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48019 31 2018-5-1
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DeputyDawgAtl
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I was on a trip to the beaches of FL this weekend and obviously took my P4P with me.

Friday I made multiple flights from the beach (not sand, but from sidewalk next to sand since I didn't have a landing pad).

No issues at all !!!

Later on that afternoon my buddy was coming back on shore. I wanted to fly out and film him coming in.  I launched from a differnt point, this time on the paved parking lot next to the pier.  Approx 1 minute into the flight (out some 400 feet and up some 130 feet) i lost control of the drone. It was going on it's own.   I initated a RTH which i could see it elevating but not quite coming back to launch point.  I cancelled RTH and while this took some effort I had some control.  Luckily I had a friend with me who was able to do a hand catch and then I cut the motors.   Could have been alot worse - fly into ocean, a boat, docks, pier, people.

Packed it up and went back to hotel. Sat am I went back to the spot I originally launched from without incident.  I did an auto take off. It went up some 3-4 feet and hovered. Once again after approx 1 minute it went off on its own with little control from me.  My friend pointed out that when it took off from auto take off, it did a jerky motion.  We tested that out again while he filmed it.  Sure enough it did it. Since it was only a few seconds into flight, I landed immeiately, no issues.      I have the video, but it won't let me attach here.  BUT I took a still of the point where it jerked to the right - which I believe you can see.

There was park table nearby so I did an IMU calibration then back to the auto take off - same issue.

Later in the am it dawned on me that the park table was covered with a metal roof.  I re-did the IMU calibration on the kitchen table of the condo. I took it out to the paved parking lot of condo and did the auto take off - NO jerky motion.    I made several flights later without incident.

So the obvious question is what happened that made it go haywire?

If I posted the log from DJI Go4 app, is that going to tell anything? If so anyone here that can read those?

Thanks,
Paul

2018-5-1
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msinger
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Check out your TXT flight log to see if it explains what happened. You can upload and view it online here. If you'd like other people to review and comment on your flight log, then please post a link back here after you upload it.
2018-5-1
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DeputyDawgAtl
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Thanks, don't have table with me at work. Will do that when I'm home in approx 3 hours

I do have the .csv file from healthy drones. I didn't see anything in that.

2018-5-1
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Genghis9
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Since it looks like we'll see your logs, that may better explain things but a couple thoughts/observations.
You said you were taking off from a paved area near the pier and condo, are we talking black top or concrete.  Concrete may mean rebar underneath, which is not good and could be the reason.

RTH: have you ever really played around with this feature, experimented with it, and used it for other than emergency needs?  If not you should.  When RTH is initiated it will climb to the RTH set altitude, if lower than the alt, and then pause, then return and descend and pause before landing.  Aircraft will also fly slower in RTH mode than you may be used to seeing happen.  When things are going wrong 5 seconds can seem like forever and you may feel something went wrong or is not working; when in fact it is doing exactly what it is supposed to be doing.  Canceling a RTH is where most operators run in to problems, and as a result can experience a fly off or crash.  Additionally, looking at a small object out several hundred feet can cause problems with your ability to judge time and distance thus thinking something is not happening or happening fast enough when it is all working as designed.  Thus the reason for learning, using, and getting used to how the RTH functions all work
You are lucky that you were even able to successfully complete an IMU calibration on your first attempt with the metal table.
Fly Safe!
2018-5-1
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DeputyDawgAtl
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Genghis... Thanks

When I was first flying earlier in the day (6 flights) they were from concrete (didn't have a landing pad so it was that or sand).  I knew that concrete had Rebar, but really would it have enough (buried within cement) to cause that?   The flight in question was over pavement (blacktop).

RTH  yes I have tested and used in emergencies.  It did climb to the Height set but when it was moving it didn't seem to be moving in the right direction hence why I cancelled it.

Also note: perhaps I didn't explain but recalibrating IMU on the table with metal roof did NOT work.  I still had the jerky motion.  It wasn't until I tried it later in the condo and then tested on blacktop parking lot of condo was it successful.

I hope this all helps.

Having said that, attached is the DJI flight log from the Go4 app.  I'm sending it to the link mentioned.
2018-5-1
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DeputyDawgAtl
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Log sent to that site.  This looks similar to HD csv file only prettier.

At 51 seconds into the flight you can see I initiated RTH so it was right before that (few seconds) that it started going on its own.

