Drone just drops out of the sky.

[msinger]

Yes, there was absolutely nothing left of the pop or its base, just the screws.

And you were using OEM DJI props or 3rd party props?

Have you ever removed and/or re-tightened them?

 

[Zbip57]

Is this your prop leaving?

 

[BobaFut]

Haven't seen this noted, but the Avata is known to fling its battery in crashes (there's even a whole etsy industry for battery retainers), so it seems likely that any "looseness" of the battery happened because of the crash rather than causing the crash.

 

[Yorkshire_Pud]

Is this your prop leaving?

View attachment 157999

How did you spot that? I went through frame by frame and can't see it but I note you have HD where as there is no indication of HD for me.

 

[Zbip57]

How did you spot that? I went through frame by frame and can't see it but I note you have HD where as there is no indication of HD for me.

I used the video from post #16, "The full Avata crash". It's goes all the way up to 4k resolution.

My screen grab is only 1080 resolution as my old laptop isn't capable of showing anything higher than that. Maybe somebody with a better monitor can get clearer shots of this object?

It's visible in two separate frames. Viewing on YouTube, you can step frame-by-frame forward by pressing the "." period key, or backward using the "," comma key.

 

[Yorkshire_Pud]

I used the video from post #16, "The full Avata crash". It's goes all the way up to 4k resolution.

Ahhh probably my ancient computer then, it can't handle 4k. Cheers

 

[Crouching Leopard]

If doing as usual with DIY FPV quads where no log exists in a similar way as for the DJI drones ... video analyzing of the incident.

The video shows that the Avata start to rotate CCW, then shortly after rolls over to the left... how it's pitching is hard to say due to the gimbal.

View attachment 157990

View attachment 157989

The Avata have a "props in" rotation configuration... meaning that the front props have a rotation direction towards the front & the rear props a rotation towards the rear. As the pic below...

View attachment 157987

As the Avata starts to yaw CCW this indicate that a CW torqueing corner fails (either rear left or front right)... & as the roll is towards the left, both indicate that the rear left corner suddenly lose thrust.

As you earlier (on the FPV forum) confirmed that the broken prop was where the usb connection is (near rear left prop)... all this tells me that the primary reason for the crash was a failing prop, the other indications like log recording that stopped, a partial connected battery & that you couldn't re-connect was secondary & possibly caused by the touch down.

Wow!. Excellent feedback. That is the prop that failed and what you say makes sense. The area were the drone landed was soft, tall grass and i checked the immediate surrounds for broken prop parts without success. This could be because they are small, but it could also be they flew off at high speed. The drone was quite close to me when the incident happened, and I do seem to remember hearing an increase in prop pitch as it occurred, although this could be false memory. 2 small score marks on the inner of the protector may be where they cut into it just before breaking. They are actual cuts and not rub marks.

I always check my props for fit, tightness, chips and cracks etc, but, being new to the Avata, didnt check the actual base for cracks. I have now developed my own small method of checking for that now by slightly pulling on 2 opposite blades to see if here is any widening as I pull, just in case that's were the problem lies.

I am going to follow up today on the finding of the set back pin on the connector, and a couple of other things, but I have learnt so much from these responses. All you guys are excellent

If/when I find out anything else, I will get back to the forum.

As an aside, this again emphasis to me the value of flying within the rules as coming down in the middle of a busy area, or over housing could lead to a different outcome. NB, the 2 people in the video were my spotters and my dog.

 

[mobilehomer]

Here is a 4K screen grab. A little better look.

 

[sar104]

What stands out to me is your estimate of ~ 5.5m alt at that point of flight issue, which does correlate to the log in general (17.7' or 5.4m) at the end of the data record.

Did you get the estimated alt of the aircraft from the screen telemetry and remember it, or did you look at the report prior to uploading the TXT ?

It just seems at the point the flight goes pear shaped, the drone looks a lot higher, perhaps triple that.
I'm basing that on estimated size of the trees nearby, and relative to the size of the people walking their dog early in the video.

The cell deviation yellow shading in the log is off, and it appears you had good battery reserve at 41%.
It is recorded you took off with a less than fully charged battery at 73% . . . was that a fresh charge, or was it perhaps slightly discharged and cell balance / voltage might have been erroneously reported in the app ?

