MM went berserk and dove into the river!

[JPthePilot]

I’ve been flying my MM for 3 months. On 05 Dec, I planned to fly it over a small river filming the coloured housings along it. GPS signal was weak at first. I proceeded to position the drone in the centre of the river, then had it move forward in C mode. After a few seconds, it went crazy... returned towards me, increased its speed, and crashed into the retaining wall behind me... then, it turned around and flew towards the river and dove right in it... i could not recover it... As i walked over the other side of the river to try to recover my drone, I saw another person operating another drone (not sure what type as he was gone when i returned aftewards to talk with him...). Could it be interferences from his remote control? Or, a malfunctions?

 

[Repaid1]

I’ve been flying my MM for 3 months. On 05 Dec, I planned to fly it over a small river filming the coloured housings along it. GPS signal was weak at first. I proceeded to position the drone in the centre of the river, then had it move forward in C mode. After a few seconds, it went crazy... returned towards me, increased its speed, and crashed into the retaining wall behind me... then, it turned around and flew towards the river and dove right in it... i could not recover it... As i walked over the other side of the river to try to recover my drone, I saw another person operating another drone (not sure what type as he was gone when i returned aftewards to talk with him...). Could it be interferences from his remote control? Or, a malfunctions?

No.

 

[Thomas B]

No, your drone and controller are uniquely linked devices

 

[Meta4]

After a few seconds, it went crazy... returned towards me, increased its speed, and crashed into the retaining wall behind me... then, it turned around and flew towards the river and dove right in it.

The explanation for the incident is clear when you look closely at the flight data.

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You must have been flying from a place where tree cover or terrain prevented the GPS receiver from having a clear sky view.
Because of this your drone never had any GPS position information at all for the flight, not even approximate position data.
Lighting conditions were good enough for the VPS sensors to detect the water surface below the drone and give a distance measurement to the water.
But the water surface does not have anything recognisasble for the VPS to lock on to and provide horizontal position holding.
So for the whole, short flight, the drone had no way to maintain horizontal position.
You had full control but it would have confused you to find that your drone had no "brakes" and would continue flying when you went hands off.
Unfortunately for you, you used lots of full stick input.

Imagine driving fast on ice with no brakes and that's what your flight was like.

I saw another person operating another drone (not sure what type as he was gone when i returned aftewards to talk with him...). Could it be interferences from his remote control? Or, a malfunctions?

No

 

[slup]

...GPS signal was weak at first.
...After a few seconds, it went crazy...
...returned towards me, increased its speed
...Could it be interference from his remote control? Or, a malfunctions?

Yeah ... the GPS signal was weak, that's one way to put it.

If you look at the blue graph here below first ... that's the #sats that was locked & it was 7 at most, too low in order to have a proper positioning & a HP recorded. Then if you look at the bright green graph in the bottom of the chart it says 0 in navhealth the whole flight. That means that the flight controller didn't had any trust in the position accuracy at all.

So all this meant that your Mini was position wise, in unaided state the whole flight. This also meant that it didn't break by itself after releasing the sticks or held position by it self.

In the chart you also have all your stick inputs ... several full 100% commands, most of them probably in panic not understanding what was going on... & that is why your Mini rapidly gained speed & crashed.

So all in this short 48sec flight was due to that you didn't waited for a position lock before you took off ... unfortunately all this is nothing else than a pilot error, it had nothing to do with interference from another drone operation or a malfunction.

(Click on the chart to make it larger)

 

[Drone Views Media]

I’ve been flying my MM for 3 months. On 05 Dec, I planned to fly it over a small river filming the coloured housings along it. GPS signal was weak at first. I proceeded to position the drone in the centre of the river, then had it move forward in C mode. After a few seconds, it went crazy... returned towards me, increased its speed, and crashed into the retaining wall behind me... then, it turned around and flew towards the river and dove right in it... i could not recover it... As i walked over the other side of the river to try to recover my drone, I saw another person operating another drone (not sure what type as he was gone when i returned aftewards to talk with him...). Could it be interferences from his remote control? Or, a malfunctions?

