My Latest Crash

[sar104]

???
Switching to atti forces the Phantom to ignore GPS data but the compass problem remains.
With most compass errors, the Phantom will have already done that (but it doesn't help).

Yes - but as a number of recent examples have shown, sometimes it does not switch to ATTI. @BudWalker has noted that recent firmware updates seem to have changed the threshold for switching so that the FC now tries harder to resolve magnetic errors.

And yes - while the compass errors remain in ATTI mode, since the FC is no longer attempting any active control of the aircraft position and will just hold attitude, the uncontrolled flight will stop and all that the pilot has to contend with is drifting with the wind.

 

[Neon Euc]

I would still be interested to see the flight log. @sar104 is right about finding the flight log, its automatically stored on the device you used to fly it with. Its pretty easy to retrieve. I'm assuming you have an android device, if you do then go to

Folders,

Dji

Flight log

Then select the last flight log (if that was the last flight you had with it that is) then upload here.

We can then see what happened and explain things in more detail

 

[San2C]

The log is on your mobile device so you can access it and post it. Without looking at that it's really hard to determine what happened, but it does look like the effect of a compass error resulting from taking off in a location with magnetic interference.

I thought that data was stored in the aircraft. I don't actually know how to access that data if it's in my iPad.

 

[sar104]

I thought that data was stored in the aircraft. I don't actually know how to access that data if it's in my iPad.

Instructions:

DJI Flight Log Viewer

 

[KevMo Photog]

It wasn't such a great platform after all.
Rule 1 for Phantom flying - NEVER launch from a steel or reinforced concrete surface.
I've lost count of the number of Phantoms wrecked from that.
When you get around to checking the flight data, it's going to show yaw errors and compass errors caused by launching in the strong magnetic field of all the steel inside the reinforced concrete.

I hear ya Meta4! But I launch from tops of parking garages all the time. I just use my Pelican case to launch off of. Never had one problem yet. But your right you'll def get errors if you launch right off of the concrete for sure. In many areas if you have concrete you'll have to deal with that from a launch standpoint.

 

[Andy9]

It's really scary knowing that this things can suddenly turned into such behaviour. Knowing that ATTI in this situation might be salvageable measure to some extent makes me a little less worry.
But what use of ATTI if AC is only a spot in the sky after a few hundreds meters or even less than that and you not have the compass data to bring the bird home? At least you must know to which direction it is heading to.

 

[PhantomWetSuits]

We also find that the magnetic Fields are a big part of GPS locks going into Atty Mode: We now use a Magnetic Field tester and have been really surprised by the results. At times when we think there must be a magnetic field , nothing shows up and when we think we are safe , it lights up and so we move to another take off position. The tricky part is why over the lake we would run into Magnetic resistance and yet we do at times. Nothing causes more yaw errors that can lead to a fly away than magnetic or electrical interference.

We got this device after I realized how sensitive the drone was to magnetic fields especially the tiny magnet inside the Phone. We have found magnetic Fields in Bridges, streets, driveways, Piers, cars, and over the lake. Not all magnetic field warning will snap the Drone into Atti mode but they will let you know , that you may be close to loosing GPS .

One Hot Tip if your drone on take off has a quick flash of Magnetic warning. LAND and start all over in a different place. Dont continue to fly just because it went away. Dont do it.

 

[KevMo Photog]

We also find that the magnetic Fields are a big part of GPS locks going into Atty Mode: We now use a Magnetic Field tester and have been really surprised by the results. At times when we think there must be a magnetic field , nothing shows up and when we think we are safe , it lights up and so we move to another take off position. The tricky part is why over the lake we would run into Magnetic resistance and yet we do at times. Nothing causes more yaw errors that can lead to a fly away than magnetic or electrical interference.

We got this device after I realized how sensitive the drone was to magnetic fields especially the tiny magnet inside the Phone. We have found magnetic Fields in Bridges, streets, driveways, Piers, cars, and over the lake. Not all magnetic field warning will snap the Drone into Atti mode but they will let you know , that you may be close to loosing GPS .

One Hot Tip if your drone on take off has a quick flash of Magnetic warning. LAND and start all over in a different place. Dont continue to fly just because it went away. Dont do it.

Good info man. But do you think that possibly your phone or that magnet in your hand is just merely blocking the GPS module in top of your bird?

 

[Timinator]

One Hot Tip if your drone on take off has a quick flash of Magnetic warning. LAND and start all over in a different place. Dont continue to fly just because it went away. Dont do it.

This. Soooooooooooooooo important. Many people tend to ignore errors on takeoff only to feel pain later.

 

[Skynet1]

We also find that the magnetic Fields are a big part of GPS locks going into Atty Mode: We now use a Magnetic Field tester and have been really surprised by the results. At times when we think there must be a magnetic field , nothing shows up and when we think we are safe , it lights up and so we move to another take off position. The tricky part is why over the lake we would run into Magnetic resistance and yet we do at times. Nothing causes more yaw errors that can lead to a fly away than magnetic or electrical interference.

We got this device after I realized how sensitive the drone was to magnetic fields especially the tiny magnet inside the Phone. We have found magnetic Fields in Bridges, streets, driveways, Piers, cars, and over the lake. Not all magnetic field warning will snap the Drone into Atti mode but they will let you know , that you may be close to loosing GPS .

One Hot Tip if your drone on take off has a quick flash of Magnetic warning. LAND and start all over in a different place. Dont continue to fly just because it went away. Dont do it.

