How far could a failed drone drift when falling?

[R.Perry]

I wasn't implying they were 107 regulations, nor did he. The professor at UC Merced was responsible for all drone flights around the campus, his authority didn't apply to the construction side of the campus however to keep peace I followed his guidelines.
I also worked with campus police when I did need to fly over the active campus, they were pretty much clueless as to drone operations.

 

[adm_geomatics]

however to keep peace I followed his guidelines.
I also worked with campus police when I did need to fly over the active campus, they were pretty much clueless as to drone operations.

Sorry, I made the assumption that by him being a Professor teaching 107 that his teaching and decision making would be in accordance. It's just another example of human interpretation and personal feeling muddying the water. I hope that he is not influencing those that he is teaching with them. You are the 107 PIC and have final decision making according to the Federal Government. That said I have the question in to an Attorney and will report back with any documentation. My main point was that these people will work with you if you can intelligently explain Federal regulations to them, display that you have them in your planning and at the same time try to understand their regulations. I had to do this with TXDOT as they were trying to enforce that they have control of the airspace over their ROW. They do have authority on the ground, but operations can be commenced outside of their ROW and the flight can occur in the roadway as long as you are observing FAA regulations.

 

[R.Perry]

Funny you mentioned air space authority. I wanted to film one of the light houses on the California coast, was told drone flights were not permitted in that state park. Went outside the park entrance, launched and flew in and around the light house.
The park ranger was pretty upset but really couldn't do anything about it, like I told him, once he left the park boundaries his authority ended.
I believe more and more people are becoming aware of the basic legalities, I know many of the law enforcement people in are area are, and some now have their 107 license. So little by little some of the misconceptions will be corrected.
As for Professor Stark at UC Merced, I think he is a pretty knowledgeable person and most likely teaches accordingly. He is attached to the engineering department at the college.

As for regulations that he and I talked about, it mostly centered around part 39, because that was the biggest issue I had to deal with. If you watched the final video you would have seen the entire campus was empty other that campus police and the flight through the cafeteria.

 

[adm_geomatics]

That said I have the question in to an Attorney and will report back with any documentation.

Didn't get allot of clarification here. Basically if you are abiding by all regulations including airspace that it cannot be controlled by them. What they do have is control of access and presence on the grounds. Still very vague information and I would assume that if it is a State-funded college then there could be some other authority there as was the case at Texas State.

 

[aerialimagery]

I appreciate all the responses. Now that I have a good idea that a drone will fall like a rock, I was able to calculate the "drift." I've been able to determine that from 400 feet it will impact the ground in 5 seconds. If hovering in a 20 mph wind, in 5 seconds it will drift 147 feet.

 

[R.Perry]

I appreciate all the responses. Now that I have a good idea that a drone will fall like a rock, I was able to calculate the "drift." I've been able to determine that from 400 feet it will impact the ground in 5 seconds. If hovering in a 20 mph wind, in 5 seconds it will drift 147 feet.

Interesting how did you come up with those trajectory figures.

 

[aerialimagery]

Interesting how did you come up with those trajectory figures.

Although I had a physics class in high school, I confess I didn't plug the numbers into a formula for determining acceleration, etc. of a falling body. Instead I use this shortcut that I found:

Free Fall Calculator

Our free fall calculator can find the velocity of a falling object and the height it drops from.

www.omnicalculator.com

Using that calculator you can plug in any height and determine how long it will take a body to fall as well as the velocity at impact. Using 400 feet the calculator comes up with 5 seconds until impact (which was confirmed by using some google searches as well). For the distance I started with a 20 mph wind (thinking that would be about the maximum wind speed I'd be flying in) and did the math from there as to how far an object wold travel at 20 mph in 5 seconds, which is 147 feet, presuming I didn't make any math errors. In a 10 mph wind it would be about 74 feet.

 

[Meta4]

I've been able to determine that from 400 feet it will impact the ground in 5 seconds. If hovering in a 20 mph wind, in 5 seconds it will drift 147 feet.

Your freefall calculator isn't worth much unless you are interested in objects falling in a vacuum.
In the real world air resistance is a real factor.
DJI drones up to the size of a Phantom reach a terminal velocity of 12-14 metres/sec fairly quickly.
I haven't seen data for an Inspire or Matrice.
If your were looking at a hypothetical Phantom or Mavic falling from that height, it would take about 10 seconds.

 

[R.Perry]

Air resistance is also different at different altitudes, temperatures, and humidity, The orientation to ground as it fell would also be a factor. I don't think the op is looking for a scientific trajectory but an estimation. Time to terminal velocity would also be effected by orientation to the ground, reality is from 400 feet is is going to hit ground at TV. One of our pilots had an Inspire 1 go dead stick at 200 feet, bottom line, it destroyed the Inspire.

 

[Meta4]

Air resistance is also different at different altitudes, temperatures, and humidity

None of which make any difference you could measure between 400 ft and the ground

The orientation to ground as it fell would also be a factor.

No .. the drone wobbles and tumbles.
It doesn't maintain a fixed position.

I don't think the op is looking for a scientific trajectory but an estimation.

