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SO when an over water flight does go wrong...what happens is..?
1130 16 2017-4-1
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Blah
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United Kingdom
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Hey Gents..Ladies. Sure there might be some

I'd been out and about on the Motorbike, scouting for places to fly and film. Found a doozie of a place. (I thought)

https://goo.gl/maps/RWXa8cJaxyG2 I was at the front of that little offshoot on the left!

So, went back with the Phan 4, set her up and switched on. Got a compass error..The pier has metal railings and metal benches... So calibrated compass, first time it ever failed, tried again and got a success! This is in Litchi btw, I keep getting freezes with the DJI app so don't really use it.

Took off, went to 15ft-20ft or so then moved out over the water and then the Phan 4 refused to ascend, quite the opposite, it started to descend!!

I pushed full up stick and the drone seemed to 'jitter' and kept descending. I was straight on the right stick back/down/towards me! (mode two) and she was creeping home again, I still had full climb (up on throttle stick) but she was still descending slowly.

Anyway, long story short, I managed to clear the railings and land her back on the Pier.

I think my mistake was not disabling the downward sensors or (more likely) I still had a bad compass?? I don't claibrate if I don't have to BTW. But as I said, litchi said to do so, so I did.

Saying that, it went up fine on the Pier and only stopped ascending after I was over the water so maybe it was the downward sensors after all??

The only reason I didn't disable the downward sensors is because Litchi 'seems' to be disable all or none where as the DJI app can turn the downward off and keep the rest. I've flown over water before with the DJI app and it was great...Until it kept freezing up on me..

Thing is, I checked the logs and there is nothing, it's only a 30 second 'flight' and everything looks normal.  I'm going out tomorrow over land this time but did any of you guys ever expierence a similar issue with the Phan 4? It's a new one and I am a new pilot, maybe 30 flights or less.

Thanks all if you got this far!
2017-4-1
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Nigel_
Captain
Flight distance : 388642 ft
United Kingdom
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Never calibrate the compass near metal!   It told you that there was a problem with the metal pier so you should have found somewhere else to fly from.

Could you post the log up on  http://www.phantomhelp.com/LogViewer/upload/ and post a link here so that we can have a look?  See what actually happened...

Make sure you do a new good calibration before you fly again ;)
2017-4-1
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Blah
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I get what you're saying. Mate, I'm agreeing with you.

I just never came across this before, the fact that it descended as I was 'asking' it (very politely) not to...It was a shock.

I have seen the logs and there is nothing, Nada, Niente, Nowt and so on.

I can do logs and stuff but really, there is nothing!. I checked em and so on and so forth. I did do the up, not that it will show anything I presume!

Question is, if you fly over water with VPS (down) enabled or have a bad compass as in what I described, Is  that the normal response??

That descend and that "jitter" It was scary and I was a bit worried

I am just wondering if anyone has had similar.

Appreciate the help, thanks!
Next flight will have a new Compass calibration BTW, guaranteed!!
2017-4-1
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Blah
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This is the log from Phantom.
http://www.phantomhelp.com/LogViewer/FU7SCNFDA50HACZ4W2OW/

**If** I'm doing it correctly, there really isn't anything I can see but I almost lost the whole thing!!


2017-4-1
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Labroides
Captain
Flight distance : 9991457 ft
Australia
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Blah Posted at 2017-4-1 04:59
I get what you're saying. Mate, I'm agreeing with you.

I just never came across this before, the fact that it descended as I was 'asking' it (very politely) not to...It was a shock.

The pier is full of steel - not just the railings.
What was it, reinforced concrete or structural steel under the decking?
If you put the Phantom down on steel, you will alsys have a compass error warning.
NEVER attempt to recalibrate the compass in the area affected by the steel giving you the error warning.
If you do you are just asking for trouble.

Go and get a good compass calibrating in a clean area and leave it alone.
If you get a compass error at the launch point, move to a clean launch point.
2017-4-1
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Blah
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Thanks. Appreciated!
I really wanted to fly here though and I did get a compass fail but then I got a Compass calibrated.

I know what you're saying but after cali it said all was fine! Obviously it wasn't. Thing is, has anyone else had similar???

I have been flying (on and off) for a long time. 3rd scale 4th scale and so on.

If a 'new' person got his calibration and thought all was good and didn't know about metal and rebar and so on, it would be in the drink FFS!!

Saying that, I *am* new to DJI and it said it was all good, albeit after a double cali.

It wasn't though.

2017-4-1
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Nigel_
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Blah Posted at 2017-4-1 05:22
This is the log from Phantom.
http://www.phantomhelp.com/LogViewer/FU7SCNFDA50HACZ4W2OW/

You can see the problem when it flies into a magnetic field line and the pitch reading from the compass goes to -26 degrees when it would actually have been more like -3 based on the speed it was doing!

