Crash while RTH - Mavic 2 Enterprise

[prohph]

Hello everyone,

I have been flying with a DJI Mini 2 for a few years (unfortunately not very regularly). For the past few months, I've been flying with a DJI Mavic 2 Enterprise Dual (in combination with the Smart Controller). Recently, I've been using it intensively for fawn rescue. During these missions, I've been using RTH (Return to Home) regularly, both automatically when the battery is low and manually after the flight ends.

Today, during the last mission on an open area in the forest, I activated RTH again to end the mission. The landing position was about 2 meters from the nearest tree. The drone was already in the correct position, about 5 meters in height, but instead of landing, it ascended to about 10 meters. I had already set the Smart Controller aside when I noticed the deviation. I tried to pull the drone up with the controller, but it only made a very quick lateral movement and ended up landing in the tree.

In the log, I saw that the flight mode changed from "Auto Landing" to "P-GPS," and then the altitude increased.

The drone is already on its way for repair - is there any way to find out exactly what happened? Was it an operator mistake?
I think that manual movement while RTH is active is not possible, is this correct?

Thank you!
Phil

 

[Yorkshire_Pud]

In the log, I saw that the flight mode changed from "Auto Landing" to "P-GPS," and then the altitude increased.

The drone is already on its way for repair - is there any way to find out exactly what happened? Was it an operator mistake?
I think that manual movement while RTH is active is not possible, is this correct?

Assuming you mean the .txt flight log and not a replay of the flight in the app then upload the log to

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

and post the URL here.

With an ordinary Mavic 2 you do have manual control during an automated descent so I would guess the same applies to the enterprise.
Again with the ordinary Mavic 2 there is a way to be able to spin the drone during the RTH flight home, it requires changing an option in the app (Go4), but I have forgotten how you do that. The Enterprise uses a different control app (DJI Pilot) and I do not know if DJI| Pilot has that option.

BTW ..... welcome

 

[GFields]

Was it an operator mistake?

Greetings from Birmingham Alabama USA, welcome to the forum! We look forward to hearing from you!


Laying the remote down while the drone is the air, yes you made a huge mistake

 

[prohph]

Thanks for your feedback and also welcome Yes, laying down the remote was very risky. I was glad that we finished the job didn't think about it anymore.

I uploaded the last Log-File: DJI Flight Log Viewer - PhantomHelp.com

Thanks,
Phil

 

[GFields]

es, laying down the remote was very risky.

Risky indeed.

It looks, to me, like the drone auto-landed into the tree; it then changed to P-GPS because it was in the tree.

I rarely, if ever, use the RTH. but when/if I do, I always keep my eyes on the drone to make sure it's going to land where I want it to land.

 

[prohph]

I never used RTH with my Mini 2 because I never trusted this function. With the Enterprise 2 it was a comfortable way while flying a mission and dont have to actively check the battery level. We could fully focus on the image. Now I have trust issues again

I can understand that the drone switched to P-GPS, but why did it also begin to ascend? Is there an explanation for that?

 

[Yorkshire_Pud]

In the folder where you found the flight log there might be another folder named MCDATFlightRecord, or similar, that contains DAT flight logs.
Are there DATs in there? Is so, if you can see one with approximately the same date and time stamp as the .txt flightlog and the number 098 in its name can you upload that log to here.
If the forum will not accept the file can you upload it to a file hosting website, make the page public and post the URL here.
I do not know if Ent DATs are readable but normal Mavic 2 DATs are readable ...... I am also assuming the smart controller creates these DATs.

Questions, was OA on during the RTH, either through your own choice or automatically ?
I am puzzled by the RTH behaviour and wondering what caused the climb that started at 610 seconds when the drone was almost home.
Were there trees in front of it? I think so but ......

 

[GFields]

but why did it also begin to ascend

Auto Landing began at 97.4' and continued to decent. The logs don't show the drone ascending as you describe.

