Took my brand new Mini 3 Pro up for her maiden voyage today. All went fine until I initiated the RTH.

I noticed it was descending very fast, but I incorrectly assumed it would start to slow down as it got close to the ground and would give me a chance to takeover and land manually. But instead it kept the same speed and crashed into the ground and bounced forward about 1 metre.


I learned my lesson about trusting RTH but it all just happened very fast. I thought the downward facing sensors should do a better job to prevent this?

The impact damaged the rubbery part of one of the little landing legs which is really annoying even if it's just cosmetic, but no other damage apart from that as far as I can tell.

I'm trying to look at the flight log to get more info on what happened but all I'm seeing is a white screen with N/A when I open up any of the logs.

Any advice here on why this happened? Also I do have DJI care refresh. Thanks!

You need to get the logs off the controller onto a computer to really look at them.
DO NOT sync your logs, you may lose the DAT flight log from the controller and that might be useful.
Have a look at https://mavicpilots.com/threads/ ... controller.127069/

That said you should have been watching the drone and not the controller.
Why did you not release the throttle or not hold it so closed when you saw the drone descending so quickly, especially when near the ground?
BTW the drone's behaviour is suspect but the logs are needed to possibly see why it behaved this way.

If you get the .txt flight log off the controller upload it to https://www.phantomhelp.com/LogViewer/Upload/ and post the resulting URL here.

I also see damage to a propeller. I would start a case to return the aircraft for replacement as it should land very gently. You said this was your first flight and that is not normal. It is a warranty issue.

Sounds like the bottom sensors were not functioning properly. Even with full down stick, my drones stop at about 18" and slowly land.

Sean-bumble-bee Posted at 3-30 14:09
You need to get the logs off the controller onto a computer to really look at them.
DO NOT sync your logs, you may lose the DAT flight log from the controller and that might be useful.
Have a look at https://mavicpilots.com/threads/ ... controller.127069/

Thanks I'll try get the logs off the controller.

I should have mentioned earlier, but my fingers were not on the sticks at all during that video clip I posted. During the RTH landing the drone automatically descended all the way down at that speed.

I previously had a Mavic Mini and anytime I landed it, even holding the stick fully down it would stop close to the ground and land slowly as Mobilehomer had just mentioned.

I've opened a service case to replace the drone as there definitely seems to have been some sensor malfunction. Thanks all for the suggestions.

Conal King Posted at 3-30 14:58
Thanks I'll try get the logs off the controller.

I should have mentioned earlier, but my fingers were not on the sticks at all during that video clip I posted. During the RTH landing the drone automatically descended all the way down at that speed.

It is very easy to become accustomed to landing protection etc. working and taking care of descent speeds. After flying Mavic style drones for a while I sent a Phantom 3 up and very nearly 'decended it' into the ground, whoops.
If that was an RTH descent then something is up with the drone, though did you notice the camera levelled just before 'thump down', something in the VPS must have been working at that point.

I do hope you can get the logs of the DJI RC I am curious to see what the VPS height was recorded as.

Hi there. Thank you for reaching out and we're sorry for the incident that happened on the unit. I'm afraid that you may consider sending the unit in for a proper diagnosis. You can contact our support team to start up a ticket at https://www.dji.com/support . Also, the warranty can be applied depending on the outcome of the damage assessment including the warranty period of your unit. Thank you for your understanding and support.

You got very nice footage though!

Sean-bumble-bee Posted at 3-30 15:14
It is very easy to become accustomed to landing protection etc. working and taking care of descent speeds. After flying Mavic style drones for a while I sent a Phantom 3 up and very nearly 'decended it' into the ground, whoops.
If that was an RTH descent then something is up with the drone, though did you notice the camera levelled just before 'thump down', something in the VPS must have been working at that point.

I followed your instructions and managed to get the logs from the RC.

https://www.phantomhelp.com/LogViewer/5G8YGD3XEVO1F2NO0SCG

Hopefully JJB etc. will weigh in.
It would be interesting to know what the descent rate, from height, in Autolanding is supposed to be.
I can't seem to find it listed in the manual etc. but the drone seemed to be trying to reach 5m/s for quite a lot of the descent. That's the Maximum descent rate in sports mode but with other drones RTH etc. sets its own 'speed' limits and I think their Autoland descent rate is a normally around their P or N descent max.

