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A question for DJI regarding the Mavic Mini and the CSC maneuver.
953 18 2020-6-12
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Sean-newbie
First Officer
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If the DJI Fly App's ''Emergency Propellor Stop'' setting is set to ''Emergency Only'' and the drone is in normal flight, will moving the joysticks to the CSC postion and holding them there for a requisite period of time stop the drone's motors with the drone in mid air? Note I do mean a normal flight without the drone encountering any collision or stalled motor or .........etc. etc. (as mentioned in the manual). A one word answer to that question would be preferred i.e. either ''yes'' or ''no''.

If yes, for how long must the CSC postion be held before the motors will stop.

My concern is that if, for example, the wind comes up and the drone is being blown away will I, with the app set to ''Emergency Only'', be able to cause the drone to literally fall to the ground rather than have it blown away and possibly fly into a building or person.

I realise that the CSC position will cause the drone to descend and, if held long enough, land but that is a slow descent and, if the drone were blown out of control range, possibly reversible.

I have tried some experiments to investigate this, with the drone tethered to the ceiling, and I found that if the CSC position is held for more than 5 seconds and the joystick are then released there is the possibility that the motor will stop as soon as the joysticks are released but that it was not a certainty that the motors would stop. My concern with this experiment is that once the tether is taut the drone is not really in free flight so it may not be a realistic simulation of an attempted motor stop during free flight i.e. it might introduce a simulation of one the 'manuals'' emergency situations.

I also found that if the CSC position was held for less than 5 seconds the motors would not stop ....full stop.

On the basis of this I have held the CSC position for 4 seconds with the drone in free flight and other the descending in a probable helix during the CSC nothing else happened. i.e. the drone resumed normal flight as soon as the joystick were moved away from the CSC position.

Going back to my tethered to the ceiling experiments, I found that if the App's ''Emergency Propellor Stop'' setting is set to ''anytime'' the motors would, with out fail, stop after the CSC position had been held for 2 seconds.




2020-6-12
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m80116
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I can confirm that within two seconds you can have the motors stopped w/ CSC, there's video on that on YT. I presume it was done with the "anytime" option active.

For what I can understand your question is fed by the fear of inability to control the drone and see the CSC props stop a solution. Personally I'd consider the CSC EPS only for extreme cases which I believe should be covered (and enabled) in real emergency scenarios, a plausible one could be a hit after which the drone becomes unresponsive and erratically flying. In such situation rather than risk the drone flying uncontrollably with tilt angles greater than it is designed for, it could be better the terminate the flight with CSC Emergency Propellers Stop.

In all other cases I think it's much wiser to have an emergency landing. Not only it is safer for those on the ground but will also probably save your drone completely and offer a convenient recovery possibility. Even if the drone is caught by wind more powerful than its capability (which shouldn't happen in the first place if you're sensible drone pilot) you can simply set your Signal Lost option to Descend and initiate your emergency landing. If you're aware if your environment you could most probably find an open patch of land where to descend before your RC loses control of the drone, at that point is very likely the drone will be out of the stronger winds and could just finalize the descent without moving too much from the chosen point, thus providing a rather safe emergency landing that is likely to offer a good chance of later recovery without any damage.
2020-6-13
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hallmark007
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It’s seems strange that you want to avoid drone flying away by using CSC, surely to switch to sport mode and left stick down is both safer for anyone beneath the drone, and also the drone.

I sometimes wonder do people think these things through, just because CSC is available doesn’t mean it has to be used.
2020-6-13
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Sean-newbie
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Thanks for the replies.
To m80116 .....With regards to my fear, "my fear" is not in losing control as such, it is of not having control in the first place.
If whether or not the CSC works is at the discretion of the software it is not, in that sense, in my control. Yes I know I have control over whether the drone is flown in "anytime" mode or "emergency only" mode but.........
This is why I seek clarification, from DJI, of precisely how the drone should behave.

