Had a fight with 'auto-land'

[TrevorTron]

A friend saw and admired my P3A, so he went out and bought his own P3P. I think he had a minor crash with it (he can be a bit hashy) and then complained that he "couldn't see the picture any more" and asked me if I could take a look. He lives in France (and doesn't speak a word of English - fair enough), he left the quad with me and headed off home.
The controller wouldn't connect to the craft so that would explain the lack of images. I got them to pair up again without any issues but I did also notice that the camera (gimbal) was lying at a rather strange angle; almost 45° form horizontal. I managed to right it using the two-right-finger trick and after an IMU cal, I sent the craft off on a small trip to check it flew OK, which it did.
Then, the other day I was heading off on a job and, knowing the area to be particularly scenic, I took the drone along with me to get some nice pictures and video.
So once I found a suitable launch point from a large balcony (buildings here are full of rebar due to the high probability of earthquakes, a plastic table does the trick) off she went over the Ria Formosa lagoon. I got some nice shots and decided to bring her home the lazy way and hit RTH. I never trust RTH to land in exactly the same spot as take-off and always take over control for the last few feet. All seemed to be OK, but it would NOT hover. As soon as I took my hands off the controls, it would start to drop and/or drift, at one point it was actually below me! I had never done a hand-catch before but in this case it was a necessity as I'd had the low (not critical) battery warning and was worried I was going to crash. I had a real job on my hands (or hand!) getting her close enough to catch - but did manage without any damage to craft or right hand. (Couldn't catch with my left hand as I needed that to maintain altitude). All in all a bit scary.
So what (if anything) did I do wrong? Looking at the flight log (HERE), I see it is saying 'Auto-land' towards the end of the flight. Why is it trying to auto-land after I had cancelled the RTH? And the drifting? Plenty of satellites and not much wind... perhaps there is still something wrong inside there, had I known I certainly wouldn't have sent her off over water!
DJI Go version 3.1.3, I would have to fire up the craft to get her f/w version - but will do if it is likely to help.
Any tips gratefully received, TIA.

 

[solentlife]

Auto Land becomes abitrary when battery gets down to under 15% ... people think it kicks in at 10% ... not true.

It kicks in before that ... mine kicks in on my P3S at about 14% ... my P3P - I have not allowed to to get that low to find out !

OK ... Auto Land .... with the Pro and Adv - you have possibility to affect landing out point, to slow descent etc. With P3S - you really are in s*** street ! Mine refused to listen to commands and just landed out where it decided.

Once Auto Land kicks in - you better hope you are over reasonable location or can hand catch it ...

So my question is : What was Battery % level in this auto land situation ?

Nigel

 

[Oso]

So my question is : What was Battery % level in this auto land situation ?

Nigel - FYI that a link to the flight log is in his original post.

Auto land began at 47% battery after RTH brought the AC to within 16-17 feet of the home point.

DJI Flight Log Viewer - PhantomHelp.com

 

[solentlife]

Sorry ... I'm so used to seeing a full link ... not a {here} 'button' ....

Ok - will be looking at his log ...

Note - My comments about % auto land though still hold for others to be aware of.

Nigel

 

[solentlife]

I just have this nagging feeling about this :

"So once I found a suitable launch point from a large balcony (buildings here are full of rebar due to the high probability of earthquakes, a plastic table does the trick) off she went...."

We look at the log and we see a lot of Compass Error once she's clear of the building in early part of log ... then it supposedly clears.

Then we get Yaw error ... just a couple of lines.

We get a cell voltage dip in middle of flight - that sorts itself ..

Then we get RTH ... and progression to Auto Land.

What I find interesting is the Auto Land wanders about so much ... as if its in ATTI mode ... but no listing in Log of ATTI ... unless having Auto Land listed over-rides stating ATTI ?
The wandering around also would be what a totally manual situation might do if Compass / GPS etc. are not working correctly and Pilot is flying totally by Sticks.
I have a feeling that location has something to do with it ... but according to log ??