Hi,

Had a look at your flightlog, the landing....

First, did you speed up the video a little ?

In a normal autoalanding the vertical speed down is reduced twice, depending on fly height
First approx between 50 - 40 meters baro height from max descent 5 to 3 m/s
Second at approx 18 meters baro height, and drone will stop at 0.5 meter height before the final slow touching down.
0.5 is info from the bottom sensor, so basicly both height measurentent acts together to get a good autolanding.

In your log the barop height and bottom sensor height differs 10 meters.
So at 17.1 baro height the actual height below your drone 7.7 meter.
At 17.7 meter descent still 2.8 m/s, but decreasing. See my chart of your data. [ red VPS height shown as (9!9 = last recorded value, so out of range or not measuring ]
But 17.7 was actual 7.7   so not enough distance / time to reduce speed.
Almost to zero at 0.2 bottom sensor height.

It it 'normal' to see baro height fluctuation upto 10 - 15 meter.  At takeoff baro height is zero`d, during flight (escpecially if max height in flight is high...) some height variations are seen to the baro height  indication. That is why at landing you will see sometimes negative numbers and sometimes positive numbers.
Plus 1 mbar airpressure change in flight gives 8 meters change in baro height.

So it might happen again....just press the pause button on the RC to cancel the autolanding if it going to fast. Or get used to landing always manually the last part, after getting your drone home using RTH.

cheers
JJB  [ by FRAP ; the 'best' software for flightlog analysis ]

JJB* Posted at 4-3 01:37
Hi,

Had a look at your flightlog, the landing....

Thanks for your detailed analysis! Very interesting.

No this video was not sped up at all. All I did was cut the video to show just the landing.

Next time I'll definitely be more ready to cancel the auto landing if it's coming down too fast, or just land manually. I'm sending the drone back to DJI tomorrow to get it checked out anyway as some others here had advised. Thanks again!

JJB* Posted at 4-3 01:37
Hi,

Had a look at your flightlog, the landing....

So the mini 3 's normal RTH descent rate is 5m/s when above 50m, is that correct?

Sean-bumble-bee Posted at 4-3 12:34
So the mini 3 's normal RTH descent rate is 5m/s when above 50m, is that correct?

Hi,

did expect your question  ;-)

Not checked all my flights, tested this yesterdat on a day with high winds.
See the chart.

RTH at 111 meter, autolanding started with approx 5 m/s, at baro height 48 meter to low height descend speed reduced. Its all seen in the chart.
At 0.9 meter in autolanding i cancelled the landing.

cheers
JJB   [ Chart by FRAP ; the 'best' software for flightlog analysis ]

Cheers JJB....

Found this thread because the same happened to me today. I've used RTH many times. Always watch the drone down, usually cancel RTH as it gets to about 2m above the ground and either land manually or hand catch it. This time it was coming down on a piece of perfectly flat tarmac with no obstacles so I was a bit less focused on being ready to stop it and was happy to let it land. By the time I realised that it wasn't going to slow it's descent it was hitting the ground pretty hard and then I had a rotor jammed warning as it had tipped and a rotor hit the tarmac.

I'd previously been very careful and very impressed by RTH but this spooked me and I'll take more care in future..

If anyone from DJI is watching this thread, should I send the drone to be checked? Are you aware of an issue with RTH with new firmware? I don't seem to have any damage but this does seem to be a failure of some kind..

djiuser_Iifbn1GuTgZL Posted at 4-8 08:13
Found this thread because the same happened to me today. I've used RTH many times. Always watch the drone down, usually cancel RTH as it gets to about 2m above the ground and either land manually or hand catch it. This time it was coming down on a piece of perfectly flat tarmac with no obstacles so I was a bit less focused on being ready to stop it and was happy to let it land. By the time I realised that it wasn't going to slow it's descent it was hitting the ground pretty hard and then I had a rotor jammed warning as it had tipped and a rotor hit the tarmac.

