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My turn for a fly-away... what caused this?
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2234 73 2018-3-5
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ColdForged
lvl.2
Flight distance : 17618 ft
United States
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I've read these accounts of Mavic Air fly-aways with some amount of doubt. I've had literally zero negative experiences with my Mavic Air. That ended yesterday.

I finished a run at my local trail and decided to send the Mavic up to capture some footage of the trail. I hooked up my phone to the controller, powered it all up and got connected, got the right ND filter on, verified versions, and walked over to a clear area for takeoff. Pressed the takeoff button in the app and it hovered in front of me, then I started applying up on the left stick to get altitude over the pine trees I planned to fly over. I was looking down at the screen to adjust the gimbal when I heard it move from left to right above me and the scene on-screen showed it moving as well. My head snapped up and I could see the drone careening away from me with no input on the right stick. I kept pressing up on the left stick to make sure it was over the trees so it wouldn't fly into them because that's what it was sure trying to do. I continued to watch it as it flew further away from me and left. I pressed RTH and it gave me the RTH indicator and still wasn't under control. Finally it appeared to settle and move sanely toward the home point, then started lowering itself. It landed without issue with my holding down on the left stick and I powered it off, shaking. $800 almost down the drain.

I uploaded my log here, but I don't see much. It looks like it finally got "sane" right when it locked 13 GPS satellites. Is there more I can look at to determine what went wrong?
2018-3-5
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DirkGerrit
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Nice to see you were able to recover your drone. I am not a specialist, but you started hoovering with only 8 satellites. That is something I would’t do.
2018-3-5
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ColdForged
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DirkGerrit Posted at 2018-3-5 07:46
Nice to see you were able to recover your drone. I am not a specialist, but you started hoovering with only 8 satellites. That is something I would’t do.

That's what I'm trying to determine. What's the minimum I should launch with? It seemed to get "sane" at 13... is 13 the new minimum I should shoot for?
2018-3-5
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QuadKid
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ColdForged Posted at 2018-3-5 07:51
That's what I'm trying to determine. What's the minimum I should launch with? It seemed to get "sane" at 13... is 13 the new minimum I should shoot for?

I never take off without a minimum of 12 Sat's Locked, then I will take off and hover a couple feet off the ground until I get the verbal "Home point has been updated" before flying out. Based on your log you didn't have enough Sat's locked in to provide stable GPS flight.
2018-3-5
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DirkGerrit
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ColdForged Posted at 2018-3-5 07:51
That's what I'm trying to determine. What's the minimum I should launch with? It seemed to get "sane" at 13... is 13 the new minimum I should shoot for?

I agree with Quadkid, the minimum for me is 12...
2018-3-5
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ghostrdr
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I don't understand why people keep trying to fly with a low satellite count. That's the first thing I check before taking off.
2018-3-5
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fansf77370fb
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I will only take off when I have 12 satellites showing. Just because it tells you to take off doesn’t mean you should.
2018-3-5
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ColdForged
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ghostrdr Posted at 2018-3-5 08:02
I don't understand why people keep trying to fly with a low satellite count. That's the first thing I check before taking off.

There it is, the judgement police have finally arrived!

I'm learning, dude. I've never had one of these before. I don't know what the count is supposed to be.

Regardless, thank you all for the input. Survived this lesson with nothing harmed but my heartrate momentarily. Sounds like 12 or more is a reasonable minimum.
2018-3-5
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fansf77370fb
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ghostrdr Posted at 2018-3-5 08:02
I don't understand why people keep trying to fly with a low satellite count. That's the first thing I check before taking off.

Then they wonder why their drones fly away. Just another pilot error.
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ColdForged
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QuadKid Posted at 2018-3-5 07:56
I never take off without a minimum of 12 Sat's Locked, then I will take off and hover a couple feet off the ground until I get the verbal "Home point has been updated" before flying out. Based on your log you didn't have enough Sat's locked in to provide stable GPS flight.

According to the flight log, it got "Home Point Recorded" 5 seconds into the flight. :/
2018-3-5
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davidmartingraf
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It is important to note, do you turn your Mavic Air on first then connect the Remote to the Controller or vice versa?
2018-3-5
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Wyke
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By way of explanation, if you have a low count of satellites locked, your drone may think it has an initial position, records Home,  but, due to the low count, this could be off by 20m  say. Then as it ascends, it gets another satellite, finds where it thinks it is, realises that this isn't the same place as the incorrectly recorded Home and so moves off to correct. More height, more locks more correction, all the while panic sets in. If a Return to Home is initiated, the drone then goes off to the wrong place and might not be seen again in one piece.

