Why I do believe there's a HUGE problem with the Mavic Mini - Flew AWAY the 2nd day

[m80116]

However, wouldn't the AC still return home upon reaching the low battery threshold? From the MM manual p. 13

Not only that but I am pretty much certain only the "AC disconnected" message was present, the remote was flashing.

 

[m80116]

Perhaps, but that doesn't explain why it didn't RTH.

Yes that's why I've always claimed I've had multiple failures.

Of course was probably my mistake to begin with... I shouldn't have flown the Mini for 300 meters above a city, it isn't built for that.

 

[m80116]

Have you sent both the txt and DAT logs to DJI?

No... they just said what was auto-uploaded from the Fly app was enough.

 

[m80116]

Did someone check the roofs??

Yes yes yes... please read my answers before and my blog if you're interested in the whole story.

We surveyed every roof possible from a skyscraper and on the ground, requesting access even to a nuns convent.

 

[sar104]

... requesting access even to a nuns convent.

Looking for consolation?

 

[m80116]

seeing his video of the flight is proof enough for me this was 100% user error.

I've never published a video of the flight. I think you're being very superficial...

Let's say it's my fault for believing the signal strength meter, and almost no warning notices during the whole flight.

Now try to explain to yourself why it drifted away from where it was and it did not even RTH.

 

[m80116]

Looking for consolation?

I was seeking for the divine providence

Redeem myself !

 

[m80116]

Looking at the map in post #54 and doing a bit of basic trig' [...]

Most of your work is very accurate. The distance and heights are pretty much spot on. The window to control the MM line of sigh was pretty much as narrow is you estimate, but I wasn't shadowed by the 6 storey building... and also I wasn't precisely at home point as I took off from there because I needed a space clear from the trees. Thanks anyway for taking your time to make such accurate analysis.

 

[m80116]

I've got mail from DJI

Here's an extract from the mail I received:

For your case CAS-3881070-T5R7Q6, we have finished the data analysis, and the result is as follows:

1. The aircraft worked under GPS mode and it responded to the pilot's commands well;
2. Flight Time T=07:21, Relative Height H=33 m, Distance to Home Point D=321.1 m, the pilot pulled back the pitch stick and the flight record ended when the aircraft was flying backward at a speed of 3.1 m/s;
3. Take-off point: 43.5666842 11.5343523; The last recorded point: 43.5651199 11.5310026.

The record ended without any sign of abnormality, so we could not verify what happened afterward.

They are offering me a 30% discount for another Mavic Mini. No options to get any other model but a Mini without the remote and the accessories, which makes me think, if you take the remote alone from a Mavic Mini package I reckon you can certainly say it's easily a 30% off the the product value... so practically they're offering me to pay for the whole thing, just sparing me the hassle of re-selling the brand new remote that every Mini ships with.

 

[Sticksandgrips]

I've never published a video of the flight. I think you're being very superficial...

Let's say it's my fault for believing the signal strength meter, and almost no warning notices during the whole flight.

Now try to explain to yourself why it drifted away from where it was and it did not even RTH.

You published the flight path. Which included multiple warnings in signal loss. And you still won’t admit you where way pst line of site.
almost no signal loss warnings are you kidding me.
Why it drifted away idk as you stated many times you where hitting buttons waiting do you not think things happen in the sky. Could be a gust of wind could have been you made contact with the sticks when slamming your finger to RTH when you realized you didn’t know what had happened.

 

[sar104]

I've got mail from DJI

Here's an extract from the mail I received:




They are offering me a 30% discount for another Mavic Mini. No options to get any other model but a Mini without the remote and the accessories, which makes me think, if you take the remote alone from a Mavic Mini package I reckon you can certainly say it's easily a 30% off the the product value... so practically they're offering me to pay for the whole thing, just sparing me the hassle of re-selling the brand new remote that every Mini ships with.

It's 30% off the price of just the aircraft, not the full package price. And that's the standard discount if you don't have an aircraft to send back to them.

 

[JAW]

It's 30% off the price of just the aircraft, not the full package price. And that's the standard discount if you don't have an aircraft to send back to them.

You might be able to up the 30% discount with a business like explanation of why you feel your MM did not behave as designed. Others have gotten the discount up to 45%, perhaps more. What you cannot explain away (even if DJI does not mention it) is the statement in the manual that you "Fly the aircraft only within your line of sight."

