The Terminal Velocity of a Falling Mavic 2

Kazzaaz · Mar 3, 2019

...seems to be about 70mph.

DJI Flight Log Viewer - PhantomHelp.com

I have an interesting ~~flight~~ crash log to share.
I was definitely pushing the limits in Manual mode (asking for it, I know) but leveled out well before I switched modes back.
Either I lost a propeller or the gyro just decided to spaz out.
I found one of the propeller "clips" stuck inside the rotor. Maybe this broke off mid-flight and obstructed the motor?

The whole thing smelled funny when I picked it up - who knows what got knocked around inside from a 1000ft fall so I'll be sending the bird to DJI.
If everything had worked the way it should, I'd still be in the air - but considering the strain I was putting on the craft I know I have a slim chance for a warranty repair

My wallet is terrified but we'll see what happens

Prmath · Mar 3, 2019

Kazzaaz said:
...seems to be about 70mph.

DJI Flight Log Viewer - PhantomHelp.com

I have an interesting ~~flight~~ crash log to share.
I was definitely pushing the limits in Manual mode (asking for it, I know) but leveled out well before I switched modes back.
Either I lost a propeller or the gyro just decided to spaz out.
I found one of the propeller "clips" stuck inside the rotor. Maybe this broke off mid-flight and obstructed the motor?

The whole thing smelled funny when I picked it up - who knows what got knocked around inside from a 1000ft fall so I'll be sending the bird to DJI.
If everything had worked the way it should, I'd still be in the air - but considering the strain I was putting on the craft I know I have a slim chance for a warranty repair

My wallet is terrified but we'll see what happens

33 FPS ? ‍

Kazzaaz · Mar 3, 2019

Prmath said:
33 FPS ? ‍

wat

sar104 · Mar 3, 2019

Kazzaaz said:
...seems to be about 70mph.

DJI Flight Log Viewer - PhantomHelp.com

I have an interesting ~~flight~~ crash log to share.
I was definitely pushing the limits in Manual mode (asking for it, I know) but leveled out well before I switched modes back.
Either I lost a propeller or the gyro just decided to spaz out.
I found one of the propeller "clips" stuck inside the rotor. Maybe this broke off mid-flight and obstructed the motor?

The whole thing smelled funny when I picked it up - who knows what got knocked around inside from a 1000ft fall so I'll be sending the bird to DJI.
If everything had worked the way it should, I'd still be in the air - but considering the strain I was putting on the craft I know I have a slim chance for a warranty repair

My wallet is terrified but we'll see what happens

That's an interesting flight profile. The resulting descent rate is impressive, but does not represent the terminal velocity of a falling Mavic because it was upside down with power on for much of the descent. The cause of that is not clear.

The descent rate does peak at over 70 mph, which is around twice the usually observed terminal velocity. I'd need to see the mobile device DAT file to try to figure out exactly what failed.

ac0j · Mar 3, 2019

Jr. Astronaut! 400m plus altitude! *clapping*

Vader869 · Mar 4, 2019

Kazzaaz said:
...seems to be about 70mph.

DJI Flight Log Viewer - PhantomHelp.com

I have an interesting ~~flight~~ crash log to share.
I was definitely pushing the limits in Manual mode (asking for it, I know) but leveled out well before I switched modes back.
Either I lost a propeller or the gyro just decided to spaz out.
I found one of the propeller "clips" stuck inside the rotor. Maybe this broke off mid-flight and obstructed the motor?

The whole thing smelled funny when I picked it up - who knows what got knocked around inside from a 1000ft fall so I'll be sending the bird to DJI.
If everything had worked the way it should, I'd still be in the air - but considering the strain I was putting on the craft I know I have a slim chance for a warranty repair

My wallet is terrified but we'll see what happens

What do u mean when you say you were in "Manual mode"?

RCdancer · Mar 4, 2019

sar104 said:
The resulting descent rate is impressive, but does not represent the terminal velocity of a falling Mavic because it was upside down with power on for much of the descent.

It committed suicide.

sar104 · Mar 4, 2019

Kazzaaz said:
I was definitely pushing the limits in Manual mode (asking for it, I know) but leveled out well before I switched modes back.

You did switch back to Sport mode at 171.6 seconds, but then back to Manual at 179 seconds, with a couple of periods of ATTI thrown in. That's the reason for the inverted flight.

Vader869 said:
What do u mean when you say you were in "Manual mode"?

He means full manual mode (0) with all position and attitude stabilization off. The sticks are controlling the motors directly.

Kazzaaz · Mar 4, 2019

sar104 said:
The descent rate does peak at over 70 mph, which is around twice the usually observed terminal velocity. I'd need to see the mobile device DAT file to try to figure out exactly what failed.

I tried looking in the "FlightRecord" folder in the app files but it was empty. Is there any other place I should look for this file?

sar104 said:
You did switch back to Sport mode at 171.6 seconds, but then back to Manual at 179 seconds, with a couple of periods of ATTI thrown in. That's the reason for the inverted flight.

When I switched back to Sport mode I made sure the drone was level, which you can see in the logs from what I can tell.
The bird was stable for a brief second before things went wrong.
When this happened I switched modes back and forth a couple times to try to reset the gyro.
But after it was on its way down any switch into P/S-mode failed and was thrown into ATTI.

IF I was thinking on my feet I would have stayed in manual and slowly applied continuous pitch or roll until my vertical speed slowed (and then full power since I know we are level)
you know what they say about hindsight though

mikemoose55 · Mar 4, 2019

It is not the velocity that kills ya it is the sudden stop at the end that does you in

mikemoose55

Drbobk · Mar 4, 2019

Based on the chart above, it looks like the drone went from 200m in altitude (@time 182 sec) to zero altitude in about 8 seconds. That’s 25m/sec, or about 83ft/sec. 30mph is 44ft/sec, so it looks like just under 60mph (which would be 88ft/sec) on that steady fall. Easy to see why the FAA doesn’t want us to fly over people.

Drbobk · Mar 4, 2019

Of course, if I had looked at the second chart I could have read that directly off the chart without the math! Sorry.

sar104 · Mar 4, 2019

Kazzaaz said:
I tried looking in the "FlightRecord" folder in the app files but it was empty. Is there any other place I should look for this file?

When I switched back to Sport mode I made sure the drone was level, which you can see in the logs from what I can tell.
The bird was stable for a brief second before things went wrong.
When this happened I switched modes back and forth a couple times to try to reset the gyro.
But after it was on its way down any switch into P/S-mode failed and was thrown into ATTI.

IF I was thinking on my feet I would have stayed in manual and slowly applied continuous pitch or roll until my vertical speed slowed (and then full power since I know we are level)
you know what they say about hindsight though

It wasn't level when you switched back - it was pitched forwards at over 50° and starting a right roll. The ATTI mode excursions at the end do correspond to the RC switch position set to "Sport". There were no compass errors and the ATTI switch was due to unspecified "Other" non-GPS errors.

sar104 · Mar 4, 2019

Drbobk said:
Based on the chart above, it looks like the drone went from 200m in altitude (@time 182 sec) to zero altitude in about 8 seconds. That’s 25m/sec, or about 83ft/sec. 30mph is 44ft/sec, so it looks like just under 60mph (which would be 88ft/sec) on that steady fall. Easy to see why the FAA doesn’t want us to fly over people.

The continuous record of descent velocity is shown in post #4 above, second graph - you don't need to do back-of-the-envelope calculations to figure it out.

EDIT - disregard - you already spotted it.