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Near loss in Atti mode (flyaway)

nottery

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Problem? Not sure why it switched out of GPS mode into ATTI mode after pressing RTH button

Was unit in a crash?
no

What have you tried so far?: reading about ATTI Mode

What device are you using? ipad mini 4

What firmware are you running ( aircraft, remote controller)? newest

What Go app version are you using? newest version

Any modification? its all a stock unit

Did you change anything or install any apps? no

Do you have a video or pictures of the problem?
Hi there,

So went for a fly the other day in fairly strong winds (30kmh), had been flying for over 10 min with no problems, when at 11m 13s i pressed the RTH button, the AC then went up to the RTH altitude (30m) then headed towards the home point, about this time the AC has entered ATTI mode and started drifting away in the wind.

To be honest at the time i had no knowledge what the difference was between GPS and ATTI modes were,
I panicked:eek:, forgot to hit the pause button, lost sight of the AC pretty quickly, tried auto land, but was warned of unsafe landing area. Eventually after being blown almost a 1km away, i managed to figure out my orientation and fly it home.

My question is, why it has entered ATTI mode?

From my understanding it has something to do with the compass and the ICU data conflicting, putting it into ATTI mode, is this correct?

Thanks Nick.
 

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sar104

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Problem? Not sure why it switched out of GPS mode into ATTI mode after pressing RTH button

Was unit in a crash?
no

What have you tried so far?: reading about ATTI Mode

What device are you using? ipad mini 4

What firmware are you running ( aircraft, remote controller)? newest

What Go app version are you using? newest version

Any modification? its all a stock unit

Did you change anything or install any apps? no

Do you have a video or pictures of the problem?
Hi there,

So went for a fly the other day in fairly strong winds (30kmh), had been flying for over 10 min with no problems, when at 11m 13s i pressed the RTH button, the AC then went up to the RTH altitude (30m) then headed towards the home point, about this time the AC has entered ATTI mode and started drifting away in the wind.

To be honest at the time i had no knowledge what the difference was between GPS and ATTI modes were,
I panicked:eek:, forgot to hit the pause button, lost sight of the AC pretty quickly, tried auto land, but was warned of unsafe landing area. Eventually after being blown almost a 1km away, i managed to figure out my orientation and fly it home.

My question is, why it has entered ATTI mode?

From my understanding it has something to do with the compass and the ICU data conflicting, putting it into ATTI mode, is this correct?

Thanks Nick.
The reason is right there - in the notifications section of the AirData page. You had multiple (hundreds) of compass error warnings from immediately after you took off. Why on earth did you think it was okay to fly 4000 ft away with those peppering your screen? I'm impressed that without any prior experience of ATTI mode that you were able to fly it back home. Pressing pause would have had no effect at all in ATTI mode - there is no ongoing process to pause.

As to the cause - when you get compass errors right after takeoff it is almost always due to magnetic interference at the takeoff point, so that the IMU yaw is initialized to the wrong value by the compass. After takeoff, when the aircraft leaves the location of the magnetic interference, the compass yaw changes to the correct value but the inertial sensors did not record any rotation, so now they disagree. That causes the errors and ultimately, since the FC cannot navigate or even hold position if it does not know which way it is facing, leads the FC to abandon P-GPS mode and switch to ATTI.

The simplest solution to prevent this from happening is to ensure, before takeoff, that the aircraft orientation arrow on your screen agrees with the direction that the aircraft is actually facing. If not, do not launch.
 

nottery

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Thanks for the quick reply sar,

Like i said, i had been flying around the oval for approx 10 min without any problems. You are right! i should have been paying more attention to the screen.

"Why on earth did you think it was okay to fly 4000 ft away with those peppering your screen? "

I certainly didn't intend for the AC to get that far away from me. What happened was, atti mode kicked in and it blew away like a balloon in the wind. It was blown / Drifted / glided away, NOT flown.

Thank you for the lesson sar, i WILL in the future take much more notice of the warnings and make sure the orientation on the screen matches the AC before takeoff.

On a different note, would the magnetic interference likely be from high voltage power lines (200m away) or some metal under the oval?
The KP index was low that day, think about a 2.

Thanks again, Nick.
 

sar104

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Thanks for the quick reply sar,

Like i said, i had been flying around the oval for approx 10 min without any problems. You are right! i should have been paying more attention to the screen.

"Why on earth did you think it was okay to fly 4000 ft away with those peppering your screen? "

I certainly didn't intend for the AC to get that far away from me. What happened was, atti mode kicked in and it blew away like a balloon in the wind. It was blown / Drifted / glided away, NOT flown.

Thank you for the lesson sar, i WILL in the future take much more notice of the warnings and make sure the orientation on the screen matches the AC before takeoff.

