Ultrasonic Systems Error

[Elbert Hill]

I'm hoping someone could review my flight log and tell me the significance of a couple of events I encountered today. After an uneventful flight, to a little over 17,000 feet away, everything went south. It forced me to land in the desert, then it took an hour to find it but to my amazement it's cam through largely unscathed....sort of.

Looking at the log, at about 16:40 into the flight I see that one of the battery cells is about 2 or 3 tenths of a volt lower than the others, and the text was in orange for that cell. About 10 seconds later I get a warning of "Ultrasonic System Error". Then other errors followed.Also, I had went ahead and let it do an automatic RTH, then I turned my attention away for a moment, and then I look back and my craft was flying AWAY from home, out over a country club where I did NOT want it to go down. Put into ATI mode, and managed to get it back over the open desert, before it landed.

Does that 2 or 3 tenths of a volt difference make a that much of a difference ? Was that the cause of the errors ? I never knew the craft had anything "Ultrasonic" on it. But today researching it it turns out to be the Vision Positioning System. I've got another moduIe I could put on it, but when I put a fresh battery in, everything checked out ok, no errors. Hence my question was the whole thing due to that one low cell ?

Oh yea.....that was a new battery too.

My log is uploaded for viewing, I'd appreciate any pointers.

Thanks

 

[Fly Dawg]

There were so many errors on this flight, I wont even bother charting them as I normally do. I took the liberty to upload the log, and reviewed the CSV's as well. This is just too much. This has nothing to do with the US sensors, nor the battery. It is first, poor planning, and second you received multiple error warnings all over the place. I generally have empathy and will review all data, but for what appears to be far past VLOS flight, and at one point over 700' in altitude, both of which violate regulations, I have to bow out on this one. But you can look for yourself....Sorry, it's flights like these that just irritate me some times.

DJI Flight Log Viewer - PhantomHelp.com

 

[GrammatonxXXxCleric]

At the 16 min mark... auto landing, 85mph and 192mph??

 

[Fly Dawg]

At the 16 min mark... auto landing, 85mph and 192mph??

Those have to do with the speed errors, compass errors etc........ Bogus most certainly.

 

[Fly Dawg]

I will appolgize to the OP, for being so blunt in my first response.

 

[GrammatonxXXxCleric]

Looking at the KML in Google earth, the stack of errors..

 

[Fly Dawg]

It wasn't the battery. Note the Speed Errors, and the way far excessive altitude. That's all I have for this one.

 

[Elbert Hill]

There were so many errors on this flight, I wont even bother charting them as I normally do. I took the liberty to upload the log, and reviewed the CSV's as well. This is just too much. This has nothing to do with the US sensors, nor the battery. It is first, poor planning, and second you received multiple error warnings all over the place. I generally have empathy and will review all data, but for what appears to be far past VLOS flight, and at one point over 700' in altitude, both of which violate regulations, I have to bow out on this one. But you can look for yourself....Sorry, it's flights like these that just irritate me some times.

DJI Flight Log Viewer - PhantomHelp.com

Thank you for your kind words ! However, all the data is skewed after 1t6 or17 min ! IFYI my altitude never exceeded abt 200 ft. And what about that single line where it says my speed was 200 mph. I mean think about it ! Do you believe that too, the 200 mph thing ? Get real dude. FYI I was trying to return when all the warnings started,

I didn't mean to offend your self righteous attitude. And I'm additionally sorry I didn't live up to your expectations. Sorry I even asked !

 

[Elbert Hill]

So no idea what the cause could be then I take it . Let me ask you this, what is an acceptable deviation of voltage from of any one cell to the others ? I see text color changed one the deviation went over .04. But looking at other flight logs I see where it exceeded .04 with no issues.

And thanks for the apology ! Accepted !

 

[Elbert Hill]

At the 16 min mark... auto landing, 85mph and 192mph??

Got some cool videos on your channel !

 

[Fly Dawg]

Do you believe that too, the 200 mph thing ?

No, that was the "Speed Error". A calculation error in the AC, which led to the other errors.The altitude I do believe, there is nothing to indicate otherwise. And yes, I saw the RTH. I never stated that this was pilot error, and I was not being self righteous. The only thing I have to go by is the data. It was the fact that these lengthy flights are extremely risky, and violate VLOS. That is all I meant by that. As for the voltage values, some deviations are fine, what you really need to be concerned with in that aspect that they are consistent. 40mv in deviation is no big deal, but the cutoff point is 3.2v per cell. The battery still looked good as far as the individual cells go. That is not to say however that you had enough total power remaining to fly much farther.