Not that it sheds any more light on what happened, but actually the log ends abruptly, for no apparent reason, 70 seconds before the loss of flight control and the crash itself. The end of the log corresponds to 1' 21" in the video, at this point:



The flight continued (red trace) without logging to the crash point:

 

[Crouching Leopard]

Is this your prop leaving?

View attachment 157999

Good spot. I noticed that but hadnt considered it might be the prop. Might be, there were birds in the area but they were in front of me. I was shooting in 4k 60fps. Finally managed to locate the data file on the avata using the Assistant for consumer drones version of the app. Getting it analysed.

I dont want to duplicate posts etc, but heres a link to it on onedrive. I have also posted the link to the fpv fliers' group but if anyone here wants to take a look, please do.

DJI_Avata_2022-12-08_13-54-19.DAT

DAT File

1drv.ms

 

[Crouching Leopard]

And you were using OEM DJI props or 3rd party props?

Have you ever removed and/or re-tightened them?

Original props. I did remove them to do some cleaning. Pretty sure I didnt overtighten when putting back, but perhaps I did. Both screws were still in place after the crash.

 

[Crouching Leopard]

I just checked the battery connector base on the drone. On the right hand side 2 small pins, the top one seems to be located in further into the assembly than the bottom mini pin by about 1.5 mm. On the battery they are both located to the same depth. I cant see any logical reason for the difference, but it would make it easier to lose contact on the top pin if there was a minor incorrect insertion of the battery. I will check out other drones at the dji repair centre tomorrow.

I have labeled it "" pushed in", but it could be manufactured that way, although, as someone who spent time on electroinic systems design, I cant see why.

I checked today against another Avata. The offset pin heights are the same, so perhaps it's to do with battery not connected warning.

 

[Crouching Leopard]

If doing as usual with DIY FPV quads where no log exists in a similar way as for the DJI drones ... video analyzing of the incident.

The video shows that the Avata start to rotate CCW, then shortly after rolls over to the left... how it's pitching is hard to say due to the gimbal.

View attachment 157990

View attachment 157989

The Avata have a "props in" rotation configuration... meaning that the front props have a rotation direction towards the front & the rear props a rotation towards the rear. As the pic below...

View attachment 157987

As the Avata starts to yaw CCW this indicate that a CW torqueing corner fails (either rear left or front right)... & as the roll is towards the left, both indicate that the rear left corner suddenly lose thrust.

As you earlier (on the FPV forum) confirmed that the broken prop was where the usb connection is (near rear left prop)... all this tells me that the primary reason for the crash was a failing prop, the other indications like log recording that stopped, a partial connected battery & that you couldn't re-connect was secondary & possibly caused by the touch down.

I have a further question on this. When you command a left yaw, what is the effect on the individual props ie which ones speed up and / or slow down. I am wondering if extra power applied to a defective prop caused it to finally give up. I double checked the flight logs and I did apply a slight left yaw immediately prior to the flip / crash. I am wondering if this control input pushed a weak prop over the edge.

 

[slup]

I have a further question on this. When you command a left yaw, what is the effect on the individual props ie which ones speed up and / or slow down...

With a "props in" rotation configuration the rear left + the front right slow down... as these 2 generate a CW torque. And the rear right + the front left speeds up... as they generate a CCW torque.

It's pretty clear that your incident was due to a lost prop... & yeah, I understand that for a guy that primarily flies photo drones a lost prop sounds scary, feels catastrophic & is something that shouldn't happen. FPV acro quad pilots on the other hand, is used to "consumed" props... it's not a matter of "if", instead of "when". Have myself at least 30 different prop types with various shapes, pitches & number of blades... & I never buy only one set of each, always several, this as I know that they will break eventually... maybe already when I clip the first tiniest branch, or as a result of long accumulated abuse with several crashes & clipped branches which chip them out, grind them down or severely bends them.

What I'm trying to say... don't worry, you will never find out the inner reason for why your prop failed. It will happen again & you need to factor that in, not flying over thing's that can be damaged... & chose soft ground instead of concrete or water if you want to damage the drone as little as possible.

