(Warning) Avoid this low battery RTH mistake

[Qoncussion]

Thanks very much for doing these experiments guys.

Would the drone behave differently if you descended to the ground with Sports Mode on compared with Sports Mode off?

What about the flying modes in the DJI GO app, such as Cinematic mode, Tripod mode, etc?

Also, when your sensors were disabled, are you able to confirm whether the drone continued storing logs and other data on it's SD card after the controller disconnected (and while it did the connection-lost RTH sequence)?

These sensor findings have really got me wondering...

Very interesting indeed!

1) Sports mode automatically disables the sensors, so the motors would remain spinning and a RTH is inevitable.

2) Various flight modes: my test says it all comes down to the state of the bottom sensors. If the sensors are on, it will land and kill the motors. If off, RTH.

3) Yes. The only thing that stops and starts new logs is killing and restarting the motors. As long as the motors continues running, then it continues record the log.

 

[Qoncussion]

I made a video of the tests. I'm disappointed in my camera's location, as you can't see the craft when it's landing at the remote location down field - you know - the reason we're all here. But my narration kinda covers my ***. Thank goodness for wireless mics...

 

[fiberdude]

3) Yes. The only thing that stops and starts new logs is killing and restarting the motors. As long as the motors continues running, then it continues record the log.

A DJI GO4 app crash/restart will also initiate the writing of a new flight log with running motors.

 

[Qoncussion]

A DJI GO4 app crash/restart will also initiate the writing of a new flight log with running motors.

^^ Ahhh yes... True story.

 

[BudWalker]

.....

3) Yes. The only thing that stops and starts new logs is killing and restarting the motors. As long as the motors continues running, then it continues record the log.

If you're talking about the .DAT on the AC then the only thing that stops the .DAT log is turning off the battery. Stopping the motors doesn't stop the .DAT log.

The .txt log starts at launch - even if the motors have been running. The .txt stops when the motors stop after landing.

 

[ScubaBob]

Thanks for posting this. Very interesting. I guess that after landing at a place where you cannot see the drone it would be a good idea to see if the drone will go up (by using the only the left joystick). If it does then you know the props are still spinning. If not then you know you have shut it down.

Hi guys,

I had a near miss. I just wanted to alert you of this so nobody loses their Mavic Pro.

I was filming a lake.
I parked my car on one side of the lake and I launched my drone from the opposite side of the lake.

I completed my filming and knew the drone's battery was pretty low at around 18%. Time to wrap things up.
I thought I would be clever and just land my drone near my car, so that I didn't need to carry it back to the car.
I landed it via the video feed and confirmed that it was actually stationary on the ground.

I unplugged my phone and turned off the Mavic controller. I completely packed everything away.

After about 5 minutes, after walking halfway back to the car, I suddenly heard my Mavic in the air!!

Confused and freaking out, I opened my bag and turned on the controller on again (without a smartphone). As soon as it connected to the drone, it immediately starts beeping, indicating that the battery was now very very low (eg, single-digit %)

Because the battery had dropped to a certain level while it sat idle on the ground beside my car, it had autonomously taken off again, climbed to the RTH altitude I previously set (100m) and heading 'home', over the middle of the lake.

It didn't have enough battery to make it home. Mid-way through it's RTH course over the lake, the battery reached the critically-low threshold and it began doing an forced-decent over the middle of the lake.

I could not override this descent - however I was fortunate on this occasion because I had a physical line-of-sight to the drone from where I was standing. I was even more fortunate that I was able to manually roll the drone sideways and steer this forced-descent onto a patch of dirt which happened to be beside this particular section of it's RTH course.
(again, my phone wasn't plugged in to the controller so I had no video feed; it was all manual)

On this occasion the drone wasn't destroyed, but this was a very, very close call.

I understand that the drone will return to home on low battery and lost signal...but I was surprised that it will do this even after the pilot has landed it somewhere else. This seems to be a loop-hole in the RTH algorithm.

If I ever want to land the drone at an alternative site, how can I land it and STAY THERE, even when the battery gets low? (assume I'm flying using just the manual controls, ie, without a smart phone)

Has this happened to anyone else?

Please be careful of this, guys.

EDIT:

Here is the flight log of the flight.
This flight was about 6 weeks ago, with many uneventful flights since. You'll have to forgive me if some of my earlier recollection of the event was inaccurate in my initial post.
I have deliberately removed all the GPS coordinates for confidentiality.
What I can tell you is: the take-off point was also the 'home point'. The landing point was not the home point.

DJIFlightRecord_2018-01-03_(11-39-13) (GPS coordinates removed).xlsx

 

[Vind]

Thanks for posting this. Very interesting. I guess that after landing at a place where you cannot see the drone it would be a good idea to see if the drone will go up (by using the only the left joystick). If it does then you know the props are still spinning. If not then you know you have shut it down.

 

[Yannie]

Thanks for posting this. Very interesting. I guess that after landing at a place where you cannot see the drone it would be a good idea to see if the drone will go up (by using the only the left joystick). If it does then you know the props are still spinning. If not then you know you have shut it down.

Yes, this is a good idea.

