RTH crash

[Kajtek]

I just received the Mavic Mini 3 Pro and I'm using the RC Pro Remote that I also use with my Mavic 3. The first flight went mostly smoothly, except for one issue. When I initiated the Return to Home (RTH) function, the drone wanted to land 3 meters away from the starting point, which wasn't as precise as I'm accustomed to with my Mavic 3. As it started descending and deviated from the starting point, I clicked cancel and manually landed it.

During the second flight, the RTH function once again wanted to land the drone 3 meters away from the starting point. This time, when I tried to cancel it, it didn't work. It seemed like the drone actually accelerated its descent (though that might have been my impression) and crashed into a bush that protected it. If there had been concrete or hard ground instead of the bush, the drone would have been damaged.

The automatic landing should have slowed down and landed the drone gently. At least, that's what my Mavic 3 does.

Additionally, I've noticed that there's no discernible difference between cine mode and normal mode. Both modes seem to have similar speeds.
Attached the log file. I cannot find explanation what happened. Anybody can analyze the last seconds?
How do I contact DJI. I found only options to send the product. Is there an option to send them files just for analysis?

 

[mobilehomer]

The Mini 3 Pro does NOT have Precision Landing. It uses GPS only. 3 meters is within consumer tolerances. Most times it lands a little closer than this.

 

[msinger]

Attached the log file

Please try attaching it again.

 

[YayAreaBoss23]

I just received the Mavic Mini 3 Pro and I'm using the RC Pro Remote that I also use with my Mavic 3. The first flight went mostly smoothly, except for one issue. When I initiated the Return to Home (RTH) function, the drone wanted to land 3 meters away from the starting point, which wasn't as precise as I'm accustomed to with my Mavic 3. As it started descending and deviated from the starting point, I clicked cancel and manually landed it.

During the second flight, the RTH function once again wanted to land the drone 3 meters away from the starting point. This time, when I tried to cancel it, it didn't work. It seemed like the drone actually accelerated its descent (though that might have been my impression) and crashed into a bush that protected it. If there had been concrete or hard ground instead of the bush, the drone would have been damaged.

The automatic landing should have slowed down and landed the drone gently. At least, that's what my Mavic 3 does.

Additionally, I've noticed that there's no discernible difference between cine mode and normal mode. Both modes seem to have similar speeds.
Attached the log file. I cannot find explanation what happened. Anybody can analyze the last seconds?
How do I contact DJI. I found only options to send the product. Is there an option to send them files just for analysis?

Try using a H landing pad then when you takeoff raise the drone 5-10 feet up and let it hover for 10 seconds, upon RTH you will notice it is much more precise usually less than 1 meter

 

[Kajtek]

The Mini 3 Pro does NOT have Precision Landing. It uses GPS only. 3 meters is within consumer tolerances. Most times it lands a little closer than this.

Lack of precision landing is not a problem. The problem is that RTH shoulld be a smooth landing not a crash. This evening I flew the drone and did three RTH and this time it behaved as expected. It slowed down and landed very slow and once even stopped 1 m above and asked if the landing was without obstacles. To my surprise all three were within 20cm of home point. I do not know now if I should contact DJI for replacement on the premise that if it did one crash it can do it again, or keep it because it behaves well and there was no damage.

 

[Kajtek]

Please try attaching it again.

I am trying again to attach

 

[Kajtek]

I am trying again to attach

For some reason it does not work I uploded to one drive . DJIFlightRecord_2023-07-08_[12-24-43] MiniPro3 Crash.txt

 

[Yorkshire_Pud]

Your log on phantom help DJI Flight Log Viewer - PhantomHelp.com
@msinger how come there is no course track? I have seen a few like that recently.

 

[msinger]

how come there is no course track? I have seen a few like that recently.

Not sure. Maybe a Google Maps issue? It shows up in Google Earth:

 

[Meta4]

Try using a H landing pad then when you takeoff raise the drone 5-10 feet up and let it hover for 10 seconds, upon RTH you will notice it is much more precise usually less than 1 meter

None of that would make any difference, since he's flying a Mini 3 which has no Precision Landing feature.

But if he did have PL, the H landing pad wouldn't be needed and he would have to raise the drone 22 feet vertically before flying off and there's no need to hover there.

 

[Meta4]

The automatic landing should have slowed down and landed the drone gently.

