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Flying forward descending, flying backward is fine.

HWCM

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So today I had an unusual situation. I flew out about a mile and up a mountain about 400 feet. Everything was normal no issues. I then turned around to fly back and down the mountain. A few seconds into coming back, the mini was moving forward very slowly and started descending slowly, about a foot a second. Full stick up and it would not gain altitude. I thought I must have hit some headwind so I yawed to the left or right, suddenly it started gaining altitude again. So I pitched it forward, again it moved very slowly forward and down. So I let it come down about 100 feet while still full stick up and crawling forward, thinking I would get below the wind. No results. I turned 90° to my left and it flew perfectly gaining altitude and moving forward about 15 MPH. I turned the mini to my right, same result, flying perfectly. Turning the mini forward to fly back to takeoff and again, the slow forward and loosing altitude. For some reason, I thought to fly home backward. It worked, I could gain altitude and get full reverse speed. I got the mini all the way back in reverse because every time I tried facing the mini forward towards the take off location, it would only move about 3-4 MPH and drop about a foot a second. Reverse worked fine. I had no warnings, no wind warnings, no prop warnings and no motor speed warnings.
Does anyone have any idea what was going on? The only thing I can figure is the rear props or motors could not maintain lift and forward speed. I thought it could have been an altitude thing, but it had the same result at 150ft as 400 ft.
Also, my battery usually will last 21-24 minutes, this flight it was at 20% within 13 minutes.
I have the latest firmware and app updates and did the "refresh" with the assistant.
I'm using the props that came on it when I bought it. I will switch those out and compare them to new ones to see if they look deformed.
I just can't understand why it flew out and up fine, but coming back it would only fly back in reverse.
Any ideas?
Will someone review the flight logs if I can figure out how to upload them?
If this continues, I will have to see what DJI will do. This thing has gotten to be unsafe to fly with these issues.
Thank you in advance and I apologize for the long post.
 
Full stick up and it would not gain altitude. I thought I must have hit some headwind
Headwinds should have no effect on the drone's ability to climb
For some reason, I thought to fly home backward. It worked, I could gain altitude and get full reverse speed. I got the mini all the way back in reverse because every time I tried facing the mini forward towards the take off location, it would only move about 3-4 MPH and drop about a foot a second. Reverse worked fine. I had no warnings, no wind warnings, no prop warnings and no motor speed warnings.
Does anyone have any idea what was going on?
This sounds very much like the problems many have had with uncommanded descent and inability to maintain proper tilt to hold speed.
The recorded flight data will show what was going on.
Will someone review the flight logs if I can figure out how to upload them?
Go to DJI Flight Log Viewer | Phantom Help
Follow the instructions there to upload your flight record from your phone or tablet.
That will give you a detailed report of the flight.
Come back and post a link to the report it gives you.
 
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That's what I was thinking too. I really think DJI dropped the ball on this one. The latest update seems to stop the warnings even though the issue is still there.
 
Yeah ... this was most probably the uncommanded descent phenomenon that we have seen so many times before for the Mini. The rear props under perform & can't generate a pitch near the specified nor lift. It's earlier been reported that flying backwards or sideways can generate headway as it's other props than the rear that generates the pitch.

The chart below from when you just have turned around ... along the yellow marking.

1590474222731.png

1590474237233.png

As seen in the black graph, the pitch where the marking is, with full elevator input only 2 degrees pitch is made & the down speed on the darker green goes positive (descending) & the heading speed, blue, goes down.
 
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This is the Flight log.
At around 6:58 you have turned the drone toward home and given it full right stick but it's only flying at a little over 5 mph.
This is because despite full right stick, pitch angle is 5° or less when it should be much more.

If we look at 7:37 the speed has come up to 13 mph and pitch is now around 10°.
This shows that despite being high, the wind was not the issue.

In Sport Mode at 9:26, speed was only 6mph with full stick and a pitch angle of about 4° rather than 20-30°

At 12:03 you've turned the drone around and reversing full stick toward home, it's pitching 24° and flying at 24 mph.