What is IMU altitude vs. VPS altitude?

I see at the very end the RED warnings. I suspect that is when my friend grabbed it for the hand catch.

Otherwise, I see no issues.  Sats looked good as did battery, voltage etc.

Towards the end, you can see the distance etc was not consistent.  That was me trying to control it while it was trying to do its own thing.

Do you think that all my flights earlier taking off from cement had a cumulative effect which toasted the IMU?

Any and all thoughts appreciated
2018-5-1
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Labroides
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If I posted the log from DJI Go4 app, is that going to tell anything?
If you don't it's going to tell nothing

I knew that concrete had Rebar, but really would it have enough (buried within cement) to cause that?
Maybe, reinforced concrete is half steel and you can't see where the bars are.
You might put your compass right on top or you might not.
Never launch or land on reinforced concrete or steel surfaces, it's just asking for trouble.

Log sent to that site.  This looks similar to HD csv file only prettier.
It has a lot more information than HD and it's a lot easier to read.

At 51 seconds into the flight you can see ...

You've uploaded and it's shown you the flight information but you haven't posted a link to the report it showed you.
No-one can see anything of it until you post the link.

Do you think that all my flights earlier taking off from cement had a cumulative effect which toasted the IMU?
You could recalibrate the IMU on the deck of the USS Nimitz and all the steel wouldn't have any effect on the IMU.
The IMU isn't affected by magnetic fields - the compass is.
Neither suffers from any cumulative effect.
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DeputyDawgAtl
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My apologies for not posting the link:

http://www.phantomhelp.com/LogViewer/PZX6LS5RKARVKHPI57EA/

So it was my assumption the IMU got all messaged up.  If I understand you are saying its the compass that got messed up??   If so how could hovering the drone cause it to go in various directions - if no throttle applied.

Trust me I learned a great lesson from this experience !!!  I was lucky no crash, lost at sea or hitting a boat, beach goer or building.
2018-5-1
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msinger
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The stick positions in your flight log look odd. The right stick is showing it was not in the center position for the entire flight. Was that the case? If not, you should try calibrating the remote controller.
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DeputyDawgAtl
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Msinger,

Can I ask where in the log you saw that please.

Funny you should mention that.  Earlier and before the IMU reset each time I powered on the drone I got that obnoxious beeping.  Shutting off the drone and doing the stick calibration solved it.  But I got it many times.  
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msinger
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Ah, well, that makes sense then. The remote controller will beep if the sticks are not in the center position when it's powered on.

You can find the stick positions in the following section of the CSV file that's linked to the flight log you uploaded above:




"1024" is the value that will appear when the sticks are in the center position.
2018-5-1
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DeputyDawgAtl
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Thanks.  I recall In The past looking for the decoder  ring for those and similar settings
Are those documented anywhere ?

So perhaps my issue was compass related from rebar plus stick issue  might explain why I was trying to move but had troubles.   

Any idea how sticks got messed up?
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Labroides
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So it was my assumption the IMU got all messaged up.  If I understand you are saying its the compass that got messed up??   If so how could hovering the drone cause it to go in various directions - if no throttle applied.
I didn't say that your compass got messed up and there's no indication of a compass error in the data.
Your Phantom commenced RTH but quickly hit a wall and couldn't get anywhere.
You were quite close to an airport.
The warningmessage that appeared several times:
Approaching a No-Fly Zone. RTH may be affected. Fly with caution
... probably explains what you encountered.
Your Phantom was trying to RTH but hit the invisible wall in the sky (airport No-fly-zone).
All the assumptions about IMU and compass together with an out of calibration right joystick added to the confusion but the advice about launching from concrete in post #7 is still valid.
Your Phantom did not fly away.
2018-5-1
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DeputyDawgAtl
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Hmmmm there were no airports in that area.  I was in a "yellow" zone which I had unlocked successfully via DJI's web site.

Also prior to that flight when I launched from a different area I flew over that area without issues.

@ msginer, I checked the csv and while there were some values of RCaileron at 1024 for so many rows together. Can you share what time index you are referring.   Is there some sort of decoder ring of what all those values mean?

One more thing to mention it.  I wasn't hiding it, but others stated it wasn't an issue so i dismissed it.  But you guys seem to know a lot about this.  Very near where I launched from the pier,  there was some sort of antennae array. i was told it was for weather data only and thus should have no impact.  But it was in this area where i launched from.  Though earlier flights launched a distance away (from concrete) did fly near this antenna.  I think i Have a pic of it, let me look around.   Could this antenna be the culprit perhaps?