But the key take home message of this is:

- Do not attempt to land the drone manually while in Sports mode (nor any other configuration which disables the downward sensors).
- Maintain line of sight to your drone, especially when you're landing

Either:
1) Hit the RTH button to tell it to land at the original "launch" home point

Alternatively, if you want to land somewhere different to the take-off site:

2) Enable downward sensors (ie, turn off Sports mode) before landing manually,

or

3) Change the home point during the flight, then hit the RTH button

 

[kakao]

3) Change the home point during the flight, then hit the RTH button

How to do this?

 

[Yannie]

QUOTE="kakao, post: 408133, member: 43542"]How to do this?[/QUOTE]
setting a new homepoint in flight

 

[Qoncussion]

Thanks for posting this. Very interesting. I guess that after landing at a place where you cannot see the drone it would be a good idea to see if the drone will go up (by using the only the left joystick). If it does then you know the props are still spinning. If not then you know you have shut it down.

I actually really liked the comment above (early in the thread), after I suggested throttling up ~another user suggested just checking the RPMs at the top right of the RC screen. Which I then implemented when I shot the test video (also above). Either way works ~but since the drone would be in a remote location from you, I think the safer option is to check the RPMs. Either way - this was a fun experiment.

 

[Qoncussion]

How to do this?

This is one of the (almost) hidden gems in the Go4 app. Simply drag your finger across the main screen, from right to left to reveal a menu with the option to reset the home point. You can also use Home Point ME in that same menu, which sets the new home point to the location of the GPS coordinates of your device (phone/tablet) connected to the RC. I haven't used this myself, but have read cautionary tales - as the home point is set to the location you are standing when you select the option - and does not follow you around if you continue moving about ~as some have thought.

 

[joejaxvic123]

Good work, Qoncussion. I will be looking you up on YouTube. I want to see some video of the old airfield.

 

[Qoncussion]

Good work, Qoncussion. I will be looking you up on YouTube. I want to see some video of the old airfield.

You know, for as often as I fly at the old airport, I have very few videos *of* the airport ~as it's really a featureless place to shoot - as far as interesting video goes. Here are the few times that the airport made it into a video:

In this one, I launched from the airport, but don't think the airport made the shot. I flew over the treeline to get away from the airport.

You can see it here:

Here's a better view - in a 360 pano:
Nevada County Sunset

 

[ScubaBob]

This is one of the (almost) hidden gems in the Go4 app. Simply drag your finger across the main screen, from right to left to reveal a menu with the option to reset the home point. You can also use Home Point ME in that same menu, which sets the new home point to the location of the GPS coordinates of your device (phone/tablet) connected to the RC. I haven't used this myself, but have read cautionary tales - as the home point is set to the location you are standing when you select the option - and does not follow you around if you continue moving about ~as some have thought.

You are right. Home Point ME is where you are located at that moment. It is not FOLLOW ME. I used Home Point Me when on a boat as the take-off location is in the water within minutes of launching. When I am ready to bring the drone back to update Home Point ME and that gets the drone heading back fairly close to my location. If I don't see it after a reasonable amount of time I update again. Usually by then my MP is within sight and I cancel RTH and bring it in manually.

 

[hasselbrook]

You likely didn't keep the throttle down long enough to stop the motors after "landing" so it was still running and "in flight" even if touching the ground. So when you turned the controller off it entered signal loss RTH.

Also if you do that it would be a good idea to set home point to aircraft location once you're there...

Don't you have to also shut off the battery in MP first.
Then Radio?

 

[PaoloOne]

I have been reading all the posts and nobody has said the obvious thing to do when you decide to land in a far away location :
You should change the default action to perform upon signal loss from "Return to home" to "Landing".
In the same way should be disabled the RTH action on low battery.
Changing the home point is instead inappropriate for that purpose.

 

[jedburgh01]

I descended until it was 30cm off the ground. I gimballed down to check the ground was safe. I then pointed the gimbal to the horizon for the final landing phase (as I usually do, to reduce the chance that something on the ground scratches the front of the camera). I then further descended it completely down to the ground. Thus, I wasn't able to see whether dirt was still blowing around when I knew the drone was on the ground. I didn't pay attention to the rpm of the motors. The drone was not in the air and the altitude was 0, at the time I turned off the controller. I thought that would be the end of the story...

I have no idea why the blades would still spin when it knows it's on the ground...why would they keep spinning when it is on the ground?

In my experience, when you land the rotors shut off and you're ok
But always turn the Mavic Pro off before the controller

 

[Kilrah]

Don't you have to also shut off the battery in MP first.
Then Radio?

No, doesn't matter a single bit.

 

[Brojon]

Speaking for myself and at least some others .DAT retrieval has gotten progressively harder since 01.03.0900. I don't know if every Mavic owner has experienced this. DATs that you know should be there don't appear. Sometimes on subsequent DJI Assistant starts a missing .DAT will magically appear. Sometimes a .DAT that was appearing will go away. I've heard some say the problem was a driver issue and could be fixed with a procedure to remove and re-install drivers. I tried this and it seemed to help for a while - could just be a coincidence though.

I discovered that it is computer dependent. I have 3 PC's and DJI A2 wouldn't/couldn't get the dat files from my MP. Then I tried my Surface Pro 3 tablet and wah-la - it worked.
I have no idea what on earth could be the issue.
We know that the "app" is based on or uses javascript so likely depends on a web engine it assumes is installed. Which one is anybody's guess since different browsers use different web engines.

Comparison of web browser engines - Wikipedia.