Very weird behaviour

RobotBee · May 1, 2020

Hi

Just wondered if anyone has come across this?

Quite often when I move forward and backwards with the right stick, the drone also moves up and down respectively.

See this video here. As you can see, I start off at 9.1m high. I pull back on the right stick only, without touching the left stick, and as well as moving backwards, the drone descends to 5m within the space of a few seconds.

If I look at the flight record, I can see the drone receiving a 77% downwards input on the left stick, even though I wasn't touching the left stick.

Now what's really weird is DJI have replaced first the controller and then the drone itself, and I'm still having the same issue. I've tried with a tablet instead of my phone, and with a different USB cable.

I've done the following with both the originals and replacements from DJI:

Calibrated the control sticks (several times)
Calibrated the IMU (several times)
Reflashed the firmware
Updated the firmware

How can I still have this problem, when the controller and drone have been replaced??

Is it just an inherent issue with the mavic air that no one's ever noticed before? I can't believe that, but I equally can't believe having an identical fault with two controllers and drones.

Any ideas anyone?

Thanks!

kwolfskill · May 1, 2020

Never seen my Air drop like that, drift like some have seen or spin as others have.

I see you were only 9 meters up when you started in the video. Does it do the same at higher altitude?

RobotBee · May 1, 2020

kwolfskill said:
Never seen my Air drop like that, drift like some have seen or spin as others have.

I see you were only 9 meters up when you started in the video. Does it do the same at higher altitude?

Never noticed it at higher altitudes, no...

kwolfskill · May 1, 2020

It almost seems like it is preparing to land or is doing object avoidance, even though the Air doesn't have upward facing sensors.

Hopefully someone with more knowledge can help.

sar104 · May 1, 2020

There's really no way to diagnose that without the txt or DAT log.

Deleted member 94047 · May 2, 2020

RobotBee said:
Is it just an inherent issue with the mavic air that no one's ever noticed before?

That is definetly not standard behaviour; mine has never done that and I have flown it close to ground several times. Like sar104 said, upload the.txt and .DAT log files of the flight and I am sure some one here (most likely sar104 himself) will figure out what is causing that.

hiflyer201 · May 2, 2020

Hey Robotbee,
I've had the same issues lately. My Mavic air has behaved for the most part perfectly except occasionally the gimbal wheel has controlled the left right right stick fuctions?? calibrating the controller has always cured that problem but lately I have had to calibrate before every take off and the drone has behaved erratically. Loses altitude and drifts. I spent some time with the nitwits on DJI assistant and after disconnects and other problems I called the 877 number and was able to get a work order to send the drone and controller in for inspection. The conversation on the 877 number was going nowhere until I mentioned that I had ordered the Mavic Air 2 and was going to put a stop on it. I had planned on selling the drone but I sure couldn't do that in good faith with it behaving this way. We'll see what happens. I was not happy to read that you are having problems with a replacement.

RobotBee · May 3, 2020

kwolfskill said:
Never seen my Air drop like that, drift like some have seen or spin as others have.

I see you were only 9 meters up when you started in the video. Does it do the same at higher altitude?

Update - tested it again today at 120m altitude and it still did it. I pulled back on right stick and as well as going backwards, it started descending pretty rapidly.

RobotBee · May 3, 2020

sar104 said:
There's really no way to diagnose that without the txt or DAT log.

Thanks. My email notifications for this thread didn't work so I've only just seen your reply.

Am uploading the txt file and will post the link shorty. If you would be kind enough to take a look it would be much appreciated.

Many thanks

RobotBee · May 3, 2020

sar104 said:
There's really no way to diagnose that without the txt or DAT log.

Hi again

Here's a link to the following:
Flight log txt file
Video of the controller and phone screen starting at 3m 18s into the flight
Video of the controller and phone screen starting at 3m 18s into the flight
DJIFlightRecord_2020-03-22_[06-15-46].txt and 3 more files

As you can see from the videos,

- at 3m 18s I push only the right stick forward. I can see from the flight replay (and I presume you can see from the txt file) that the drone registers around 32% forward on the left stick, even though I'm not touching it.

- at 3m 58s I push only the right stick backwards. I can see from the flight replay that the drone registers 77% back on the left stick, even though I'm not touching it.

Any light you could shed on this would be very much appreciated!

Yesterday I recalibrate the IMU, controller and vision sensors (at the request of the retailer I got it from). Today, it's still doing the same thing so none of that fixed it.

Many thanks
Jack

RobotBee · May 3, 2020

Doppler said:
That is definetly not standard behaviour; mine has never done that and I have flown it close to ground several times. Like sar104 said, upload the.txt and .DAT log files of the flight and I am sure some one here (most likely sar104 himself) will figure out what is causing that.

Just uploaded - hopefully someone will be able to help me!

