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Crash without reason

jefmob_1

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It was my second battery when a crash occurs.
I realy don't know what happened... like a flyaway... but...
2 propellers are missing (I checked them with a magnifying glass ) after reading the Agustine thread "Guess what I found today" two days ago.
I've nothing noticed.
 

AaronB

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I notice the image of the Anafi at 0:51 shows both rear legs in the closed position. Is this how you found it after the crash?
 

AaronB

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My take on this:
At 0:18 first prop is thrown - Anafi immediately becomes unstable but manages to recover flying on just the remaining prop (but unable to hold position).
At 0:22 the detail in the branches of the trees is quite blurry - probably due to vibration from the missing prop.
At 0:27 the final prop is thrown - the sudden jarring could even be the prop hitting the Anafi - at which point the Anafi drops out of the sky.

Because the arm is hinged, I suspect the motor with the single propeller will freely (and very rapidly) oscillate with minimal damping affect from the rest of the drone. This probably explains why the second propeller often breaks free also.
 
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Agustine

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Did you see how it was flying forward and then when the prop broke it immediately started flying uncontrollably backwards? This is exactly what mine did. No matter how much forward stick I gave it just kept going.
 

AaronB

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Did you see how it was flying forward and then when the prop broke it immediately started flying uncontrollably backwards? This is exactly what mine did. No matter how much forward stick I gave it just kept going.
If you think about it, the direction of drift would be directly related to the arm with the missing prop - it is after all missing half the thrust required to keep it level. In an attempt to get level, the stabilisation software would also be taking the motor up to maximum rpm - probably resulting in the Anafi flying off at considerable speed in the direction of the broken propeller.
 
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AaronB

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These fly away's should be preventable via software. The stabilisation system should be able to quickly detect that increasing speed on the broken prop is not working – and immediately go into recovery mode by lowering the speed on the remaining good props instead. Sure the Anafi may not maintain hover, but hey, you probably want to be landing at this point anyway.

Better to come down slowly than hit something at 42mph !?
 
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Moonfly

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Hello. I'm sorry. How many flight hours do the propellers when you had the crash?
 

Landbo

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It was my second battery when a crash occurs.
I realy don't know what happened... like a flyaway... but...
2 propellers are missing (I checked them with a magnifying glass ) after reading the Agustine thread "Guess what I found today" two days ago.
I've nothing noticed.

Sorry you crashed.

It is hard to say exactly what has happened. Your log might reveal more than your video if we have to watch it.

Regards, Leif.
 

AaronB

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It is hard to say exactly what has happened. Your log might reveal more than your video if we have to watch it.

I think the video evidence is pretty compelling that it was prop failure:

1) The broken arm (which must have been the main point of impact with the ground) still has the props intact.
2) Both rear arms are closed against the body and yet one has both propellers attached and the other has none.
3) The blurriness of the video at 0:22 would indicate the drone was undergoing significant vibration - which you would expect from a single missing propeller blade. The Anafi also seems to be drifting backwards and towards the right - in the direction of the arm that ends up with the missing propellers.
 
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jefmob_1

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Thanks a lot for yours attempts to explain the crash.
I've spent time to make this video explaining why I am not sure this was due to propellers...

http://npmedia.com/anafi/vids/log1.mp4

My propellers was checked the day before with an magnify lens and I've nothing noticed
My props are 4 hour old.

Let me know if something bother you in the video.
 

AaronB

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My propellers was checked the day before with an magnify lens and I've nothing noticed
My props are 4 hour old.

I'm sorry about the loss of your Anafi, and I'm definitely not accusing you of not having done the required pre-flight checks. I am just trying to help by pointing out the most likely cause of the Anafi behaviour. If the props did fail, then as to why, we will never know - it could be from an insect or fatigue?

Personally I think the propellers are a weak point in the Anafi design in terms of reliability - discussing engineering improvements will benefit the Parrot Pilot community as a whole and help make flying the Anafi a lot safer.
 
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AaronB

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Thanks a lot for yours attempts to explain the crash.
I've spent time to make this video explaining why I am not sure this was due to propellers...
http://npmedia.com/anafi/vids/log1.mp4

Your final point with the streamer hitting the drone was certainly spectacular :) and I realised you may have misunderstood my explanation - when I say the first propeller was thrown, I mean only a single blade is lost - the Anafi is still flying on 3 and a half propellers! Enough to remain airborne but not necessarily controllable.
 

Landbo

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I think the video evidence is pretty compelling that it was prop failure:

1) The broken arm (which must have been the main point of impact with the ground) still has the props intact.
2) Both rear arms are closed against the body and yet one has both propellers attached and the other has none.
3) The blurriness of the video at 0:22 would indicate the drone was undergoing significant vibration - which you would expect from a single missing propeller.

Sorry AaronB, but I dont think I needed to discuss my theory about what might have happened to you. I have asked jefmob_1 for a simple question and expect an answer from there, and not a one-sided discussion with you !!!
 

AaronB

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Sorry AaronB, but I dont think I needed to discuss my theory about what might have happened to you. I have asked jefmob_1 for a simple question and expect an answer from there, and not a one-sided discussion with you !!!
Of course. I look forward to your theory on the incident - I always keep an open mind.
 

Kilrah

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These fly away's should be preventable via software. The stabilisation system should be able to quickly detect that increasing speed on the broken prop is not working – and immediately go into recovery mode by lowering the speed on the remaining good props instead.
That means lowering speed of the others to 0, aka shutting down so doesn't really achieve anything good.
 

AaronB

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That means lowering speed of the others to 0, aka shutting down so doesn't really achieve anything good.
That does not make sense, if only one prop blade is thrown then the arm with the single blade will still provide 50% maximum thrust. It is quite probable that reducing the thrust on the three good sets of props will allow the Anafi to be balanced out for a stable descent.
 

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