 

[Dakarenduro]

Considering the facts aeound your claim I would be super happy with a 30% discount.

 

[Meta4]

One of the judgement errors I've made is that I've scanned both 2.4 GHz and 5 GHz bands with my mobile phone

A lot of people have posted comments and advice and quite a lot is incorrect.
The wind, firmware, interference, battery level, flying out of sight and distance definitely were not an issue.
None of those should have prevented the drone from coming home.
There was a suggestion that the drone did not enter RTH, but there is no evidence to support that.
There's no evidence for anything after signal was lost.
Since the drone is programmed to RTH on loss of signal, and RTH is very reliable, the drone probably did start RTH but never made it home.

We have a case of a drone that should have made it home, but didn't.
Possible reasons for a case like this include:

1. Wind too strong for RTH
2. Battery level too low
3. Obstacles on the RTH path
4. Drifting without GPS
5. Sudden loss of power
6. Birdstrike or collision
7. RTH cancelled

1. NO - There was almost no wind and the light breeze would have helped the drone towards home anyway
2. NO - Battery level was at 76% and the drone was only 300 metres away
3. No obstacles high enough on the path from Loss of Signal to home point - OA & RTH OA was disabled
4. Unlikely as GPS was working well and the drone was in clear air
5. Only a very rare chance - there were no sudden control inputs prior to end of data
6. No - pitch, roll and yaw were all stable at end of data. If there was a collision ,it would show in the data
7. Maybe but low probability

If RTH was initiated as would be expected on LoS, we are left with 3, 5 or 7 as possible explanations.
The probability of each of these appears to be quite low.
This is one of those uncommon and very frustrating incidents where the cause of the loss of the drone is a mystery.
It can't be stated with any certainty what happened to the drone and it's impossible to blame either the pilot or DJI.
There just isn't any evidence to point to any cause at all.

 

[Deleted member 94047]

As pointed out by earlier by @slup in this thread, a cable disconnect between the RC and the mobile device can explain the sudden end of the log and why the AC did not RTH. The OP says all the lights on the RC were flashing; I don't know what that means - does the MM RC behave differently than the other remotes? In the MA for example, you can tell if the RC is connected to the AC by the colour of the connection status indicator led on the remote (Green=Connected; Red=Disconnected - there is no flashing). I think at this point, a cable disconnect remains very plausible.

 

[m80116]

I think at this point, a cable disconnect remains very plausible.

Even though I've verified my claim to having seen channels meter working I can't reproduce that with the remote alone.

What I can reproduce though is the message atop the camera view screen which says "Aircraft not connected to RC" when this not linked and I am almost 100% sure this was the case, as opposed to "RC not connected to mobile device" which is a very different one and easily self-explanatory error.

 

[m80116]

Possible reasons for a case like this include:

1. Wind too strong for RTH
2. Battery level too low
3. Obstacles on the RTH path
4. Drifting without GPS
5. Sudden loss of power
6. Birdstrike or collision
7. RTH cancelled

[...]
The probability of each of these appears to be quite low.

Thank You @Meta4 I am pretty much in line with your reasonable conclusions which still weight down my mind.

I feel I share a great deal of responsibility for the loss. I also feel I've been BETRAYED by a badly calibrated signal meter and aerial quality control information system. I have no idea how busy the 5.8 GHz band was which I considered back up if it was able to switch to it automatically at all.

My mistake was to believe the indicators. Whatever the reason was for the RTH to fail I still feel guilty for flying my MM with such a low power remote in such a challenging airspace.

 

[Deleted member 94047]

Even though I've verified my claim to having seen channels meter working I can't reproduce that with the remote alone.

What I can reproduce though is the message atop the camera view screen which says "Aircraft not connected to RC" when this not linked and I am almost 100% sure this was the case, as opposed to "RC not connected to mobile device" which is a very different one and easily self-explanatory error.

You saw these images from slup's post (#60) right? This is how GO4 displays a cable disconnect between the remote and the mobile device (first image) and a signal disconnection between the RC and AC (second image).




EDIT: I have been made aware that the MM's Fly app does not display disconnects like this and the MM's remote controller lacks the AC connection status indicator light.

