

I always worry about this when I am flying down valleys - when the drone is below me. I assume when RTH is initiated it just takes a straight line back - is that correct?

RTH will stay at its current altitude if that altitude is higher than what is set in DJI Pilot. If you are below the set altitude it will stop and go straight up until it reaches the set altitude and then fly straight line back home and then come straight down.

 

[Chris Vedeler]

You can see my whole video of the mountain here:

 

[TAZ]

I always worry about this when I am flying down valleys - when the drone is below me. I assume when RTH is initiated it just takes a straight line back - is that correct?

No... It will climb to your Failsafe Altitude (measured as height above home point). The only way it will return directly is if your current altitude is above your Failsafe Altitude. If your bird is below its home point, it's height will read as negative... However, that won't prevent it from climbing to your Failsafe Altitude.

 

[Wibble]

Valley flying sounds pretty safe then.
That mountain video is awesome but illustrates very well why an arbitrary 500m limit is stupid.

 

[Meta4]

I always worry about this when I am flying down valleys - when the drone is below me. I assume when RTH is initiated it just takes a straight line back - is that correct?

Return to home is an extremely important function and he manual has 2 full pages on it.
it's important to understand it - not make assumptions.
There are lots of tales of crashed Phantoms because of owners not knowing how it works.

 

[Wibble]

Which manual? I found that my Phantom only came with a very basic quick start guide. My Vision 2+ came with an encyclopedia!!!

 

[Meta4]

Which manual? I found that my Phantom only came with a very basic quick start guide. My Vision 2+ came with an encyclopedia!!!

Take a trip over to ... http://www.dji.com/product/phantom-3/download
The manual is also included in the app.

 

[nhoover]

Yes, you really have to think about this. I had mine set to 100m from a previous flight and was doing some long flights over the ocean. I was flying at 20-25m and at one point lost control and RTH kicked in. It was disconcerting to see it immediately climbing instead of just returning home. Worse, there was a fog bank not that much higher. No big deal - I had control back quickly and cancelled the RTH, but you really do need to think about the setting. Too low or too high can be bad. And as was said above, no assumptions - know how it works!

 

[Meta4]

Definitely .. too high a setting could be an issue if you are low on battery and there's no need for the Phantom to climb into the stratosphere before flying home, and worse, have to descend slowly from a great height.
You can always cancel and resume control and you can fly the Phantom faster than RTH will when you need to get home quickly.

 

[Chris Vedeler]

Definitely .. too high a setting could be an issue if you are low on battery and there's no need for the Phantom to climb into the stratosphere before flying home, and worse, have to descend slowly from a great height.
You can always cancel and resume control and you can fly the Phantom faster than RTH will when you need to get home quickly.

The Pilot App seems to take into account the battery power required to get up to the RTH altitude and back down again. When I forget to set mine back to 70 meters from 500 meters I'll get a low battery warning at around 55%. I tend to error on a little too high vs. too low. What is the tallest thing you are likely to fly over and add 20 meters.

 

[unclejas]

Wow, I am thoroughly impressed. Incredible video. Thank you.

 

[Joao Carlos]

Quick P3 newbie question. I always set my failsafe alt on the MC settings of the DJI GO app, lets say I set 100m. However when I reset the Home point, using the "H" icon on the main screen it says "set current aircraft position", obviously, but it also says "aircraft will return to this point at minimum altitude of" and get the current height from the ground as reference. If I do this reset with the Phantom landed, it will say 0m!! Does this mean the aircraft will RTH and/or Failsafe back at 0m height? If so this is extremely dangerous.

 

[TAZ]

Quick P3 newbie question. I always set my failsafe alt on the MC settings of the DJI GO app, lets say I set 100m. However when I reset the Home point, using the "H" icon on the main screen it says "set current aircraft position", obviously, but it also says "aircraft will return to this point at minimum altitude of" and get the current height from the ground as reference. If I do this reset with the Phantom landed, it will say 0m!! Does this mean the aircraft will RTH and/or Failsafe back at 0m height? If so this is extremely dangerous.

View attachment 26747

This is a know bug in the application. On screen it is incorrectly displaying your current altitude 0.0M. I'm assuming you tested this when on the ground. If you happened to fly it up to 55M...that's what would display.

I can confirm though, that in spite of the confusing display dialog...the craft does respect and follow your FailSafe altitude.

BTW...you can see this same behavior in the simulator as well...if you want to test it out.

 

[Joao Carlos]

This is a know bug in the application. On screen it is incorrectly displaying your current altitude 0.0M. I'm assuming you tested this when on the ground. If you happened to fly it up to 55M...that's what would display.

I can confirm though, that in spite of the confusing display dialog...the craft does respect and follow your FailSafe altitude.

BTW...you can see this same behavior in the simulator as well...if you want to test it out.

I only did my 2nd flight today (so not really a test pilot here), but this got me thinking... it is true what you said that if I go higher it will set the home point at a higher altitude (eg 50m). And failsafe should follow whatever is set on the advanced settings (one can only hope). But what about RTH? If pressed, maybe instead the Phantom will return but stay hovering at 50m instead? That sounds interesting, so it could return but not land yet. Worth a test I guess and also Ill review the manual to see if theres anything about it.

 

[TAZ]

I only did my 2nd flight today (so not really a test pilot here), but this got me thinking... it is true what you said that if I go higher it will set the home point at a higher altitude (eg 50m). And failsafe should follow whatever is set on the advanced settings (one can only hope). But what about RTH? If pressed, maybe instead the Phantom will return but stay hovering at 50m instead? That sounds interesting, so it could return but not land yet. Worth a test I guess and also Ill review the manual to see if theres anything about it.

Awesome that even on your second flight your thinking/testing in detail. That sort of thing will keep you in the air much longer.

Up until GO 2.0, the behavior simply ignored the display... It always just returned home as normally using the FailSafe Altitude (no hover). However, now with 2.0 there is a 3rd FailSafe option (Land, RTH and Land...or Hover). I've not tested the new Hover option...in connection with the Set Homepoint to Aircraft...my guess is it'll still ignore it. It seems to be incorrectly just displaying current altitude, rather than FailSafe. But worth a test.

 

[Chris Vedeler]

You should always test the behavior of your P3 under controlled conditions. I see this as part of learning to fly it. I want to be able to predict how it will behave given most situations. In this situation when I lost contact, I knew I had the RTH set to 500 meters. I knew the summit of the mountain was about 480 meters above where I took off. While I did panic a bit since it was so high and so far away, I was reasonably confident I could recover. As it turns out as soon as it flew up above the ridge I was able to regain control and continue my flight. In this case the RTH just allowed me to re-establish control.

 

[Joao Carlos]

You should always test the behavior of your P3 under controlled conditions. I see this as part of learning to fly it. I want to be able to predict how it will behave given most situations. In this situation when I lost contact, I knew I had the RTH set to 500 meters. I knew the summit of the mountain was about 480 meters above where I took off. While I did panic a bit since it was so high and so far away, I was reasonably confident I could recover. As it turns out as soon as it flew up above the ridge I was able to regain control and continue my flight. In this case the RTH just allowed me to re-establish control.

That was impressive indeed, reminded a lot that famous "drone hits rock" video that is on youtube, except with a happy ending.