Also maybe i can post a map of this area showing the various points i'm referring to - for clarification.

I sincerely appreciate everyones help.  But i'm getting more confused as to what the heck happened.  Did the concrete/rebarb impact the compass in such a way that it simply didn't know where it was going - which way was which??  Earlier I had some 6 successful flights all launched from the concrete.  The flight in question launched from blacktop.

I do know NOT to take off from concrete or metal as it can interfere with compass.
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Labroides
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DeputyDawgAtl Posted at 2018-5-1 17:12
Hmmmm there were no airports in that area.  I was in a "yellow" zone which I had unlocked successfully via DJI's web site.

Also prior to that flight when I launched from a different area I flew over that area without issues.

Hmmmm there were no airports in that area.
None at all .... except for the one that was one mile to the west of your position.
And that's the one that the app was warning you about.

I checked the csv and while there were some values of RCaileron at 1024 for so many rows together.
The Aileron went to 1024 when it was centred but the Elevator didn't.  It was at 822 when at rest.
That would have made the Phantom move backward when the right stick was centred.

The antenna array is unlikely to have had any influence.

i'm getting more confused as to what the heck happened.  Did the concrete/rebarb impact the compass in such a way that it simply didn't know where it was going - which way was which??  Earlier I had some 6 successful flights all launched from the concrete.  The flight in question launched from blacktop.
I can't see any compass related issues in your description of the event or the recorded data.
I can see the app warning you that the NFZ could affect your RTH and I see clear evidence that RTH hit a wall in the sky which is exactly what happens if you try to fly into a NFZ..
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msinger
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Here are the values used for the stick movements in my log viewer:



I'm not sure how your sticks got out of calibration, but that seemed to be your only issue.
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Genghis9
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Labroides Posted at 2018-5-1 17:40
Hmmmm there were no airports in that area.
None at all .... except for the one that was one mile to the west of your position.
And that's the one that the app was warning you about.

Labroides
I think you are on to something here, obviously because of the NFZ warnings received.  However, I'm seeing disconnects between DJI's geo fence data and the FAA sectional for that area.  That airport at most is a Class E airspace field, which requires, per FAA drone regs, that all flights be outside 5 mile radius unless defined otherwise, in this case it applies.  More likely it is a Class G field but the 5 mile rule still applies.  This means that the OP at a minimum would have to obtain tower or airfield manager approval, since in this case it is an uncontrolled field (no control tower) he would likely have to coordinate with the field manager, whomever that is.  In part, technically it requires FAA authorization first then airspace coordination which may have to be the local RAPCON, many of the 107 folks differ on just which and what is actually required, as the FAA is still sorting out just how that process is supposed to work.  Also, it greatly depends on whether he is flying under 107 or 101 rules, my guess its 101.  For now airfields like this are more in the wild west category.
Now with the FAA techno stuff out of the way, the geo fence data shows a yellow circle that is only indicating a 1.5 mile radius, not that I'm complaining about that I am not, but it does not synch with the FAA rule set.  However, the more curious problem I see is that the OP was taking off and operating within the circle, by as much as a half of a mile per your own calculation.  Clearly, the OP stated he unlocked this zone, and he must have as he was able to operate in there, would he not?  Either that or he just thought he did but actually didn't.  Since DJI does a poor job of actually stating the differences in their defined zones and what those zones are supposed to represent i.e. red is Class B, C, D airspace and yellow is Class E & G I think; even that is a problem as drones can operate in class G airspace with restrictions as noted above.  DJI definition: Authorization Zones. In these Zones, which appear yellow in the DJI GO map, users will be prompted with a warning and flight is limited by default. Authorization Zones may be unlocked by authorized users using a DJI verified account.
So, my point is, would he have been able to takeoff in an authorization zone without unlocking it?  
If so, then what does limited mean?  
If not, then he must have successfully unlocked the zone, so then why get a warning at about 1 mile distance when the circle goes out to 1.5 miles?  
Worse why would the bird be acting like it was hitting the wall at 1 mile, especially if it was unlocked?

