First crash, repair, but loss of confidence in the drone

[stberlin]

It's my first flyaway / crash since I bought the drone in Feb 2018. I've flown this drone in Iceland, Hawaii, Italy, but mostly downtown where I live (before traffic and tourists). Not once it disconnected and flew in reverse on its own.

In Alaska, it flew backwards at 20 mph. But I guess, I'm lucky that it hit a tree, or it would have flown to the mountains or deeper into the forest. I recovered the drone but I didn't try hard enough to find the right rear arm that snapped off -- a mistake.


What might have happened:

1. I was getting several update messages which I usually ignore including the No-Fly Zone update. I might have updated the NFZ first. But I think one of the updates triggered a forced update of other wares including firmware.

Some "features" of the AC will not function if I don't update.
Another required for things to be "in synch."
I might have updated the Go 4 app along with the rest.
Finally, a firmware update to fix the issue of lost connection in Panama.

2. When the app prompted to calibrate the compass the next day, I did so on the side of the road, close to a guardrail.

3. DJI Go also says that I have low space on my phone.


Here's the log: DJI Flight Log Viewer - PhantomHelp.com I don't know how to read this. So I hope someone else can shed light on what really happened. Right now, I'm just guessing.

quick repair:



New arm bracket. I should've looked for that broken arm. I didn't pay attention to how it snaps close or open the arm. I had to redo while the wires were already soldered. I hope I didn't pull the wires too much away from the motor.



New motor/arm assembly with temporary prop lock screws and spring from a click pen. By not recovering the arm, my new motor did not come with a propeller lock, screws and spring. The arm also needed two screws to secure it to the bracket. The Mavic Air screw set from Rotorlogic have those arm screws but not for the prop lock.



+PLU Series Fabtech adhesive.




Overkill? Replaced GPS and IMU modules because, first, I lost confidence in the drone. Second, my drone always yaws to the left about 5 degrees during first take-off of the day. It didn't fix that problem upon test, and the new GPS module from Rotorlogic is faulty. I get the "satellite positioning off" error and the satellite connection count constantly changes every second by 2-3 satellites. Reinstalling the original module fixed these issues. The older module has a better lock on the satellites.

 

[stevenqx]

Overkill? Replaced GPS and IMU modules because, first, I lost confidence in the drone. Second, my drone always yaws to the left about 5 degrees during first take-off of the day. It didn't fix that problem upon test, and the new GPS module from Rotorlogic is faulty. I get the "satellite positioning off" error and the satellite connection count constantly changes every second by 2-3 satellites. Reinstalling the original module fixed these issues. The older module was a better lock on the satellites.

Sorry for what happened...mine do the same about yawing 5 degrees after take off when i push all the way up. But i live with that, it's happening after 1.5 firmware update, I don't think is a big problem, i read that someone solve this by demagnetize the compass...

 

[sar104]

It's my first flyaway / crash since I bought the drone in Feb 2018. I've flown this drone in Iceland, Hawaii, Italy, but mostly downtown where I live (before traffic and tourists). Not once it disconnected and flew in reverse on its own.

In Alaska, it flew backwards at 20 mph. But I guess, I'm lucky that it hit a tree, or it would have flown to the mountains or deeper into the forest. I recovered the drone but I didn't try hard enough to find the right rear arm that snapped off -- a mistake.


What might have happened:

1. I was getting several update messages which I usually ignore including the No-Fly Zone update. I might have updated the NFZ first. But I think one of the updates triggered a forced update of other wares including firmware.

Some "features" of the AC will not function if I don't update.
Another required for things to be "in synch."
I might have updated the Go 4 app along with the rest.
Finally, a firmware update to fix the issue of lost connection in Panama.

2. When the app prompted to calibrate the compass the next day, I did so on the side of the road, close to a guardrail.

3. DJI Go also says that I have low space on my phone.


Here's the log: DJI Flight Log Viewer - PhantomHelp.com I don't know how to read this. So I hope someone else can shed light on what really happened. Right now, I'm just guessing.

quick repair:

View attachment 73168 View attachment 73169

New arm bracket. I should've looked for that broken arm. I didn't pay attention to how it snaps close or open the arm. I had to redo while the wires were already soldered. I hope I didn't pull the wires too much away from the motor.

View attachment 73167

New motor/arm assembly with temporary prop lock screws and spring from a click pen. By not recovering the arm, my new motor did not come with a propeller lock, screws and spring. The arm also needed two screws to secure it to the bracket. The Mavic Air screw set from Rotorlogic have those arm screws but not for the prop lock.

View attachment 73166

+PLU Series Fabtech adhesive.


View attachment 73170 View attachment 73171

Overkill? Replaced GPS and IMU modules because, first, I lost confidence in the drone. Second, my drone always yaws to the left about 5 degrees during first take-off of the day. It didn't fix that problem upon test, and the new GPS module from Rotorlogic is faulty. I get the "satellite positioning off" error and the satellite connection count constantly changes every second by 2-3 satellites. Reinstalling the original module fixed these issues. The older module was a better lock on the satellites.

If you looked at the log viewer you may have noticed the aircraft orientation arrow at takeoff:



Was that the direction it was pointing? It seems unlikely given that you said it flew backwards. Looking at the yaw vector during the flight indicates it flew forwards:



If that was incorrect, which is likely the case from your description, then it's consistent with the reported compass errors, and the uncontrolled flight resulted from the IMU yaw being incorrect and the FC consequently applying the wrong corrections to stabilize the aircraft.

 

[stberlin]

Was that the direction it was pointing? It seems unlikely given that you said it flew backwards. Looking at the yaw vector during the flight indicates it flew forwards:

Thanks for checking.

I usually position the drone facing the direction where it's headed, towards the awesome view.
or I could have placed it facing to the right of this photo, down the highway. but I doubt that.
I calibrated the compass right there when it asked, between the car parked on the side and that guardrail.
When it hit the tree at 20 mph, it broke off the rear arm, not one of the front arms or camera, so I thought it was positioned facing south of this photo. Off course it happened so fast, it could have changed direction. But I do remember seeing the horizon on the screen on take-off, not the trees.

 

[stberlin]

Sorry for what happened...mine do the same about yawing 5 degrees after take off when i push all the way up. But i live with that, it's happening after 1.5 firmware update, I don't think is a big problem, i read that someone solve this by demagnetize the compass...

Yes, I learned ignore it. I thought I read somewhere here that DJI would fix it by replacing the main core board.