I aim for 12. I think I did read somewhere there was a reason for this arbitrary number but can't remember what it was.
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ghostrdr
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Call me the judgement police if it makes you feel better but since you're at level 2, you're not a total newb to this forum. I probably should have said that I go through a mental checklist before flying and that includes a visual inspection and satellite check before I even leave the ground. IMU and compass also. And I always hover and make sure everything seems ok before departing. There are no guarantees but there are things you can do to mitigate the risk.
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Wyke
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Not too keen on Auto Take Off either. I like to be able to control TO, and landing for that matter.
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Dirty Bird
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I'm chuckling at the minimum "12-13" satellite minimum.  NOT because it's a bad idea but because I recall my Vision+ would sometimes take 3-4 minutes just to lock the 6 required for Home lock.  
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Aardvark
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That's the strange thing here, there are no error messages in your report, and yet it shows the almost 'toilet bowl affect' where a badly calibrated compass conflicts with GPS data until switched to ATTI mode. Or at least that's how I might first think about it if it were a P4. Might be worthwhile getting DJI to check the data. The P4 (as a comparison) doesn't lock home point until it has more than 8 satellites in view. Thereafter I've not had any problems (  yet ;-)  ).

If you've not done so yet I would run through all the Air calibrations (IMU, Gimbal, Compass, RC, visual sensors ? ).
2018-3-5
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Wachtberger
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First of all I am very happy that your MA returned safely! I would also say in your particular situation it was the right decision to bring it first above tree level. In open area bringing it down immediately would have been my first choice. Apart of that the only explanation I can provide is the very weak satellite link indeed. Quite a bit into the flight there were insufficient satellites, only later it had reached the absolute minimum (from what I have learned) of 11 satellites.
And the advice given by our fellow pilot Aardvark here above is very good as well, he has far more experience than I do.
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Bekaru Tree
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ghostrdr Posted at 2018-3-5 08:02
I don't understand why people keep trying to fly with a low satellite count. That's the first thing I check before taking off.

hey dude - you can see that he is a newbie -
this forum is exactly the right place for him to be
his issue is typical newbie thing to come up against and want to learn about
his is a perfectly normal question to ask.
\The understanding for "why people keep trying to fly with low satellite count" is almost always because at the point they either did not know better or did not fully appreciate the importance of acquiring sufficient satellite linkage.
That understanding is so obvious to me yet to you its not - thats ok - this is how we learn.

Was checking your satelites, since your very first flight always the first thing you checked?
If so its because you learned it from some where - thats what he is doing.

No reason to be demeaning in your replies.
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Bekaru Tree
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i do not know how many satelites are required - around 12 rings a bell and sounds about right. Personally the only time i ever check how many satelites i have is when people stop to ask me questions, its usually one thing i mention. so if i never check how many satelites how do i survive? The one and only thing i do with regards to satelite connection is to wait a few moments for the green bar top left of app screen. I think it says home point updated, ready for take off. I will never launch until this bar turns green. i never check how many satelites it picked up or linked to in that time. i only watch for the green bar and a small notice saying home point is updated. Then i take off and on this system never had a problem. I learned this system because once i did have a problem similar to yours and having found a similar answer like i gave you i applied it and made it a fixed part of my preflight check - i have never again experienced that issue. hope it works for you too.
2018-3-5
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ColdForged
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Thanks for all the additional inputs and clarification! I'll still consider myself supremely lucky that I escaped with no damage from this lesson.
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ghostrdr
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Was checking your satelites, since your very first flight always the first thing you checked?
If so its because you learned it from some where - thats what he is doing.