As a side note... quad props rarely shatter or "explode". It will be chipping, scratches & bending of the blades & only in the worst crashes a blade will be broken off. A shattered hub is rare... & usually indicate manufacturing flaws, too tighten down prop screws/nuts, that thread locker have been used that have smeared onto the prop making the plastic brittle... or that they have chosen a too hard plastic to begin with.

 

[Yorkshire_Pud]

Just as a matter of interest I just 'flew' these with a Mavic Mini, one is yaw with the motors at idle the other is yaw with the drone hovering

 

[slup]

It's all about balance & counter forces... as a quad copter doesn't have a tail rotor countering the rotational torque like helicopters, it uses two pairs of props rotating in the different direction instead. The yaw axis also have far less authority compared to pitch & roll... this as the later works by means of thrust which is much more powerful than only rotational torque.

 

[Crouching Leopard]

With a "props in" rotation configuration the rear left + the front right slow down... as these 2 generate a CW torque. And the rear right + the front left speeds up... as they generate a CCW torque.

It's pretty clear that your incident was due to a lost prop... & yeah, I understand that for a guy that primarily flies photo drones a lost prop sounds scary, feels catastrophic & is something that shouldn't happen. FPV acro quad pilots on the other hand, is used to "consumed" props... it's not a matter of "if", instead of "when". Have myself at least 30 different prop types with various shapes, pitches & number of blades... & I never buy only one set of each, always several, this as I know that they will break eventually... maybe already when I clip the first tiniest branch, or as a result of long accumulated abuse with several crashes & clipped branches which chip them out, grind them down or severely bends them.

What I'm trying to say... don't worry, you will never find out the inner reason for why your prop failed. It will happen again & you need to factor that in, not flying over thing's that can be damaged... & chose soft ground instead of concrete or water if you want to damage the drone as little as possible.

As a side note... quad props rarely shatter or "explode". It will be chipping, scratches & bending of the blades & only in the worst crashes a blade will be broken off. A shattered hub is rare... & usually indicate manufacturing flaws, too tighten down prop screws/nuts, that thread locker have been used that have smeared onto the prop making the plastic brittle... or that they have chosen a too hard plastic to begin with.

Fantastic!. You have taught me so much. Although I have flown the FPV ""acro"" its not my favourite style and I purchased the avata to do more of that type of flying training with a more robust drone (vs the flying wineglass, which I do actually love flying at its screaming speeds and tight turns). As a video and phot shooter, the Avata has already rewarded me with shots I wouldn't dare to get with my other drones, plus the shear joy of doing some low, tight flying!

I fully take on board the point about the increased prop break instances, as it now all makes sense. I have flown the avata in some pretty tight spaces, through tree canopies and have occasionally clipped a small twig, or very tall, thick grass and, to be honest, never thought anything of it (but as I said, I do check the props). I check for damage before and after each flight but will now include an inspection of the hub.

You are right. As a Cine drone pilot, the thought of losing a prop is terrifying. I need to start thinking like an fpv pilot when flying the avata and fpv

This entire thread has been fantastic. I have learnt so much, from the difference in the data files on the drone and in the goggles, to data analysis, visual analysis of crash video, prop physics and the value of flying within the rules. It has brought back my confidence in the drone. A small incident (that's what I treat it as now) has revealed a wealth of information from the forum. Thank you to everyone who responded.

As an aside, time to get onto etsy and print myself some battery retainers and protectors. Drones and 3d printing, a matched pair

 

[Crouching Leopard]

Just as a matter of interest I just 'flew' these with a Mavic Mini, one is yaw with the motors at idle the other is yaw with the drone hovering

May I ask. Which programme did you use to view the data. Was it datcon. Also, I thought the dat files were encrypted, or is that just in later drones.

 

[Yorkshire_Pud]

May I ask. Which programme did you use to view the data. Was it datcon. Also, I thought the dat files were encrypted, or is that just in later drones.

CsvView = CsvView Downloads

The phone DATs of the Mavic Mini = Mini 1 and M2P/Z are not encrypted. Mini 2 DATs are encrypted. I don't know about other Mavics but at a guess the post Mavic Mini drones will have encrypted pahne DATs Post Fly app 1.2.4 and the .txts are also encrypted...... beep, beeep beeeep,

 

[msinger]

the .txts are also encrypted

And those TXT flight logs can be decrypted and viewed with my flight log viewers.