Now again, I think you have a point here and may be correct, however, something is not adding up.
Thanks
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DJI Susan
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Hey Paul, has the drone been retrieved? If not, data analysis will be suggested to check the exact status if the drone is still under warranty period. Please kindly start a case from here: https://www.dji.com/support
2018-5-1
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Labroides
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Genghis9 Posted at 2018-5-1 19:26
Labroides
I think you are on to something here, obviously because of the NFZ warnings received.  However, I'm seeing disconnects between DJI's geo fence data and the FAA sectional for that area.  That airport at most is a Class E airspace field, which requires, per FAA drone regs, that all flights be outside 5 mile radius unless defined otherwise, in this case it applies.  More likely it is a Class G field but the 5 mile rule still applies.  This means that the OP at a minimum would have to obtain tower or airfield manager approval, since in this case it is an uncontrolled field (no control tower) he would likely have to coordinate with the field manager, whomever that is.  In part, technically it requires FAA authorization first then airspace coordination which may have to be the local RAPCON, many of the 107 folks differ on just which and what is actually required, as the FAA is still sorting out just how that process is supposed to work.  Also, it greatly depends on whether he is flying under 107 or 101 rules, my guess its 101.  For now airfields like this are more in the wild west category.
Now with the FAA techno stuff out of the way, the geo fence data shows a yellow circle that is only indicating a 1.5 mile radius, not that I'm complaining about that I am not, but it does not synch with the FAA rule set.  However, the more curious problem I see is that the OP was taking off and operating within the circle, by as much as a half of a mile per your own calculation.  Clearly, the OP stated he unlocked this zone, and he must have as he was able to operate in there, would he not?  Either that or he just thought he did but actually didn't.  Since DJI does a poor job of actually stating the differences in their defined zones and what those zones are supposed to represent i.e. red is Class B, C, D airspace and yellow is Class E & G I think; even that is a problem as drones can operate in class G airspace with restrictions as noted above.  DJI definition: Authorization Zones. In these Zones, which appear yellow in the DJI GO map, users will be prompted with a warning and flight is limited by default. Authorization Zones may be unlocked by authorized users using a DJI verified account.

I don't know.
There is uncertainty in the original description of events and in trying to match things to DJI's NFZ map.
I can only comment on what is definite.
The RTH stopped just a few feet from the home point and the app warned of approaching an NFZ.
The app warned of a NFZ three more times, each when the Phantom returned to within 16 ft of the launch point but at different directions to/from the home point and the airport.
Bumping into the invisible wall confused the OP because the Phantom wasn't responding normally to joystick inputs, particularly when this was happening right around the launch point.
The flyer didn't leave the Phantom hovering for long enough to easily see how the joystick calibration affected flight.
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Genghis9
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Labroides Posted at 2018-5-1 20:06
I don't know.
There is uncertainty in the original description of events and in trying to match things to DJI's NFZ map.
I can only comment on what is definite.

Copy all thanks
I think there are issues with the geo fence but can't prove it and your assertion warrants merit.  Also agree there appears to be a RC stick calibration problem too that confounds everything.
Cheers
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DeputyDawgAtl
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WOW... great information all - thanks so much for taking the time to review, offer help and educate me

I guess what is still confusing is earlier in the day when I launched from a different area (concrete sidewalk) I flew over the pier area and had no issues. If I hit a NFZ why wasn't it impacted then?   The other confusing part is I knew ahead this was a yellow zone. So I did all that I was required to unlock which it let me do.   I wasn't aware of the airport near by. I guess that is why it was a yellow zone. I didn't notice the airport but that area is a big nature persevere which is why i thought it was yellow

@msinger - thanks for the decoder ring. That will be quite helpful and is a good reference to have.

@labroides - reason the RTH cancelled was me.  It didn't appear to be coming home correct (i say appear in " ").  This all happened with in seconds.

This weekend there is a big park near me with open space. I will do some more testing.  But think my drone is OK now.