Undoubtedly a deliberate CSC with the intention of stopping the motors is an extreme measure but it is 'provided' for a reason. As such its behaviour needs to be unambiguously known and understood and, at the moment, its behaviour is, for me, unknown. If in "emergency only" mode it can not be relied on to stop the motors it, in my opinion, fails in its purpose. Besides and referring to the manual and its emergency situations, to my mind many of the situations cited in the manual as emergencies would bring down the drone with out a CSC being applied.
Yes I know I could fly in "anytime" mode but to be honest a 2 second delay is a very slim trigger time and I would prefer a 4 or 5 second delay. Yes I fly Phantom 3s and they more or less run in "anytime" mode but the delay is from memory greater than 2 second and I have never accidentally triggered one, But YES I have, as an experimant, deliberately done a mid air CSC and restart with my phantom. I was realtively comfortable doing that as I have seen it done BUT I would not risk it with the Mini as I am uncertain if the Mini is stable enough to remain upright enough during freefall to allow motor restart.

To Hallmark007, the flyaway was just an example, chosen as perhaps the most obvious situation, I could equally well have chosen any other scenario where I mught want to get the drone out of the sky quickly. Yes I have thought it through, I would not be asking this question if I had not, I know it is an emergency measure and I am perfectly well aware that its use should not be an every day occurrence but if it is needed and ''emergency only'' mode prevents it operating at the pilots command it is a liability not an asset.

All the above said I did not really start this thread for it to become a debate or even a discussion over whether or not CSC should be used, it IS availble and I, for one, would like to be certain of the circumstances under which it will work.

2020-6-13
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m80116
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Tbh I don't remeber the manual [QUOTE]: "many of the situations cited in the manual as emergencies would bring down the drone with out a CSC being applied" mentioning an emergency that brings the dron down (free fall from EPS), I guess some misunderstanding is going on here. Of course I acknoledge every other normal emergency landing or drone brought down, for example for battery depletion or as a normal auto-RTH.--

If you'd like to be clarified the -during an emergency- situation I am totally with you.

For the CSC test I highly advise nobody does a test mid-air because I am pretty sure a Mavic Mini would tumble, it's not the kind of balanced aerodynamic drone that could restart like a Phantom. I am even amazed to know a Phantom can do that...



2020-6-13
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Sean-newbie
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M80116 with regard to  "many of the situations cited in the manual as emergencies would bring down the drone with out a CSC being applied" the relevant section of the manual reads as follows

"Stopping Motors Mid-flight
Stopping motors mid-flight will cause the aircraft to crash. The motors should only be stopped mid-flight in an emergency situation such as if a collision has occurred or if the aircraft is out of control and is ascending/descending very quickly, rolling in the air, or if a motor has stalled. To stop the motors mid-flight use the same CSC that was used to start the motors. "

From my 'experiments' large angles of roll and or pitch stop the motors, I thnk this is the basis of the grab and twist shut down method. I think it's safe to say a stalled motor, assuming it remains stalled, will bring the drone down. I realise there are videos of drones remaining airborne after a collision and I find that impressive but in general I'd expect a collision to bring the drone down.

Anyhow ....I got fed up with not knowing so, flying in C flight mode, I tried several CSC in free flight with the shut down mode set to "emergency only". I started low, 4 - 5ish m, enough to give me 5 seconds of descent, and could not get the motor to shut down. I ended up with 9sec + CSC's and couldn't get the motors to shut down.
Because of the increased descent etc. rates  in P and S mode I am not inclinded to try them to 5 seconds + although the resulting gyrations of the drone would probably more closely resemble an "emergency".

In "anytime" mode the motors shut down when the CSC position is held for arounf 2 seconds but as that descent started at a height of around 5 to 6 ft the freefall was only a foot or so and onto grass.


Regarding the mid air CSC and restart with the Phantom, looking at the screen it was impressively undramatic and seemed to be a stable flat spin, however the flight logs do show it wobbled quite a bit during the freefall so the gimbal did one heck of a good job.

2020-6-14
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hallmark007
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Sean-newbie Posted at 6-14 06:26
M80116 with regard to  "many of the situations cited in the manual as emergencies would bring down the drone with out a CSC being applied" the relevant section of the manual reads as follows

"Stopping Motors Mid-flight

It works fine, maybe not doing it right or set wrong.


2020-6-14
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Sean-newbie
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Hallmark007 did you happen to notice that at around 1:50 he talks about switching to "anytime" mode and appears to do so.

