Phantom 3 fell from the sky and crushed the roof of a moving car

[sar104]

Welcome, Djalma!
The one thing no one has mentioned: This thing was moving much faster than just falling. First pic indicated a motor failure, second one says GPS lost. Now it's upside down with only a barometer (compass is screwed when spinning that fast). So guess what? It senses the altitude changes and sends full power to the remaining props, increasing the spin and the downward velocity.
I'd say she's lucky it didn't crumple enough to knock her out cold!

That is not really correct. The impact speed is pretty clear from the times and reported heights, and is corroborated by the reported vertical speeds. It hit at around 22 m/s. Had it free fallen from 100 m it would have reached a much higher speed - around 63 m/s ignoring drag.

 

[Techcop50]

There's also a 3-axis Gyro and 3-axis Accelerometer.

True...but nothing is going to keep it from falling with a motor out, but it was obviously trying it's best.

 

[Techcop50]

That is not really correct. The impact speed is pretty clear from the times and reported heights, and is corroborated by the reported vertical speeds. It hit at around 22 m/s. Had it free fallen from 100 m it would have reached a much higher speed - around 63 m/s ignoring drag.

What did I miss? Where did you get these speeds?

 

[sar104]

True...but nothing is going to keep it from falling with a motor out, but it was obviously trying it's best.

Yes - it is actually quite impressive how well it managed to slow its fall even with one motor (presumably) out.

 

[sar104]

What did I miss? Where did you get these speeds?

The screen shots in the included photos give two data points, at 92 m and 4 m, with approximate times (resolution 1 s) and vertical speeds.

 

[eaglegoaltender]

The hit side would have a pulling effect on the metal on the other side trying to stretch it...not push it down.

One would think so - however, if there were no centre support there would likely be just one dent/crater across the top of the roof

How does hitting one side and crushing it in crush the other side down also.

Think that is due to the support channel making it look like two separate impacts, in other words if no support channel in the middle (where it shows very little "crush") it would be just one complete indentation or crush or crater or whatever ya wanna call it.

EDIT: just remember we are all theorizing here........"open mind opinion only"..............LOL

I'm not saying the damage as shown is from a single Phantom impact - just that I would not be surprised at all if it was - which does seem so however with those 4 discreet/equally spaced indents!

 

[eaglegoaltender]

The fundamental and reasonable question, however, is why does the damage to the roof extend so far from what appears to be the obvious impact point?

I would hazard a guess there is a centre support channel in the middle of the roof that prevented that part of the roof to collapse - hence giving it the appearance of two separate impacts when it is very feasible there was just one large "crater" type damage.

 

[sar104]

I would hazard a guess there is a centre support channel in the middle of the roof that prevented that part of the roof to collapse - hence giving it the appearance of two separate impacts when it is very feasible there was just one large "crater" type damage.

If anything, I think it is more likely that there is no significant longitudinal member in that section of the roof, and that the impact caused a widespread depression, with partial rebound of the roof material in the middle due either to residual stresses or because there is more mass attached to the inside middle of the roof (interior lights, console etc.). That's the only feasible explanation I can come up with for the topography of the damage.

 

[Techcop50]

The screen shots in the included photos give two data points, at 92 m and 4 m, with approximate times (resolution 1 s) and vertical speeds.

My bad, I looked at the time between the screenshots, did not notice the altitudes. But I find it hard to believe the props turning (while obviously inverted) slowed it's descent. How can that be?
Maybe "active braking"?

 

[sar104]

My bad, I looked at the time between the screenshots, did not notice the altitudes. But I find it hard to believe the props turning (while obviously inverted) slowed it's descent. How can that be?

The flight control systems on these aircraft have very fast response to orientation changes. My guess would be that, even while spinning out of control, it is able to apply power when upright and cut power when inverted to attempt to control attitude and altitude. Just a guess, but the data are fairly unambiguous - it did fall that slowly, relative to free fall.

 

[Monte55]

If anything, I think it is more likely that there is no significant longitudinal member in that section of the roof, and that the impact caused a widespread depression, with partial rebound of the roof material in the middle due either to residual stresses or because there is more mass attached to the inside middle of the roof (interior lights, console etc.). That's the only feasible explanation I can come up with for the topography of the damage.