@DJI Susan.   The drone never crashed (as stated). I was able to finally do a hand catch to retrieve it.  I do have DJI care on this and did call DJI.  No offense to you but they were their typical poor support.  The first person told me to send it in for repair - but nothing is wrong with it I said and i'm not doing without a drone for weeks just so they can tell me nothing is wrong.  The second agent didn't seem to listen and asked me the same questions over and over.   Finally I got someone who listened BUT was very resistant to opening a ticket for analysis.  Once he agreed, I offered the video that I mentioned here that shows the jerky-ness with auto take off. He resisted accepting that, but finally agreed.  I wasn't thrilled with DJI support at all. I  stated don't you want to know the reason this happened to better your product etc.
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Genghis9
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msinger Posted at 2018-5-1 19:20
Here are the values used for the stick movements in my log viewer:

[view_image]

The values indicating deflection, are they supposed to indicate full stick or just any degree of deflection?
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DeputyDawgAtl
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yeah some of my values for those stick controls don't map to your chart
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Labroides
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Genghis9 Posted at 2018-5-2 05:09
The values indicating deflection, are they supposed to indicate full stick or just any degree of deflection?

Each joystick has a range of movement from 364 to 1684 with the normal centre point being 1024.
Full speed climb will be 1684 on the throttle
Full reverse will be 364 on the elevator.
Hovering will be 1024, 1024, 1024, 1024
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Labroides
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DeputyDawgAtl Posted at 2018-5-2 04:40
WOW... great information all - thanks so much for taking the time to review, offer help and educate me

I guess what is still confusing is earlier in the day when I launched from a different area (concrete sidewalk) I flew over the pier area and had no issues. If I hit a NFZ why wasn't it impacted then?   The other confusing part is I knew ahead this was a yellow zone. So I did all that I was required to unlock which it let me do.   I wasn't aware of the airport near by. I guess that is why it was a yellow zone. I didn't notice the airport but that area is a big nature persevere which is why i thought it was yellow

@labroides - reason the RTH cancelled was me.  It didn't appear to be coming home correct
That's all obvious in the recorded data.
It wasn't coming home after it hit the NFZ which the app advised about.

I offered the video that I mentioned here that shows the jerky-ness with auto take off. He resisted accepting that, but finally agreed.  I wasn't thrilled with DJI support at all. I  stated don't you want to know the reason this happened to better your product etc.

The video is not very useful for incident investigations.
The data is what's needed.
You've had better help and better explanation here than you'd get from DJI anyway.
Take the Phantom, calibrate the joysticks and try flying somewhere away from NFZs and if it flies normally (it will), then you'll know that there's nothing wrong with the Phantom and the explanations you've been given are accurate.
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Genghis9
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Labroides Posted at 2018-5-2 05:43
Each joystick has a range of movement from 364 to 1684 with the normal centre point being 1024.
Full speed climb will be 1684 on the throttle
Full reverse will be 364 on the elevator.

ah...the blind man sees
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DeputyDawgAtl
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Thanks Lab

There is a BIG park near me defiantley NO NFZ (i fly there almost every weekend).   Weather permitting I plan to do some testing
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DeputyDawgAtl
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just for giggles, where did you get all that stick info? I looked and couldn't find it anywhere

Now that I know what to look for. I may take some of my flight data from earlier other days - just to compare.
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Antonio76
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Maybe I don't understand, but when you did the two IMU calibrations on the different tables, did you actually check that they were perfectly horizontal? How?
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DeputyDawgAtl
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@ antonio I wasn't sure. They looked very flat.   The first one out by the beach had a metal roof, which I assumed may have interfered.  The second one back at the condo was on the kitchen table which again appeared very flat to me.  I didn't have a level to check, but they both looked flat
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Antonio76
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DeputyDawgAtl Posted at 2018-5-2 10:02
@ antonio I wasn't sure. They looked very flat.   The first one out by the beach had a metal roof, which I assumed may have interfered.  The second one back at the condo was on the kitchen table which again appeared very flat to me.  I didn't have a level to check, but they both looked flat

DeputyDawg, I am not sure that an improper IMU  calibration was the cause of your problem, of course, but from what I have learned, the surface on which it is performed MUST be absolutely horizontal, not merely "flat", which is not synonimous to "horizontal" (a wall is usually flat, but by no means it can be called "horizontal'' . It MUST also be vibration-free, otherwise it is impossible for the IMUs  to be properly calibrated, and this will have its effect on the drone's attitude while in the air...
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Vendex
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DeputyDawgAtl Posted at 2018-5-2 10:02
@ antonio I wasn't sure. They looked very flat.   The first one out by the beach had a metal roof, which I assumed may have interfered.  The second one back at the condo was on the kitchen table which again appeared very flat to me.  I didn't have a level to check, but they both looked flat

It's very important to do calibrations perfectly, take a note
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