Cut motors to drop altitude fast

[RallySoob]

Say your mavic is way high in altitude & for whatever reason you only have a percent or two of battery power to get it landed or else its due to lose power before auto land would be able to get it to the ground.

Would u consider cutting the motors to allow it to free fall and try to restart/recover the craft at low altitude in attempt to save the craft?

Anyone ever tried this?

Could the mav do that?

Just curious... i got stuck in menu & started to panic the otherday..this scenario possibility came to mind

 

[Mavic_Ward]

Lemme know how that works out!

 

[Anthony Viscomi]

Lemme know how that works out!

And take a video...

 

[John Shaw]

Clearly the best answer is to not get in that saturation. A responsible pilot would not get operate that way and the crash would clearly be pilot error. My guess is that you would have a very hard time judging when to start the motors back up. The vertical speed in free fall is huge and with the motors stopped the Mavic has no way to keep itself upright. If you find yourself in that situation, give it a try but I doubt it will work. A few years ago we had a Phantom pilot that ran out of power at what we estimated was about 4000 feet. Despite our help from watching the video that was downloaded and his extensive search with the help of the local farmers keeping an eye out - he never found it.

 

[RallySoob]

Im assuming u already got urself in the situation... tis the question

The latter is implied

 

[Kilrah]

I would expect the motors not to restart with the thing tumbling down since you already can't always start them if it rocks a bit on a boat.

 

[F6Rider]

Do you REALLY need to ask this question??? Really?

 

[RallySoob]

Do you REALLY need to ask this question??? Really?

Ya i did. Did u need to post ^ ? Really? Did u rwally

I had just seen a vid where one drained out its battery power at altitude and then hit the ground shattering. So this idea of a fast fall recover came to mind and I've seen race quads do similar things so naturally i want to know if its been done before jic i need to decide one day rather or not i have battery to make it back down. Or if its even possible to restart in air/freefall. Maybe sum1 accidentally csc up high & had to restart to save it ya never kno

E4taD|k litchi scurs me

 

[F6Rider]

Ya i did. Did u need to post ^ ? Really? Did u rwally

I had just seen a vid where one drained out its battery power at altitude and then hit the ground shattering. So this idea of a fast fall recover came to mind and I've seen race quads do similar things so naturally i want to know if its been done before jic i need to decide one day rather or not i have battery to make it back down. Or if its even possible to restart in air/freefall. Maybe sum1 accidentally csc up high & had to restart to save it ya never kno

E4taD|k litchi scurs me

There has been a couple of people over on the Phantom board who did an accidental CSC in midair, every one ended in a freefall to the ground. As the Mavic will not even start the motors if the IMU detects it is tilted to far common sense dictates that it will not restart while tumbling to the ground. This is not a 3D racing drone.

 

[Tony Perry]

You could test this by suspending it by two opposing arms between two stationary objects (c stands, saw horses, whatever). Give it a spin and see if you are able to start the motors while its spinning.

 

[PropPilot]

The mavic is not aerodynamic. It will tumble and when you power on again the props will drive it in the direction it was last tumbling to. There would be no mechanism to bring it upright before spooling up.

 

[Lees23]

It won't auto-rotate like a helicopter will?

 

[John Shaw]

Helicopters can auto rotate due to the inertia that can be stored in the spinning blades. As they start auto rotation the pilot lowers the pitch of the blades and the airflow caused by the descent keeps the blades spinning. As the helicopter nears the ground the pilot will increase the pitch on the blades to decrease the vertical speed for landing. It's got to be timed right, if the pilot increases pitch to early and runs out of the momentum stored in the spinning blades the helicopter will drop out of the sky. So our quads have a couple of problems. The blades are light and can store very little momentum. The pitch of the blades can not be changed, so it won't lower pitch during the descent and then increase it to cushion the landing. In addition I am not sure what the hinged blades of the Mavic would do without the centrifical force of powered flight. I suspect the terminal velocity of an unpowered Mavic is high enough to be fatal.

 

[Shoruk3n]

This guy has a valid question. Too many people are too quick to take up their pitchforks. Put down your righteousness for a moment ffs.

Situations requiring an emergency landing or descent occur sometimes. Why do you think autorotations exist? Or do you live in a world devoid of equipment failure?

To answer your question, I wouldn't recommend it. The Mavic has an initialization procedure that probably won't work while airborne. It's not set up like many of the toy-grade quads out there where you can cut the throttle and recover from a 30 foot drop in the space of 2 feet.

 

[waykewl]

If the battery level is too low, as soon as you shut off the motors you will get "cannot take off" message and the aircraft won't let you restart. So I this won't work.

 

[maikm]

So our quads have a couple of problems.

Well, they do not need to store inertia, because the motors can provide the necessary energy instead.

The mavic is not aerodynamic. It will tumble and when you power on again the props will drive it in the direction it was last tumbling to. There would be no mechanism to bring it upright before spooling up.

Oh I think it will, because it can sense the tumbling through the gyros and apply force through the motors in any direction. Racing quads do it all the time when they flip 360 degrees mid air. I even think this would be covered by the general algorithm about how the drone stabilizes itself, and wouldn't need any special consideration in the Mavic's software.

You could test this by suspending it by two opposing arms between two stationary objects

I'm afraid that isn't a suitable test, because the Mavic's accelerometers will sense the 1g acceleration towards the ground, and thus determine that it's not falling. Behaviour could be different in real free fall.

Anyway, as @waykewl pointed out, the scenario posted by the OP will probably not work because I believe the Mavic doesn't let you start up the motors if the battery is nearly empty. But if you try it with 80% battery, just as a stunt, it could theoretically work. I say let @Winiwinston try it out for us

 

[Jordan]

Test.
1. Battery level above 12%
2. get a tester to hold the mavic in the air
3. start the mavic
4. get the tester to spin in circles with the mavic and cut the motors
5. try and start it again while the mavic is upside down.

 

[PropPilot]

Yes the motors will restart

The Mavic will not inherently upright itself from the tumble it will be in.

If at the instant of motor restart the props are facing down, it will drill itself into the ground.

RC helicopters can do it because you can control the blade pitch both cyclically and collectively.

If you do do it, please video and post !!

 

[maikm]

Yes the motors will restart

The Mavic will not inherently upright itself from the tumble it will be in.

If at the instant of motor restart the props are facing down, it will drill itself into the ground.

How do you know this?

 

[4wd]

If the situation has arisen where your options are not being able to get down [somehow] before battery will deplete or try stopping and restarting it makes sense to try it.
People have done this with the Phantom 2 but it didn't work everytime and you typically didn't get chance to try to restart repeatedly..
With the Phantom 3 for some reason it didn't seem to work.
Eventually someone might try it with a Mavic maybe one with a busted gimbal.