The difference is subtle and it is easy to mistake one for the other*; since in both cases you lose the live feed from the AC's camera and flight telemetry and you get a blank screen with a lot of "N/A"s displayed where there should have been flight telemetry data. But I can't stress the importance of recognizing the difference between the two because while the AC will enter into RTH mode in the case of the second (if configured to do so), the AC will not respond to the first type of disconnect because it is still connected to the remote controller and will execute any commands given to it. But since the link between the remote controller and the mobile device is severed, the app cannot receive any data from the AC **. The pilot does not have real time flight data and visual feedback but still has full control of the AC.

Having said all that, I have never flown the MM and I don't know how similar the DJI Fly app is to GO4 in this regard. Some one who has flown with both can perhaps fill us on this detail. I am unable to comment on your claim that the Fly app displays "Aircraft not connected to RC" and "RC not connected to mobile device" but I am skeptical that this is the case. I am also confused by this claim you make

I've verified my claim to having seen channels meter working

Did you do this at the time of the incident; i.e., after you lost connection with the AC. Or are you saying you verified you can do this without the RC needing to be connected to the AC post the incident?

Finally, I urge you to rethink this "I know everything I need to know and I know what I am doing" attitude of yours. The capacity to be critical about your self, your skills, knowledge, and responses in the case of emergencies is one you require if you want to be a better pilot in the future. No, I am not saying this unfortunate incident was your fault. But you started from a position that aggressively maintained you were not part of what caused the incident. As the pilot in command, you have the biggest and most important part to play in any flight. Caution, situational awareness, and preparedness to handle unforeseen and unexpected events is what separates a good pilot from a not so good one. So please, get a little more self critical as that will help you a lot in learning and being better prepared in the future to handle situations like this. This is meant as a friendly advice, you can take or leave it; your choice.

_______________
* In case one is not certain about the specific nature of the disconnection, a quick look at the RC-AC connection status light will confirm a signal loss between the RC and AC; as I mentioned in an earlier post, the connection status indicator turns red in the case of a connection loss between the two. EDIT: this does not apply to the MM as its remote does not have this indicator.

** This includes flight data coming from the AC which is received by the RC, which is then fed to the app used to fly the AC through the physical link (the USB cable) between the RC and the phone, which is then recorded by the app into the mobile device memory as a flight log. This means that when the physical link between remote and mobile device is severed, the flight log ends - most of the time abruptly.

 

[ea4eob]

I believe the prompt goes on and it initiates auto-RTH automatically when no key is pressed to cancel it. I've already tested this feature.

I lost the signal 29 Dic 2019 and when I had restared the RC, the link has been stablished and the M2P was autolanding (over the sea!!!), GPS sats sincronizad was 0 Sats... Disconection and lost GPS at time and could not star RTH... only autolanding...

Only turn off and on the RC could save the M2P...

Best regards.

Rafa

 

[Dakarenduro]

A lot of people have posted comments and advice and quite a lot is incorrect.
The wind, firmware, interference, battery level, flying out of sight and distance definitely were not an issue.
None of those should have prevented the drone from coming home.
There was a suggestion that the drone did not enter RTH, but there is no evidence to support that.
There's no evidence for anything after signal was lost.
Since the drone is programmed to RTH on loss of signal, and RTH is very reliable, the drone probably did start RTH but never made it home.

We have a case of a drone that should have made it home, but didn't.
Possible reasons for a case like this include:

1. Wind too strong for RTH
2. Battery level too low
3. Obstacles on the RTH path
4. Drifting without GPS
5. Sudden loss of power
6. Birdstrike or collision
7. RTH cancelled

1. NO - There was almost no wind and the light breeze would have helped the drone towards home anyway
2. NO - Battery level was at 76% and the drone was only 300 metres away
3. No obstacles high enough on the path from Loss of Signal to home point - OA & RTH OA was disabled
4. Unlikely as GPS was working well and the drone was in clear air
5. Only a very rare chance - there were no sudden control inputs prior to end of data
6. No - pitch, roll and yaw were all stable at end of data. If there was a collision ,it would show in the data
7. Maybe but low probability

If RTH was initiated as would be expected on LoS, we are left with 3, 5 or 7 as possible explanations.
The probability of each of these appears to be quite low.
This is one of those uncommon and very frustrating incidents where the cause of the loss of the drone is a mystery.
It can't be stated with any certainty what happened to the drone and it's impossible to blame either the pilot or DJI.
There just isn't any evidence to point to any cause at all.

But if the flight was kept within VLOS then there would be no guessing and perhaps a drone recovery, correct?