PSA / WARNING: This Can Happen To You

[ianwood]

Exactly. Only the operator is supposed to be drunk! Not the bird itself!

Uncovering some bizarre stuff. Something went really weird in the NAZA.

Right before it lost control, the reported speed went from a very normal 1.36m/s to a slightly fast 769,361m/s (1.7million MPH)!

At impact, some 5 seconds later, the NAZA reported its speed had slowed to 172,227m/s or 385,260 MPH.

All things considered, I am surprised you all didn't feel it or see the mushroom cloud that followed. I'm lucky to be alive! Then again, at that speed, after only 5 seconds, the Phantom would have covered the distance between LA and Hawaii. Hawaii, you still there?

 

[Fyod]

Is the Naza V2 (non-lite) also known for these flyaways?

 

[Fyod]

I'm testing a device that has invalid GPS data and this is what comes from the NMEA translation.
Eager to see if you have similar data since you mentioned 240 satellites.

It seems to be an antenna problem in this case, not certain yet.

 

[mfflyingstudios]

What is your drone type exactly?

 

[RoyVa]

Sorry for the crash however, the unknown is always an irritant. But it is computers you are dealing with in the sensors, Naza and main board. The Phantom has to continually update the data to the main controller during flight as it receives the signals from the controller. The problem is that a small interruption in processing can provide corrupt data and mis information. We see this all the time in Personal Computers and Laptops. Not as noticeable as these units are stationary. But it happens, not often but a lot of time we shrug it off as a glitch, loss of internet for a second, unknown rebooting, can't find a file then it does etc. As long as their is the passing of data along with electrical impulses at micro millisecond speeds we will see errors but may not recognize them. When in the air and having to adjust to the controls as fast as it has to if it gets a corrupt pulse then the data it's processing a lightening speed can be mis read and it follows the bad data hence a fly a way. No proof just years of chasing data and computer glitches. They can do funny things. And no one has an answer other than it " just happens like that sometimes". Sure glad it's not often! The other unknown is not if its going to happen but when. It's called ELECTRONICS.

 

[timmer]

...Right before it lost control, the reported speed went from a very normal 1.36m/s to a slightly fast 769,361m/s (1.7million MPH)! ...

I have not seen this thread before and I am sorry for your losses. What, if anything, has DJI said regarding this?

Oh, the quote above reminds me of when I was in a Navy bomber squadron. One of the ECM systems I worked on had routine it would use for certain Soviet era SAM's. It would receive the incoming signal and send back telemetry to say that we are really not here, but accelerated past the speed of light and we are on next horizon. The accompanying radar dish for the SAM would spin around so quickly that it would either break the radar mast or turn over the mobile trailer the radar was in.

 

[westlightaerial]

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I didn't think they were real. I thought they only happened to people who didn't pay attention to the details. They weren't really flyaways. Well, not any more.

Today, I had a flyaway. It was a perfectly normal flight for 11 minutes. I was reshooting a location I had shot two weeks ago. I had the P2 in a static hover about 10m off the ground (15m from me) while I figured out my last few shots.

It then took off at ~25 degrees down angle at full speed and smashed into the street. Both gimbal and Lightbridge ripped clear off and tumbled across the street. It was over in two seconds. The battery had half-way dislodged and was still on (1 solid, 1 blinking). All four props were destroyed, two right at the hub.

I gathered all the pieces, cursing profusely and took them home. I then checked everything out in detail.

• The battery is fine. 22 cycles. Balanced. Test flight on my backup P2 was 14.5 minutes.
• IMU, no calibration needed as per the Phantom Assistant. Had advanced calibrated 2 weeks ago.
• Compass MOD is 1403.
• I had checked the props prior to flight and they were fine. Not so much now.
• I ran stress tests on the ESCs / motors. Totally fine. No unusual noise. Balanced bell housings.
• RC calibration is perfect.
• I went back to the site, looked for any magnetic, EMI, RF sources. Nothing.

So that leaves really one maybe two possibilities:

• Lightbridge commanded the movement (no idea if that's even possible).
• More likely, the IMU and / or Naza locked up or received bad IMU data.

With bad data or a frozen IMU, the Naza would get bad reference data for where gravity is and then would command the motors to correct for it. That would create an unrecoverable situation.

Either way... It was a flyaway. They're real. And they can happen to you. Fortunately, it happened in an area where it was recoverable. Gimbal is bent beyond repair. The GoPro somehow took the brunt of the impact. It's gone as are the last 20 seconds of the video so no crash.

If you are flying down town with a lot of building and GLASS Buildings, your GPS signal can get confused and do this,
Same thing happened to a friend of mine just after we tested it at another location where it worked perfectly. If you are downtown, I would advise to fly attitude only. If not, you are just taking a risk.