On a different note, would the magnetic interference likely be from high voltage power lines (200m away) or some metal under the oval?
The KP index was low that day, think about a 2.

Thanks again, Nick.
Ah - apologies - I had not noticed how quickly it switched to ATTI, which is quite unusual. The compass error must have been large. If you want to post the mobile device DAT file then we can take a look at how bad it was.

KP index is not relevant except in the most extreme, rare conditions. Power lines don't have a significant magnetic field. My suspicion would be irrigation pipes under the grass.
 
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sleebus.jones

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My suspicion would be irrigation pipes under the grass.
Those are usually HDPE or PVC, both non-metallic. Iron/steel pipes are usually buried 6' or greater down, so unlikely to be a factor.
 

sar104

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If you mean the .dat file from the DJI app inside the FlightLogs folder, then i have attached it below.
Confusingly there are DAT files in various places. The one you need is from the FlightRecords folder, not the FlightLogs folder.
 
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aokusman

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Problem? Not sure why it switched out of GPS mode into ATTI mode after pressing RTH button

Was unit in a crash?
no

What have you tried so far?: reading about ATTI Mode

What device are you using? ipad mini 4

What firmware are you running ( aircraft, remote controller)? newest

What Go app version are you using? newest version

Any modification? its all a stock unit

Did you change anything or install any apps? no

Do you have a video or pictures of the problem?
Hi there,

So went for a fly the other day in fairly strong winds (30kmh), had been flying for over 10 min with no problems, when at 11m 13s i pressed the RTH button, the AC then went up to the RTH altitude (30m) then headed towards the home point, about this time the AC has entered ATTI mode and started drifting away in the wind.

To be honest at the time i had no knowledge what the difference was between GPS and ATTI modes were,
I panicked:eek:, forgot to hit the pause button, lost sight of the AC pretty quickly, tried auto land, but was warned of unsafe landing area. Eventually after being blown almost a 1km away, i managed to figure out my orientation and fly it home.

My question is, why it has entered ATTI mode?

From my understanding it has something to do with the compass and the ICU data conflicting, putting it into ATTI mode, is this correct?

Thanks Nick.
Why are you fling in 30mph winds?
 

sar104

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Third time lucky... :)
Interesting - there are multiple compass errors in the log, including "out of range". Initialization looks fine, yaw is initialized and then adjusted for the local declination (11° E). After takeoff the discrepancy between magnetic yaw and IMU yaw varies somewhat wildly, which is the source of all the errors and the ATTI switch, but I'm struggling to see the cause:

2018-08-17_10-53-58_FLY035_01.png

The DAT files for the Mavics don't seem to contain data for both compasses - I need to follow up on that.

You might want to take a look at the compass values in the DJI GO app settings.

@BudWalker?
 

nottery

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Ok, will have a look at the values tomorrow, and let you know. Thanks for your time and effort sar, it’s very much appreciated.
 

BudWalker

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Interesting - there are multiple compass errors in the log, including "out of range". Initialization looks fine, yaw is initialized and then adjusted for the local declination (11° E). After takeoff the discrepancy between magnetic yaw and IMU yaw varies somewhat wildly, which is the source of all the errors and the ATTI switch, but I'm struggling to see the cause:

View attachment 43862

The DAT files for the Mavics don't seem to contain data for both compasses - I need to follow up on that.

You might want to take a look at the compass values in the DJI GO app settings.

@BudWalker?
The tablet .DAT doesn't have the individual magnetometers data. Just the data from the one it's using which is shown in the IMU record.

The compass errors seen in the converted .txt are probably coincident with the OSD.compassError signal which doesn't exist in the tablet .DAT. Comparing the .txt and the tablet .DAT it looks to me like OSD.compassErrors might be coincident with magMod excursions. The compassError signal does exist in the AC .DAT. Don't know that I've ever seen compassError with a value of True.

@nottery it looks to me like you're running FW 01.04.0400? If so, there is a good chance the AC .DAT will be available. Could you try to retrieve that? Look here to see how. You'll need to upload it to Dropbox or GoogelDrive and then provide the link to the uploaded .DAT
 
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BudWalker

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Something else I noticed. IMUEX(0):err isn't coincident with OSD:compassError. I'm speculating OSD:compassError is purely a compass status signal - not related to the FC's attempts to use the magnetometer data in it's calcs.
 

Starz

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Those are usually HDPE or PVC, both non-metallic. Iron/steel pipes are usually buried 6' or greater down, so unlikely to be a factor.
Without X-ray vision, underground objects can be anywhere and any material. As long as I’ve been around the excavation industry,( no, I’m not in the excavation business) you would be amazed at what metal stuff comes out of the ground and where it can be found.
 
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