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Auto-Land aborts and reverts to RTH when control signal lost.
2237 21 2019-12-27
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Zbip57
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Edit: This issue has been fixed, sort of, with the release of Fly app v1.0.8.  Read on...


I ran a series of experiments to determine what happens.

Let's say my Mavic Mini is in danger of being blown away by the wind.    If I wait too long the Mini might drift downwind far enough that I lose  control signal.  Then it will automatically go into Return-to-Home with no other option  available.  If the wind is too strong it may never return.  There are plenty of YouTube videos showing exactly that happening.

A better choice would be, before losing the control signal, instead immediately try to land in an attempt to safely ditch in a safe spot.  But if you lose signal on the way down, the Mini will again go into RTH mode and climb back up into the strong wind and still be carried away.


So instead, choose to have it automatically Land-in-Current-Location, so that even if you do lose the signal you're  confident it wiill land no matter what.  

But it doesn't!!!


Whenever the Mini loses control signal, even if commanded to Auto-Land, 11 seconds after losing the signal the Mini will always go into RTH mode and climb back to RTH altitude!!

Unless you have control signal all the way down, there is no guarantee that the Mini will actually land in the location you've chosen.  You may be surprised when this happens.


Here are three sets of videos demonstrating what happens.






2019-12-27
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InspektorGadjet
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That is an interesting test, it should have the option to force landing.
2019-12-27
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JJB*
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Great to see and understand better what is possible to do during RTH, thanks!
cheers
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2019-12-27
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Zbip57
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On my Phantom 3 there was a menu option to select the desired Failsafe response to loss of control signal. You could choose between RTH, Land at current Position, or just Hover and Wait.
The Mini shows a choice of Land or RTH.
You would think choosing Land would cause it to Land no matter what.  But a loss of signal always causes a RTH response, even if you had commanded it to Land.
2019-12-27
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the1shark
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Basically, this is the most important post here in recent days IMHO. Do yourself a favor and watch those videos. It may save your drone from fly away..
2019-12-28
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Zbip57
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the1shark Posted at 12-28 07:40
Basically, this is the most important post here in recent days IMHO. Do yourself a favor and watch those videos. It may save your drone from fly away..

Thanks!  I was quite alarmed when I discovered this behaviour.  I thought if you deliberately choose Auto-Land, rather than RTH, this decision would over-ride any automated RTH response.

There are MANY youtube videos of people losing their Minis in high winds.  They press RTH and expect it to come back.  If the wind is strong enough the Mini will be carried away and eventually video and control signal is lost.  The telemetry signal then also ceases to be recorded on your display device.  The Find my Drone feature only shows the last known position when the telemetry stopped.  Good luck finding your drone after that.

If you see your drone being carried away by the wind, immediately descend to a lower altitude where the wind might be less strong.  In worst case, choose an emergency landing location while you still can and set it down where it might be easier to find later.

However, if you lose control signal on the way down, 11seconds later the drone will go into RTH and climb back up into the strong wind to your set RTH altitude before trying to come Home again!

If you instead choose Land at Current Location rather than RTH, it will ONLY do that if you have a continued good control signal all the way down.  If it loses control signal, despite being told to Auto-Land, it will instead again revert to RTH and try to climb back up to your set RTH altitude.

If you have already lost video and control signal, contrary to what you expected it to do, you may not even know that it HASN'T successfully landed!

In the 3rd video, I marked my emergency ditching location as my new Home Location.  That way, even if the landing fails, it will at least try to return to that newly marked Home location, instead of all the way to the original Home location.  As long as the Mini remains within 20m of the marked Home Location, it WILL continue to Auto-Land.  But if the wind is strong enough to push the drone outside of a 20m radius of the Home Location, if control signal is lost, 11secs later it will AGAIN revert to RTH and climb to your set RTH height...

There has to be a way to force it to continue Auto-Landing, especially when control signal is lost.


This is on current firmware v01.00.0300.
2019-12-30
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Ice_2k
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Great test, thank you! This feels like a huge bug in the Mini’s firmware. An official response from DJI would be great.
2019-12-30
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Antshill
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First of all, this is a fantastic post. Thank you for taking time to test this.


I dont have my drone yet...