I know what the CSC command does in "anytime" mode and this is mentioned, above, in connection with both the tethered and free flight experiments.

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2020-6-14
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hallmark007
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Sean-newbie Posted at 6-14 08:59
Hallmark007 did you happen to notice that at around 1:50 he talks about switching to "anytime" mode and appears to do so.

I know what the CSC command does in "anytime" mode and this is mentioned, above, in connection with both the tethered and free flight experiments.

It’s hard to know what it is your looking for. Anytime will cut motors, emergency stop is when drone comes into contact, ie if flew into someone’s hair, if it crashed and was with motors running upside down on the floor then CSC will cut the power. So what I’m reading is you want to cut motors without contact so use anytime, it’s that simple.
2020-6-14
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Sean-newbie
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Hallmark007 I think we could write to each other indefinitely concerning this and not see eye to eye, let's leave it at that.
2020-6-14
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m80116
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Fair enough, this goes to show the CSC only during emergency can't be accidentally be activated. the safest option to leave set up imho.
2020-6-14
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hallmark007
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Sean-newbie Posted at 6-14 09:43
Hallmark007 I think we could write to each other indefinitely concerning this and not see eye to eye, let's leave it at that.

Well it would help if you made some real sense as to why you want to cut motors in midair by bypassing the very setting that will allow this. But yes when it begins to make no sense it’s a nonsense to continue to discuss it .
2020-6-14
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Sean-newbie
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ok...........
2020-6-14
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Droneflier
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Sean keep doing your crazy tests on the MM in a safe manner, the kid in all of wants to try them out but we don't have the balls to push the MM to its limits
2020-6-27
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Sean-newbie
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It's not a question of testing the limits as such, it's more "I want to know how the darn thing works". It is not 'the place' for ambiguity.
2020-6-27
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Sean-newbie
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ignore........wrong place

2020-7-11
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A J
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The 'emergency only' is if the drone experiences a critical error in flight thus performing a CSC meanuver with no critical errors will be ineffective. If you do not set to 'emergency only' then performing CSC will cut the motors in any event. That is why there are two options. If the drone is being flown off course due to heavy wind gusts then switching to sport mode and lowering altitude whilst you manually fly the drone out of the gust would be far safer and prevent losing the drone which is the point made by Hallmark007 and is a valid one. The combined stick command is reserved as an absolute last resort - ultimately to avoid collision with a manned aircraft. Thankfully it is something I have never had to use in over a thousand flgihts.   
2020-7-11
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Sean-newbie
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Thanks for the post AJ.
I am well aware that a CSC, if needed, is a measure of last resort, I have never, ever, questioned that.

However I would point out that "emergency only" is the default option.
I would also suggest that, going by the description given in the manual for the circumstances in which an "emergency only"-mode CSC will work, the drone would be fallling even without the CSC.

I am not disputing and never have disputed that, to get out of a blown away situation, descending and or switching to sports mode is preferable to crashing the drone, as would be a emergency landing at distance.

But, with regards to being blown away, I would suggest that if loss of connection is likely before being able to either get out of the wind or perform an emergency landing and, assuming that the drone will, for whatever reason, remain aloft once it is out of control range, then it is better to get the drone down rather than have it blown somewhere possibly worse. In such circumstances both a failsafe RTH and hover would leave the drone at the mercy of the wind and there is a chance that it will reject a failsafe landing and thereby remain at the mercy of the wind.

Using your example of an imminent collision with an aircraft, I would point out that an "emergency only"-mode CSC would NOT avert the collision. In such circumstances how many mini pilots are going to remember to switch to "anytime" mode whilst they are panicing.
2020-7-11
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hallmark007
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Sean-newbie Posted at 7-11 10:39
Thanks for the post AJ.
I am well aware that a CSC, if needed, is a measure of last resort, I have never, ever, questioned that.

I think CSC emergency was designed with impact in mind and mostly where people are involved, for instance if drone flew into some one with long hair, if it flew into a child’s pram as we have seen on one occasion in UK where an infant lost his eye, indoors if craft ends up on its side etc and props are still spinning etc, so default is correct IMO, there are many more immediate needs to turn off motors in emergency mode.
2020-7-11
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