Sudden MM descent into pond...

[FleetPhil]

Swapping them out for what? New stock DJI ones, or something different?

 

[RodPad]

Swapping them out for what? New stock DJI ones, or something different?

I'm guessing front to rear, like when you rotate your tires?

Do this at each battery change.

Rod

 

[cybervet]

It's been demonstrated fairly conclusively that it's the props - the back ones, in particular, end up requiring far too high motor speeds to produce the necessary lift, and swapping them out significantly reduces the motor speeds.

Yes I think that is a fact , but we don't know yet for how long they will last and what is the reason that they deformed in the first place.

 

[lenabanana]

This whole thread is making me nervous. Are there any aftermarket props that might be more reliable?

 

[sar104]

Swapping them out for what? New stock DJI ones, or something different?

Front swapped with rear.

 

[Saigondroner]

This whole thread is making me nervous. Are there any aftermarket props that might be more reliable?

I’m eagerly awaiting 4 pairs of carbon fiber props.

This Corona hysteria has really affect shipping services. I literally can’t have a pizza delivered at the moment. I have to meet any deliveries outside my bldg.

Will post flight logs ASAP.

 

[Mavic_Mini_Pilot]

They are likely deformed for the entire flight. In the logs that have been posted of this behavior, one or more of the motors is typically close to maximum, but the props are more effective when they are not descending into disturbed air - i.e. when they are climbing or moving laterally. When they do start to descend they seem to lose lift.

ok this finally makes sense to me.. So a good thing to do is, before every flight - force add a tiny little bit of pitch to the props ourselves. Bend a little pitch into them and make sure they have enough bite!

Although if you think about it the power the Mini has when it is going up - the fluffy, disturbed air that the Mini is descending through should really be nothing for the Mini - so I thought it makes sense but it still doesn't really..

 

[Mavic_Mini_Pilot]

I like that point. I remember years ago when flying a big Mikrokopter Okto XL that with it's eight 12 inch props that moved a lot of air, that the descent was much more stable if I gave it some forward movement into cleaner air. I can imagine the mini being so much lighter, loosing some lift capabilities while descending thru it's own turbulence.

Yes, true - BUT think about it....

The power it has and the way it is able to ascend and go up so fast.... I know when ascending it is going up into clean, stable air and it is somewhat normal for it to climb up this way - but the disturbed air, I mean how disturbed is it, it has to be half-gone altogether for the Mini not to have enough power and "prop pitch/bite" to go back up, or at least to slow down the descent, and as we see there was no such thing. It was a constant speed(kinda) descending amd he immediately gave up command - if what you are saying is true then this up command was supposed to at least slow the descent down initially, meanwhile the real results were that the mini has no response at all to the up command!

This is the real issue for me, OK lets say that the Mini's propellers do deform and they, over time, lose some of their pitch/bite. Eventually they lose enough so that the Mini cannot control descents because of its own prop-wash/air-disturbance turbulence. When this descent begins it was commanded to do so, so it starts falling now through its own prop-wash and is unable to even respond to full up!? The air is so disturbed and turbulent that full up has no effect at all on the craft, not even slowing the descent by a little bit..

I don't know hey, I'm most probably wrong about all this, but for me this is a Firmware Bug of some sort.

You can't tell me that the same Mini that just did this uncontrolled descent can be restarted and flown again in the exact same place and now after the restart it is able to go up and down full speed with no problems at all. The thing is that right after the descent, the same Mini will not do this anymore. So one moment it can't control its descent through its own prop-wash, and after a restart it all of the sudden can descend in its own prop wash!

It should be reproducible if the real cause is found out.

cool cool

 

[new2mavic]

Another kind of Mini descending when it should not :

 

[Mavic_Mini_Pilot]

Another kind of Mini descending when it should not :

see now his is a bit more reproducible....

 

[Mavic_Mini_Pilot]

Another kind of Mini descending when it should not :

Bro, is that all the time!? Is that how your Mini flies everyday. every flight? If my Mini was doing that I'd most definitely return it, especially after getting on video what you did. Have you been looking after your Mini? Do you think that you may have deformed some of its props somehow?

can you actually have a normal flight?

 

[new2mavic]

Bro, is that all the time!? Is that how your Mini flies everyday. every flight? If my Mini was doing that I'd most definitely return it, especially after getting on video what you did. Have you been looking after your Mini? Do you think that you may have deformed some of its props somehow?

can you actually have a normal flight?

Umm..... that's not my video. I just found it by chance. I will test if my Mini has the same problem, hopefully tomorrow.

 

[Mavic_Mini_Pilot]

Umm..... that's not my video. I just found it by chance. I will test if my Mini has the same problem, hopefully tomorrow.

Oh, sorry - got confused and thought this be your Mini.

I have already tried to see if mine does this and it does not. I've tried all sorts of going up and down, in S, P even C moving mode and mu Mini just seems to behave 100% as expected. If there is anyone out there who has this problem and can reproduce it please help us out by writing here in this forum/thread.

I'm just starting to gain the confidence to fly mi mini far and high out, and I really really don't want an uncontrolled descent, I fly over other buildings, roads, trees, places where if it had to go down I'll never be able to get my drone back. So for me it is vital that we sort this out, at least as much as we can. Like I said I haven't had, nor have I observed my Mini doing anything similar to this uncontrolled descents. I've also seen another video where this guys flies his Mini out his car and its really cold and the drone does the same thing, but not only down, also up!