Thanks

RobotBee · May 3, 2020

hiflyer201 said:
Hey Robotbee,
I've had the same issues lately. My Mavic air has behaved for the most part perfectly except occasionally the gimbal wheel has controlled the left right right stick fuctions?? calibrating the controller has always cured that problem but lately I have had to calibrate before every take off and the drone has behaved erratically. Loses altitude and drifts. I spent some time with the nitwits on DJI assistant and after disconnects and other problems I called the 877 number and was able to get a work order to send the drone and controller in for inspection. The conversation on the 877 number was going nowhere until I mentioned that I had ordered the Mavic Air 2 and was going to put a stop on it. I had planned on selling the drone but I sure couldn't do that in good faith with it behaving this way. We'll see what happens. I was not happy to read that you are having problems with a replacement.

No, it's not good. I can't understand how I've got the same issue with two consecutive drones.

I had another 3 Airs before that, and none of them had this issue.

Let me know how you get on with yours.

Good luck!

sar104 · May 3, 2020

Oh yes - that is very strange. There is clearly some kind of crosstalk going on between elevator and throttle on several occasions, and it isn't just random interference on the throttle signal - it is well correlated with the elevator input. It doesn't happen every time you apply throttle though:

I've never seen that before - my guess would be that you have a faulty RC. Are you sure that it was replaced?

RobotBee · May 3, 2020

sar104 said:
Oh yes - that is very strange. There is clearly some kind of crosstalk going on between elevator and throttle on several occasions, and it isn't just random interference on the throttle signal - it is well correlated with the elevator input. It doesn't happen every time you apply throttle though:

View attachment 100419

I've never seen that before - my guess would be that you have a faulty RC. Are you sure that it was replaced?

Thanks so much for looking at it, and so quickly. Is the "RC_elevator" the right stick, and the "RC_throttle" the left stick? So the weird behaviour is when the black line replicates the red line, but to a lesser degree?

They def replaced the controller - the one on the left is the one I sent in, and the one on the right is the one they sent back, that I've got now.

I will pass your analysis on to the retailer and ask them to try another controller before replacing the whole drone.

Many thanks again

sar104 · May 3, 2020

RobotBee said:
Thanks so much for looking at it, and so quickly. Is the "RC_elevator" the right stick, and the "RC_throttle" the left stick? So the weird behaviour is when the black line replicates the red line, but to a lesser degree?

They def replaced the controller - the one on the left is the one I sent in, and the one on the right is the one they sent back, that I've got now.

View attachment 100423

I will pass your analysis on to the retailer and ask them to try another controller before replacing the whole drone.

Many thanks again

That is very strange. So you replaced everything and it is still happening - exactly the same problem?

RobotBee · May 3, 2020

sar104 said:
That is very strange. So you replaced everything and it is still happening - exactly the same problem?

View attachment 100424

Yes - in a bit more detail...

Since this problem started, they've replaced the controller once and the drone once

Controller A & Drone A - this problem, but worse - not only was the drone going up and down with the right stick, when it was hovering it would repeatedly try to fly itself into the ground - I had to push up full on the left stick to stop it hitting the ground

(replaced controller)

Controller B & Drone A - this problem

(replaced drone)

Controller B & Drone B - this problem

So, although it would seem really unlikely, most likely explanation is two faulty controllers you think?

Assuming the black line on the graph is the throttle (i.e. up/down on left stick), why might it be showing a downwards reading between 170 and 200 seconds, when the drone was just hovering without me touching anything?

Many thanks again

sar104 · May 3, 2020

RobotBee said:
Yes - in a bit more detail...

Since this problem started, they've replaced the controller once and the drone once

Controller A & Drone A - this problem, but worse - not only was the drone going up and down with the right stick, when it was hovering it would repeatedly try to fly itself into the ground - I had to push up full on the left stick to stop it hitting the ground

(replaced controller)

Controller B & Drone A - this problem

(replaced drone)

Controller B & Drone B - this problem

So, although it would seem really unlikely, most likely explanation is two faulty controllers you think?

Assuming the black line on the graph is the throttle (i.e. up/down on left stick), why might it be showing a downwards reading between 170 and 200 seconds, when the drone was just hovering without me touching anything?

Many thanks again

No - it was actually descending during that time:

RobotBee · May 3, 2020

sar104 said:
No - it was actually descending during that time:

View attachment 100425

Yes, but what I mean is that during that time I'm pretty sure I wasn't touching either of the sticks, yet the left stick is still registering downwards slightly and causing the drone to drop slowly...

Thanks

sar104 · May 3, 2020

RobotBee said:
Yes, but what I mean is that during that time I'm pretty sure I wasn't touching either of the sticks, yet the left stick is still registering downwards slightly and causing the drone to drop slowly...

Thanks

Right - that is what is happening - spurious throttle input with no elevator input.

dawgpilot · May 3, 2020

I've had this same issue pop up sporadically too. I'm also on my 2nd controller after DJI replaced the original one, and still see it. Unfortunately I'm out of warranty now so further warranty replacements aren't an option for me anymore.

I'm upgrading to the Mavic Air 2 next week, so hopefully these ghost inputs don't follow me to the new model!