Does Mini 2 continue flying at 21 mph for 11 seconds after controller Signal Loss , does it stop, or backup 50 meters-then try Failsafe RTH?

[Dasher]

Can you please help with your flight experiences for these circumstances ?

Mini 2 controlled with Litchi
Failsafe RTH = Set at RTH (not landing or hovering)
No RTH Height was set (Blank in Litchi, might have been set at 165 feet in DJI-Fly)
Compass & IMU are good.

Returning home under manual control.
Drone is ~ 635 feet above takeoff and one mile out. P-GPS is excellent.

Battery draining abnormally fast, is Down to 11%, with RTH cancelled at 25%.
In Autoland mode.

Problem: Signal lost going behind steep rock ridge on way home.

Last Litchi Log entry -
Forward @ 21 mph (~70 degrees from RTH direction -- looking-down-clockwise)
(aiming to land on grassy hilltop, rather than side of steep rocky slope)
Down @ 6.5 mph

Question 1 -- After controller signal is lost,
until 11 seconds pass and RTH kicks in,
how will drone's speed across landscape change ?

1) Will Mini 2 continue forward @ 21 mph and down @ 6.5 mph for 11 seconds?
2) or stop immediately ? (forward & down)
3) or slow to a stop? (forward & down)
4) or after 3 seconds, slow to a stop, then backup 50 meters, then try Failsafe RTH?
5) Other?

21 mph = 30.8 feet per second
3 seconds = 93 feet
11 seconds = 341 feet (104 meters)
50 Meters =

Question 2 -- Same Question - but first 3 seconds.
After controller signal is lost,
until 3 seconds pass,
how will drones speed across landscape change?

Have you actually tested or witnessed circumstances similar to these ?

Thank you.

 

[Yorkshire_Pud]

I have not witnessed a loss of signal whilst the drone was moving and I have never thought to check any video that it was recording but my suspicion is that.

The drone will brake as soon as the signal is lost. The severity of the braking being either the preset default or, if the option exists, at the level set in the App's menus. I think some of the more recent app versions allow the user to set the braking severity.
It will commence the 50m retrace 11 seconds after the signal is first lost. At the end of the retrace and if connection was not regained it will start the set failsafe behaviour, RTH in your case.

However, with the battery at 11% and the drone at a height of 635ft I am fairly sure it would soon have been starting the forced landing phase so, in calm conditions, I doubt it would have actually moved that far from the disconnection point before it started to descend and I think it would have ceased any attempted RTH once the forced landing phase etc. commenced but that is conjecture.

Questions.
1) Was the drone executing an RTH when connection was lost? I do not understand what you have said about that. 21mph is below the RTH speed of 23.5mph.
2) If the drone was not in RTH, were you giving the drone full elevator? 21mph is well below the stated maximum speed in sports mode, 35.8mph.
Your "Battery draining abnormally fast" comment and your "21mph" makes me wonder if the drone was encountering significant head wind. The relevance of which is that, in possibly the forced landing phase and certainly in the critical landing phase the drones ability to fight wind is increasingly reduced.
If the drone was in a significant wind and at significant AGL height then during the descent I think it is quite likely to have been blown downwind. I do not remember the normal automated descent rate but the maximum descent rate in sports mode is, according to the manual, 11.5ft/s.

From where does the reference to 3 seconds come?

 

[Dasher]

Thank you for your helpful thoughts Yorkshire_Pud.

Idea 1) "Your 'Battery draining abnormally fast' comment and your "21mph" makes me wonder
if the drone was encountering significant head wind. The relevance of which is that,
in possibly the forced landing phase and certainly in the critical landing phase
the drones ability to fight wind is increasingly reduced.

Response 1: Yes, good thought. There was a small headwind during return (~7mph),
which helps explain some of the rapid battery decline.

Idea 2) "Drone will brake as soon as the signal is lost.
The severity of the braking being either the preset default or,
if the option exists, at the level set in the App's menus.

Response 2: While that may be true, its no better than my own conjectures.
This needs someone with empirical, physical experience.
(I don't recall any setting for braking severity in DJI-FLY.)

If no one comes up with anything, I will set up some experiments
to investigate this - when I am flying again.

Q1) Was the drone executing an RTH when connection was lost?
Q1b) 21mph is below the RTH speed of 23.5mph.

