Sudden "crazy", then crash

[kevinlieb]

I am new to this forum so please let me know if this is posted in the wrong place or is just not appropriate.


I have been flying my DJI Phantom Pro 3 for like 2 years and mostly without incident. I would consider myself an experienced but not expert pilot. I have crashed a couple of times but nothing like this.

The drone took off as normally but i heard a strange vibration / noise as it left the ground. I commented to my friend on this but continued to fly. Around 45 seconds later, as I was looking at the camera on my phone and lining up my shot the drone went crazy and just started tumbling out of the sky. At the time I heard the strange noise / vibration again, it tumbled and flipped, hit a wire on the way down and hit the ground.

I had aftermarket carbon fiber props on the drone at the time. I have flown with these 10-15 times without incident. They are much stiffer than the stock props but have flown just fine.

My theory is that a prop was cracked on take-off, then failed in the air, but I have no way to prove this. Nobody saw a piece fall off the drone before losing control but 2 props were cracked / damage on crash: which might have happened when they hit the ground or when they hit the wire. Unfortunately I was not recording when the incident happened.

I have a few "speed error" and "compass errors" in the logs but I don't know exactly what this means.

Any help analyzing the log would be greatly appreciated! I bought a new frame and new props to rebuild it but want to make sure the fault was not motors or electronics or battery before flying again.

Thanks!

 

[msinger]

It looks like you lost a prop at about 49 seconds into the flight. You can see your Phantom spinning in circles at that point in the flight log.

DJI Flight Log Viewer - PhantomHelp.com

Where was the missing prop when you retrieved your Phantom? Or were they all attached?

 

[With The Birds]

Improperly installed and/or poor quality rotors.

Unfortunately.

 

[Fly Dawg]

Sure looks like a lost prop.

 

[kevinlieb]

Thanks for the super quick responses!
I think these were the props I was using:
https://www.bestbuy.com/site/digipo...m-3-drones-pair-black/4653348.p?skuId=4653348

All props were attached when i retrieved the drone. One was significantly chipped (1/2 inch or so broken off tip) and one had a blade completely sheered off but it was unclear whether it happened in flight or during the crash.

 

[msinger]

one had a blade completely sheered off

Ah, well, that explains why it appeared you lost a prop mid-flight.

it was unclear whether it happened in flight or during the crash

According to your flight log, it happened at about 49 seconds into the flight. If you review your DAT flight log, I'm sure you'll also see that motor was spinning unusually fast after the prop sheered off.

 

[sar104]

Those flight characteristics are consistent with partial loss of a prop. The periodicity of the pitch, roll and yaw is longer than normally seen with complete prop loss, suggesting less of an angular momentum imbalance.

The aircraft pitched up, rolled left and entered a CCW spin, suggesting that it was a CCW prop, probably the rear left based on the initial pitch and roll excursion. The DAT file would confirm, either way.

 

[kevinlieb]

I extracted the .DAT version of the flight and put it up here:
It does seem like one motor got up to like 9k rpm which has to be a "bad thing"

I guess lesson learned is: if something seems funny: land!
Check your props before taking off, every time

Thanks for all the help and info! I had no idea about these DAT files and all the info they contain. I will rebuild and fly again!

 

[4thdpi]

It looks like you lost a prop at about 49 seconds into the flight. You can see your Phantom spinning in circles at that point in the flight log.

DJI Flight Log Viewer - PhantomHelp.com

Where was the missing prop when you retrieved your Phantom? Or were they all attached?

There is a rampant amount of failures in the rem software and circuit

 

[4thdpi]

A rampant report of crashes as it happened to me last week are esc software or boards are failing. Mine was in clear air at 380 ft. It happened the camera showed it started to wobble on its own then tumbled out of the sky. The error said over rpm of one engine and then stopping one engine. The esc controls the rotation of engines so it can stabilize or accept commands from you to fly directional and vertical. This is an issue the faa is becoming aware of. Over a crowd someone could get hurt or killed. I have sent my phantom 3 advanced in for service at dji repair.. also to fix the resultant damage of the rem going bad. Now the engines won't start.. This issue is not. pilot but a failure of the esc. Ill know more next week what dji repair says. I told this repair should be of No cost since their control mechanized failed, not pilot error.

 

[BigAl07]

I guess lesson learned is: if something seems funny: land!
Check your props before taking off, every time

Yes if something seems strange while flying land Land LAND!

I don't mean this to sound harsh but since you continued flying after "but i heard a strange vibration / noise as it left the ground " this one goes down under the heading of operator error. When in doubt check it out.

Good luck and hopefully the repairs will be minimal

 

[Andy9]

" This is an issue the faa is becoming aware of. Over a crowd someone could get hurt or killed. I have sent my phantom 3 advanced in for service at DJI repair"

Yes, this is exactly the situation that (including the FAA) we all afraid of the most. You can't do nothing but looking the drone falling down.
All recommendations and prohibitions for safe flying is mostly because of this.

 

[sar104]

I extracted the .DAT version of the flight and put it up here:
It does seem like one motor got up to like 9k rpm which has to be a "bad thing"

I guess lesson learned is: if something seems funny: land!
Check your props before taking off, every time

Thanks for all the help and info! I had no idea about these DAT files and all the info they contain. I will rebuild and fly again!

That Airdata summary of the DAT data doesn't display the important information - i.e. individual motor speeds and motor command values. Their beta DAT reader is not very good. That requires the original DAT file.

 

[sar104]

There is a rampant amount of failures in the rem software and circuit

This was almost certainly mechanical prop failure, with third-party props.

 

[4thdpi]

Yes if something seems strange while flying land Land LAND!

I don't mean this to sound harsh but since you continued flying after "but i heard a strange vibration / noise as it left the ground " this one goes down under the heading of operator error. When in doubt check it out.

Good luck and hopefully the repairs will be minimal

 

[4thdpi]

Props should be hand tightened only. The spin direction also keeps them tight. The day before I noticed it was wobbling coming down to land. I test flew it 10 times after it going up 50 ft only. I ran it through its paces turns, quick up and downs fast. It can perfect. The following day the first run went perfect. The second flight I saw the drone and also on camera. At 380 ft I started bringing it down fast . The wobble the error msg said one prop motor is corrupt and stopped. Tumbled to earth. The emc is the logic based board and software that syncs the props to do what you want it to do or just hover. I hate electrical or software problems, cuz they are intermittent. Dec phd

 

[happydays]

After all these years, it still beats me why anyone would want to use carbon props on a DJI quad. They are known to be useless compared to the standard props which are pretty good, actually.

 

[Forgotten_Fox]

This is why DJI has listed in their drone tips section to hover for 30 seconds and check the Drone’s stability. Best of luck with the repairs though, when in doubt, swap it out. I wouldn’t fly on questionable parts, as it’s not only a safety hazard, but it endangers your quad.

 

[kevinlieb]

To add more detail here: I had a very stable 8 minute or so flight just before this crash. Here is part of it:

(not very thrilling but very stable)

I landed, swapped batteries and took off again. That is when the trouble happened.

Carbon fiber (looking) props: only reason I bought them is I had a close-encounter-of-the-tree-kind one day and broke 2 stock props. I went to best buy to get new props and this is all they had. Then I never replaced them again. Lesson learned for everyone I hope!

Raw DAT file: Dropbox - FLY205.DAT

 

[Fly Dawg]

Looks like the left rear prop may be the culprit.