This all fits with what has been tested in this thread:
... and the weird things happening with the Mini.
You did well to find the way to bring it home.
 
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Thank you for the explanation. I appreciate the help.
I guess changing the props should help?
Yeah ... this was most probably the uncommanded descent phenomenon that we have seen so many times before for the Mini. The rear props under perform & can't generate a pitch near the specified nor lift. It's earlier been reported that flying backwards or sideways can generate headway as it's other props than the rear that generates the pitch.

The chart below from when you just have turned around ... along the yellow marking.

View attachment 102532

View attachment 102533

As seen in the black graph, the pitch where the marking is, with full elevator input only 2 degrees pitch is made & the down speed on the darker green goes positive (descending) & the heading speed, blue, goes down.
 
Thank you also for the detailed explanation.
I've been flying DJI for years and have never had any of them act this way.
I will change the props and see if that helps at all.
I really don't trust the mini anymore really...
At around 6:58 you have turned the drone toward home and given it full right stick but it's only flying at a little over 5 mph.
This is because despite full right stick, pitch angle is 5° or less when it should be much more.

If we look at 7:37 the speed has come up to 13 mph and pitch is now around 10°.
This shows that despite being high, the wind was not the issue.

In Sport Mode at 9:26, speed was only 6mph with full stick and a pitch angle of about 4° rather than 20-30°

At 12:03 you've turned the drone around and reversing full stick toward home, it's pitching 24° and flying at 24 mph.

This all fits with what has been tested in this thread:
... and the weird things happening with the Mini.
You did well to find the way to bring it home.
 
tbh I think I'd ask DJI to replace the drone given that description above ... nothing to lose..
 
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I will change the props and see if that helps at all.
It should improve matters but for how long?
I've been flying DJI for years and have never had any of them act this way.
I really don't trust the mini anymore really...
There have been too many incidents with the Mini failing to maintain proper pitch angle.
The uncommanded descents where even full throttle won't stop it are even worse.
The Mini is in a different league from the other DJI drones.
 
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tbh I think I'd ask DJI to replace the drone given that description above ... nothing to lose..

There's nothing wrong with the Mini itself - it's the lack of thrust from the rear props, which are easily deformed. There is currently no solution to the problem other than new rear props whenever it occurs and, in cases like this, flying backwards.
 
I changed out the props, no wonder it would not maintain lift or speed. They are flat compared to the new ones.
I think it's the fly more case. I had been using a case made for the mini I bought from Amazon. It has a molded cut out for the remote and mini. But, it's soft foam. I've used this case for months, since buying the mini. It has sat in that case for weeks at a time with zero issues.
Two weeks ago I bought a DJI mini case that comes with the combo. The mini was in that case for about a week, now the props are flat.
I always pay close attention to the orientation of the bottom props when I put it in the case...but. I think the props still rest on the bottom of the case, as the bridge it rests on is too shallow. I put a piece of tape sticky side up in the case where the props rest, put the mini in and closed the case. Sure enough, the tape was stuck to the props after taking the mini out. I put two pieces of 3mm foam in the case where the gimbal cover and mid body of the mini rests, this lifts the mini up a bit and stops the props from resting on the bottom. (see pictures) I Aldo will start positioning the front props differently when in the case, forward instead of folded on top of each other.
I also ordered some carbon props. Hopefully they are not junk.
Check out the pictures to see how bad the props are.
Also, when I fly the mini, the bottom gets pretty **** warm. Flying it, then folding it up and putting it in the case with pressure on the props might be kind of making a pressure heater to deform the props? Just a thought. IMG_20200526_055507.jpegMVIMG_20200526_055421.jpegIMG_20200526_055325.jpegMVIMG_20200526_052230.jpegMVIMG_20200526_052214.jpegMVIMG_20200526_052037.jpegMVIMG_20200526_051858.jpegMVIMG_20200526_051827.jpeg
 
