Tale of woe

[Rifleair]

This is my tale of woe, My mavic lost connection on saturday when I was in the area shown below

after disconnection I pressed RTH but the distance counter carried on increasing, so I cancelled and tried to fly it home but although the distance away decreased it never came close enough to see or hear.
The closest it came was 82m, then the battery warning came on and it said returning home, except that the distance kept increasing, then it was landing somewhere about 690m away.
I think that I was bringing it back and forth in line with the last track shown, where I thought that it was coming back to me, whatever its now gone, but if one of you is close enough to solihull and fancies trying to replicate my last flight in order to give some idea of where it went, well that would be great!

[OzoneVibe]

Sorry you’ve had this experience.

@Rifleair

fancies trying to replicate my last flight

Hmmm … difficult to replicate something where you’re not really sure what happened or where it went, or why/how control was lost.

[PingSpike]

What’s the outer red ring? Is that a 690m radius?

I’m guessing the ‘find my drone’ tool did bugger all after it had landed?

Gutted for you mate

[Njoro]

@Rifleair

This is my tale of woe, My mavic lost connection on saturday when I was in the area shown below

after disconnection I pressed RTH

Sorry, you lost it, but doesn’t RTH require a connection for the RTH button to work? Did you try walking towards the direction you had flown it because sometimes all it takes is a few steps to regain control?

[OzoneVibe]

@Njoro

doesn’t RTH require a connection for the RTH button to work

You’re right - but …

@Rifleair

but the distance counter carried on increasing

… so there was a connection.
And …

@Rifleair

then the battery warning came on and it said returning home, except that the distance kept increasing

… shows the connection continued even after the self induced RTH.

[OzoneVibe]

@Rifleair Was it a Mavic Pro or Mavic Air?

[Njoro]

Flight log will show something though eh!

[Rifleair]

Indeed the biggest problem is what was actually happening, the phone went dark and video was lost, however when I went out of the fly part of the app, the front page said connected go fly, on going back in there was no picture and it said no connection.Foolishly I spent too much time trying to reestablish the connection to the phone instead of flying the aircraft.
The find my drone tool said that the drone was exactly at the end of the yellow line, but it wasn’t., and yes the outer ring is the 690 point.
Yes, the controller was connected so I was getting telemetry giving height, speed and distance away but trying to work out which way to go was a headache, all you really have is the distance away counter, but if it is counting down that doesn’t mean that it is coming directly towards you, only in your general direction.
But the really confusing thing is why the RTH took it further away. On set up the map showed exactly where I was, the compass was facing the right way and the initial part of the flight followed the path shown on the map, so why didn’t it come back?
It was a mavic pro and the flight log shows exactly what you see on the map, indeed it was taken by a guy called sar104 from mavic pilots forum and he is a genius at reading the logs, unfortunately you can’t read what ain’t there!

[opochka]

Looks like you did not double check that the home point was actually the place you were standing when you took off…

[OzoneVibe]

With the MP you don’t have to double-check anything. It tells you, as it takes off: “… the home point has been set …”

[opochka]

Didn’t calibrate compass at the new location before launching …

5 Ways to Prevent Flyaways

[OzoneVibe]

Personally, I’m far less sure that is the cause.

Over the last 5 years of drone ownership I’ve driven to Italy, and around Italy, and back, twice … once with my Phantom 2, and more recently for 3 months with my MP …. and around the UK with both.

I recalibrated the compass on the P2 just once, when I got it, because it said you should.
As yet, I’ve never recalibrated the compass on the MP even once.

The change in magnetic declination in Europe is too little to make much difference wherever you are.

On drone/DJI/phantom/MP forums, over those 5 years, I’ve read a good many reports of flyaways and come to my own conclusions …
a) If it flies OK the first time … don’t fiddle with it
b) the more times it’s recalibrated, the more chance there is that one of the calibrations goes wrong, and you’re worse off than not having done one.
c) I’d look at that chart if I’ve travelled much further, and decide whether to bother with a recalibration.