 

[prohph]

upload that to here

Here is a onedrive link: Microsoft OneDrive

Questions, was OA on during the RTH

I am not sure if it was on during RTH, but it was definitely on after start. We checked it multiple times today.

610 seconds

Which timestamp is this? I use Flight-Reader

Auto Landing began at 97.4'

Which timestamp is this?
I used Flight-Reader to analyze the logs: At 9m 59,6s the flight mode changed to Go Home and the Home Distance was 19,4m. At 10m 28,0s the Flight Mode changed to Auto Landing and the Home Distance was 0,0m. Then, at 10m 38,6s the Home Distance was 6,5m and the Flight Mode switched to P-GPS - which i interpreted as the climb. Then the Home Distance is increasing until 10m 40,5s to 8,3m and the message is "IMU attitude limit." The next line says "Not enough force (ESC error)".

In the variable OSD.altitude i also don't see any climbing. But the drone definitely started to climb again, this was the moment when my mate informed me about the strange behavior

I think the crash happend at 10m 41,7s when the speed changed to 4,8m/s.

Were there trees in front of it?

Not in front of the camera directly, but maximum 2m sideways.

In the distance of approximately 100m of to the homepoint there are High-Voltage power lines.

 

[Yorkshire_Pud]

Which timestamp is this?

Column D "OSD.flyTime " = 10min 10sec

Below are various CsvView plots derived from the PhantomHelp CSV, that CSV should be almost identical to the flightreader CSV since @msinger is responsible for both.

Here is a onedrive link: Microsoft OneDrive

The DAT is readable, perhaps @slup , @BudWalker , @sar104 will have a look

In the variable OSD.altitude i also don't see any climbing.

look at OSD.height [ft]

Then, at 10m 38,6s the Home Distance was 6,5m

you gave the drone a squirt of full aileron around 637- 638seconds which might account for the added distance.

 

[Yorkshire_Pud]

@prohph I was looking to see if you took video or photos of the homepoint but seemingly not.
Whilst doing that I noticed the card is reported as full, I hope you removed it from the drone.

 

[Meta4]

In the log, I saw that the flight mode changed from "Auto Landing" to "P-GPS," and then the altitude increased.

The altitude increase started at 10:19.7 during the RTH process.
Flight Mode changed to autolanding at 10:28
The change of Flight Mode from Autolanding to P-GPSoccurred at 10:38.6

is there any way to find out exactly what happened? Was it an operator mistake?
I think that manual movement while RTH is active is not possible, is this correct?

When RTH was initiated the drone was only 19.5 metres from the homepoint and 10.5 metres high.
RTH brought the drone to a point 1.5 metres from the homepoint and only 1.5 metres away and then started to ascend while still in RTH.
It climbed to 30 metres and when directly above the homepoint, started to autoland.
While descending, the drone started to stray away from directly over the home point.

At 10:36.9 as it descended past 23 metres and was 4.5 metres off the homepoint, the data shows 1.3 seconds of joystick input to rotate the drone clockwise and fly to the right.
This moved the drone to 6.7 metres off the homepoint to where it collided with tree branches about 20 metres up.
The RTH autolanding cancelled at the same time.
The drone tumbled 14 metres (possibly through tree branches?) and the data stops at 10:43.7.

The main problem was that you set a homepoint too close to trees.
You need to have a clear space around your homepoint at least 10 metres from any obstacles to allow the drone to come down without the risk of hitting something.

Your joystick input was not sufficient to prevent the drone from hitting tree branches.

If you have set the homepoint close to obstacles, you need to manually land the drone away from obstacles rather than trust the drone to find its way through them.

 

[msinger]

While descending, the drone started to stray away from directly over the home point.

The drone might have been attempting to use the precision landing feature -- auto adjusting its position as it neared the ground.