 

[Fly Dawg]

If you notice in the last chart above, the speed errors were in and out of normal ( 30mph or so) to 200mph. That's where things went bad.

 

[Fly Dawg]

At 819 seconds is where you had the Ultrasonic System Error. There was a short spike in the Barometer which came right back to normal. You began giving throttle up. The throttle and altitude match up so there is no reason to believe that this altitude is incorrect. This is why said what I said. Just wanted to clarify that. I do believe this was an AC issue and as I said, not pilot error.

 

[solentlife]

Aside from the 'other aspects' of violations ... lets look ...

8:13.9 - RTH kicks in because you are at calculated range and battery level that is only enough to Get home - without any head wind etc.

Up unitl that point you have been doing a fair old speed averaging 35mph ... which is max speed in ATTI mode ... so you must have had a slight wind WITH you going out and that would be a head-wind to be against coming back. With minimum battery kicking in - you are praying you will make it all way home.

8:16 at zero horizontal speed so why ? She's hovering with no indication of problem but still in Go Home mode ... are you holding her there ?

There are repeated stops in horizontal and indication that you are turning her at one point as it tries to align for GO Home ..

These stops are making sure you definitely will never have enough battery to get home.

There is a comment that it is ascending to RTH altitude ... ? You have 98Ft set at start and appear to be 376ft when it starts to 'ascend' ??

8:19 ... back to P-GPS ... so RTH cancelled and already you are pushing back out again

8:25 - you start coming back ..

10:36 - Go Home kicks in again - was that you ? ... but to be honest - I'm looking at your battery level and range to go ... its IMHO not good at all ... you don't have enough battery left.

12:02 - you revert to P-GPS ... with low battery and still a reasonable distance out from home ?

12:52 - you start to get warnings ...

13:05.9 ... you enter a Warning Class E zone ...

13.09 Speed errors show up ... speed errors are usually due to bad GPS positional info as speed is calculated by referencing repeated GPS positions. It is possible that GPS suffered an anomaly then and it threw out silly numbers that Flight Controller rejected ... it would then need time to correct by subsequent GPS positions.

13:10 - we are now getting down near to Low Battery status for any flight and still out at reasonable distance from home. GPS appears to have intermittent problems throwing up silly numbers for calculating speed.

13:13 - That could be GPS has now locked in again and the error of positions previous give crazy speed. You have to remember that GPS positions are frequent and only a small positional error can throw up huge speed errors. If the averaging doesn't catch it because of repeated errors - then this happens. Note that speed then quickly reverts to acceptable levels.

13:15 ... again GPS throws a 'googly' and of it goes again .. the silly thing is - position can still be reasonably accurate - but because of the small time interval between positions and calculation of speed - that can be crazy.

13:20 Appears to correct itself again ...

But from now on even the positional info is into trouble. It is jumping around and this will make it exceedingly difficult for the FC to bring that AC anywhere near home.

Basically - now the FC is taking the info GPS etc. is feeding it and confused - it cannot RTH even though it says Go Home. With the distance out - you cannot even switch to ATTI and bring her home visually.

13:39 It says US systems error ... To be honest - with all that was going on - I wouldn't trust any warning and would have landed out - to retrieve manually by driving to it. There is no way that baby is coming home.

14:14 .. you really are suffering ... that GPS is really in the crapper ...

14:26 .... back into P-GPS mode ? with naff all battery left ??

14:33 ..... its signed and sealed ... its just a matter of time before it goes down.

16:34 - I'm surprised its lasted this long .. she's going down !

17:39.9 .... is that it ? Seems like from 16:34 till this - you were fighting against the inevitable ... but with such a battery pushed so far ? and a GPS that IMHO was given out bad information too often - the best thing would have been to land that baby out long before she ever did it herself.

I know we all do it - we hope we can save it by pushing .. refusing to give in - but this one ? GPS failure and pushing too far ... cancelling RTH ... trying to hold of Auto-Landing ... she was doomed.

That's my interpretation anyway - I may be wrong on a few points - but basically I suggest your GPS was the biggest problem ... then Flight Controller was totally bamboozled by the conflicting info it was getting.