I'd previously been very careful and very impressed by RTH but this spooked me and I'll take more care in future..

Can you post the flight log and DAT please?

djiuser_Iifbn1GuTgZL Posted at 4-8 08:13
Found this thread because the same happened to me today. I've used RTH many times. Always watch the drone down, usually cancel RTH as it gets to about 2m above the ground and either land manually or hand catch it. This time it was coming down on a piece of perfectly flat tarmac with no obstacles so I was a bit less focused on being ready to stop it and was happy to let it land. By the time I realised that it wasn't going to slow it's descent it was hitting the ground pretty hard and then I had a rotor jammed warning as it had tipped and a rotor hit the tarmac.

I'd previously been very careful and very impressed by RTH but this spooked me and I'll take more care in future..

Thanks for adding to the discussion, that's interesting that you had a very similar experience to mine. My hard landing also resulted in a rotor jammed warning. It's possible it could be related to the new firmware like you say, as I did update to the latest firmware before my first flight where this issue occurred.

I've already sent my drone back to DJI last week requesting a replacement. Will post back here with the outcome after they check it out.

It's a bit late, but here's what the data for the relevant part of the flight shows.

I noticed it was descending very fast, but I incorrectly assumed it  would start to slow down as it got close to the ground and would give me  a chance to takeover and land manually. But instead it kept the same  speed and crashed into the ground and bounced forward about 1 metre.

When things happen fast, it's common for the data to show something different from what the brian thinks it saw.
It's late, but here's what the data for the relevant part of the flight shows.

The data tells a slightly different story.
Here's the relevant part of the data for the last three seconds of your flight.
The blue column is the height avove the ground in feet.
The mauve column shows the horizontal speed.
Pink is the descent speed in mph.

The lower part in pale brown is after the drone had landed with the yellow part showing the horizontal speed at landing.
This shows what caused your crash.

It's clear that below 30 ft, the descent speed did slow, from 6.5 mph to 1 mph as it reached 2 ft and it continued to slow after that.
But as the video shows, something caused the drone to fly forward as it came close to the ground.
It's not normal and the joystick data shows this was not caused by joystick input.
Obstacle avoidance perhaps?
Was something close behind the drone as it landed?

The drone tipping forward on landing (the pitch angle going to -26.5 degrees)caused the front propellers to contact the ground or weeds. causing the motor blocked message.

It's possible it could be related to the new firmware like you say.
This is most unlikely.
Although firmware updates are often suggested as causes of problems, they almost never are.
If it was an issue, there would have neen many similar incidents

Hi,

Obstacle avoidance does prevent to fly close to an obstacle, it does not command a drone to fly away from an obstacle.

Test yourself : OA on, hover at some height free on any obstacle, land in front off obstacle  (few cm..) and notice to the OA will see the obstacle but will not steer te drone away from the obstacle.

The only situation where OA does command away from an obstacle is in RTH mode.

cheers
JJB

JJB* Posted at 4-9 09:34
Hi,

Obstacle avoidance does prevent to fly close to an obstacle, it does not command a drone to fly away from an obstacle.

Obstacle avoidance does prevent to fly close to an obstacle, it does not command a drone to fly away from an obstacle.
You should have noted the question mark I put after the OA comments.

Something caused the drone to accelerate forward as it touched down.
What did that?

JJB* Posted at 4-9 09:34
Hi,

Obstacle avoidance does prevent to fly close to an obstacle, it does not command a drone to fly away from an obstacle.

To be fair, I thought I had already replied to this thread, my thought and reply was that it was the OA picking up on that wall behind it, it was very close to it. The reason I thought the OA was involved is that I am fairly sure that I read/heard that sometimes when hand catching this Mini 3 Pro will sometimes move horizontally away from the hand, I have had an issue hand catching myself, but I cannot remember exactly what it was now, this is why some choose to either turn off the OA on landing or like myself, switch to sports mode. It was something that worried me enough to always shut down the OA using sports to land, I mean, that's risky in itself but I am 100% certain that the AC did something that worried me more than landing and hand catching in sports.

I think this issue came about pretty much soon after the release date.