You cancelled the autolanding before the VPS was able to tell how high the drone was above the ground.
The VPS picked up the ground a second later at 18 ft above ground (or bush).
The bush and/or lighting conditions might have reduced the VPS ability to read the dround as it could read it to 36 feet when you launched.

It's common and normal for the barometric sensor to drift a little over the duration of a flight.
But rather than the usual 10 ft of so, yours is showing a 160 ft difference between launch and landing.
You should recalibrate the IMU to see if that fixes the issue.

Additionally, I've noticed that there's no discernible difference between cine mode and normal mode. Both modes seem to have similar speeds.

When are you switching to Cine Mode?
When you launch, the drone is in Normal Mode, regardless of the switch setting.
You need to switch modes after launching.

 

[Kajtek]

You cancelled the autolanding before the VPS was able to tell how high the drone was above the ground.
The VPS picked up the ground a second later at 18 ft above ground (or bush).
The bush and/or lighting conditions might have reduced the VPS ability to read the dround as it could read it to 36 feet when you launched.

It's common and normal for the barometric sensor to drift a little over the duration of a flight.
But rather than the usual 10 ft of so, yours is showing a 160 ft difference between launch and landing.
You should recalibrate the IMU to see if that fixes the issue.



When are you switching to Cine Mode?
When you launch, the drone is in Normal Mode, regardless of the switch setting.
You need to switch modes after launching.

I was switching in the air and there was no difference. In my evening flight after the crash there was a difference

 

[Kajtek]

I was switching in the air and there was no difference. In my evening flight after the crash there was a difference

You cancelled the autolanding before the VPS was able to tell how high the drone was above the ground.
The VPS picked up the ground a second later at 18 ft above ground (or bush).
The bush and/or lighting conditions might have reduced the VPS ability to read the dround as it could read it to 36 feet when you launched.

It's common and normal for the barometric sensor to drift a little over the duration of a flight.
But rather than the usual 10 ft of so, yours is showing a 160 ft difference between launch and landing.
You should recalibrate the IMU to see if that fixes the issue.



When are you switching to Cine Mode?
When you launch, the drone is in Normal Mode, regardless of the switch setting.
You need to switch modes after launching.

Thank you .The drone was descending very fast and when I cancelled should not it stop to descend?. The day was very bright and visibility should not be a problem. Here is the video
RTH Crash.mp4
The drone thought it was 50 m above ground and it was only few meters. I still think that it should stop the descend when I cancelled RTH. Anyway in my evening testing after the crash the drone was landing as expected. The question is. Was it my fault and if yes then what it was to avoid iun the future or was it a drone and should be replaced.

You cancelled the autolanding before the VPS was able to tell how high the drone was above the ground.
The VPS picked up the ground a second later at 18 ft above ground (or bush).
The bush and/or lighting conditions might have reduced the VPS ability to read the dround as it could read it to 36 feet when you launched.

It's common and normal for the barometric sensor to drift a little over the duration of a flight.
But rather than the usual 10 ft of so, yours is showing a 160 ft difference between launch and landing.
You should recalibrate the IMU to see if that fixes the issue.



When are you switching to Cine Mode?
When you launch, the drone is in Normal Mode, regardless of the switch setting.
You need to switch modes after launching.

 

[Meta4]

Thank you .The drone was descending very fast and when I cancelled should not it stop to descend?

It was descending at a steady 4.4 metres/sec.
It takes time for the "brakes" to overcome inertia.
You cancelled autolanding at 12:17.9 and the descent slowed.
At 12:18.7 the VPS started to read whatever was below it and descent had slowed to 2 m/s.
Half a second later it was 0.2 m/s and VPS showed something 5.4 m below.

The drone thought it was 50 m above ground and it was only few meters.

No ... the drone "thought" it was 50 metres higher than the launch point, but had no idea how far it was above the ground until VPS found it at 12:18.7 - 5.4 m below.

I still think that it should stop the descend when I cancelled RTH.

As explained above ... it did stop.

The question is. Was it my fault and if yes then what it was to avoid iun the future or was it a drone and should be replaced.

I'm not convinced that there was any problem except for the large difference in the barometric height reading.
But that had no effect on your landing anyway.

 

[Vic Moss]

I just received the Mavic Mini 3 Pro and I'm using the RC Pro Remote that I also use with my Mavic 3. The first flight went mostly smoothly, except for one issue. When I initiated the Return to Home (RTH) function, the drone wanted to land 3 meters away from the starting point, which wasn't as precise as I'm accustomed to with my Mavic 3. As it started descending and deviated from the starting point, I clicked cancel and manually landed it.