Nigel

 

[solentlife]

Very quiet here now ?

Nigel

 

[Fly Dawg]

Very quiet here now ?

Very much so. It's still a mystery to me as to why the OP continued fighting RTH. At the 8min mark, it most likely would have completed RTH with no issues. Hard to say but more likely than not.

 

[solentlife]

Very much so. It's still a mystery to me as to why the OP continued fighting RTH. At the 8min mark, it most likely would have completed RTH with no issues. Hard to say but more likely than not.

That is also my thought as well ... and why I spent a long time actually reading every line !! Trying to figure out why.

The more I consider it - the more I conclude the GPS was faulty and initiated the mess. Because the GPS could not provide consistent and reliable position info - the speed calculations kept falling outside acceptable parameters and Flight Controller could not command effectively.
At 8 mins - the best would have been see if RTH completed, if not then switch to ATTI and continue the path home .... anything else IMHO doomed it to failure.

Nigel

 

[BudWalker]

I'm hoping someone could review my flight log and tell me the significance of a couple of events I encountered today. After an uneventful flight, to a little over 17,000 feet away, everything went south. It forced me to land in the desert, then it took an hour to find it but to my amazement it's cam through largely unscathed....sort of.

Looking at the log, at about 16:40 into the flight I see that one of the battery cells is about 2 or 3 tenths of a volt lower than the others, and the text was in orange for that cell. About 10 seconds later I get a warning of "Ultrasonic System Error". Then other errors followed.Also, I had went ahead and let it do an automatic RTH, then I turned my attention away for a moment, and then I look back and my craft was flying AWAY from home, out over a country club where I did NOT want it to go down. Put into ATI mode, and managed to get it back over the open desert, before it landed.

Does that 2 or 3 tenths of a volt difference make a that much of a difference ? Was that the cause of the errors ? I never knew the craft had anything "Ultrasonic" on it. But today researching it it turns out to be the Vision Positioning System. I've got another moduIe I could put on it, but when I put a fresh battery in, everything checked out ok, no errors. Hence my question was the whole thing due to that one low cell ?

Oh yea.....that was a new battery too.

My log is uploaded for viewing, I'd appreciate any pointers.

Thanks

I took a look at this flight. In summary I agree that the problem is some kind of hardware problem, but I think it's more than just a bad GPS. There was also a SmartBattery RTH that didn't contribute any real problems, except making it more difficult to determine what happened. Kind of a perfect storm thing I think.

Looking at the ultrasonic height there was a glitch at 425 secs which by itself is not so unusual. The glitch noted by @Fly Dawg at 819 secs was just the first of many.

The regularity of these glitches indicates, to me at least, some kind of HW issue.

It's difficult to tell if the gpsHealth drop was due an actual increase in dilution of precision or some other issue. If you could retrieve the .DAT we may be able to determine this. Look here to see how to do that.

There are a couple of more things to note.

1) The switching through different states - RTH, GPS+ATTI, etc described above in post #14 didn't actually happen. What did happen is that at 495 secs the SmartBattery system decided it was time to RTH which remained in effect through the remainder of the flight. It didn't switch out of RTH and into GPS+ATTI at 499 secs. Instead, it switched to RTH and GPS+ATTI. The AirData presentation can be confusing. Far better to use the TXTtoCSVtool converter to see what actually happened.

2) At 910 secs the RC was switched to F mode not A mode.

3) I didn't see where the AC was flying away from the HP.

 

[Fly Dawg]

3) I didn't see where the AC was flying away from the HP.

Neither did I, but just to add another note on this, digging a little deeper, the Ultrasonic Error Spike did indeed effect the altitude readings.
It jumped from 367.1 ft to 517.7 ft in 100ms. Impossible in reality. But it did return to normal. This is another one of those....Hmmmm....moments.....

 

[BudWalker]

Neither did I, but just to add another note on this, digging a little deeper, the Ultrasonic Error Spike did indeed effect the altitude readings.
It jumped from 367.1 ft to 517.7 ft in 100ms. Impossible in reality. But it did return to normal. This is another one of those....Hmmmm....moments.....

Yeah, it's hard to tell if the ultrasonic sensor spike coincided with height spike as would be the case if there was an underlying cause to both. Or, if height is computed from the barometer and the ultrasonic height.

@Elbert Hill any chance of retrieving the .DAT?