A1: No, it was not in RTH when signal lost. It was Returning home under manual control.
A1B: Pretty sure drone was in Normal Mode, Not Sport.
22 mph ~ top speed in Normal mode.

2) If the drone was not in RTH, were you giving the drone full elevator?
21mph is well below the stated maximum speed in sports mode, 35.8mph.

A2: I'm having trouble verifying this, but I believe I had full forward @ Signal Lost,
and Full Down (Down logged @ 6.5 mph). I'll update when I get the info.

Idea 3) "If the drone was in a significant wind and at significant AGL height
then during the descent I think it is quite likely to have been blown downwind.
I do not remember the normal automated descent rate but the maximum descent rate
in sports mode is, according to the manual, 11.5ft/s."

Response 3: There seems to be no dispute what occurs after 11 seconds.
But we need actual facts about speeds before the 11 seconds are up.
In this case it is vital to know what happens to Mini 2 speeds (forward and vertical)
in the first few seconds after Controller Signal is lost - Before the 11 seconds is up.

Thank you

 

[slup]

Response 3: There seems to be no dispute what occurs after 11 seconds.
But we need actual facts about speeds before the 11 seconds are up.
In this case it is vital to know what happens to Mini 2 speeds (forward and vertical)
in the first few seconds after Controller Signal is lost - Before the 11 seconds is up.

The drone will stop it's movements when the RC connection is lost in the same way as if you just releases the sticks to neutral from a full forward & descent stick command... because this is what happens when the connection is lost, the stick commands no longer reach the drone.

The drone will brake & pretty much stop it's commanded movements on the spot, it will not continue according to the last transferred stick commands & it will not gradually decrease the speeds during some 3sec period.

If you want help to pinpoint a possible location where your drone might have ended up... please share your flight log instead.

 

[Yorkshire_Pud]

I have just done three tethered flight indoors in Cine, Normal and sports modes. I gave the drone full elevator in each mode and held that whilst I switched the controller off. In each flight the drone more or less levelled itself as soon as connection was lost, it didn't have to brake as it had no forward movement to halt but the levelling was instantaneous.
I realise this is not an exact match to free flight with functioning GPS and my drone wanted to land, which it could not do if pitched forwards but I think it's a fair match of a test. Take the tests as you choose.

Have you lost the drone?

 

[RodPad]

Dasher

mavicpilots.com

Welcome to the forum!
As posted, "Have you lost the drone?"

Did this actually happen?

Rod ..

 

[Dasher]

I have just done three tethered flight indoors in Cine, Normal and sports modes. I gave the drone full elevator in each mode and held that whilst I switched the controller off. In each flight the drone more or less levelled itself as soon as connection was lost, it didn't have to brake as it had no forward movement to halt but the levelling was instantaneous.
I realise this is not an exact match to free flight with functioning GPS and my drone wanted to land, which it could not do if pitched forwards but I think it's a fair match of a test. Take the tests as you choose.

Have you lost the drone?

Thank you again Yorkshire_Pud
Over and above call of duty to conduct an experiment for this !
Thank you. And yes drone is currently waiting for me up on my hill.
Good understanding of this Mini 2 programming controls
will dramatically narrow where I look and the amount of time spent
with another drone "filming" potential resting places.

Your test is persuasive for elevation control, and somewhat persuasive for forward movement.
My remaining question is what happens to Mini 2's speed when it is going 21 mph and connection is lost?
Because that's a good amount of inertia.

We know that with good controller Signal, there are at least 2 different Stop modes, maybe 4:
Instant-Halt if you stab controller RTH button once. (Stop in maybe 2-4 feet)
And Slow to a Stop by releasing controls. (Stop in maybe 5-10 feet)
And maybe a third (or fourth) Lazy Stop when you press RTH onscreen or on controller.
Which, if any, of these modes used when controller signal is lost?

Having a bit of computer headache getting Flight log again, will post when I do.
In meantime, here's a 3-D pic I took from Gaargle-Earth showing the last moments of telemetry.
Drone is moving to Left / forward at ~21 mph towards yellow Pin, and descending (at ~ 4.5 mph).
Thin white line is Return to Home direction.
(Blue and red lines at top are unrelated to this flight.)

 

[Yorkshire_Pud]

I have actually done three free flights, Cine, Normal, Sports but they were away-from-me/towards-me as there are trees to either side of the flight route.
It appears to brake as soon as the control signal is lost.