During the second flight, the RTH function once again wanted to land the drone 3 meters away from the starting point. This time, when I tried to cancel it, it didn't work. It seemed like the drone actually accelerated its descent (though that might have been my impression) and crashed into a bush that protected it. If there had been concrete or hard ground instead of the bush, the drone would have been damaged.

The automatic landing should have slowed down and landed the drone gently. At least, that's what my Mavic 3 does.

Additionally, I've noticed that there's no discernible difference between cine mode and normal mode. Both modes seem to have similar speeds.
Attached the log file. I cannot find explanation what happened. Anybody can analyze the last seconds?
How do I contact DJI. I found only options to send the product. Is there an option to send them files just for analysis?

This is why folks shouldn't use RTH as a routine.

Fly it home, it's safer.

 

[Yorkshire_Pud]

@Kajtek You might find this thread interesting, Very fast RTH descent caused hard landing - Mini 3 Pro

 

[Kajtek]

It was descending at a steady 10-11 feet/sec.
It takes time for the "brakes" to overcome inertia.
You cancelled autolanding at 12:17.9 and the descent slowed.
At 12:18.7 the VPS started to read whatever was below it and descent had slowed to 4.7 ft/s.
Half a second later it was 0.4 ft/s and VPS showed something 10.8 ft below.

No ... the drone "thought" it was 50 metres higher than the launch point, but had no idea how far it was above the ground until VPS found it at 12:18.7 - 17.7 ft below.

As explained above ... it did stop.

I'm not convinced that there was any problem except for the large difference in the barometric height reading.
But that had no effect on your landing anyway.

Thanks again. I bought the Mini 3 Pro because of the obstacle sensors. I believe that regardless of the barometric height, the system should have enough time to stop the drone or slow it down before it hits the ground. The descent speed seems to be too fast, or perhaps the obstacle sensors are not efficient enough. The lesson for me is to check the reported height, or even better, to use Return to Home (RTH) mode only until the drone reaches the home point and begins descending. At that point, I will stop RTH and land manually. Thanks again for your assistance. Understanding the deficiences helps ensure safe flying.

 

[Kajtek]

Thanks again. I bought the Mini 3 Pro because of the obstacle sensors. I believe that regardless of the barometric height, the system should have enough time to stop the drone or slow it down before it hits the ground. The descent speed seems to be too fast, or perhaps the obstacle sensors are not efficient enough. The lesson for me is to check the reported height, or even better, to use Return to Home (RTH) mode only until the drone reaches the home point and begins descending. At that point, I will stop RTH and land manually. Thanks again for your assistance. Understanding the deficiences helps ensure safe flying.

It was descending at a steady 10-11 feet/sec.
It takes time for the "brakes" to overcome inertia.
You cancelled autolanding at 12:17.9 and the descent slowed.
At 12:18.7 the VPS started to read whatever was below it and descent had slowed to 4.7 ft/s.
Half a second later it was 0.4 ft/s and VPS showed something 10.8 ft below.

No ... the drone "thought" it was 50 metres higher than the launch point, but had no idea how far it was above the ground until VPS found it at 12:18.7 - 17.7 ft below.

As explained above ... it did stop.

I'm not convinced that there was any problem except for the large difference in the barometric height reading.
But that had no effect on your landing anyway.

"Meta 4, I find your analysis very helpful, and in an attempt to understand, I analyzed the video recording using Premiere Pro to calculate times. Here's what I found:

The data log stops at 12.21.3 with a warning about the IMU. I referenced this point to the moment in the movie when the warning appears on the screen, which I call the IMU time warning.

At 12 minutes and 20.7 seconds (06 seconds before the IMU warning), there is a warning about the motor being unable to rotate. In the movie, this happens 0.82 seconds before the IMU warning.

At 12 minutes and 20.3 seconds (2.2 seconds before the IMU warning), the data log shows that the gimbal changes its angle from 90 to 49. This corresponds exactly to what is shown in the movie when I see the drone hitting the bush and the gimbal angle changing.

The movie shows a red warning about down obstacles 1.8 seconds before the IMU warning, which corresponds to 12 minutes and 19.5 seconds. The data log shows that the vertical speed is 0 (the same is shown in the movie, indicating that the downward speed is 0), but the drone is still descending and hits the bush 0.8 seconds later.