Yes! I knew that because I studied religiously here BEFORE I took my first flight. If something didn't feel right I landed right away until I did feel comfortable. And if you still don't know how many satellites it takes to get a good GPS lock, you haven't been paying attention!
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Wachtberger
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Bekaru Tree Posted at 2018-3-5 09:55
hey dude - you can see that he is a newbie -
this forum is exactly the right place for him to be
his issue is typical newbie thing to come up against and want to learn about

You have my highest appreciation for this response, thank you indeed! All of us had to go through this learning process when we started and asking questions here is the right thing to do. I am most grateful to all those who have answered my questions and continue to do so.
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Wachtberger
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Bekaru Tree Posted at 2018-3-5 10:04
i do not know how many satelites are required - around 12 rings a bell and sounds about right. Personally the only time i ever check how many satelites i have is when people stop to ask me questions, its usually one thing i mention. so if i never check how many satelites how do i survive? The one and only thing i do with regards to satelite connection is to wait a few moments for the green bar top left of app screen. I think it says home point updated, ready for take off. I will never launch until this bar turns green. i never check how many satelites it picked up or linked to in that time. i only watch for the green bar and a small notice saying home point is updated. Then i take off and on this system never had a problem. I learned this system because once i did have a problem similar to yours and having found a similar answer like i gave you i applied it and made it a fixed part of my preflight check - i have never again experienced that issue. hope it works for you too.

From what I have learned thanks to more experienced pilots I can at least provide you the answer for that, which is 11 minimum. According to DJI specifications you need to be linked to at least 6 GPS or GLONASS satellites for a stable positioning. Thus you can only be sure to have 6 of either when the total of links is 11 or above.
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Wachtberger
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ColdForged Posted at 2018-3-5 10:17
Thanks for all the additional inputs and clarification! I'll still consider myself supremely lucky that I escaped with no damage from this lesson.

You are most welcome and I can well imagine the initial shock, would not have been different for me. I wish you always happy landings in the future as well.
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Bekaru Tree
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Wachtberger Posted at 2018-3-5 10:28
You have my highest appreciation for this response, thank you indeed! All of us had to go through this learning process when we started and asking questions here is the right thing to do. I am most grateful to all those who have answered my questions and continue to do so.

Thanks wachtberger, i appreciate your support
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hallmark007
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ColdForged Posted at 2018-3-5 10:17
Thanks for all the additional inputs and clarification! I'll still consider myself supremely lucky that I escaped with no damage from this lesson.

6 is the number of satellites you need to fly your drone, but your drone receives both glonass and gps signals.
Your telemetry May say 8 satellites this could mean you only have 4 of each but you need at least 6 of gps or 6 of glonass , so if you use the number 11 satellites then you will be guaranteed at least 6 of one type.

Although sometimes you can take off with 8 satellites it’s because you have 6 of one and 2 of the other.
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Bekaru Tree
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Wachtberger Posted at 2018-3-5 10:35
From what I have learned thanks to more experienced pilots I can at least provide you the answer for that, which is 11 minimum. According to DJI specifications you need to be linked to at least 6 GPS or GLONASS satellites for a stable positioning. Thus you can only be sure to have 6 of either when the total of links is 11 or above.

cool - thats good to know - i guess in the background of my mind is a peripheral sense of what looks right and what looks abnormal.
i knew it was a double digit number and feel sure it would catch my eye if it dropped to single digits.
But good to know the actual correct value - thanks
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Wachtberger
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Bekaru Tree Posted at 2018-3-5 10:46
cool - thats good to know - i guess in the background of my mind is a peripheral sense of what looks right and what looks abnormal.
i knew it was a double digit number and feel sure it would catch my eye if it dropped to single digits.
But good to know the actual correct value - thanks

Above your post right now you have the even better answer of my best teacher :-)
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sidtx
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Wachtberger Posted at 2018-3-5 10:35
From what I have learned thanks to more experienced pilots I can at least provide you the answer for that, which is 11 minimum. According to DJI specifications you need to be linked to at least 6 GPS or GLONASS satellites for a stable positioning. Thus you can only be sure to have 6 of either when the total of links is 11 or above.

And that's why I love this forum!!!

Someone will have the knowledge we need to keep flying safely.   I knew about the min number of satellites, but not the reason.   Now I do.

Sid

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TroutboyNZ
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I don't know why, but here in New Zealand, I would never get 12 satellites initially without waiting for 20+ minutes! I often lift with the bare minimum (about 8 I think)?? And have never had an issue, always picks up more quickly in-flight and hovers nicely, there is no doubt the Mavic Pro picked up a faster GPS lock and more satellites though, it was a speed-demon for fast locks, the Air... not so much.
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Wachtberger
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TroutboyNZ Posted at 2018-3-5 11:43
I don't know why, but here in New Zealand, I would never get 12 satellites initially without waiting for 20+ minutes! I often lift with the bare minimum (about 8 I think)?? And have never had an issue, always picks up more quickly in-flight and hovers nicely, there is no doubt the Mavic Pro picked up a faster GPS lock and more satellites though, it was a speed-demon for fast locks, the Air... not so much.