So today I had an unusual situation. I flew out about a mile and up a mountain about 400 feet. Everything was normal no issues. I then turned around to fly back and down the mountain. A few seconds into coming back, the mini was moving forward very slowly and started descending slowly, about a foot a second. Full stick up and it would not gain altitude. I thought I must have hit some headwind so I yawed to the left or right, suddenly it started gaining altitude again. So I pitched it forward, again it moved very slowly forward and down. So I let it come down about 100 feet while still full stick up and crawling forward, thinking I would get below the wind. No results. I turned 90° to my left and it flew perfectly gaining altitude and moving forward about 15 MPH. I turned the mini to my right, same result, flying perfectly. Turning the mini forward to fly back to takeoff and again, the slow forward and loosing altitude. For some reason, I thought to fly home backward. It worked, I could gain altitude and get full reverse speed. I got the mini all the way back in reverse because every time I tried facing the mini forward towards the take off location, it would only move about 3-4 MPH and drop about a foot a second. Reverse worked fine. I had no warnings, no wind warnings, no prop warnings and no motor speed warnings.
Does anyone have any idea what was going on? The only thing I can figure is the rear props or motors could not maintain lift and forward speed. I thought it could have been an altitude thing, but it had the same result at 150ft as 400 ft.
Also, my battery usually will last 21-24 minutes, this flight it was at 20% within 13 minutes.
I have the latest firmware and app updates and did the "refresh" with the assistant.
I'm using the props that came on it when I bought it. I will switch those out and compare them to new ones to see if they look deformed.
I just can't understand why it flew out and up fine, but coming back it would only fly back in reverse.
Any ideas?
Will someone review the flight logs if I can figure out how to upload them?
If this continues, I will have to see what DJI will do. This thing has gotten to be unsafe to fly with these issues.
Thank you in advance and I apologize for the long post.


I had a similar problem. After 15 minutes of flying in a medium wind, when I wanted to bring the Mavic Mini back towards me in forward flight, facing the wind, it started to move backwards! After a few maneuvers I thought about flying backwards. So I turned 180 degrees and the drone fought the wind well and got closer. When I got to my height I turned it 90 degrees to get back to forward flight, and it started to descend!
From an altitude of 7-8 meters, it descended to the ground without me being able to prevent it. Unfortunately it landed halfway in a puddle of salt water.
There was no way to make it work again. Luckily I got the Care Refresh and sent it to DJI.
I think it's a software problem...
 
I had a similar problem. After 15 minutes of flying in a medium wind, when I wanted to bring the Mavic Mini back towards me in forward flight, facing the wind, it started to move backwards! After a few maneuvers I thought about flying backwards. So I turned 180 degrees and the drone fought the wind well and got closer. When I got to my height I turned it 90 degrees to get back to forward flight, and it started to descend!
From an altitude of 7-8 meters, it descended to the ground without me being able to prevent it. Unfortunately it landed halfway in a puddle of salt water.
There was no way to make it work again. Luckily I got the Care Refresh and sent it to DJI.
I think it's a software problem...

It's primarily a hardware problem - the rear props become deformed and don't produce enough thrust. It's possible that the firmware could be altered to sacrifice pitch to prevent uncontrolled descent, but that's not the root cause.
 
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No, it's definitely a hardware issue. Check out the pictures I posted above. You can see how flat the props were compared to the new ones.
I put new rear props on and flew thee batteries today in mild wind. I flew one flight three miles out and back (six miles total) in sport mode. Full stick both ways. No issues.
I feel much better about flying it now that I know what the issue is.
I had a similar problem. After 15 minutes of flying in a medium wind, when I wanted to bring the Mavic Mini back towards me in forward flight, facing the wind, it started to move backwards! After a few maneuvers I thought about flying backwards. So I turned 180 degrees and the drone fought the wind well and got closer. When I got to my height I turned it 90 degrees to get back to forward flight, and it started to descend!
From an altitude of 7-8 meters, it descended to the ground without me being able to prevent it. Unfortunately it landed halfway in a puddle of salt water.
There was no way to make it work again. Luckily I got the Care Refresh and sent it to DJI.
I think it's a software problem...
 
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