Emergency propellor stop

RoosArt · May 11, 2023

Does anyone know the difference between the two settings that you can chose under advanced safety settings - emergency propellor stop on the DJI RC. One setting states 'anytime (use with caution)' and the other 'emergency only'. As I recently saw a guy on YouTube crash his drone by accidentally moving the controls in the downward 45 degree position while making a video it got me wondering what the difference is between the two settings.

Yorkshire_Pud · May 11, 2023

The names for the options vary depending on which app you are using. In fly they are, I think, "Emergency Only" and "Anytime".

"Emergency Only" is the default and, with that option set, the CSC WILL NOT stop the motors unless the drone itself thinks it has suffered some sort of emergency, we do not know what precisely it considers to be an emergency.
In a routine flight, with no such emergency, the CSC will cause the drone to descend in a helix, all under perfect control. As soon as you release the sticks the drone will hover.

"Anytime" means that the motors will stop with the drone in mid-air or anywhere else ONCE you have held the CSC position for around 1.7 seconds, no warnings, no nothing, just boom, stopped motors and a falling drone.

In my opinion 1.7 seconds is FAR TOO SHORT a delay period to be a safe option for normal flying.
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If your you tuber was flying a Mavic style drone then they most likely had the option set to Anytime or what ever the relevant name is....... or were VERY, VERY unlucky.
If they were flying a Phantom then things are different.

old man mavic · May 11, 2023

@RoosArt ,just to add to @Yorkshire_Pud 's excellent post above
emergency is any situation when the drone is falling to earth because of the fact that it is out of control
such as a bird strike, loss of propellor, or hitting an obstruction of some sort
because it is not in the normal flight parameters, and out of control ,then the IMU allows the emergency stop to activate ,this is the best setting to use

Yorkshire_Pud · May 11, 2023

old man mavic said:
e ,this is the best setting to use

I would go further than that and say it is the only safe setting to use for normal flights.
I recollect at least two threads where we have been able to deduce that the drone fell from the sky because of an inadvertent the evidence being the CSC stick position being held for around 1.7 seconds and the log end. In the last line of at least one of those logs the "motor on or up" signal switched to whatever value corresponds to the motors being switched off.

Droning on and on... · May 11, 2023

As a real example, the video below is a CSC on an Avata, about 18 inches off the ground hovering. The CSC is initiated when you see the view start to yaw to the right, motors stop when the video ends.

The delay from CSC to stop was 1s, Avata was in N mode, total offset from the hover position to cutoff was about 18".

It seemed like the drone or controller was "aware" of the CSC state immediately, because the drone did not yaw and translate nearly as fast as it should have. The response was very gentle.

Droning on and on... · May 11, 2023

Okay, here at the field. Just repeated the experiment with the A2S. Similar results as with the Avata, although the offset and yaw were larger.

Performed the CSC in C mode, hovering over a landing pad with very soft ice plant and grass all around. Did it 3 times, carefully duplicating the initial conditions (heading, settings, height). Same landing spot within 6" of each other. IOW, it's predictable.

From CSC to motor stop, about 1s just like the Avata. Greater yaw and translation, about 200° and 4.5 ft, ±6". Still quite gentle, and you can reliably count on the short flight path and drop location, so you can plan around it. 2' drop to the ground, no damage,scuff marks etc. at all. Here's a picture of try #3:

Droning on and on... · May 11, 2023

I would add that the CSC was set for emergency only when I flew it out over the field. I was able to switch it to ALWAYS while hovering, and then use it.

So, if you're thinking of using this method to land, say on a stationary boat pitching up and down so much the drone refuses to land, you don't have to risk this setting while in-flight on the mission but can enable it at the end to force a landing.

Just make sure the boat deck is large enough, and you've practice many times in a safe setting so you know where it's going to end up.

It's a little more complicated maneuver than some, but very useful if planned right.