There has to be support members in the roof section. These cars have to pass rollover tests etc in their design. I have seen cars sitting on their roof without that kind of damage.

 

[eaglegoaltender]

If anything, I think it is more likely that there is no significant longitudinal member in that section of the roof, and that the impact caused a widespread depression, with partial rebound of the roof material in the middle

That makes sense to me for certain - distance from one side of the indentation to the other would possibly allow for it to pop out there.................OR

The car owner or someone else possibly tried to push out the depression and managed to pop it up in the middle part only.

I agree also it is more likely horizontal support across the roof versus a parallel channel down the middle - as is the usual for support in the event of a "roll over".

 

[Techcop50]

The flight control systems on these aircraft have very fast response to orientation changes. My guess would be that, even while spinning out of control, it is able to apply power when upright and cut power when inverted to attempt to control attitude and altitude. Just a guess, but the data are fairly unambiguous - it did fall that slowly, relative to free fall.

I guess it should not be surprising, they certainly could have code in there to deal with almost anything. Amazing.

 

[Techcop50]

Another thought: the spin of the aircraft itself might negate the effect of the spinning props, causing some weird wind resistance (drag) to the downward fall...?

 

[sar104]

There has to be support members in the roof section. These cars have to pass rollover tests etc in their design. I have seen cars sitting on their roof without that kind of damage.

Actually I don't think most sedans have longitudinal roof support at the front - it is usually laterally between the door pillars. Longitudinal supports would get in the way of sunroofs, etc.. In terms of damage to the roofs of inverted vehicles, don't forget that the force is typically not very localized, so a larger area of roof supports it.

In terms of the actual force, if we generously assume that a 1.5 kg Phantom is brought to rest from 22 m/s over a distance of around 5 cm (guessing dent depth), then the transient force applied to that small area of roof over the deceleration time of around 4.5 ms will be over 1000 lbs.

 

[sar104]

Another thought: the spin of the aircraft itself might negate the effect of the spinning props, causing some weird wind resistance (drag) to the downward fall...?

That is possible. A helicopter in autorotation also falls much more slowly than free fall.

 

[DCDrone]

I don't care if it's authentic or not. Things similar to this (or worse) are going to happen if people continue to fly over roads or people. I think the folks hung up on the issue of authenticity want to deny that there's a problem with that activity. It's one of the things that has put our hobby in jeopardy, and it will continue to cause problems. As of this moment, no American has ever been seriously injured by a drone. That fortunate statistic isn't going to last forever, but I hope it isn't some innocent person under a reckless operator.

 

[Techcop50]

In terms of the actual force, if we generously assume that a 1.5 kg Phantom is brought to rest from 22 m/s over a distance of around 5 cm (guessing dent depth), then the transient force applied to that small area of roof over the deceleration time of around 4.5 ms will be over 1000 lbs.

i can see right now i need to move back to the kid's table in time for dinner...

 

[eaglegoaltender]

think the folks hung up on the issue of authenticity want to deny that there's a problem with that activity

Agreed......denying ---- is often a coping mechanism that kicks in for some that require time to adjust to realities and/or distressing situations!

I also agree - authentic or not - it is most certainly a vivid reminder of what can happen and something we need to remind ourselves of as to safe piloting!

 

[GoodnNuff]

The philosophy of "I have not experienced this, therefore it must be false" is some pretty faulty logic and lacks common sense.
Members here at one point argued that a spinning Phantom prop could not possibly cause any harm, let alone a laceration. Then photos started cropping up showing exactly what a spinning prop can do to flesh.

Members here used to get in heated arguments about whether a falling Phantom could hurt anyone. Steve Mann used to argue that it would cause the same damage that a nerf ball would cause on impact.
Then we started getting reports of people who were hit with Phantoms and of course the damage was nothing like a nerf ball...

A few weeks ago a couple of forum members reported that they were contacted by the FAA via social media - they were branded liars by quite a few here, until they got the follow up letters from the FAA showing that indeed, they had been approached on social media sites.

So yeah, seems to be a significant number of members here who deny the possibility of any truth outside of their own realm of experience. They further blind themselves by patting their own backs, proud of the "common sense" they are convinced they have employed to arrive at their conclusions.