As to why my reply never posted, unsure, perhaps i thought i had and it was my last reply before finishing up, i then hit the power on the lappy and it then goes into hibernate but more often than not, my Chrome browser has a nasty habit of crashing and closing so i never picked up on it not posting.

Bashy Posted at 4-9 18:35
To be fair, I thought I had already replied to this thread, my thought and reply was that it was the OA picking up on that wall behind it, it was very close to it. The reason I thought the OA was involved is that I am fairly sure that I read/heard that sometimes when hand catching this Mini 3 Pro will sometimes move horizontally away from the hand, I have had an issue hand catching myself, but I cannot remember exactly what it was now, this is why some choose to either turn off the OA on landing or like myself, switch to sports mode. It was something that worried me enough to always shut down the OA using sports to land, I mean, that's risky in itself but I am 100% certain that the AC did something that worried me more than landing and hand catching in sports.

I think this issue came about pretty much soon after the release date.

i tested this recently latest firmware etc,  OA does not steer back from an obstacle.
Just find something you can land closely behind or in front of your drone, land vertically from a free area.

Well, i do not have all dji drones, but don`t think DJI will change this in various types.

Will make a video for this.

cheers
JJB

Labroides Posted at 4-9 16:32
Obstacle avoidance does prevent to fly close to an obstacle, it does not command a drone to fly away from an obstacle.
You should have noted the question mark I put after the OA comments.

What i see in the log is the following...

Drone landed, bounced back, not nicely just up but with forward drone attitude   so it moved forward.
see my chart of the log.

cheers
JJB

JJB* Posted at 4-10 00:17
What i see in the log is the following...

Drone landed, bounced back, not nicely just up but with forward drone attitude   so it moved forward.

So look at the video.
The drone's descent slowed to near zero, as the data shows.
It didn't land fast enough to bounce.

Labroides Posted at 4-10 01:02
So look at the video.
The drone's descent slowed to near zero, as the data shows.
It didn't land fast enough to bounce.

i see it different in the data, so we disagree on this  (wich is not a problem, we often disagree  ;-)  )

OP wrote "But instead it kept the same speed and crashed into the ground and bounced forward about 1 metre.  [ so bounced first before moved forward... ]

cheers
JJB

JJB* Posted at 4-10 01:35
i see it different in the data, so we disagree on this  (wich is not a problem, we often disagree  ;-)  )

OP wrote "But instead it kept the same speed and crashed into the ground and bounced forward about 1 metre.  [ so bounced first before moved forward... ]

OP wrote "But instead it kept the same speed and crashed into the ground and bounced forward about 1 metre.  [ so bounced first before moved forward... ]
The OP wrote that but the data tells a different story.
I guess the data must be lying?

JJB* Posted at 4-10 00:07
i tested this recently latest firmware etc,  OA does not steer back from an obstacle.
Just find something you can land closely behind or in front of your drone, land vertically from a free area.

It took me about 30 pages to go through but i found what i was referring to...

https://forum.dji.com/forum.php? ... D776%26typeid%3D776

Labroides Posted at 4-10 02:14
OP wrote "But instead it kept the same speed and crashed into the ground and bounced forward about 1 metre.  [ so bounced first before moved forward... ]
The OP wrote that but the data tells a different story.
I guess the data must be lying?

Data almost * never lies...see my chart of his data.
Wich is what was seeing by the remote pilot, i value eye-ball mark one vision more than your do.

You just have different opinion, wich i think it not correct. So why continue posting back to me?

* except when data in the log  does not reflect correct values, like the VPS height numbers when VPS height is out of reach.  Just one example when data 'lies'

cheers
JJB

Bashy Posted at 4-10 03:45
It took me about 30 pages to go through but i found what i was referring to...

https://forum.dji.com/forum.php?mod=viewthread&tid=271333&extra=page%3D23%26filter%3Dtypeid%26typeid%3D776%26typeid%3D776

Mode changes are not ontime after starting to fly.

Start a fllight with bypass ON , see that after take-off this is not in the log directly, but after short moment change to the correct setting.

