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Speed/Yaw & compass errors?
376 9 2018-5-3
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djmokoia77
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Flight distance : 451627 ft
United Kingdom
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Finally got some decent weather this morning, so I went out to do some practice flying.

I got a number of warnings/errors during the flight, some of which I only became aware of when reviewing the flight logs.

Before I had taken off and then a couple of times afterwards, while I was doing my control check, there are signal loss errors. These did not persist during the flight.

Then during the flight there are warnings about speed and yaw errors (which I did not notice while flying) and compass errors, which I did notice but iwas very brief.

I had been flying in P mode before switching to atti and there was nothing particularly noticeable about the behaviour, although I think that it did say at one point that it was switching to atti

https://app.airdata.com/main?share=zKOGyX

On the second flight, I started in atti mode and all was well until I switched to GPS mode, when I started getting errors and noticed that it appeared that the controls were not responding as expected. I switched back to atti for landing then did a compass calibration.

https://app.airdata.com/main?share=mtCLxo

I plan on going out again this evening at which point I will do another compass calibration before flying to see wheter it's responding to controls.

Anything else I should check? If there is a better way of sharing flight logs please let me know.

I have flown in this location before without running into any errors, there aren't any powerlines or anything else nearby that I'm aware of that could be causing interference.

2018-5-3
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Labroides
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Flight distance : 9991457 ft
Australia
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If there is a better way of sharing flight logs please let me know.

Yes ... Airdata isn't much help at all.
Go to http://www.phantomhelp.com/LogViewer/Upload/
Follow the instructions there to upload your flight record from your phone or tablet.
Come back and post a link to the report it gives you.

Also can you give some information about the area where you launched.
Specifically, was it on reinforced concrete or close to a lot of steel or live electric cables?
2018-5-3
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Eric13
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Flight distance : 7061053 ft
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You want to upload your flight record here for the specialists to investigate this.
Once you did upload provide us with the link:
http://www.phantomhelp.com/LogViewer/Upload/
2018-5-3
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djmokoia77
lvl.4
Flight distance : 451627 ft
United Kingdom
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Thanks both. Like this:

http://www.phantomhelp.com/LogViewer/6OAN3HI8104C272ZNWRR/

http://www.phantomhelp.com/LogViewer/DDFGA7N18P968W8SUMWK/

?

It's an open, grassy area, no concrete, steel or powerlines nearby. I have flown here before on a number of occasions without issue.
2018-5-3
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hallmark007
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Although it might be a grassy area we are never to sure what’s buried beneath the ground, and your P4Pro shows similarities of picking up interference on the ground, also if you have added anything to the aircraft that might cause interference, and although we don’t always see warnings when we set aircraft on the ground it’s worth checking your compass heading against the heading of your aircraft, you can do this by checking small red triangle lower left corner of your telemetry, I will try to explain what happens when you place aircraft on likely magnetic interference.
Although this may not have been the cause of your problem, it won’t do any harm to be aware.

The best way I can explain this is. If you put your Aircraft on the ground in normal circumstances, start it up, then lift it up and turn it 90 degrees to the right both your compass heading and IMU will remain at 0.
If you put your Aircraft on the ground and there is magnetic interference only the heading of your compass will change, your aircraft will still take off. But when it clears magnetic interference compass will then move to correct heading which you would think was great. But No, what happens is IMU is then conflicted and confused because of this sudden movement by compass, so you receive IMU exceptional heading warning, yaw errors speed errors, your aircraft cannot deal with data conflict so decides to switch to Atti mode dropping gps in favour of compass simply because aircraft can fly without gps but not compass.

While I can’t be certain you picked up interference from the ground or surrounding area it is the most common cause.
I have seen many cases where people start their aircraft in or on their car in their house and then bring it outside so damage is already done and we will see exact same warnings and and reaction from aircraft.

We all should check our compass when we start our aircraft and maybe more of this could be avoided, you can do this by checking the small red triangle in the lower left corner of your telemetry.

One last thing I will say is we must always try to land aircraft immediately when this occurs.
2018-5-3
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djmokoia77
lvl.4
Flight distance : 451627 ft
United Kingdom
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Hi,

Thanks for the response and whilst I understand what you're saying, I'm not sure that I completely agree with your analysis.

