Strange messages during normal flight

[adavis]

Heres the flight log, hopefully someone can tell me what is going on here.
My Mavic Mini has been working great, and I went to put it up for a magic sunrise this morning, but had issues.

Firstly the app made me do an IMU recalibrate and a compass calibrate.
Did that , then did auto takeoff and it was a but squirrelly in hover.
Took it up and then the warning started.

There was zero wind, dead calm.
There was no extra weight on the mini.

Anyway, it made we not want to do anything risky, so thought that I would get the experts here to have a look

 

[Capt KO]

What exactly did the warning say? Just guessing that you did the calibrations in an area that was not suitable. When you flew out of that area, even a few feet, your mini was getting lost. Of course when somebody looks at the records you’ll know exactly what happened. GLuck

 

[adavis]

What exactly did the warning say? Just guessing that you did the calibrations in an area that was not suitable. When you flew out of that area, even a few feet, your mini was getting lost. Of course when somebody looks at the records you’ll know exactly what happened. GLuck

Yeah fair point, I should have said that

this was the message:

Not Enough Force/ESC Error. Aircraft max power load reached. Decrease altitude and fly with caution. If this issue persists, land immediately (Code: 30168). Max power load reached. Fly with caution

When descending, it was moving all over the place with only down stick.

 

[sar104]

Yes - serious attitude instabilities on descent, and one short period of uncommanded descent.



There are numerous cases with this exact signature, and I would say that it is clearly a design flaw in the aircraft or props. Any chance that the mobile device DAT file ending FLY047.DAT is still on your device? I still haven't seen one for these events due to DJI's cunning deletion scheme.

 

[adavis]

Yes - serious attitude instabilities on descent, and one short period of uncommanded descent.



There are numerous cases with this exact signature, and I would say that it is clearly a design flaw in the aircraft or props. Any chance that the mobile device DAT file ending FLY047.DAT is still on your device? I still haven't seen one for these events due to DJI's cunning deletion scheme.

Is this worth reporting to DJI?

It's your lucky day, here we go, attached.

 

[slup]

Is this worth reporting to DJI?

It's your lucky day, here we go, attached.

The right rear motor is maxed out during the whole flight, the Mini can't control pitch/roll with this ... any damages on the props there, motor feels smooth to rotate by hand?

 

[sar104]

The right rear motor is maxed out during the whole flight, the Mini can't control pitch/roll with this ... any damages on the props there, motor feels smooth to rotate by hand?

Agreed - to an extent. It's controlling pitch and roll pretty well for most of the flight - except during descent.



It appears that the rear right prop is marginal for lift for the entire flight - hence the high RPM, but that during descent it doesn't have enough to control the aircraft. I really am starting to think that it is a form of VRS triggered by bad props, or prop in this case.

 

[adavis]

OK interesting, I did just replace one set of props due to damage.
When you say right rear, is that with the camera facing you or looking away?

I did replace the props on one side at the rear due to previous damage, and this side the motor offers what seems a lower turning resistance.
This is the right rear when the camera is pointing away from you.

Does that sound like a damaged motor then?

EDIT: Now that I look closer, I replaced the front left props and these ones on the right rear have an ever so slight dent in the trailing edge.
I wouldnt have thought that could be so drastic though.....

 

[slup]

The AC camera is pointing away from you, then right rear ... check that prop change again, can the blades swivel easy & freely? Have more blades perhaps change again & try carefully taking off again (low & slow of course)

 

[adavis]

The AC camera is pointing away from you, then right rear ... check that prop change again, can the blades swivel easy & freely? Have more blades perhaps change again & try carefully taking off again (low & slow of course)

Yup OK, so replaced props and checked all that, all seems to be fine.
heres the new logs.
It seemed OK, but the first up and down had a weird action on the way back down, it kept stopping the descent but I didnt change the stick position.
No errors on screen though, havent checked the logs

 

[slup]

Revs looks healthy ... no oddities seen in the logs now, AC does what's commanded.



Your throttle movement during the first descent ... you released the throttle 2 times.