Which I gave to show that his number was out by a factor of 100%

Time to terminal velocity would also be effected by orientation to the ground

It achieves it in the first second regardless of orientation

 

[aerialimagery]

Your freefall calculator isn't worth much unless you are interested in objects falling in a vacuum.
In the real world air resistance is a real factor.
DJI drones up to the size of a Phantom reach a terminal velocity of 12-14 metres/sec fairly quickly.
I haven't seen data for an Inspire or Matrice.
If your were looking at a hypothetical Phantom or Mavic falling from that height, it would take about 10 seconds.

Could you link to your source for the 12-14 meters/sec terminal velocity please?

If this figure is based on surface area and resistance, wouldn't it depend upon its angle as it's falling? For example is it possible this figure presumes it is falling upright or in a normal position while instead it might be falling sideways and with less air resistance?

 

[Meta4]

Could you link to your source for the 12-14 meters/sec terminal velocity please?

Sorry .. that number should be 14-16 metres/sec.
I've analysed the flight data from hundreds of flight incidents, including some where the drone had power on as it fell from the sky.
That's where my data comes from.

 

[aerialimagery]

Thanks for the info. So it should take about 8 seconds instead of 5 and based on the 20 mph wind scenario would drift around 235 feet. Most likely I wouldn't be flying in 20 mph winds, probably more like 10 or less, so the drift would be under 120 feet. And that's considering maximum altitude. Just curious about when you analyzed flight data if in any of the cases the drone tended to sail in one direction instead of drop straight down or stay in a tight spin.

 

[Meta4]

Thanks for the info. So it should take about 8 seconds instead of 5 and based on the 20 mph wind scenario would drift around 235 feet. Most likely I wouldn't be flying in 20 mph winds, probably more like 10 or less, so the drift would be under 120 feet. And that's considering maximum altitude. Just curious about when you analyzed flight data if in any of the cases the drone tended to sail in one direction instead of drop straight down or stay in a tight spin.

The fall is always close to vertical with only a small drift if in high winds or the drone was flying fast when things came undone.

 

[R Martin]

Didn't get allot of clarification here. Basically if you are abiding by all regulations including airspace that it cannot be controlled by them. What they do have is control of access and presence on the grounds. Still very vague information and I would assume that if it is a State-funded college then there could be some other authority there as was the case at Texas State.

We, as a state funded institution, have a UAS policy that I was fortunately part of during creation. That said, its just policy just like the no smoking on university grounds policy. It is not really legally enforceable but it looks really good on paper. The good part is that campus law enforcement and policy makers were in complete agreement on the no recreational flights on campus section, and that is enforced 100%. Probably will not stand up in court if one of the students is smart enough to take it that far.

 

[adm_geomatics]

That's exactly how it should happen. Get the University involved right up front and be professionally prepared when meeting them. They will figure out quickly that these are not toys and that we are very safety conscious. One of our proposal documents is the Safety Operating Procedures manual for our entire company along with our insurance and references. My group is blessed to be under an organization that pushes the adoption of technology and allows us to do what we need to do in order to be a vital part of the Team.

 

[R Martin]

That's exactly how it should happen. Get the University involved right up front and be professionally prepared when meeting them. They will figure out quickly that these are not toys and that we are very safety conscious. One of our proposal documents is the Safety Operating Procedures manual for our entire company along with our insurance and references. My group is blessed to be under an organization that pushes the adoption of technology and allows us to do what we need to do in order to be a vital part of the Team.

I knew there was a reason I liked you...

 

[R.Perry]

None of which make any difference you could measure between 400 ft and the ground

No .. the drone wobbles and tumbles.
It doesn't maintain a fixed position.

Which I gave to show that his number was out by a factor of 100%

It achieves it in the first second regardless of orientation

Do you have an aeronautical engineering background? Reason I ask, is all the factors I mentioned can affect how an object will fall. It wouldn't be measurable at such a short distance, or even a factor. If you fly out of a high altitude airport on a hot summer day, your rate of climb will be decreased due to air density. That is a very simple example, but it proves the fact that air density is a factor on flight.

 

[Meta4]

Do you have an aeronautical engineering background?

No, but I understand the physics well enough.

Reason I ask, is all the factors I mentioned can affect how an object will fall. It wouldn't be measurable at such a short distance, or even a factor. If you fly out of a high altitude airport on a hot summer day, your rate of climb will be decreased due to air density. That is a very simple example, but it proves the fact that air density is a factor on flight.

I'm not sure what your point is.
You agree that it wouldn't make any measurable difference in a fall from 400 ft.
But then talk about how air density is a factor when flying planes from higher altitudes on a hot day.

 

[R.Perry]

My point was the op wasn't looking for a scientific explanation, but an approximation I assume to insure a safe perimeter. My explanation was an example of how just one factor can effect flight. With aircraft we have proven flight characteristics based on extensive testing and known performance. With non military drones we have no such data so we throw the old book out the window and guess. For me, if my estimation was 147 feet, I would add another 20 to 30 feet to insure I don't end up with a SNAFU.
The pilot that lost the Inspire 1 lost all power, so all four motors shut down simultaneously, there was no wind but he stated the Inspire landed about 35 feet from where it went dead stick. He was doing panos at the time so he was hovering and had GPS data up to the time the power was lost. I'm assuming he he came up with the distance from loss of power to impact area based on aircraft data, but I'm not sure and forgot to ask him.
Based on that experience estimating trajectory or lack of sounds pretty difficult to come up with a formula that could be applied to drones.