Hopefully we'll realize exactly why this is happening and just get it off our TODO list.

 

[slup]

... When this descent begins it was commanded to do so, so it starts falling now through its own prop-wash and is unable to even respond to full up!? The air is so disturbed and turbulent that full up has no effect at all on the craft, not even slowing the descent by a little bit...

Well ... if this is a VRS phenomenon giving throttle will make the bad lift even worse, the only way to escape is to give elevator/aileron inputs.

If looking at all those events we have seen lately many have had forward speed meaning going away from the disturbed air ... even the attached YT clip here shows forward speed.
I'm not fully convinced that this has anything to do with VRS, but I'm not ruling it out in this stage.

In all cases I've looked into nearly all have had forward speed ... which have been slowed down by the Mini's sudden inability to maintain pitch angle for forward thrust. When this happens one or both rear motors have been maxed out ... & in some cases the front motors have started to go slower with rear still maxed when the descent starts.

 

[RogerDH]

Well ... if this is a VRS phenomenon giving throttle will make the bad lift even worse, the only way to escape is to give elevator/aileron inputs.

If looking at all those events we have seen lately many have had forward speed meaning going away from the disturbed air ... even the attached YT clip here shows forward speed.
I'm not fully convinced that this has anything to do with VRS, but I'm not ruling it out in this stage.

In all cases I've looked into nearly all have had forward speed ... which have been slowed down by the Mini's sudden inability to maintain pitch angle for forward thrust. When this happens one or both rear motors have been maxed out ... & in some cases the front motors have started to go slower with rear still maxed when the descent starts.

Just an aside about recovering from VRS, I have several toy drones that easily get in that state, and I've found that the best way to recover is to first, counter-intuitively, CUT the throttle for a split second (to stop powering the vortex ring and fall away from it), then give full throttle and full forward pitch.

 

[BigAl07]

This video is about MANNED helicopters but the physics etc are the same. I've selected to start the video where is shows an excellent VISUALIZATION of VRS :

It's key to note that VRS is very easy to avoid and get out of and with very minimal horizontal movement. I would venture to say that if the aircraft has any horizontal movement it's not in VRS.

 

[grahamjohnson10]

They are recorded but then appear to be deleted by the DJI Fly app when it syncs the records. I'll look at the txt log later, but in the meantime you can check out a number of other similar reports:

Search results for query: mini uncommanded descent

mavicpilots.com

I'm totally pissed off with the way "autosync" uploads the flight logs and then deletes the DAT file.

I contacted DJI and requested my uploaded DAT files but was told they could not provide them.
I'm sure that this is illegal, as all I'm asking is access to my own data.

 

[BigAl07]

I'm totally pissed off with the way "autosync" uploads the flight logs and then deletes the DAT file.

I contacted DJI and requested my uploaded DAT files but was told they could not provide them.
I'm sure that this is illegal, as all I'm asking is access to my own data.

If you read the terms of service that came with the aircraft you'll soon realize they can do whatever they want and we all agreed to it.

 

[sar104]

This video is about MANNED helicopters but the physics etc are the same. I've selected to start the video where is shows an excellent VISUALIZATION of VRS :

It's key to note that VRS is very easy to avoid and get out of and with very minimal horizontal movement. I would venture to say that if the aircraft has any horizontal movement it's not in VRS.

It will depend on the ratio of lateral to vertical speed. And this is not going to be full-blown VRS, but it could be that even marginal loss of lift from a severely under-performing prop is enough for the aircraft to lose stability.

 

[Mavic_Mini_Pilot]

It will depend on the ratio of lateral to vertical speed. And this is not going to be full-blown VRS, but it could be that even marginal loss of lift from a severely under-performing prop is enough for the aircraft to lose stability.

I've decided to add pitch to my props, just to see if what you're saying is really like that. Yesterday, last night I was watching Dad of Random Channel on YouTube, he flew out his mini to the top of some mountain and then he visually turned around without looking at his map and came home completely the wrong way like over 70 degrees off. Anyway, his Mini did the same thing, just uncontrolled descent, although his battery was already low.

I was thinking can this be a combination of an abused battery during the flight, and also abused drone!? I've seen these videos and also read of people complaining that they power up their drone, take off, switch it into S mode immediately and just push the stick forward all the way! They fly at the maximum speed the lil fella can get to, and they do this for extended periods of time. I think that they have charged their battery like 3 or 4 days ago to 100% and then not flown it, and then because of the time passed with the battery being fully charged and not used - it starts to discharge and lose its ability to deliver good current also! So they basically abuse the battery and drone, at start of flight battery is 91% or something, then the full speed forward in Sports mode, kinda drains the battery in its currently weak state even more. After that the Drone now just needs a tiny little bit of VRS or just "fluffy" air and the uncontrolled descent begins! Even a down command should be able to initiate this type of descent if I'm correct.

I also think I may be right because when the drone is restarted it seems to fix this issue for a while. so this may be because the battery had a small good rest - to regain some of its current sending abilities, until the next time all this repeats.

So I say its a combination of the battery not being able to deliver enough current when abused and the abuse of the actual Mavic Mini - expecting and forcing the little drone to fly like its bigger siblings is not correct. This is not a Mavic Pro or something, it should be used with caution and not abused.



as always - all the above is just me thinking, so don't take anything for facts..

cool cool