Nigel

 

[TrevorTron]

Thank you both for taking the time to reply, it has re-assured me somewhat to see that it's not something silly I have done or overlooked.
The compass errors at the start of the data were undoubtedly due to the iron in the building at the aborted launch site, there was no error showing at take-off. (If the error showed up again after take-off, I confess I did not see it, there are just too many things to watch at once).
Would it be worth pulling the flight data off the craft itself? Something I've never done but I'm sure I'd manage.....

 

[solentlife]

Personally - I would avoid flying of such location again ... I think your building is the problem despite your plastic table.

Test fly out in the open field away from any influences ... see what you get then.

Nigel

 

[TrevorTron]

Personally - I would avoid flying of such location again ... I think your building is the problem despite your plastic table.

Test fly out in the open field away from any influences ... see what you get then.

Nigel

Agreed Nigel, it's not ideal. But I often fly my own P3A from my roof terrace which is the same; no-go from the floor but flies fine from a plastic table and never had any issues, which is why I didn't give it a second thought on this occasion.
But yes, I will take it out to the back of beyond, re-do the IMU & compass cal's and try it again.
Thanks again

FWIW here is one of the images I captured, the lifeboat station in Fuzeta. Note horizon still off by about 5°, I'll start another thread on that.

 

[solentlife]

I used to spend quite a bit of time in Setubal ... for me better than Lisbon. I preferred the smaller more village character. And the fantastic Fish in the market.
Plus taking the water taxi out to the island !
I used the Hotel up on the hill overlooking the estuary entrance to the bay ...

Lovely.

 

[Rance Pederson]

I learned the hard way with the low battery thing. Was within 6 inches of touchdown on a nice wooden deck where I was sitting on a bench. Landing due to low battery warning. Suddenly my craft launched itself straight up, stopped, and as I was fighting with everything I had to come back down, it took off for it's launch point, which was about 30 yards from the deck. Sadly there was a spruce tree directly in it's path and the drone struck the tree top at top speed. Pretty much wiped out the gimbal hitting that tree top. I learned a couple valuable lessons. #1, adjust the RTH altitude for your surrounding area. #2, when you get a low battery warning, don't be messing around...land that sucker while you still can!

 

[TrevorTron]

I vaguely remember reading another thread a while back about a similar situation where a member felt (rightly) felt that DJI, through their programming, had effectively taken control of the craft away from the operator by invoking this autonomous behaviour, and his argument was - had there been an unfortunate (or expensive) incident, DJI should be held responsible for any damage caused. I think he had a point and wonder if subsequent updates may have quietly removed this folly.

 

[Terry Evans]

Agreed Nigel, it's not ideal. But I often fly my own P3A from my roof terrace which is the same; no-go from the floor but flies fine from a plastic table and never had any issues, which is why I didn't give it a second thought on this occasion.
But yes, I will take it out to the back of beyond, re-do the IMU & compass cal's and try it again.
Thanks again

FWIW here is one of the images I captured, the lifeboat station in Fuzeta. Note horizon still off by about 5°, I'll start another thread on that.

View attachment 91700

Very nice picture!

 

[TrevorTron]

Very nice picture!

Thank you for the compliment. Sometimes I think we forget that this is the real object of the hobby. Of course it is nice to get the gear back in one piece too!
We are spoiled for choice around here with beautiful scenery. I do try my best not to take it all for granted.

 

[peter west nz]

I have had something like this happen a year ago or so. I too was flying from a building with a large partly enclosed veranda, and I flew off a table as well. When it was 50ft up, it decided that it had a compass problem and switched in and out of atti by itself [it had plenty of gps]. I too used the rth [which I almost never use], because it was going out of sight over a wall. I had to fight it all the way back and eventually hand caught it. I swore not to try that again! I thought that the large, steel lamp posts were the problem, but maybe not.