I am just back from some test flight, OA does not steed drone away from an obstacle.

cheers
JJB

JJB* Posted at 4-10 06:30
Data almost * never lies...see my chart of his data.
Wich is what was seeing by the remote pilot, i value eye-ball mark one vision more than your do.

Because I can't understand why you aren't seeing what's in the data.
It says something quite different from what I think you're trying to say (but can't besure because of language difficulties).
I don't need to look at yours, I posted a much clearer version myself and it clearly shows the drone slowing just as it's supposed to and accelerating forward as it touches down ... just as the video also shows..

Labroides Posted at 4-10 06:36
Because I can't understand why you aren't seeing what's in the data.
It says something quite different from what I think you're trying to say (but can't besure because of language difficulties).
I don't need to look at yours, I posted a much clearer version myself and it clearly shows the drone slowing just as it's supposed to and accelerating forward as it touches down ... just as the video also shows..

Sorry that you cannot understand my posts and understand charts.
Many people on here do understand my writings and can read charts.

cheers
JJB

JJB* Posted at 4-10 06:39
Sorry that you cannot understand my posts and understand charts.
Many people on here do understand my writings and can read charts.

What ... not even a comment on my post?
What do you think I got wrong?

Labroides Posted at 4-10 06:58
What ... not even a comment on my post?
What do you think I got wrong?

No problem Labroides,

Hope you can understand my text and chart, chart now with the values for the X and Y speed component.

Drone in Autolanding, so distance in the log to HomePoint is zero or almost zero, normally.
In this log AutoLandoing startet at height 227 meter, distance to home 0.1 meter.

At 6m51.0 sec IR height started to measure again, height 7.7 meter. Downspeed 2.8 m/s.
Distance to HP still 0.1.

At 6m53.6 at 0.2 height down speed minus 0.3, distance to home 0.1 meter.

So drone came down in a perfect on the spot to the ground....no lateral (left/right/fwd/aft) moves in there.
Check drone Pitch and Roll angles and X Y speed, see my chart with the X Y speeds.

Next record IR height 0.0 meter, at this very moment the X speed component from zero to -0.6.
In this record also drone pitch attiude change  from to 26.2 degrees, in green = pitching down = forward move (as in the video).

This is also seen as distance to HP is increased the moment height is zero. As the bottom sensor is very accurate, zero in the log is zero = touching the ground.
So all this make me think, with the text of the operator, that drone indeed descende to fast, 'hit; the ground and moved bit forward.

Normal in an oke descent the cam is automatically from down to zero pitch before last part of landing is executed. As you can see in the video and in the log ; drone almost landed, sign of going too fast in the autolanding last part. Beacuse of this cam move to zero it looks likes the drone moves forward earlier...

But no problem if we have a different analysis, always nice to read the thoughts of others on here.

cheers
JJB

JJB* Posted at 4-10 11:24
No problem Labroides,

Hope you can understand my text and chart, chart now with the values for the X and Y speed component.

I give up, the message just isn't getting through.
Perhaps if we had a common language .....

If data is available and does not lie, how can there be 2 different interpretations?

RoZis Posted at 4-10 21:27
If data is available and does not lie, how can there be 2 different interpretations?

If you cannot read my chart in post #41 than ofcourse you stick with your own interpretation.

If you can read my chart and understand it....you know who is correct.

cheers
JJB

Labroides Posted at 4-10 14:57
I give up, the message just isn't getting through.
Perhaps if we had a common language .....

hahahah  

did not expect this type of answer from you after asking for explanation why you are wrong in post #41

cheers
JJB

JJB* Posted at 4-10 22:48
If you cannot read my chart in post #41 than ofcourse you stick with your own interpretation.

If you can read my chart and understand it....you know who is correct.

If you can read my chart and understand it....you know who is correct.
It's the same data, only my version is a lot clearer and easier to read, than yours with all that irrelevant material across the page.
It's your interpretation that's different.

JJB* Posted at 4-10 22:51
hahahah  

did not expect this type of answer from you after asking for explanation why you are wrong in post #41

And you still haven't explained what you think I got wrong.

What I was giving up on, was hoping too get a clear answer or explanation from you.
The language difficulty is too frustrating, too often.