 

[ianwood]

Sorry for the crash however, the unknown is always an irritant. But it is computers you are dealing with in the sensors, Naza and main board. The Phantom has to continually update the data to the main controller during flight as it receives the signals from the controller. The problem is that a small interruption in processing can provide corrupt data and mis information. We see this all the time in Personal Computers and Laptops. Not as noticeable as these units are stationary. But it happens, not often but a lot of time we shrug it off as a glitch, loss of internet for a second, unknown rebooting, can't find a file then it does etc. As long as their is the passing of data along with electrical impulses at micro millisecond speeds we will see errors but may not recognize them. When in the air and having to adjust to the controls as fast as it has to if it gets a corrupt pulse then the data it's processing a lightening speed can be mis read and it follows the bad data hence a fly a way. No proof just years of chasing data and computer glitches. They can do funny things. And no one has an answer other than it " just happens like that sometimes". Sure glad it's not often! The other unknown is not if its going to happen but when. It's called ELECTRONICS.

Well designed modern electronics don't exhibit these low level issues if they are used within their design limits. The issues that you describe are either faulty components or logic level errors. Some components can exhibit intermittent issues but they would still be considered faulty.

If you are flying down town with a lot of building and GLASS Buildings, your GPS signal can get confused and do this,
Same thing happened to a friend of mine just after we tested it at another location where it worked perfectly. If you are downtown, I would advise to fly attitude only. If not, you are just taking a risk.

The Phantom handles GPS multi-pathing very well. There were no glass buildings near any of the 3 incidents. And GPS multi-pathing would not cause a sudden tipping over and rapid descent.

I have not seen this thread before and I am sorry for your losses. What, if anything, has DJI said regarding this?

Oh, the quote above reminds me of when I was in a Navy bomber squadron. One of the ECM systems I worked on had routine it would use for certain Soviet era SAM's. It would receive the incoming signal and send back telemetry to say that we are really not here, but accelerated past the speed of light and we are on next horizon. The accompanying radar dish for the SAM would spin around so quickly that it would either break the radar mast or turn over the mobile trailer the radar was in.

Interesting. Maybe someone sent similar GPS signals to my Phantom.

Glad you brought this up. There's more to the story. See the next post...

 

[ianwood]

The latest chapter:

The suspect P2 involved in the previous 2 crashes was boxed up to go back to DJI for analysis and I bought a new P2 to resume shooting. I rigged it with the same Lightbridge air unit that had survived the first two crashes. For about 15 flights it was fine, and then...

It did the same **** thing. Exactly. It started to tip over and rapidly lose altitude. Above is a screenshot of the initial loss of control. Notice it is completely sideways.

Switched to ATTI. Nothing. Still falling towards the building I was filming. Full throttle up. Boom. It recovers, shoots up in the air. My heart is racing. It's on the other side of the building at this point. I can't see it. Lightbridge enters F/S but no update to image or telemetry. I hear it faintly and then see it coming over the top of the building. Phew!

I take control from the F/S and start to bring it in. It's working perfectly as if nothing ever happened. Then... 15 seconds later, it does it again. I again give it max power but it's so far titled over that it doesn't help. This time it slams into the building's balcony (on the left in the picture above). It took a lot of convincing to get it back.

I told DJI about the 3rd incident. I didn't get the response I wanted. They clearly don't care about finding the problem. Here's some excerpts from my dialog with them:

I was about to put the other P2 in the mail to you tomorrow but now I need to swap shells. I think I should send you the LB air unit instead and maybe the anti-interference board as well just to be thorough. Those are the only two things in common between the 3 crashes.

I can provide video of the crash or more specifically the anomaly leading up to the crash.

Please ship the P2 back to us as we had planned.

I understand the deal was to get the P2 back to you... ...Sending a perfectly working P2 back makes no sense. Being that the P2 is definitely not the source of the problem and given that the Lightbridge is the top suspect, it makes sense for DJI to look at the Lightbridge air unit. I do recall some posts on RCG about people who got faulty air units out of the box and had them replaced.

I am asking that you return the P2 as was originally discussed... ...You can open a ticket on the LB but we will have limited ability to test without a unit to test it on.

I can send you what's left of the P2 if that's what you really want. It seemed pretty clear when we first discussed it that you wanted me to send it in so you could try to diagnose the problem... ...So if you still really want to diagnose what's been happening, I'm giving you a new data point that shifts the focus to the [Lightbridge] air unit.

Thank you for your cooperation. As I stated, you can open another ticket with the LB.

Basically DJI said: "Go [blank] yourself and your attempt to find the cause of this problem."

 

[Deleted member 29014]

I will probably get shot down here, but are we looking for complexity where there is none?
A device that requires 2.4/5.8ghz, GPS and a digital compass to fly will, at some stage, behave unexpectedly in area with large amounts of steel, flat surfaces (multipathing) and potential interference.
Surely one, or any combination of the above are more likely candidates than errant coding?

right on!