POI, While this info is helpful, Is it a certainty the phone is causing the disruption. I say this because I've found that by simply placing my hand over top the upper portion the the model has caused it to switch from GPS to Atti. Perform the same test absent your cell phone, try and grasp the model from the top of the shell and see if you get the same results or not.

 

[San2C]

I would still be interested to see the flight log. @sar104 is right about finding the flight log, its automatically stored on the device you used to fly it with. Its pretty easy to retrieve. I'm assuming you have an android device, if you do then go to

Folders,

Dji

Flight log

Then select the last flight log (if that was the last flight you had with it that is) then upload here.

We can then see what happened and explain things in more detail

Here ya go, thanks.

My flight map:

 

[sar104]

Here ya go, thanks.

My flight map:

You had a compass error of 20 - 30° CW for the entire flight, most likely due to the takeoff location. The first notification was at 11 seconds. That eventually led to the runaway toilet bowl flight once you started significant maneuvers. You could still have recovered control by switching to ATTI but, without that, once the FC lost control in P-GPS it was game over.

 

[San2C]

You had a compass error of 20 - 30° CW for the entire flight, most likely due to the takeoff location. The first notification was at 11 seconds. That eventually led to the runaway toilet bowl flight once you started significant maneuvers. You could still have recovered control by switching to ATTI but, without that, once the FC lost control in P-GPS it was game over.

I still don't understand how "compass error" translates to antonymous flight. Oh also, I was in ATTI mode the whole time.

 

[sar104]

I still don't understand how "compass error" translates to antonymous flight. Oh also, I was in ATTI mode the whole time.

You were in P-GPS mode, also known as GPS-Atti mode, not ATTI mode. That means that the FC is attempting to control the aircraft location - holding position when sticks are centered or holding track according to heading and elevator/aileron inputs. So it is combined pilot/FC control.

The compass error affects the FC control because the FC has incorrect information on the aircraft heading, and so corrections to maintain position or heading don't have the expected outcome - it applies thrust in the wrong direction.

Depending on the magnitude of the compass error, that can result in various uncontrolled flight patterns, including the toilet bowl spiral that you observed. The error also shows up clearly in the increasing discrepancy between the IMU-computed position vs. the actual GPS location as the flight progresses:

If you switch to ATTI mode then the FC stops trying to correct and the problem goes away - you are just left with the problem of correcting for wind-induced drift yourself and, of course, dealing with the different flight characteristics of ATTI mode.

The best way to ensure that this doesn't happen is to check that the aircraft orientation arrow on the map at takeoff is pointing in the same direction as the actual aircraft orientation. In this case the arrow will have been pointing around 30° south of the actual orientation, which was around NE.

 

[Timinator]

You were in P-GPS mode, also known as GPS-Atti mode, not ATTI mode. That means that the FC is attempting to control the aircraft location - holding position when sticks are centered or holding track according to heading and elevator/aileron inputs. So it is combined pilot/FC control.

The compass error affects the FC control because the FC has incorrect information on the aircraft heading, and so corrections to maintain position or heading don't have the expected outcome - it applies thrust in the wrong direction.

Depending on the magnitude of the compass error, that can result in various uncontrolled flight patterns, including the toilet bowl spiral that you observed. The error also shows up clearly in the increasing discrepancy between the IMU-computed position vs. the actual GPS location as the flight progresses:

View attachment 96906

If you switch to ATTI mode then the FC stops trying to correct and the problem goes away - you are just left with the problem of correcting for wind-induced drift yourself and, of course, dealing with the different flight characteristics of ATTI mode.

The best way to ensure that this doesn't happen is to check that the aircraft orientation arrow on the map at takeoff is pointing in the same direction as the actual aircraft orientation. In this case the arrow will have been pointing around 30° south of the actual orientation, which was around NE.

This is what I love about this forum; I learn something new and very useful every day. I've started practicing flight in Atti mode just in case I run into a similar situation.

 

[San2C]

You were in P-GPS mode, also known as GPS-Atti mode, not ATTI mode. That means that the FC is attempting to control the aircraft location - holding position when sticks are centered or holding track according to heading and elevator/aileron inputs. So it is combined pilot/FC control.

Thanks for the comprehensive explanation, but I don't know what P-GPS mode is. I had the controller set to "A".

 

[sar104]

Thanks for the comprehensive explanation, but I don't know what P-GPS mode is. I had the controller set to "A".

According to the log file you were in flight mode P (P-GPS) for the entire flight.

DJI Flight Log Viewer - PhantomHelp.com

 

[San2C]

Did you generate that graph from the flight record? I know for a fact that the controller was always set to Atti mode so this is getting even weirder.

 

[Meta4]

I know for a fact that the controller was always set to Atti mode so this is getting even weirder.

The flight data shows your Phantom in P-GPS mode.
The most likely explanation is that you did not have Multiple Flight Modes enabled in the app.
If Multiple Flight Modes is not enabled, the mode switch will have no effect.
The setting is among those that get reset to default values after firmware updates.
You won't be able to confirm the setting unless the Phantom is connected.

 

[sar104]

Did you generate that graph from the flight record? I know for a fact that the controller was always set to Atti mode so this is getting even weirder.

Everything I've posted is directly from the flight log. And it is completely obvious from the initial flight behavior that the aircraft was in P-GPS mode because it was holding position in the wind with no stick inputs. I suspect that @Meta4's suggestion is correct - that you did not have multiple flight modes enabled. And in addition to that - why on earth would you fly in those conditions in ATTI mode? That makes no sense at all.