The movie shows an orange warning of a down obstacle 2.8 seconds before the IMU warning, which occurs at 12 minutes and 18.5 seconds. The data log shows a downward speed of 5.8 mph at that time.

The data log shows that the drone started decelerating at 12 minutes and 18.1 seconds from a speed of 10.5 meters per second before.

It appears that the timing in the data log and the movie of the IMU, motor warning, and the time when the drone hits the bush match each other. However, it is not clear why the data log shows zero descent speed before the drone hits the bush, even though it was actually descending. If the data log was correct, the drone would have stopped around 1 meter above the bush."

My excel file of the last part with movie reference

MiniPro3 Crash last seconds.xlsx

Microsoft Excel Workbook

1drv.ms

 

[Meta4]

At 12 minutes and 20.7 seconds (06 seconds before the IMU warning), there is a warning about the motor being unable to rotate. In the movie, this happens 0.82 seconds before the IMU warning.

Both of those warnings are caused by the props catching in the bush and the drone rolling upside down.

The data log shows that the vertical speed is 0 (the same is shown in the movie, indicating that the downward speed is 0)

The data shows zero descent speed from 12:19.5 until 12:20.3 because the barometric sensor showed no change in that time.

, but the drone is still descending and hits the bush 0.8 seconds later.

The movie shows an orange warning of a down obstacle 2.8 seconds before the IMU warning, which occurs at 12 minutes and 18.5 seconds. The data log shows a downward speed of 5.8 mph at that time.

The data log shows that the drone started decelerating at 12 minutes and 18.1 seconds from a speed of 10.5 meters per second before.

The descent speed was initially 2.6 metres/sec.
At the time the VPS was not reading anytjing below the drone.
That immediately slowed when the VPS sensed something 5.4 metres below the drone.
VPS is good at measuring to a hard, flat surface.
But it's going to have trouble measuring accurately to the top of a bush.

It appears that the timing in the data log and the movie of the IMU, motor warning, and the time when the drone hits the bush match each other. However, it is not clear why the data log shows zero descent speed before the drone hits the bush, even though it was actually descending. If the data log was correct, the drone would have stopped around 1 meter above the bush."
The video time starts when you pressed the video button.

The flight data starts when you started the motors.
I can't comment on how or whether your times actually match.
The VPS is what slows the descent but VPS won't be as reliable when you descend toward a less than optimal target like the top of a bush, with leaves and thin twigs in layers at different heights.

 

[Kajtek]

Both of those warnings are caused by the props catching in the bush and the drone rolling upside down.

The data shows zero descent speed from 12:19.5 until 12:20.3 because the barometric sensor showed no change in that time.

The descent speed was initially 2.6 metres/sec.
At the time the VPS was not reading anytjing below the drone.
That immediately slowed when the VPS sensed something 5.4 metres below the drone.
VPS is good at measuring to a hard, flat surface.
But it's going to have trouble measuring accurately to the top of a bush.

The flight data starts when you started the motors.
I can't comment on how or whether your times actually match.
The VPS is what slows the descent but VPS won't be as reliable when you descend toward a less than optimal target like the top of a bush, with leaves and thin twigs in layers at different heights.

Yes, the warnings occur when the drone hits the bush, and I synchronized the timing not from the start of the video, but by matching the points in time that corresponded to easily recognizable events in both the movie and the log file. When the camera angle changes in the movie, it corresponds to the moment when the gimbal angle changes from 90 degrees in the data log. By matching two such points, I believe there is enough evidence for a linear comparison.

I believe the system failed because, regardless of the barometric pressure, the purpose of the VPS is to prevent crashes, and the sensors should recognize obstacles and halt the descent. If it indeed recognized the obstacle 5.4 meters below, there should have been enough time to stop the drone.

The problem lies in the fact that the data log shows a vertical speed of zero, yet the drone was still descending.

The vertical speed is 0.8 seconds before the gimbal changes its angle, precisely (within milliseconds) when the drone hits the bush.

You explained that vertical speed is calculated from barometric pressure. If the speed is based on barometric pressure and it indicates that the drone is not descending, but in reality, the drone is still descending, then the algorithm is incorrect because it relies on inaccurate or unreliable data. I believe that once an obstacle is recognized, the drone should come to a stop and prompt the operator for further instructions. During one of my evening tests, the drone stopped 1 meter above the ground and asked for confirmation that the landing spot was suitable. I cannot recall the exact wording. I would appreciate your critique of my conclusion if you are still willing to discuss it.