Lost but don't know the reason.

[Espen W]

Genuine DJI props used?

 

[BudWalker]

He's approximately correct - the aircraft lost a propeller 378 seconds into the flight:

View attachment 69027

There was around 20 seconds of unstable flight leading up to that as well, which suggests some kind of damage to the prop or the mounting system.

I don't know that we've ever seen an incident like this. I agree that it's clear that the incident started at about 357 secs with a partial loss and then gradually got worse.

@eyz can you retrieve and provide the tablet .DAT? Look here to see how to do that
Retrieving a V3.DAT from the tablet

 

[sar104]

I don't know that we've ever seen an incident like this. I agree that it's clear that the incident started at about 357 secs with a partial loss and then gradually got worse.

@eyz can you retrieve and provide the tablet .DAT? Look here to see how to do that
Retrieving a V3.DAT from the tablet

Agreed - the precursor behavior is very odd, but the subsequent behavior is very characteristic of one prop missing.

 

[Espen W]

Will it stay airborne with half a prop missing (ie. rivet failure on one side)?
(I suspect not)

 

[sar104]

Will it stay airborne with half a prop missing (ie. rivet failure on one side)?
(I suspect not)

I haven't seen any data on that. It might be able to hold altitude in that configuration. At the end, however, the prop was completely missing.

 

[Espen W]

I haven't seen any data on that. It might be able to hold altitude in that configuration. At the end, however, the prop was completely missing.

Interesting. That would indicate either failure of both pivot pins or the center section (like broken tabs).
Or a poorly made aftermarket prop: I have seen aftermarket props where the fit on the shaft is so tight that the prop would stay on for a while even without being ''clicked'' properly into place.

 

[sar104]

Interesting. That would indicate either failure of both pivot pins or the center section (like broken tabs).
Or a poorly made aftermarket prop: I have seen aftermarket props where the fit on the shaft is so tight that the prop would stay on for a while even without being ''clicked'' properly into place.

That's definitely a possibility. I retrieved a P4P for someone locally that had aftermarket props that simply came apart mid-flight.

 

[xspwhite]

No - it was most unlikely to be incorrectly mounted - that would have come off much sooner. And while these aircraft will fly with partially broken props, if that was the case then it must have failed during flight.

My thought was that maybe he hit a tree branch or something similar.

 

[sar104]

My thought was that maybe he hit a tree branch or something similar.

At an altitude of 650 ft over open water?

 

[Espen W]

At an altitude of 650 ft over open water?

That was my first reaction too, but he could have sustained some such damage on the way out, with the prop finally coming apart over the water. Partly fractured blades, etc.

 

[sar104]

That was my first reaction too, but he could have sustained some such damage on the way out, with the prop finally coming apart over the water. Partly fractured blades, etc.

There was no evidence of any issues earlier in the flight, so at this point it's total speculation as to when and how damage may have occurred.

 

[Espen W]

There was no evidence of any issues earlier in the flight, so at this point it's total speculation as to when and how damage may have occurred.

True. Including (undetected) prop damage sustained on a previous flight.

 

[xspwhite]

At an altitude of 650 ft over open water?

650 feet ??? Maybe a big bird then?

 

[sar104]

650 feet ??? Maybe a big bird then?

I don't think it was a collision - there is no indication in the pitch and roll data of anything hitting the aircraft.

 

[Ex Coelis]

I enjoy reading these post mortem threads...
Very educational & enlightening!
Thanks....

 

[eyz]

thanks for the further analysis on this. I'll try to get the dat file.

 

[MavicMikeK]

Pretty amazing that you can get all that info from the file, like having a real airplane with a flight data recorder (black box) or actually orange in color. This is what sets DJI apart from all the toy and hobby drones on the market.

 

[eyz]

haven't got the dat file.

but got this final moment of the flight log

http://dl.dropbox.com/s/z0levn3upb3eocq/SVID_20190412_214128_1.mp4?dl=0

 

[sar104]

haven't got the dat file.

but got this final moment of the flight log

http://dl.dropbox.com/s/z0levn3upb3eocq/SVID_20190412_214128_1.mp4?dl=0

All the information seen there is in the txt flight log that you posted previously.

 

[Dur8an Poison]

How can I learn to read the flight data? are there any instructions posted anywhere?

The folks on this forum impress me not only by the massively technical nature of the info and expertise freely shared, but also the intricate knowledge of reading these kinds of logs. I've found so many unfortunate events that have happened to others (with Murphy's law my turn to teach through my misfortune I'm sure is coming one day) I've really learnt a lot more and am that much more aware. So just a shout out to those who assist all the rookies like me and others on here. I'm impressed on so many levels. Thank you.