But in emergency situations - can you:

1. use S mode - to get it down in altitude as quickly as possible...
2. set home in new location (trick here is gauging how bad the winds are at the given altitude)

Watching this guy: https://youtu.be/stxjFpVkT5Q?t=451

Hes flying at about 15 feet above the ground and gets blown almost 1200 feet away. Its ultimately a gamble - this guy measured 19mph winds at ground level and did the wind test. My newbie opinion is he got VERY lucky. At about the 9:11 mark hes deciding whether he should emergency land. The reason I say hes lucky is the winds died down just enough for him to power through it and make it back home. If he hit the same winds he did at the 7:23 mark while he was 1100 feet away - it could have potentially been blown 2000 feet away. Into residential area, and likely into a tough area to recover.

Does that sound accurate to you guys?
2019-12-30
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Zbip57
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Antshill Posted at 12-30 09:58
First of all, this is a fantastic post. Thank you for taking time to test this.

Obviously that was risky flying in such strong wind, but he did the right thing in keeping it low and searching for a suitable ditching spot.  Just imagine how that might have turned out differently if it had drifted far enough downwind to lose the control signal.  At that point it would have gone into RTH mode and climbed straight up into even stronger winds.  There has to be a way to force an emergency landing and have it continue to land even if the control signal is subsequently lost.

Here's another example from quite a while ago using a Phantom-4.  He flew it too far out over water and it struggled to come home against a headwind.  He admits it was stupid, but he did something really smart and headed for the nearest point of land instead of trying to continue home.  It hit critical battery level just as it reached firm ground and started to descend in forced auto-landing.  Just before touching down it dropped below line-of-sight of the controller and lost video & control signal.

The pilot assumed it had landed safely so he loaded up his family and gear into his car and drove to the landing site.

Note in the video, as the control signal was lost the Phantom aborted the auto-land and automatically went into RTH mode and started climbing again.  Fortunately it was already in a critical battery state and immediately gave up on RTH and instead landed exactly where it was supposed to.  That could have ended much differently.  


Let's say the pilot merely decided to manually land it safely there, and chosen Land-in-Current-Location while there was still sufficient battery power left, and then lost control signal.  He would siimilarly have assumed it had landed as commanded.  But, upon loss of signal,  the drone would have gone into RTH, climbed to RTH atltude an headed for Home, only to run out battery over the water.

There needs to be a way to force an emergency landing in a chosen spot, even if control signal is subsequently lost during descent.



2019-12-30
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Zbip57
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Well, looky there!  They fixed it!

In the latest version of DJI Fly v1.0.8 for the Mavic Mini they now provide a choice between three loss-of-signal failsafe responses:

  • Return-to-Home,
  • Descend, or
  • Hover.

Previiously the only response available was RTH.

I encourage everyone to experiment with these options so you are fully aware of how they behave, as there are advantages/disadvantages to each option.

The MOST IMPORTANT thing is to understand what each option does and to be dead certain you confirm that is what you actually want for your particular situation!


Thank you, DJI !



2020-4-10
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hallmark007
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Zbip57 Posted at 4-10 05:58
Well, looky there!  They fixed it!

In the latest version of DJI Fly v1.0.8 for the Mavic Mini they now provide a choice between three loss-of-signal failsafe responses:

I find it strange anyone would set Rth to land unless you’re under cover of trees indoors etc.

You seem to be setting it because of high winds, yet you already know about high winds before you start and you go ahead with only one plan land and you don’t have a choice where you land water someone’s property on a road children’s playground. It would seem much safer when wind is to strong 1/ don’t fly 2/ only use outward journey into the wind a much better and safer option than just land anywhere, so who in their right mind would opt for this option when other options afford a much better outcome.

Land and hover are for very specific missions you might be flying, I wouldn’t ever advise people use this as a failsafe for lost signal .
I mean think about it, why would you set out to fly knowing you might not get back .
2020-4-10
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Zbip57
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"I mean think about it, why would you set out to fly knowing you might not get back?"

Have you actually read my previous comments or watched the test videos I posted above?


Of course, it's stupid to fly in high wind conditions.  But there already are many, many, many, Youtube videos showing people losing their Mavic Mini because they have under-estimated the strength of the wind or over-estimated the ability of the Mini to fight back against those winds.

If you, or I, ever made a similar mistake and saw our Mini being carried away by a strong wind, what would be the correct response (other than freezing in panic)?

In most of the videos I've seen the wind continued to carry the Mini away until inevitably the control signal was lost, after which the ONLY failsafe response was RTH.  And THAT, as we have seen, is an inappropriate response if the first reaction is for it to climb higher to RTH altitude where the wind might be even stronger.  Depending on how much battery power level is left, the Mini can be carried a long long distance by the wind.  And with no signal connection, your tracking flight log stops at the point where connection was lost.


