My Mavic Air falled from the SKY! Can anyone explain why?

[salimco]

Hello, Yesterday while I fly mavic air, it suddenly stop working and falled from the sky to the snowy ground. Two propellers broke and I don't know if it is working now or not. It is waiting in rice now in case of get water inside) Weather was calm, little bit foggy but no raining or snowing. Temperature is around 0 Celsius. This happened for the first time in last 4 months I start using it. I really wonder why this happened? I got the flight record and sharing them as well. Can anyone interpret this values? Before the drop, I see that it gives motor obstracted error but what could be the reason for this error? Just before it stopped, I feel something is wrong with it because it was shaking in air and I started to bring it down but it stopped suddenly I really believed in DJI quality until this happened and I don't know how can I fly it anymore especially over lakes and seas anymore. DJI Flight Log Viewer | Phantom Help Upload and view flight logs from your DJI drones www.phantomhelp.com Thank you Salim

 

[Mulberry]

Flying in fog at 0 Deg temperature almost certainly led to icing on your props. This would cause the motor overload, erratic flying behaviour and eventually the failure of the flight altogether.

 

[bumper]

Besides gravity, and just a guess, falling may have been assisted by fog, visible moisture, in freezing conditions. This has the potential to cause ice to build rapidly on surfaces including propeller blades. Ice can cause an imbalance, perhaps resulting in the shaking you observed. Air, along with that moisture, also flows down through the motors for cooling, if it's cold enough, ice could form in the motor too (although the motor windings tend to warm things, might not have been enough.

Edit: Didn't see Mulberry's post when I wrote the above . . . we're thinking the same thing.

 

[salimco]

Flying in fog at 0 Deg temperature almost certainly led to icing on your props. This would cause the motor overload, erratic flying behaviour and eventually the failure of the flight altogether.

Thank you for your reply. I know it is not the optimum condition to fly but I think it should be smart enough to warn like "don't take off" or after take off "low tempeture, emergency landing" in cold weather conditions etc.

The thing I wonder actually, is flight records tell the exact reason?

 

[Olav van Gerven]

The flight record (as far as I understand) shows three issues, two of them seem to be related:
1) You get a warning that the batterytemperature at start is to low and you should warm the battery. This at first seems to be a not so critical information but...
2) During the flight you have several severe battery problems. i.m.o. they are related to the warning at the start: Your battery was to cold.
and then the final and fatal error to the end of the log:
3) There are three warnings of an obstructed motor. Though not directly related to the battery temperature warning, this warning gives a good indication why you crashed: Most likely is, what was stated before by the other comments, that you had ice build up on your props and possibly in the motor. This, combined with a battery that had some issues only moment before, might have led to the crash.

Conclusion: The hardest conclusion in tihs is, that it was a clear pilot error. You ignored the warning and if the only damage after all indeed is two damaged props, you are very lucky. The idea of drying the drone after this incident is good, as the ice melts, water comes and even if it is not much, it might cause further damage.

 

[salimco]

The flight record (as far as I understand) shows three issues, two of them seem to be related:
1) You get a warning that the batterytemperature at start is to low and you should warm the battery. This at first seems to be a not so critical information but...
2) During the flight you have several severe battery problems. i.m.o. they are related to the warning at the start: Your battery was to cold.
and then the final and fatal error to the end of the log:
3) There are three warnings of an obstructed motor. Though not directly related to the battery temperature warning, this warning gives a good indication why you crashed: Most likely is, what was stated before by the other comments, that you had ice build up on your props and possibly in the motor. This, combined with a battery that had some issues only moment before, might have led to the crash.

Conclusion: The hardest conclusion in tihs is, that it was a clear pilot error. You ignored the warning and if the only damage after all indeed is two damaged props, you are very lucky. The idea of drying the drone after this incident is good, as the ice melts, water comes and even if it is not much, it might cause further damage.

Thank you for the reply. Yes, it is probably occured as you mentioned. This was an important learning moment for me as I didn't think it can crash in this way. Will be more careful in future trys.
Thanks

 

[Lastrexking]

Thank you for your reply. I know it is not the optimum condition to fly but I think it should be smart enough to warn like "don't take off" or after take off "low tempeture, emergency landing" in cold weather conditions etc.

The thing I wonder actually, is flight records tell the exact reason?

It is smart enough. You had multiple warnings on battery temperature. You ignored them. Also, you should have known not to fly in those conditions- that’s your responsibility.

 

[Olav van Gerven]

It is smart enough. You had multiple warnings on battery temperature. You ignored them. Also, you should have known not to fly in those conditions- that’s your responsibility.

To the defent: Looking back, it is obvious that the filght was not a good idea, but if you are an unexperienced pilot and see what some experienced pilots come away with, you might be tempted to try it anyway. Add to that, that the drone even after the warning about the battery before take-off, seemed to operate normal, I can imagine that this mistake was made.
The pilot learned his, maybe expensive, lesson and others might benefit from his mistake.

 

[salimco]

To the defent: Looking back, it is obvious that the filght was not a good idea, but if you are an unexperienced pilot and see what some experienced pilots come away with, you might be tempted to try it anyway. Add to that, that the drone even after the warning about the battery before take-off, seemed to operate normal, I can imagine that this mistake was made.
The pilot learned his, maybe expensive, lesson and others might benefit from his mistake.