 

[Prismatic]

... I really am starting to think that it is a form of VRS triggered by bad props, or prop in this case.

I gather that a helicopter is most likely to experience a VRS in a too-fast vertical descent. It can escape the VRS by changing the collective (which reduces the potency of the VRS, at the price of altitude), or by using the cyclic to get some horizontal velocity (which moves the aircraft into vortex-free air).

UAVs don't have collective control of course, but it would seem that pretty much any significant horizontal movement should take the aircraft out of the VRS, at least as long as it maintains some horizontal speed. And likewise, a VRS should not manifest during ascent (I think ?).

So I have two layman's questions:

1. Is my (beyond just weak) understanding of VRSs in the first paragraph more-or-less correct?
2. Can a drone that's experiencing a VRS "fly out" of the problem with right-stick input? (Assuming the RC is in Mode 2.)

I may be out in the weeds, but I don't understand how these problems could be related to a VRS during ascent, or whenever the drone has some significant horizontal motion. Specifically, that right-rear motor was near max speed even during ascent, when a VRS should not manifest. (He said, as if he knew jack about the topic! )

EDIT: Now that the OP has replaced the props, all seems well. Motor speeds are normal, etc. There was definitely something hinky about the old props, perhaps "a form" of VRS as you have speculated.

 

[adavis]

Revs looks healthy ... no oddities seen in the logs now, AC does what's commanded.



Your throttle movement during the first descent ... you released the throttle 2 times.

OK that is very odd then, because I didnt think that I changed the stick position, I was going to say, I definitely didnt, but you know *maybe* I did, however I was descending and thought "hang on a minute, why did you stop? oh started again, hang on you stopped again, get on the ground fast"

I am very surprised about the props being the solution, there was almost nothing visibly wrong with them except an ever so slight ding in the drailing edge. I would never have even thought to replace them.
The ones that I replaced had a chunk out of them and I had been flying with that with no perceived issue.

 

[sar104]

I gather that a helicopter is most likely to experience a VRS in a too-fast vertical descent. It can escape the VRS by changing the collective (which reduces the potency of the VRS, at the price of altitude), or by using the cyclic to get some horizontal velocity (which moves the aircraft into vortex-free air).

UAVs don't have collective control of course, but it would seem that pretty much any significant horizontal movement should take the aircraft out of the VRS, at least as long as it maintains some horizontal speed. And likewise, a VRS should not manifest during ascent (I think ?).

So I have two layman's questions:

1. Is my (beyond just weak) understanding of VRSs in the first paragraph more-or-less correct?
2. Can a drone that's experiencing a VRS "fly out" of the problem with right-stick input? (Assuming the RC is in Mode 2.)

I may be out in the weeds, but I don't understand how these problems could be related to a VRS during ascent, or whenever the drone has some significant horizontal motion. Specifically, that right-rear motor was near max speed even during ascent, when a VRS should not manifest. (He said, as if he knew jack about the topic! )

EDIT: Now that the OP has replaced the props, all seems well. Motor speeds are normal, etc. There was definitely something hinky about the old props, perhaps "a form" of VRS as you have speculated.

The Phantom 2 suffered from wicked VRS and, as expected, you could fly laterally out of it. I don't think it is classic VRS, but a marginal under-performing prop might conceivably fall below the threshold for control when descending into even slightly disturbed air.

 

[EricJT]

The Phantom 2 suffered from wicked VRS and, as expected, you could fly laterally out of it. I don't think it is classic VRS, but a marginal under-performing prop might conceivably fall below the threshold for control when descending into even slightly disturbed air.

I have a Phantom 2 Vision and twice I got myself into a VRS situation.

The first time I naively decided to cut full throttle back from about 100 feet up to see how quickly it would descend. That was a DOH moment as it approached terminal velocity....my brain finally kicked back in and fortunately full throttle stopped its plummet about 10 feet from the ground.

The second time I was descending straight down at a modest rate and the AC began accelerating downwards even though I began giving it up throttle.....I got out of it by remembering to move laterally and break out of the vortex.

The old sphincter muscle got a workout but I must admit I learned valuable lessons from the situations.