So what should one do differently if you find yourself in this unfortunate situation?

If it is not possible for the Mini to fight its way back against the wind, then set it DOWN immediately.  Emergency land it as soon as possible while you still have a control and tracking signal.

The problem is (was) that if, on the way down, the control signal is lost because the Mini has descended behind a tall building or hillside or forest, the only available failsafe loss-of-sgnal response was Return-to-Home.  And we've seen many Youtube videos where RTH didn't work against a strong wind.

The Fly app had a RTH button on the left side of the display screen.  Pushing that brought up two choices.  RTH or Land in Current Position.  Except, as I demonstrated in the videos above, the Land in Current Position option only worked as long as the Mini maintained a control signal all the way down.  If the control signal was lost during descent, the Mini would again revert to RTH.


The point is, after control signal is lost, you've effectively run out of options to save your Mini and you then rely entirely on the chosen Failsafe response, which was ONLY RTH.

But now (v1.0.8) we have different options.  If you see that your situation is hopeless, i.e. the Mini is being carried away by the wind, and you want to force an emergency landing:


  • BEFORE losing connection, switch your failsafe setting from RTH to "Descend",
  • While you still can, drop the throttle to attempt a landing in a ditching site of your choice,
  • If control signal is lost on the way down, at least you know the Mini  will now continue to descend and will hopefully land within a searchable radius  of your chosen ditching site.




2020-4-10
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Zubayer.Khan
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Thanks for sharing
2020-4-10
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BobWinNV
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Great videos.  Thanks for sharing
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Zbip57 Posted at 4-10 07:38
"I mean think about it, why would you set out to fly knowing you might not get back?"

Have you actually read my previous comments or watched the test videos I posted above?

Again it’s actually you who should read what I wrote.
I’ll explain, everyday I fly, I know what the wind speed is, I know which direction the wind is coming from and from this I can decide how I’m going to fly, you on the other hand have decided to advise that it is now somehow better to change Rth setting to land on the chance you won’t get home, but you haven’t a clue where the drone is going to land, a complete Willy Nilly idea, land option on your drone for loss of signal is specific to certain missions and normal flying is not one of them.

If the wind is to strong for Mavic mini and that’s wind below 8 m/s then you shouldn’t be flying Mavic mini.

Tell me if you’re flying over water over the top of trees over peoples houses over roads do you honestly think you should have the freedom to land your drone anywhere you like or it’s a good idea to risk your drone landing where you cannot recover it.

You’re whole thing here is if you get caught in wind that’s much to strong for your drone that landing would be better, but 99 times out of 100 you can land at any time and in a place of your choosing, I know what you’re talking about drone waiting for safe place to land , but that’s not a problem because you can force land .

I can safely say around here on this forum I have not seen any experience flyer lose his drone to the wind, what does that tell us, well for me it says he can read the wind and fly quite happily in the wind knowing the limits of his drone, and I don’t believe they would advise going out to fly and risk their drone by setting Rth to land.

You need to explain, are you now going to set Rth to land always sometimes judge the wind take a chance and use land. But I do know this is not what land is designed for and it’s not a good idea to advise it to be used for this type of flying.
2020-4-10
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Zbip57
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Whoa, whoa, whoa.  Hold on there.  Not so fast, Tiger.  Take a deep breath and have a little think about this (for a change).

Judging from your responses it's quite obvious that you either haven't read my earlier posts, or you've completely failed to comprehend what I'm talking about.  I'll type a little s-l-o-w-e-r  for you as you seem to be having difficulty keeping up.

You write:

  • "I  can decide how I’m going to fly.  You on the other hand have decided to advise that it is now somehow better to change Rth setting to land on the chance you won’t get home, but you haven’t a clue where the drone is going to land, a complete Willy Nilly idea."


I have NEVER suggested anyone should change their default Failsafe setting to "Descend" for normal flying.  Return-to-Home is the best option for 99% of the flying people do.

You write:

  • "99 times out of 100 you can land at any time and in a place of your choosing, I know what you’re talking about drone waiting for safe place to land , but that’s not a problem because you can force land."


Please, watch the videos I posted above.   I demonstrated potential situations where you cannot force land the Mavic Mini.  If for any reason your control signal is interrupted on the way down to landing, Failsafe will automatically trigger Return-to-Home.  In that case, the drone will not continue to land in your chosen spot, but will instead climb to RTH height and attempt to come Home.