I first had that impression as well when I had just received my MA. It took longer than my Spark to link to sufficient satellites. But in a number of reports (not related to MA) I have also read that after a major change in location (in my case delivery from China to Europe) this is normal. In the recent flights my MA linked up quite quickly but I shall keep on monitoring.
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GazFromBrum
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There is lots of talk on this thread of number of sats required...... I'm not sure anyone remembers that these things will fly without GPS holding your hand. The initial story tells how the Mavic started to drift and a climb was initiated to avoid trees....  there is even the comment "no input on right stick"..... there's no mention of trying to fly back or control the aircraft...... no mention of lack of control.

The Mavic Air as all DJI drones don't require GPS at all to fly or to return to take off position..... they just require a pilot that's prepared to fly their drone.
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hallmark007
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GazFromBrum Posted at 2018-3-5 13:22
There is lots of talk on this thread of number of sats required...... I'm not sure anyone remembers that these things will fly without GPS holding your hand. The initial story tells how the Mavic started to drift and a climb was initiated to avoid trees....  there is even the comment "no input on right stick"..... there's no mention of trying to fly back or control the aircraft...... no mention of lack of control.

The Mavic Air as all DJI drones don't require GPS at all to fly or to return to take off position..... they just require a pilot that's prepared to fly their drone.

If you checked out OP’s log you would see that yes he did try bring his aircraft to safety, first raising aircraft will increase his chances of getting good gps and as soon as he done this he tried his best to regain control and return safely, these aircraft are sold with GPS receivers having gps makes these aircraft much safer.
I do agree that pilots should always be aware if they have problems they need to react and realize that they can still control their aircraft.
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GazFromBrum
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hallmark007 Posted at 2018-3-5 13:42
If you checked out OP’s log you would see that yes he did try bring his aircraft to safety, first raising aircraft will increase his chances of getting good gps and as soon as he done this he tried his best to regain control and return safely, these aircraft are sold with GPS receivers having gps makes these aircraft much safer.
I do agree that pilots should always be aware if they have problems they need to react and realize that they can still control their aircraft.

I just went on what was posted in thread..... there's no mention of trying to control aircraft either from the OP or anyone else.  
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hallmark007
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GazFromBrum Posted at 2018-3-5 13:48
I just went on what was posted in thread..... there's no mention of trying to control aircraft either from the OP or anyone else.

I think you will see OP did mention that he raised aircraft to avoid hitting trees, you can also see this in his stick movements in his log, sometimes we are hard on ourselves when things go wrong and it looks like we are loosing control but there was a reaction from OP which did help save his craft.
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GazFromBrum
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I'm not attacking the OP...... I did say that a climb was initiated but the OP does say there was no input on right stick. I was just surprised how many people rely on GPS and that no-one commented on taking control of the aircraft...... several comments of "do not take off until you have 11 or 12 sats"...... I've only had my Mavic Air a couple of weeks and its my first drone of any kind..... but I've taken off several times without GPS but that's because I have 15 years flying RC planes and Heli's and don't rely on GPS.
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AG0N-Gary
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It may help to also know that WHERE the satellites are located will determine the quality of the location fix.  If they are all nearly overhead with strong signals, etc., they won't have as accurate a fix as they would if they were spread around the horizon.  By the way, for elevation information to be more accurate, you need many birds overhead.  It is having a good mix of these that gives the most accurate spacial fix of location.
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GazFromBrum
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Anyway..... if you listen to the flat earthers on YouTube there's no such thing as satellites.....lol
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hallmark007
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GazFromBrum Posted at 2018-3-5 14:08
I'm not attacking the OP...... I did say that a climb was initiated but the OP does say there was no input on right stick. I was just surprised how many people rely on GPS and that no-one commented on taking control of the aircraft...... several comments of "do not take off until you have 11 or 12 sats"...... I've only had my Mavic Air a couple of weeks and its my first drone of any kind..... but I've taken off several times without GPS but that's because I have 15 years flying RC planes and Heli's and don't rely on GPS.

I didn’t say or think you were attacking anyone and you made a very valid point on which I agree, I was just pointing out that OP did not simply give in whether he knew it or not, he did react.
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GazFromBrum
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I didn't say you said or thought  I was attacking anyone.....lol

this could be a very long thread.
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