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Turn props off in mid-air for fast descent (and on again :-)

mariachi76

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Hello,
a rather theoretical question:
The Mavic 2 props can be turned off by pulling both sticks down/inside. With the same function they can be turned on again.
Can that be used in mid-air for a fast descent?

When flying up to 500m, the descent takes very long because the descent rate is rather slow (~2-3 m/s). So what would happen if I just turn off the props at 500m above ground, and turn them on ~200m above ground? Would the Mavic 2 stabilize again, or crash?
Anyoney ever tried?

best regards
mariachi76
 

msinger

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Can that be used in mid-air for a fast descent?
It's possible to turn the motors back on, but there's no guarantee they will turn on and/or that the Mavic will be able to stabilize itself before it hits he ground.

You certainly shouldn't try this experiment with a Mavic you want to keep :)
 

sar104

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Here's a link to a recent discussion that included the DAT flight logs showing power-off descent, plus a close look at the resulting flight characteristics:
 
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FatherXmas

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I recall seeing a YouTube where someone did that and was successful. Personally, I wouldn't - too much risk that the drone didn't flip upside down or be in some other attitude for it to work.
 

msinger

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I recall seeing a YouTube where someone did that and was successful
Are you thinking of a Mavic Pro video? I haven't seen any Mavic 2 videos.
 
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FatherXmas

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Are you thinking of a Mavic Pro video? I haven't seen any Mavic 2 videos.
Yep, been awhile ago. I'd think a M2 would act similar to a MP in this scenario.
 

sar104

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I recall seeing a YouTube where someone did that and was successful. Personally, I wouldn't - too much risk that the drone didn't flip upside down or be in some other attitude for it to work.
There are 3 datasets for this maneuver referenced above, with one shown. Why are you still guessing what might happen?
 

jason38

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Dont try this!!! If motors are shot down in mid-air, the drone will just fall like a stone, and it will rotate on all axis due to air forces against the drone frame...
So if you turn motors on again, and the drone is not in flight position, it will just flip and flip again until it hits the ground...(already tried with a small toy-drone, and it crashed on each trial...)

Even if the drone fall flat (keeping its flight position), I think it will get lot of vertical speed very quickly, and the motors and props will not get enough power to stop the fall...

Bad idea!!

BTW it's true that descent speed is very low with mavics, but I guess it's normal, because when you pull throttle stick fully down, you can ear motors and esc working hard to keep the drone as flat as possible...
Motors speed is very low at this time, and it can't stabilize the drone as well as it does when you're climbing or in normal flight...
 

sar104

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Dont try this!!! If motors are shot down in mid-air, the drone will just fall like a stone, and it will rotate on all axis due to air forces against the drone frame...
So if you turn motors on again, and the drone is not in flight position, it will just flip and flip again until it hits the ground...(already tried with a small toy-drone, and it crashed on each trial...)

Even if the drone fall flat (keeping its flight position), I think it will get lot of vertical speed very quickly, and the motors and props will not get enough power to stop the fall...

Bad idea!!

BTW it's true that descent speed is very low with mavics, but I guess it's normal, because when you pull throttle stick fully down, you can ear motors and esc working hard to keep the drone as flat as possible...
Motors speed is very low at this time, and it can't stabilize the drone as well as it does when you're climbing or in normal flight...
Are you incapable of reading a simple graph?
 

FatherXmas

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Why are you still guessing what might happen?
Because I'm not a scientist or mathematician and those data sets mean nothing to me. I'm entitled to my opinion and really don't appreciate snarky remarks.
 
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sar104

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Because I'm not a scientist or mathematician and those data sets mean nothing to me. I'm entitled to my opinion and really don't appreciate snarky remarks.
Of course you are entitled to your opinion, even if the data trivially show that your opinion is wrong. However, it's not being snarky to point out that you are obviously wrong. And in any case, if you don't understand the data, why are you posting random guesses that are clearly contradicted by the interpretation of the data by those who do?
 

CanadaDrone

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You can do it, and you can find videos of people doing it successfully, but there is really never any reason to ever do this except to make a video. As sar104 demonstrated above, nothing happens quickly and you will lose a lot of altitude very quickly. There is a very good chance you'll crash the drone trying, and I imagine the stress on the aircraft is pretty extreme during that maneuver. No point to ever try this unless you have a sponsored drone looking for YouTube views, in my opinion.
 
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msinger

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I imagine the stress on the aircraft is pretty extreme during that maneuver
Excellent point! I'm also wondering what kind of negative affects this has on the drone's hardware.
 
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sar104

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Excellent point! I'm also wondering what kind of negative affects this has on the drone's hardware.
I don't think it's particularly stressful. The deceleration rate after motor restart in the example above was approximately 5 m/s², so 0.5 g. So the forces are only 50% higher than it experiences in a stationary hover.
 

jason38

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Are you incapable of reading a simple graph?
Didnt see that graph at first read, not enought network to load it...
Sorry about that, and sorry that it seems to make you angry... ;)

But personaly I wouldn't try this "trick" with a 1500$ drone anyway.... If a simple graph can convince you to try it, let's do it and see....
 

sar104

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Didnt see that graph at first read, not enought network to load it...
Sorry about that, and sorry that it seems to make you angry... ;)

But personaly I wouldn't try this "trick" with a 1500$ drone anyway.... If a simple graph can convince you to try it, let's do it and see....
OK - apologies for my impatience there but the thread was getting cluttered with bad information. Personally I don't think I would try this with any of mine either. I'd be worried about the restart and would feel very foolish if I crashed trying. But - it's clear that it does work and that the motors are easily able to arrest the resulting descent.
 
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FoxhallGH

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OK - apologies for my impatience there but the thread was getting cluttered with bad information. Personally I don't think I would try this with any of mine either. I'd be worried about the restart and would feel very foolish if I crashed trying. But - it's clear that it does work and that the motors are easily able to arrest the resulting descent.
In your opinion, is there any danger that the drone might flip over, or be at too great an angle (pitch or roll) to prevent restart?
 

sar104

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In your opinion, is there any danger that the drone might flip over, or be at too great an angle (pitch or roll) to prevent restart?
I'd be worried about that. The examples that I was looking at showed no issues, but I'm not sure if all the firmware versions behave similarly.
 

Camino Ken

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I don't think it's particularly stressful. The deceleration rate after motor restart in the example above was approximately 5 m/s², so 0.5 g. So the forces are only 50% higher than it experiences in a stationary hover.
The deceleration at the air mass to land mass interface would however result in fairly high stress values. ha ha
 

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