You write,

  • "Land option on your drone for loss of signal is specific to certain missions and normal flying is not one of them."


Again, I did not recommend changing the Failsafe setting to "Descend" under normal flying conditions.  I recommend it for this specific situation.

Now (v1.0.8) we have different options.  If you see that your situation  is hopeless, i.e. the Mini is being carried away by the wind, and you  want to force an emergency landing:
  • BEFORE losing connection, switch your Failsafe setting from RTH to "Descend",
  • While you still can, drop the throttle to attempt a landing in a ditching site of your choice,
  • If  control signal is lost on the way down, at least you know the  Mini  will now continue to descend and will hopefully land within a  searchable radius  of your chosen ditching site.


If anyone ever arrives in the unexpected situation of having their Mini struggling to fight its way back Home against a strong wind (even in Sport-mode), or worse actually being carried away backwards by the wind, pick a safe spot to land while you still have control.  There are far too many Youtube videos ("Mavic Mini Flyaway") out there with people selecting Return-to-Home in a failed attempt to save their Mavic Mini.


If you wait too long and eventually lose your control signal, the Mini will automatically go into Return-to-Home Failsafe mode (which also automatically switches to the slower P-mode).  If that happens, the Mini may stay in the air until the battery runs out, while being carried away by the wind.  That is the very definition of "you haven’t a clue where the drone is going to land, a complete Willy Nilly idea."

If you wait too long before deciding to choose a safe ditching location, the Mini may already be nearing the limit of its control signal range.  If the Mini then descends behind trees or buildings that will further degrade the control signal.  So, even if you are attempting to force a landing, if the control signal is lost the Mini will itrigger a Return-to-Home response and instead climb right back up again.

If the"specific and certain mission" is to force a landing in the emergency ditching site of your choosing, that would be the time to have your Failsafe set to "Descend".


2020-4-10
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hallmark007
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Zbip57 Posted at 4-10 15:02
Whoa, whoa, whoa.  Hold on there.  Not so fast, Tiger.  Take a deep breath and have a little think about this (for a change).

Judging from your responses it's quite obvious that you either haven't read my earlier posts, or you've completely failed to comprehend what I'm talking about.  I'll type a little s-l-o-w-e-r  for you as you seem to be having difficulty keeping up.

What you’re saying makes no sense, when craft is going backwards you get a warning and now you get two new one being vibration, your warning tells you to land immediately and you say we should ignore this in favour of going into the app try finding Rth setting and change to land, no while you still have RC signal you should just land , if we were to go through what you’re saying we would lose valuable time and ground instead while we still have control of everything manually we should land believe me you can land much quicker manually than auto, I have never heard of or read about this phenomenon happening so it’s highly unlikely, so weigh it up by the time you change your Rth setting you will be most likely on the ground.

But everything above is completely preventive and for most if not all experience flyers this never occurs and for new users who are almost certain to panic, teach them how to fly in the wind and if they get caught out just left stick down very simple nothing else to think about and if the get to 30ft and wind is to strong then they made a huge mistake starting out, but continue left stick down forget about changing app to land and I’m not even sure this is possible while flying hope not it’s dangerous .
2020-4-10
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Ice_2k
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oh, for f*&%'s sake, here we go again....

@Zbip57 The rest of us got it, thank you! Save your breath.
2020-4-10
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hallmark007
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Ice_2k Posted at 4-10 15:55
oh, for f*&%'s sake, here we go again....

@Zbip57 The rest of us got it, thank you! Save your breath.

The idiot speaks once again . But says nothing.
2020-4-10
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Zbip57
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"What you’re saying makes no sense"


Here's a very simple and clear example.  Try to pay attention, as this will be my last attempt at explaining it to you.


"I have never heard of or read about this phenomenon happening, so it’s highly unlikely."

Unlikely, but certainly not impossible, as this video example demonstrates.

Bottom line, everyone should experiment with the various settings available through the app.  Familiarize yourself with how the various settings affect the behaviour of your aircraft.  Practise using the various settings.  That way, when something "highly unlikely" or completely unexpected happens you'll be less likely to panic and make the situation worse by doing the wrong thing.  If you only ever fly within the safe confines of your living room, you'll never lose track of where it crashes.  Don't be afraid to test the limits of your aircraft, but do so in a controlled environment so you'll be prepared to deal with unexpected results.