I'm sorry to hear that you lost your MM; unfortunately this one goes down to user error. One of my golden rules is to never take off without a proper GPS lock, especially since most of my flights are over water

 

[boblui]

I have taken a deeper look at the flight log and my conclusion is that the sudden increase in the speed of the craft was due to the craft switching to ATTI mode in which the speed change is a lot more sensitive to stick input compared with that in tripod mode ( or C mode ) which was selected throughout the flight.

This chart summarizes the forward/backward ( or elevator ) control applied. Basically you flew the craft out by appling forward stick and then back by backward stick. The orientation of the craft has not changed much , ie, the nose kept facing the river.



The next chart shows what caught you by surprise. The GPS signal was too weak to to be usable and the craft kept switching between vision and ATTI mode. In vision mode, the craft braked automatically whenever the stick was released ( the black circles ) so you didn't feel anything abnormal even when GPS was not available.

For Mini the max speed in C mode is limited to 4 m/s which corresponds to a maximum steady tilt of about 7 degrees as shown in the earlier part of the flight. However, in ATTI mode, the allowed tilt is much larger so if the craft switches from C mode to ATTI mode under full elevator input, the tilt will suddenly jump and the speed abruptly increase. This has occurred twice in the later part of the flight. In the first occurrence you released the stick immediately and by coincidence the craft switched back to C mode at the same time and braked automatically. No harm done. Then after about 5 seconds later it happened again and you applied full counter elevator input but unfortunately the craft switched back to C mode and therefore could not tilt enough to stop in time. Collision followed immediately.

 

[JPthePilot]

I have taken a deeper look at the flight log and my conclusion is that the sudden increase in the speed of the craft was due to the craft switching to the ATTI mode in which the speed change is a lot more sensitive to stick input compared with that in tripod mode ( or C mode ) which was selected throughout the flight.

This chart summarizes the forward/backward ( or elevator ) control applied. Basically you flew the craft out by appling forward stick and then back by backward stick. The orientation of the craft has not changed much , ie, the nose kept facing the river.

View attachment 119167

The next chart shows what caught you by surprise. The GPS signal was too weak to to be usable and the craft just switched between vision and ATTI mode. In vision mode, the craft braked automatically when the stick was released as indicated by the black circles.

For Mini the max speed in C mode is limited to 4 m/s which corresponds to a maximum steady tilt of about 7 degrees as shown in the earlier part of the flight. However, in ATTI mode, the tilt is much bigger so if the craft switches from C mode to ATTI mode under full elevator input, the tilt will suddenly jump and the speed abruptly increase. This has occurred twice in the later part of the flight. In the first occurrence you released the stick immediately and by coincidence the craft switched back to C mode at the same time and braked automatically. No harm done. Then after about 5 seconds later it happened again and you applied full counter elevator input but unfortunately the craft switched back to C mode and could not tilt enough to stop in time. Collision followed immediately.

View attachment 119168

Wow! I appreciate the analysis and the level of details. I underestimated the importance of flying with GPS connection... Experience comes at a cost unfortunately... Now, I have to buy a new MM (alone) $$$ thanks all for input!

 

[Starz]

“Home point recorded”
words to live by if you fly DJI

 

[DanMan32]

Even better, she tells you to verify the HP.

"The home point has been updated, please check it on the map"

 

[Michael Ainsworth]

Don’t have MM, but I Never take off without the “Home point has been updated please check it on the map”. Many people fly without this and get away with it but at some stage there will be a problem.
I am OCD, can’t afford replacement drones and am afraid of going back home to my financial manager to tell her I lost my drone. ?

 

[Platinum 4 ever]

Wow! I appreciate the analysis and the level of details. I underestimated the importance of flying with GPS connection... Experience comes at a cost unfortunately... Now, I have to buy a new MM (alone) $$$ thanks all for input!

Well... look on the bright side..you have a good excuse to get a mini 2..[emoji41]. Just remember. They are not fond of water [emoji97]

 

[MM2]

Wow! I appreciate the analysis and the level of details. I underestimated the importance of flying with GPS connection... Experience comes at a cost unfortunately... Now, I have to buy a new MM (alone) $$$ thanks all for input!

Maybe read the manual first before you buy otherwise you will be at risk of wasting even more of your money