Whatever the case, attempting to auto land while 2 meters away from the nearest tree is a possible disaster waiting to happen. That's certainly a scenario where it would be important to have the remote controller in hand and ready to manually take over if needed.

 

[Meta4]

Now I have trust issues again.

You need to be able to trust that the operator avoids launching from close to obstacles.

I can understand that the drone switched to P-GPS, but why did it also begin to ascend? Is there an explanation for that?

Perhaps this from p19-20 of your manual?

 

[Yorkshire_Pud]

The drone might have been attempting to use the precision landing feature -- auto adjusting its position as it neared the ground.

I wondered about that too, due to the yaw at 629sec. But the take off didn't climb vertically to 7m, does the Ent have different takeoff criteria?

Can you think of any reason for the uncommanded climb other than perhaps OA kicking in? I can't lol but that's no guarantee of anything.
I had something similar happen with an ordinary mavic 2 when I was experimenting with that current altitude thing and forgot to switch it off and OA was on (which is a rarity for me, it scared the ... out of me.

 

[rjwmorrell]

I never used RTH with my Mini 2 because I never trusted this function. With the Enterprise 2 it was a comfortable way while flying a mission and dont have to actively check the battery level. We could fully focus on the image. Now I have trust issues again

I can understand that the drone switched to P-GPS, but why did it also begin to ascend? Is there an explanation for that?

My guess is it sensed the ground wasn't flat or didn't recognize it as ground but an obstacle. But I didn't look at logs.

 

[Meta4]

My guess is it sensed the ground wasn't flat or didn't recognize it as ground but an obstacle. But I didn't look at logs.

The data shows that at the time, the drone wasn't landing and the VPS sensors weren't sensing the ground.

 

[prohph]

Hello Drone Experts,

Thank you very much for your amazing support!

Here are my conclusions:

• I initiated the Return to Home (RTH) in a very poor environment, with the nearest tree only about 2 meters away.
• The drone was almost in its landing position when the Obstacle Avoidance (OA) took over.
  • At this point, I had already put the controller away
• When the drone reached its maximum altitude of 30 meters, I attempted to regain control using joystick input.
  • I couldn’t fly higher due to the 30-meter limit.
• Unfortunately, the crash occurred.
  • I’m not sure if the crash was caused by my joystick input or the OA maneuver.

Here are my key takeaways:

• NEVER, EVER put away the controller before the drone is safely on the ground!
• Avoid using RTH when there isn’t sufficient space (at least a 10-meter radius).
• Set the maximum altitude to at least 80 meters.

I hope the repair costs won’t be too high; but lets see It was my mistake and I hopefully learned a lot from my first drone crash.

Thanks again,
Phil

 

[Yorkshire_Pud]

Avoid using RTH when there isn’t sufficient space (at least a 10-meter radius).

I think that should be ammended to.
"Be wary of letting autoland land the drone when there are trees nearby OR BE PREPARED and able to give manual commands whilst it is in autoland.
I frequently use RTH from a take off point that is all but surrounded by tree but I never let the drone autoland there, or anywhere really.
About the only time I have let a drone autoland was when I was testing the precision landing and that wasn't near trees. At other times when I have let autoland reduce the drone's height I have had my finger on the elevator/aileron joystick and from memory adjusted the position as I felt was needed and then finally cancelled the auto land and landed the drone manually or hand caught it.

All that said there are other important points that you have missed in your summary.
1) RTH behaviour depends on the distance from the home point, you need to familiarise yourself with the thresholds. Read the maual thoroughly.
Your the RTH in this incideint was initiated inside the outer threshold.
2) It also appears that you had the "Current Altitude" option enabled which further complicated the RTH behaviour The final point is that
3) I think OA was switched on whilst the drone was low and approaching the home point, drones do not normally RTH low down and in your case I think the OA caused the climb.
OA being on whilst the drone was low down nearly cost me my M2P in my first flight with it. I didn't know what was causing the problems I was encountering as none of my previous drones have OA.