Here, just for you, is a concrete example of this "highly unlikely" scenario occurring.


Yes, this guy admits he did a dumb thing by flying his Phantom a long distance out over water.  But he then did a smart thing in heading for the nearest shoreline when he realized he didn't have enough battery power remaining to bring his Phantom all the way Home.  He chose a safe emergency ditching site and set the bird down there.  Because it was still a long way from where he was located, the drone lost control signal during descent moments before touching down as it dropped behind a headland.  He assumed it had landed safely, so he packed up his gear and drove to retrieve the drone from its landing site.

What he didn't know until much later in reviewing the video footage was that when the drone lost connection with the controller signal, it automatically went into Return-to-Home mode, it aborted the landing, and starting cliimbing again.

Lucky for him, the battery was already at a critically low level, forcing the drone to automatically abort the RTH all by itself and instead do a forced landing right where it was.  Had there been only just a little bit more battery power left, the drone might have climbed to RTH height and started heading for Home, only to run out of power shortly thereafter and drop into the sea.  It was pure luck that it instead auto-landed right where he wanted it.

What he should have done, in this "specific and certain mission" (i.e. emergency forced landing) given that the Phantom (unlike the Mavic Mini) has always included this option, is change his Failsafe mode to Land-in-Place rather than RTH.  That way in the "highly unlikely" case of the control signal being interrupted (as it was) on the way down to an emergency landing, the drone would have automatically continued to perform the forced Land-in-Place in his chosen ditching spot, rather than attempting to Return-to-Home contrary to the expectation of the pilot, after which he wouldn't "have a clue where the drone is going to land, a complete Willy Nilly idea".

Note:  I am NOT suggesting he should have changed that setting any time earlier while flying normally over water.  I am saying he should have changed it once safely over the chosen emergency landing site in order to preclude and prevent any inadvertent and undesired RTH.

Here's the video:



2020-4-10
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Zbip57
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With everythng updated on my Mavic Mini, DJI Fly app v1.0.8, and firmware v01.00.0500, I ran another test today to see what happens if the control signal is lost during an emergency ditch landing.  Here's what I found...

When the drone is more than 20m away from the recorded Home Position, pressing the RTH button on the left side of the App screen pops up a choice of "Land" or "Return to Home".  Let's say, for whatever reason, you choose to have the drone "Land" at that remote location.  Your battery level is too low to get Home, or the wind is too strong, or whatever.  You could try to manually ditch the drone at your chosen landing site, or you can select that auto "Land" feature.

Either method works ONLY as long as you have a continuous control signal all the way down.  Depending on the drone's location at the time, if it descends behind a hill, thick forest, tall building, whatever, causing it to lose control signal on the way down, then 11 seconds after loss of signal that "Land" procedure will be interrupted and the drone will automatically revert to its programmed Failsafe response.

As demonstrated in the video below, that remains true even with the latest software and firmware versions!


Prior to the latest v1.0.8 of the DJI Fly app, the ONLY possible signal-loss Failsafe response was Return-to-Home.  However, as of v1.0.8, we now have a choice of:
  • Return to Home,
  • Descend, or
  • Hover (until automatically landing due to critically low battery level).

If you ever find yourself in the dire situation where a remote ditching is your only option, before descending and possibly losing control signal on the way down, first go into the Settings menu, Safety, scroll to the bottom to select Advanced Safety Features, and choose "Descend" rather than "Return to Home".

Here's the video:  





2020-4-28
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Deucalion
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Zbip57 Posted at 4-28 12:01
With everythng updated on my Mavic Mini, DJI Fly app v1.0.8, and firmware v01.00.0500, I ran another test today to see what happens if the control signal is lost during an emergency ditch landing.  Here's what I found...

When the drone is more than 20m away from the recorded Home Position, pressing the RTH button on the left side of the App screen pops up a choice of "Land" or "Return to Home".  Let's say, for whatever reason, you choose to have the drone "Land" at that remote location.  Your battery level is too low to get Home, or the wind is too strong, or whatever.  You could try to manually ditch the drone at your chosen landing site, or you can select that auto "Land" feature.

Thanks! I actually saw a YouTube of a flyer who was running out of battery but and wanted to land instead of RTH, and every time he tried to manually land, the trees would block the signal when he got close to the ground and the drone would then try to RTH. He overrode it, as you show here, by changing the signal loss response to land. I didn't realize that this did not work in prior releases. This was always my backup plan. Good to know it works now.
2020-4-28
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