I think you were a bit lucky not to loose it there.

If you want to fly there then you need to take off somewhere else and keep at least 20 meters altitude.  I wouldn't risk it though, the steel in that structure must have a fairly strong magnetic field stored in it.

Get the compass calibrated at least 20m away from any metal or concrete and then don't touch it again until it's next annual service.  If you calibrate it on the pier then it will fly as long as it is still within the magnetic field of the pier, once it flies out of the magnetic field then it won't fly in a controllably manor and maybe not at all.  If you get a compass / magnetic interference warning then don't fly in that location.
2017-4-1
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Nigel_
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With regard to your VPS question, there have been some warnings about using it over water but with recent firmware the only real difficulty seems to be that if it can see the water moving, or ripples on the water moving, then it may try to maintain position relative to those moving ripples making it difficult to control.  I think you can always gain altitude to regain control.
2017-4-1
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Blah
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I was very lucky and thanks.

Lots to learn and lots of fun to be had, right.
2017-4-1
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Rodger8
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United States
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You should disable the VPS. It doesn't like water.
2017-4-2
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Labroides
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Flight distance : 9991457 ft
Australia
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Blah Posted at 2017-4-1 05:40
Thanks. Appreciated!
I really wanted to fly here though and I did get a compass fail but then I got a Compass calibrated.

"I did get a compass fail but then I got a Compass calibrated.
I know what you're saying but after cali it said all was fine! Obviously it wasn't".

NEVER calibrate your compass in a distorted magnetic field close to a lot of steel.
You managed to "successfully" calibrate your compass on top of the steel.
What that means is that you corrected your compass so it would work while it was within the distorted field of the steel ... but when you get away from that your compass doesn't know how to deal with the earth's normal magnetic field.
Do you want to fly just above the concrete pier or high in the air well above it?

When you first got the compass error, that's not saying that your compass is malfunctioning.
It to warn you that the (perfectly working) compass has detected a problem with the magnetic field around it.
The correct action is to move away from the magnetic disturbance.
And don't try to launch from on top of steel with or without calibrating.
Launch from somewhere else if you want to keep your Phantom.
2017-4-2
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Blah
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Labroides Posted at 2017-4-2 05:21
"I did get a compass fail but then I got a Compass calibrated.
I know what you're saying but after cali it said all was fine! Obviously it wasn't".

For sure. And with the above and my 'suspicious' mind I get that

I think DJI just might have came across this and informed folks? I have 25 flights or so. I have flown planes and other drones, new folks would  be WTF??

2017-4-2
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9245
Second Officer
Flight distance : 69455 ft
United States
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To answer your auestion:

Getting a drone back from water is tricky.  I did it and it took a scuba team to get it back.  One thing you might try is the getterback:



Many use it, and it works well, but you have to be able to actually grab it to use it, which might mean getting a boat (ignore the price in the video, they are much cheaper than that).  Another option is to attach floats, you can make some out of pool noodles, but again, assuming you can't take off again, you will need to be able to get to it.  Water will trash these things, you may get lucky, but it will probably mean that you have to get a new drone.
2017-4-2
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Labroides
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9245 Posted at 2017-4-2 21:54
To answer your auestion:

Getting a drone back from water is tricky.  I did it and it took a scuba team to get it back.  One thing you might try is the getterback:

"Another option is to attach floats"

The idea of floats appeals to timid newbies and there are frequent posts from people hoping to use them.
But you never see posts from anyone using them regularly.
There is a big downside that could contribute to losing rather than saving a Phantom.
They are going to affect your flight characteristics, speed and battery life.
They are going to catch the wind
They are going to get in your camera's view.
There's a good chance that they'd float your Phantom  ... upside down in a crash.
2017-4-2
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Nigel_
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Labroides Posted at 2017-4-2 23:13
"Another option is to attach floats"

The idea of floats appeals to timid newbies and there are frequent posts from people hoping to use them.

To be able to float the Phantom the correct way up and with enough stability to stay the right way up, the floats would have to be so big that they would be in the way of the sensors and then, like with gimbal guards, they would result in a very high crash risk.
2017-4-3
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9245
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Labroides Posted at 2017-4-2 23:13
"Another option is to attach floats"

The idea of floats appeals to timid newbies and there are frequent posts from people hoping to use them.

I didn't say they were a good option, but he was asking about water crashes.  It might still destroy the drone, but it might make recovering the wreck easier.
2017-4-3
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Labroides
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9245 Posted at 2017-4-3 10:35
I didn't say they were a good option, but he was asking about water crashes.  It might still destroy the drone, but it might make recovering the wreck easier.

That's not much consolation if the reason he lost his drone was the ridiculous floats he attached.
2017-4-3
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