Drone crashed - video and log

[Bryce steiner]

So, I go to do a test. I wanted to see about how fast I could rise vertically and move horizontally with different sets of props. I was only into the initial test two minutes with the regular 2 blade props when the drone starts going crazy. I was not far from home and I was able to turn around when it started going funny. It crashed on my property. The damage was to the front left leg. I could have fixed it farily quickly with JBweld but since I was on the plan I decided to just send it back for a replacement.

Video:

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

I'm not sure if there was a computer error or if something hit it or something else at 1:22 in the video something hits the Mavic. It was still flying but I could tell something was not right as the camera cannot stay steady. I was trying to come down quickly but it wouldn't go. A prop flew off just before it hit the ground.

So what do you think on this?

 

[BD0G]

@sar104

 

[Gryphon962]

I think one front right blade came off - or partially off - you can see the blade at 1:21 extending far further into view than normal. Later, i think you lose the whole prop.

 

[BD0G]

The Flight log will be what needs to be deciphered to determine what actually happened.
With that said if I was arm chair quarterbacking this one I would agree that one of the props appears to loosen and then come off. The loosening caused the unstable camera and flight characteristics.

Lets wait for SAR104 to chime in after he examines the flight log. Thats why I "tagged" him above.

 

[Meta4]

I'm not sure if there was a computer error or if something hit it or something else at 1:22 in the video something hits the Mavic. It was still flying but I could tell something was not right as the camera cannot stay steady. I was trying to come down quickly but it wouldn't go.

From 1:31.2 in the flight data, things go very wrong.
The drone had been stable up till then but it starts pitching up and down, rolling and spinning as well as losing height.
You gave it some full left stick down for part of the descent.
From around 1:46 the pitch, roll and yaw becomes steady again and that might be the crash.
All data after that is post-crash garbage.

A prop flew off just before it hit the ground.

Maybe some serious prop issue contributed to the crash?
It's unusual for a prop to come off before impact.
How can you be sure the prop separated from the drone in the air?
What condition were the props in?

 

[MrEdCeD]

1:21 broke propeller falling...

 

[rfc]

So, I go to do a test. I wanted to see about how fast I could rise vertically and move horizontally with different sets of props.

So, the props you had on at the time of the crash were stock, DJI props?

 

[Bryce steiner]

From 1:31.2 in the flight data, things go very wrong.
The drone had been stable up till then but it starts pitching up and down, rolling and spinning as well as losing height.
You gave it some full left stick down for part of the descent.
From around 1:46 the pitch, roll and yaw becomes steady again and that might be the crash.
All data after that is post-crash garbage.

Maybe some serious prop issue contributed to the crash?
It's unusual for a prop to come off before impact.
How can you be sure the prop separated from the drone in the air?
What condition were the props in?

That's kind of my thoughts too. I think maybe a bird hit the prop causing it to break off. The entire hub came off a few seconds later, which is disconcerting.

The props did not look in bad condition when I took off. I inspected them before because I was intending to do the comparison between the 2 and 3 blade props. I've had blades, chip or crack, but never had one completely break in flight.

I did try to bring it down as quickly as possible safely. I'm thinking now that I should set the "T" mode to be ATTI mode. I'm not sure that would have helped here but I did get a lot of strange errors.

I used the drone a lot last week for my county. Between tornado damage for the NWS and a body search in the river, they kept me busy! I'm just glad I didn't have a problem while using it for them.

I hadn't changed props in a while. Is it something that I should change regularly, like tires? As in, they just wear out?

 

[putz]

I couldn't get a great frame off the prop coming apart, but I agree with everyone before me that says the prop definitely fell apart in flight.

 

[Bryce steiner]

It's not great but this is where something hits and/or the initial blade falls apart. The errors showing no prop are later.

Three frames after this you can see a broken piece fly from left to mid right, mid to lower frame over a three frame set.

Edit: Now I'm not sure. in a frame at 1:54 and again at 1:55 you can see that prop there and working.

 

[sar104]

Yes, it definitely lost propulsion - probably rear left. It would need the mobile device DAT file to confirm. It looks like it partially failed at 63 seconds and then completely failed at 91 seconds. The objects visible in the video are at the 63 second point of the flight log.

 

[Bryce steiner]

Yes, it definitely lost propulsion - probably rear left. It would need the mobile device DAT file to confirm. It looks like it partially failed at 63 seconds and then completely failed at 91 seconds. The objects visible in the video are at the 63 second point of the flight log.

I think your right. I've gone through frame by frame and can see both front props until it hits the ground.

It's interesting how the height keeps dropping below -100' (same as where I took off) even though it's stopped on the ground.

 

[sar104]

I think your right. I've gone through frame by frame and can see both front props until it hits the ground.

The lost prop has to be a CCW prop, since after it is lost the aircraft spins CCW, meaning it has more CW props than CCW props. That means front right or rear left. Since the initial attitude excursion at both 63 seconds and 91 seconds is pitch up and roll left - that implies rear left propulsion was lost.

 

[Peter doran]

I think one front right blade came off - or partially off - you can see the blade at 1:21 extending far further into view than normal. Later, i think you lose the whole prop.

And at 1:23 app says “max motor speed reached” just for a second which seems like what your would get right after a prop comes off mid flight

 

[sar104]

And at 1:23 app says “max motor speed reached” just for a second which seems like what your would get right after a prop comes off mid flight

The prop had not come off at that point - because the aircraft was still in approximately level, stable flight - although it may have broken. My guess is that one side had snapped off, which is why the motor increased speed to compensate. Once the prop failed completely the aircraft began to spin, because it had two CW props and only one CCW prop, giving a net CCW angular momentum to the aircraft. It also threw a "motor idling - prop loose or missing" error at that point.

 

[Gryphon962]

The prop had not come off at that point - because the aircraft was still in approximately level, stable flight - although it may have broken. My guess is that one side had snapped off, which is why the motor increased speed to compensate. Once the prop failed completely the aircraft began to spin, because it had two CW props and only one CCW prop, giving a net CCW angular momentum to the aircraft. It also threw a "motor idling - prop loose or missing" error at that point.

In the verbose .csv I see the 'OSD.isPropellerCatapult' goes TRUE for a few rows, back to FALSE, then finally goes TRUE again until the crash. Is that parameter directly related to prop transients like this?

 

[sar104]

In the verbose .csv I see the 'OSD.isPropellerCatapult' goes TRUE for a few rows, back to FALSE, then finally goes TRUE again until the crash. Is that parameter directly related to prop transients like this?

Probably, but how it is calculated I do not know.

 

[kilomikebravo]

MAN THE CATAPULTS....CHARGE!

 

[Bryce steiner]

The lost prop has to be a CCW prop, since after it is lost the aircraft spins CCW, meaning it has more CW props than CCW props. That means front right or rear left. Since the initial attitude excursion at both 63 seconds and 91 seconds is pitch up and roll left - that implies rear left propulsion was lost.

Attached is the DAT file from the flight logs folder.

 

[Bryce steiner]

I cleaned out the mud, did some small repair work and put new props on this morning and turned it on. It seems to fly fine but I'm getting this error:

"Switched to Backup IMU"

Did the main IMU get damaged or was the IMU part of the problem?

Surprisingly the camera and gimbal seemed okay.

tomorrow I'll send it in for repair.