Yes for sure this was an important learning for me

 

[Deleted member 94047]

Yes for sure this was an important learning for me

I am glad you took this as a good learning opportunity. You had plenty of warning. The first was obviously the app telling you the battery temp was too low. The second warning you should have taken notice of is the voltage of the battery cells. You started with a fully charged battery and you should see a voltage of around 4.25v per cell at the start. Yours started at 3.6v, way too low for a fully charged battery. The cell voltage dropped to below 3.6 within the first 20 seconds of your flight while your battery was still showing 97% capacity. That should have also been a warning the battery was not performing well if you had taken notice. Normally, a battery voltage of 10.8v and individual cell voltages of about 3.60v are what you would expect at around 25-30% of battery and you ought to be landing soon. In your case, these were the voltages you had at take off with a fully charged battery.

For next time, check the individual cell voltages of the battery before take off and once in a while while in flight. The battery percentage is not always the best indicator of the state of your battery.

 

[new2mavic]

I don't think neither the battery temperature nor "motor obstructed" are the causes of the "crash" because the craft did keep flying right ? The craft responded correctly to the throttle stick input throughout the flight and starting from 4 min 1.8 sec, the throttle stick was held fully down until it hit something at about 90 ft ( trees? ). It looks like a normal landing to me.

 

[Deleted member 94047]

I don't think neither the battery temperature nor "motor obstructed" are the causes of the "crash" because the craft did keep flying right ? The craft responded correctly to the throttle stick input throughout the flight and starting from 4 min 1.8 sec, the throttle stick was held fully down until it hit something at about 90 ft ( trees? ). It looks like a normal landing to me.

View attachment 90752

The throttle stick was indeed held down at the end of the recorded flight; the AC descended from a height of 48.6m to 25.2 and then the log ends. Hard to say it landed normally at 25m above ground.

 

[Simmo]

@sar104 ?

 

[new2mavic]

The throttle stick was indeed held down at the end of the recorded flight; the AC descended from a height of 48.6m to 25.2 and then the log ends. Hard to say it landed normally at 25m above ground.

View attachment 90756

The VPS altitude dropped to zero at the end of the log. May be the craft considered the flight ended and shut off the motors ?

 

[Olav van Gerven]

I don't think neither the battery temperature nor "motor obstructed" are the causes of the "crash" because the craft did keep flying right ? The craft responded correctly to the throttle stick input throughout the flight and starting from 4 min 1.8 sec, the throttle stick was held fully down until it hit something at about 90 ft ( trees? ). It looks like a normal landing to me.

View attachment 90752

I looked at the flightpattern in Google Earth (using the KMZ file from the log). There seems to be no obstacle as the drone crashed. The downwards move stopped just before the first obstrucion warning came.

 

[new2mavic]

I looked at the flightpattern in Google Earth (using the KMZ file from the log). There seems to be no obstacle as the drone crashed. The downwards move stopped just before the first obstrucion warning came.

I came to the judgment that it hit something because the VPS altitude dropped to zero and the craft suddenly tilted to one side near the end of the log. May be it hit a tree branch. Google earth can only show the height of the ground surface in 3D but not other objects on the ground such as trees, poles and most man-made structures

 

[InvisibleName]

Thank you for your reply. I know it is not the optimum condition to fly but I think it should be smart enough to warn like "don't take off" or after take off "low tempeture, emergency landing" in cold weather conditions etc.

The thing I wonder actually, is flight records tell the exact reason?

Sorry for your 'accident' but I don't think you can blame DJI - maybe you should have been "smart enough" to consider the weather conditions and not fly? After-all, you, as the pilot, were responsible for the safety of yourself, the drone and others around you!

 

[salimco]

I came to the judgment that it hit something because the VPS altitude dropped to zero and the craft suddenly tilted to one side near the end of the log. May be it hit a tree branch. Google earth can only show the height of the ground surface in 3D but not other objects on the ground such as trees, poles and most man-made structures

Actually it didn't hit to anything, I was watching the drone and it stop suddenly and start falling. As I started to bring it down, it was little bit foggy and maybe it could sense the fog as a ground and perceived it as landed?
After it dropped there was another warning "Vision Sensor Calibration Error ".

By the way, I just changed the propillar and recalibrate it and it is surprisingly working fine I guess.

 

[dkuhne]

Actually it didn't hit to anything, I was watching the drone and it stop suddenly and start falling. As I started to bring it down, it was little bit foggy and maybe it could sense the fog as a ground and perceived it as landed?
After it dropped there was another warning "Vision Sensor Calibration Error ".

By the way, I just changed the propillar and recalibrate it and it is surprisingly working fine I guess.

Lucky man!
You can use ‘hand warmers’ to warm your batteries if you must fly in the snow/cold.

ive heard never to fly in fog, as the bottom sensors cannot be turned off. (Even when you turn the rest of them off)

 

[new2mavic]

Actually it didn't hit to anything, I was watching the drone and it stop suddenly and start falling. As I started to bring it down, it was little bit foggy and maybe it could sense the fog as a ground and perceived it as landed?
After it dropped there was another warning "Vision Sensor Calibration Error ".

By the way, I just changed the propillar and recalibrate it and it is surprisingly working fine I guess.

You meant the motors stopped in the air ? if that was the case, it probably thought it has landed.
I did notice the message "Downward altitude sensor data error. Please contact DJI Support for help." but as it has appeared only once I haven't paid much attention to it. May be it has momentarily detected some negative VPS height hence the error message.