It was quite interesting as the retrace included the shimmies to line every thing up prior to the full speed flight. The sports mode did seem to have noticable braking distance.
The manual does state "The maximum speed and braking distance of the aircraft significantly increase in Sport mode. A minimum braking distance of 30 m is required in windless conditions." but I doubt it took that distance.
My 'speed runs' started at a distance of 70ish m and flew towards me so 30m would have been quite evident.

With regards to

We know that with good controller Signal, there are at least two different Stop modes:
Instant-Halt if you stab controller RTH button once. (Stop in maybe 2-4 feet)
And Slow to a Stop by releasing controls. (Stop in maybe ?? feet)
And maybe a third (or fourth) Lazy Stop when you press RTH onscreen or on controller.
Which, if any, of these modes used when controller signal is lost?

I think you are over thinking things.
I think it is safe to say that in windless conditions your drone, if lost, would be quite close to the disconnection point. If the wind and AGL height were significant then all bets are off.

With regards to the logs where are you looking?
For me the path to Litchi logs, seen by a Windows computer, was
Computer/phone's_name/Phone/DJI/com.aryuthere.visionplus/Flightrecord.

 

[RodPad]

I'm still lost.

Dasher

mavicpilots.com

You know exactly where it is?

Rod ..

 

[Deleted member 84685]

675ft & 1 mile out ,asking for trouble

 

[Dasher]

I have not witnessed a loss of signal whilst the drone was moving and I have never thought to check any video that it was recording but my suspicion is that.
...
...... remember the normal automated descent rate but the maximum descent rate in sports mode is, according to the manual, 11.5ft/s.

From where does the reference to 3 seconds come?

YP: Where does the reference to 3 seconds come?"

A: "Failsafe RTH happens when your drone loses signal for 3 seconds when using the remote controller
or 20 seconds if using Wi-Fi."

DJI Guides - DJI Store (United States)

Online shopping for a great selection of at the official DJI Online Store.

store.dji.com

 

[Yorkshire_Pud]

A: "Failsafe RTH happens when your drone loses signal for 3 seconds when using the remote controller
or 20 seconds if using Wi-Fi."

That appears to come from an interesting 2017 document relating to the use of a Go4 using drone.
The mini 2 is a FLY App using drone for which the manual states
"If the Home Point was successfully recorded and the compass is functioning normally, Failsafe RTH automatically activates after the remote controller signal is lost for more than 11 seconds."

 

[Dasher]

Thank you again Yorkshire_Pud,
I've read both, but not fully persuaded by either.
Feeling pretty strong that (just like Max Altitude of 500meters)
Autoland and Failsafe RTH are in AirCraft Firmware - not in Fly or Go apps.
(But any good evidence otherwise could change my mind)

I'm kind of settling on -
My GUESS is that Failsafe RTH and Retrace RTH never kicked in after Autoland took over at 11% battery.
1) Fact: Autoland was in control for last Telemetry update.
2) Educated Guess: But the Mini2's 21mph momentum probably carried it forward
for at least a second or three until Signal reduction, then loss, slowed its forward movement to zero.
3) Wild-*** Guess: Then it continued descending and landed with what remained of its 11% battery.

Anything in that scenario look fatally flawed ?

Tomorrow I'm heading up to lay out ribbons to more firmly tag places I've searched
by foot and by a second drone. (FoxTails on the steep sided rocky hill - make it tough going. )
Will let you know how my theory matches up with physical reality.
Cheers

 

[Yorkshire_Pud]

"I've read both, but not fully persuaded by either." just to be clear, read both what?

Most settings are stored in the drone but can be accessed and changed via a connected App, I don't/didn't think that is/was under debate.
If you think about it, it would in many situations need to be that way, otherwise, in a disconnection, how could a disconnected drone act on settings stored in a disconnected controller or APP?

As for precisely when, down to the milli second, disconnection occurs and failsafe action commences, how can we tell?
We do not know precisely what the drone considers to be a disconnection, a milli second interruption in signal or a half second or .... there are plenty of logs about with gaps in telemetry yet the drone seems to have carried on its way.
All we can go by is visual observation and in my experiments the braking seem to be what I would consider immediate, that will satisfy me.
If you are really going to try to nail down a position then I think you would also have to take into consideration GPS error and possibly in your case wind drift as the battery charge decreased.

If you are lucky time will tell.