3rdof5 · May 11, 2023

Yorkshire_Pud said:
The names for the options vary depending on which app you are using. In fly they are, I think, "Emergency Only" and "Anytime".

"Emergency Only" is the default and, with that option set the CSC WILL NOT stop the motors unless the drone itself thinks it has suffered some sort of emergency and we do not know what precisely it considers to be an emergency.
In a routine flight, with no such emergency, the CSC will cause the drone to descend in a helix, all under perfect control. As soon as you release the sticks the drone will hover.

"Anytime" means that the motors will stop with the drone in mid-air or anywhere else ONCE you have held the CSC position for around 1.7 seconds, no warnings, no nothing, just boom, stopped motors and a falling drone.

In my opinion 1.7 seconds is FAR TOO SHORT a delay period to be a safe option for normal flying.

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If your you tuber was flying a Mavic style drone then they most likely had the option set to Anytime or what ever the relevant name is....... or were VERY, VERY unlucky.
If they were flying a Phantom then things are different.

Speaking of CSC motor shut off with a Phantom, yes there is no such settings (emergency or anytime) with Phantoms. If you perform the CSC in flight the motors WILL stop after a few seconds. However, there is one video I have seen where this was done purposely with a P4 from max altitude and the pilot was able to successfully restart the motors and recover. But you need ALOT of altitude cause they fall fast lol.
This is a legally required feature as the pilot is obligated to avoid crashes with manned aircraft, at all costs, even if it means shutting down your aircraft in flight and letting it crash to save lives.

Yorkshire_Pud · May 12, 2023

I have done a mid air shut off and restart with a P3.
Though I had height to play I think that the necessary height would primarily stem from how long you leave between the motor stop 'CSC' and the motor start 'CSC'. They MUST be separate actions.
With the P3 you also have to give it throttle to halt the fall after restart, the motors start at idle, that nearly cost me the drone.
I suspect more modern drones might realise they are falling and rev their motors etc. but ........

I get the impression that free fall terminal velocity for drones is in the region 14m/s to 16m/s.

With a Mavic Pro. ....
I haven't tried it with any mavic style drone as I think there is a chance it might tumble and they will only restart when the drone is within a window of 'acceptable tilt'.
Someone here tried it with a Mini 2 but, from memory, against instructions they DID NOT release the motor stopping CSC and apply a separate motor start CSC, they held the motor stopping CSC the whole way down...........resulting in a splat.

DARKSeifer · May 12, 2023

Anytime means if you do that midflight, accidentally or not, and say goodbye to the drone.

Midflight restart will mostly fail 95% of the time as at its terminal velocity it can roll or tilt, and the IMU will just say no thanks. They just got lucky on that YT stunt, maybe maintaining the command hoping for the IMU to say yes can do it, if you are high enough, but it's just idiotic behavior overall.

Yorkshire_Pud · May 12, 2023

DARKSeifer said:
maybe maintaining the command

If by that you mean maintaining the motor stopping CSC then that is a death sentence for the drone, unsuccessful attempts with mini 2, PLUS it looks as if the drone inverted

If you mean maintaining the separate motor start CSC then that is, I think, the only hope with a DJI drone.
Found a third but successful restart, no subtitles so can't tell what the narration is like
So it may be that the early mavics fall more or less horizontally but as for the rest.....

Anyway anyone who tries this does so at their own risk lol.

Dbez1 · May 12, 2023

Thanks for the info in this thread. It not something I’ve thought about (or tried). Nor will I, but it’s good to know.

Droning on and on... · May 13, 2023

I had a thought for another test... what happens if the drone is executing the landing procedure from holding the throttle down or pressing the Land button on the screen, and the emergency stop CSC is invoked? Would it still move horizontally, or would the motors stop after 1s and drop over the same spot?

The Manual likely address stick input during landing, and I'll go look. I suspect it aborts the landing process and obeys the stick input, but if not, this gives more possibilities in difficult landing scenarios.