My reason for saying that is that this is a location where I have flown on multiple occasions in the past. I've not had any issues prior to today. I did not start the aircraft on, or near any large metal objects.

I wasn't aware of the data link errors until after I got home and started looking at the logs.

When I took off for the first flight and did the usual control check, all of the controls were responding as normal, so there was no indication of any problems at this stage.

I was flying in atti mode. I deliberately switched to atti mode part way through the first flight and (iirc) kept it in atti mode for most of the flight (I think I switched back to P briefly when I over cooked it slightly on one of the manvouveres but switched back as soon as I had got the aircraft back to where I wanted it to be).

The second flight was I think, entirely in atti mode, from take off to landing. I did switch to P mode at one point and I think that's when I noticed what appeared to be some control issues, I so I switched straight back to atti mode before landing.

Given that this was this morning, my memory of the exact sequence of events is a little hazy. I don't recall getting any warnings whilst flying in atti mode and I don't think there was any indication that there was something wrong when I was flying in P at the start of the first flight.

Like I said, I did do a compass calibration at the end of the second flight, but of course, this was in the location where I was flying, so if there is interference there then my compass will now be properly screwed! However if there was something at that location, I would expect to have encountered issues before now when flying there.
2018-5-3
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djmokoia77
lvl.4
Flight distance : 451627 ft
United Kingdom
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hallmark007 Posted at 2018-5-3 04:57
Although it might be a grassy area we are never to sure what’s buried beneath the ground, and your P4Pro shows similarities of picking up interference on the ground, also if you have added anything to the aircraft that might cause interference, and although we don’t always see warnings when we set aircraft on the ground it’s worth checking your compass heading against the heading of your aircraft, you can do this by checking small red triangle lower left corner of your telemetry, I will try to explain what happens when you place aircraft on likely magnetic interference.
Although this may not have been the cause of your problem, it won’t do any harm to be aware.

I've been back out this evening, to the same location, for a quick couple of test flights. A couple of things I noticed:

1. There was a large metal gate relatively close to where I took off this morning (lying on the ground, so obscured by grass and I only noticed when watching the video back later today)
2. I am wearing a new watch strap, with a magnet on it. I took this off this evening and placed it well away from the drone before switching it on but I was wearing it this morning when I was setting up (but not when I calibrated the compass).

I did another compass calibration and all seemed well. I did the check you suggested of noting where the triangle was pointing on the map and moving the drone and the arrow was pointing in the correct direction the whole time.

I took off and did my usual control check and noticed that (especially on turning) it looked quite wobbly. It also lost a couple of feet in altitude whilst hovering. Although windier tonight (gusts up to 12 mph and winds of 8mp) it looked a lot less stable than I expected.

I landed and swapped the props for a brand new set and had another go but it still looked wobbly to me.

The forecast tomorrow is for much lower wind speeds, so I am going to go through the same process again and if it still looks unstable then I think I am going to have to contact DJI.
2018-5-3
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hallmark007
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djmokoia77 Posted at 2018-5-3 11:11
I've been back out this evening, to the same location, for a quick couple of test flights. A couple of things I noticed:

1. There was a large metal gate relatively close to where I took off this morning (lying on the ground, so obscured by grass and I only noticed when watching the video back later today)

It might also be worth doing correct IMU just to be on the safe side, wobbly and loosing altitude is what makes me say this.
2018-5-3
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djmokoia77
lvl.4
Flight distance : 451627 ft
United Kingdom
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hallmark007 Posted at 2018-5-3 11:15
It might also be worth doing correct IMU just to be on the safe side, wobbly and loosing altitude is what makes me say this.

Thanks, I'll give that a shot tomorrow. If I remember correctly, that requires a flat surface?
2018-5-3
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hallmark007
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djmokoia77 Posted at 2018-5-3 11:46
Thanks, I'll give that a shot tomorrow. If I remember correctly, that requires a flat surface?

Very flat, also best to leave Aircraft in cold room for 30/40 minutes before calibration.
2018-5-3
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