Indeed, the compass accuracy is needed whilst in flight. If you recalibrate where there is some very localised warp in the magnetic field on the ground, once it’s flying and away from this anomaly you’ve basically just built in an error.

Interestingly, of all the people I’ve known that virtually never do a compass calibration, none have had a flyaway, and of the ones that I have read about that had a flyaway, most are reported with " … I did the usual recalibrations before the flight … ".

Personal opinion, and I’m sure there’ll be exceptions and those that want to disagree, but … if you understand what it is you’re recalibrating, why/when it “might” be necessary, and the limited impact one that is slightly out of calibration can have on a flight … you’d probably reach a similar conclusion to myself.

I realise that this doesn’t bring back your MP and, should you follow them, my thoughts mean you’re no closer to understanding what DID happen.
Believe me … I’d really like to know the real reason, if it can be found an proven, even if it means I have to completely change my thoughts on the compass recalibration issue.

[callum]

Personally I never calibrated Mavic until prompted to do so.

Think that’s the advice from DJI these days, calibrate only when asked to do so.

Too easy to blame the pilot but fact is the tech is not fool proof and errors are going to occur.

It’s just a shame that there is no flight logs and recourse with DJI.

[OzoneVibe]

@callum

until prompted to do so

Hmmm - yeah … and no.
If the cause is a local anomaly … I’d rather move 10-20m and see if it still asks me to.
As I say above, a local anomaly can have the opposite effect to that required.

[callum]

Yeah but have you ever tried to do a bad calibration Dave?
It dosent let you, pure and simple. The only option is to move the Mavic.

I did some testing while back. If you introduce a magnetic field wether it ferrous material, rocks or even a magnet, calibration will always fail unless the magnetic field is moving on same axis as the magnetometer.

But your right, get a compass error, move and if that fails calibrate.

[OzoneVibe]

@callum

Yeah but have you ever tried to do a bad calibration Dave?

Errrr - I’ve only ever done one!

There’s all sorts of folklorey type stuff around this. “Don’t wear your iWatch”, etc., which I somewhat take with a large amount of salt. I’ve yet to see conclusive proof.

“You can’t take off from something large and steel - it screws the compass calibration” … you’ve seen my manhole cover take-off vid. But then a concrete (I assume reinforced) trig-point and it throws a wobbly! (The top-plate is brass - so non-ferrous). But a recalibration wouldn’t have helped. It just didn’t like being on a trig point.

I know people have been unable to take off from the decks of cruise ships … but there’s also plenty of vids out there that show it happens, too.

As to whether you CAN do a bad calibration … I’m sure it’s possible … even if most times it will prevent you from doing so. And I also think the current generation of DJI drones are better than the early ones.
What is more certain is, that you’re less likely to get a bad calibration if you don’t do them.

Edit: I was actually mid writing a post as to what happens if your compass is incorrectly calibrated as a post here. I think I’ll use it to start a new thread to discuss the subject. I’ll make it more detailed, in that case.

[callum]

The watch thing is sort of true.

I need to calibrate a lot as fly with and without a tracker.
Wearing my watch will result in a failed calibration 9 times out of ten.

[OzoneVibe]

But why were you recalibrating in the first place?
Mine has never asked to be recalibrated in 18 months.

Or does wearing an iWatch cause it to request a recalibration? … which is what I understood and, whilst I don’t have one, my friend and I cable-tied his to my MP and it booted up, and flew, without any issue.

[callum]

No I’m calibrating because I’m using or not using the GPS tracker. I try to leave it on all the time so it’s not an issue but often forget it.

Its not an apple watch, just a normal stainless watch. Watches are only a problem if your doing a calibration, that’s why I said sort of true.

[OzoneVibe]

Ah - OK - I’d read iwatch specific scare stories.
That early morning vid of a sailing boat motoring along off the south coast … the iWatch was on the MP then.
My friend was going frantic as it flew off nearly 1km over the sea after I’d said I’d just try a hover after take-off … and then … wheeeeeeeeeeeeeeee
LOL!