Crashed my MA2. Drone or pilot error? [logs+pics]

[szakeetm]

Could you help me determine what happened?

I flew in a mountaineous area. I started ascending.

- Until 2:00 business as usual, I climb.
- 2:01, 460m above takeoff point: "motor error, check propellers" message. I immediately started descending.
- 2:25, 400m above: the descent rates accelerates from 10km/h to 17km/h but recovers after a few seconds
- 2:35, 385m above: second "motor error" message
- 3:04, 297m above: "max power load reached" message appears and stays on for the rest of the flight
- 3:20, 225m above: descent rate is already 20km/h
- 3:25, 200m above: I can hear the drone spinning at max RPM, descent rate suddenly increases to 35km/h
- 3:27, 174m above: descent rate 71km/h (!), "sensor error" message
- 3:29, 105m above: last data point, 65km/h descent rate, "sensor error"

Then I heard a thumpf as the drone crashed and the RC disconnected.

Luckily, the last GPS position was accurate so I found it in the forest:



Evident damage: propeller damage, cracked camera cover, but the drone body doesn't show damage signs, yet can't take off due to ESC error:




Initially it wouldn't turn on at all, then 5 minutes later (cool down? dry out?) it turns on, connects, but exhibits "ESC error".

Log files and pics here:

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I have DJI refresh, so one way or other I'll get this sorted out, but I wonder if it's a warranty case. Thanks!

 

[Meta4]

Could you help me determine what happened?

Your flight data looks like this:

DJI Flight Log Viewer | Phantom Help

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Your Mavic was holding altitude when you left it hovering for 4 seconds after 2:05.9.
Then you descended until 3:02 and the Mavic was unable to maintain altitude while hovering.
It just continued descending at 3 m/sec, the same as it had done while you held the left stick full down.
At around 3:03 something happened which started the drone rocking up to 40° to the left and right.
By 3:10 the speed of descent had increased to 4.7 m/s.
At 3:21.6 you tried to fly forward but the drone just started tumbling and the descent accelerated to at least 17 m/s.
There are some higher speeds shown after that but they may be due to false GPS readings while the drone was tumbling fast.

The data stops at 3:29.6 when the drone would have been about 48 metres above ground level.

The data suggests some kind of malfunction rather than a user error as the cause.
It was not a battery problem as it still had full power during the crash.
All props and motors were working normally, but something prevented the drone from braking after the descent finished at 3:02.

It's hard to tell if using the left stick might have helped, but you didn't try that at all during the descent.

You should synch your flight data and contact DJI's online support to see what they say.
You might be lucky and have a case for a warranty replacement.

 

[DanMan32]

400m above TO? Not related to the failure but why?

 

[szakeetm]

Thank you @Meta4 for the time you looked at my data.
When looking at the Airdata analysis, I get several "motor is blocked" errors (first at 3:24). According to your analysis, however, they were working fine until the end. When I recovered the drone, one of the prop fastening clips was broken and in the motor, which can either be the cause or a result of the crash, we'll never tell.

As for the altitude, I was at the bottom of a steep hill, above takoff was much more than above ground (around 150m).

 

[Meta4]

Thank you @Meta4 for the time you looked at my data.
When looking at the Airdata analysis, I get several "motor is blocked" errors (first at 3:24). According to your analysis, however, they were working fine until the end. When I recovered the drone, one of the prop fastening clips was broken and in the motor, which can either be the cause or a result of the crash, we'll never tell.

You descended until 3:02.2 when you centred the sticks but the drone kept descending.
If one motor was malfunctioning, the drone would have dipped where the faulty motor was and started spinning.
But the drone was descending and not spinning until 3:23.3 when it started tumbling and spinning.
Obviously there was another issue from then on which cause the drone to tumble but the cause of the crash is evident 20 seconds earlier in the data.

 

[Heindrich1988]

400m above TO? Not related to the failure but why?

Presumably he's flying uphill.

 

[Howard70]

Could you help me determine what happened?

I flew in a mountaineous area. I started ascending.

- Until 2:00 business as usual, I climb.
- 2:01, 460m above takeoff point: "motor error, check propellers" message. I immediately started descending.
- 2:25, 400m above: the descent rates accelerates from 10km/h to 17km/h but recovers after a few seconds
- 2:35, 385m above: second "motor error" message
- 3:04, 297m above: "max power load reached" message appears and stays on for the rest of the flight
- 3:20, 225m above: descent rate is already 20km/h
- 3:25, 200m above: I can hear the drone spinning at max RPM, descent rate suddenly increases to 35km/h
- 3:27, 174m above: descent rate 71km/h (!), "sensor error" message
- 3:29, 105m above: last data point, 65km/h descent rate, "sensor error"

Then I heard a thumpf as the drone crashed and the RC disconnected.

Luckily, the last GPS position was accurate so I found it in the forest:



Evident damage: propeller damage, cracked camera cover, but the drone body doesn't show damage signs...

Hello Zakeetm:

Do you think there is any chance that a bird may have attacked your drone? I had a similar occurrence (although my drone recovered and I managed to land it) this summer when flying along cliffs in New Mexico. When I examined the drone there was prop damage and small nicks in the drone’s body that appear to have been caused by talons. Like yours, my drone was a couple hundred feet above ground and far from any potential for collision.

Howard

 

[Meta4]

Hello Zakeetm:

Do you think there is any chance that a bird may have attacked your drone?

No .. if it was the pitch, roll and yaw data would have shown sudden large changes to indicate the collision/attack.
But the drone is stable when the problem starts .. except that it cannot maintain altitude.

 

[szakeetm]

I agree with @Meta4 that the problem seems to start "gradually", with no abrupt change hinting at a collision. Also, a drone with its 7000rpm blades is scarily noisy, I guess most birds would avoid it (it certainly scares smaller birds on the ground away, noticed when flying over fields).

One last thing I can think of is it was a day with 5C temp and 70%+ humidity at takeoff point. At 460m above, I might have just crossed the dew point (minus few degrees), so maybe quick condensation caused a malfunction? Then again, the drone, the battery and the motors are warm in flight, and people get away with flying their drone in the rain. Also, the problems started at ~3 minutes, a little too quick for fatal condensation buildup.



Opened a case with DJI, waiting for the return label, asked for detailed analysis instead of the quicker DJI refresh option. Will share updates.

 

[DanMan32]

Presumably he's flying uphill.

I interpreted "above TO" as directly above rather than TO just being a 0 reference point lik sea level with height directly below AC at a more reasonable height.

 

[szakeetm]

I believe this is exactly what happened to my drone:

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The benign, light fog at takeoff point (5C temp, 76% humidity) was actually a freezing fog 460m above. The fast airstream that the drone generates probably iced up the props, creating imbalance and extra weight.

The drone is on the way to DJI, I asked for a full crash analysis (instead of the quick&easy DJI care refresh exchange), will report back when they do.

 

[szakeetm]

DJI just got back to me: this is a warranty case and they will repair the drone for free.

 

[boblui]

Thanks for sharing the flight log which is very helpful in understanding how the drone will behave when prop icing occurs.

124 seconds into the flight the current drawn from the battery started to increase and the voltage decreased at an accelerated rate. The current near the end of the flight was around 9 A compared with 3.3 A at the beginning.




Prop icing started occurring at the right-front motor followed by the left-front and left-back motors. The right-back motor seems to be not affected.



The speeds of the affected motors actually did not increase as reported. As a matter of fact, the speed of the right-back motor, the only one not suffering from prop icing, was redued. The perception of increase in RPM is probable due to the air being broken up by the ice accumulated on the prop.