UAS Kinetic Energy Impact Ballistics Table

[KI5RLL]

Yes I have the full .xls, Pages and PDF chart if you want it. This is a .jpg of it for upload here.
Removed names and such as we are not allowed to advertise on this forum.

Unmanned Aircraft Systems Ground Collision Severity Evaluation
• What are the severity criteria for Unmanned Aircraft System (UAS) collisions, such as weight, kinetic energy, etc.?
• What is the severity of a UAS collision with person or property on the ground?
• How can the design of a UAS minimize potential damage during a ground collision?
• Can we categorize the severity of a UAS collision with a person or property on the ground based on the UAS and what would those categories look like?

What is the impact energy of your craft at the speed you usually fly? Over 11 ftlb? Over 25 ftlb? What UAS Category would that put you into?

Will you be flying Cat. I, Cat. II, Cat III, or Cat. IV?
How near to people will you be allowed to fly?
Is everyone learning all this and getting ready for its implementation?
It is coming.

 

[thispilothere]

It's more about freefall speed from 400 feet, right? What's the freefall speed of an MA2? Or my unopened M3M?

 

[Meta4]

It's more about freefall speed from 400 feet, right? What's the freefall speed of an MA2? Or my unopened M3M?

About 35-38 mph

 

[KI5RLL]

Flying head-on into someone at 35-38 mph, or falling from above at 35-38 mph, is still the collision.

 

[SethB]

Will you be flying Cat. I, Cat. II, Cat III, or Cat. IV?
How near to people will you be allowed to fly?
Is everyone learning all this and getting ready for its implementation?
It is coming.

I don’t think everyone is learning all this and getting ready for implementation. A few people have assembled Cat I drones and posted about it on this forum, but there doesn’t seem to be much interest.

In a previous thread I asked specifically if readers felt this was important to them - not many responded, and of those that did respond there were not many use cases mentioned.

Operations Over People - What would you do (if you could)?

There are a few obstacles before we get to legal operations over people. Category 1 drones (under .55 lbs, don’t lacerate skin) are difficult to come by in a useful form, and Category 2 and 3 drones won’t be with us until manufacturers apply to FAA and Remote ID is up. (See Pilot Institute’s...

mavicpilots.com

It's more about freefall speed from 400 feet, right? What's the freefall speed of an MA2? Or my unopened M3M?

About 35-38 mph

Shouldn’t free-fall speed be part of the table to fully evaluate kinetic impact. I too had thought of drones falling out of the sky as the primary liability. Maybe that’s wrong, I don’t know.

The table invites one to consider the maximum speed of the drone plus wind allowance as the primary liability.

 

[KI5RLL]

Thank you for input and discussion.
Hard to measure gravity fall speed (especially from a failure) compared to known velocity forward shown on the controller. Several data points go into that.
I tend to think forward collisions will far outnumber fall failures. They certainly do at least right now. Yes there are formulas to calculate that. Even to terminal velocity. But they take longer to solve than the time it takes to fall.
We would have to do that post-collision (with ground or person). With altitude the fall started and more.
A separate chart is possible yes of course. Will need altitude start, craft mass, and several other data points. I could write it also yes. But I need to keep the math sub-calculus so any user could run the numbers on their own calculator etc. I can write an input formula program that gives the answer, but it needs to run on any pilot’s phone or tablet etc. *Numbers are no good without proofs.* So any user must be able to prove it by reasonable means.
And a person hit in the head at 35mph from above, versus 35mph from the side, probably doesn’t care to discuss the direction of impact damage.

Yes there can be more data on the chart. I would probably just need to write another one. I already should separate out Metric and Imperial. But eventually it could be a book of charts.
I wanted a readable quick reference that was the most valuable volume of data.
We have to start somewhere!

Safe flying,
KI5RLL

 

[SethB]

.…..
And a person hit in the head at 35mph from above, versus 35mph from the side, probably doesn’t care to discuss the direction of impact damage.

Yes there can be more data on the chart. I would probably just need to write another one. I already should separate out Metric and Imperial. But eventually it could be a book of charts.
I wanted a readable quick reference that was the most valuable volume of data.
We have to start somewhere!

Safe flying,
KI5RLL

The formula for terminal velocity seems straightforward for an object falling from 400’, but the drag coefficient of various drones may not be readily available.

I suppose calculating it for one drone (if data was available) would help establish whether the potential kinetic energy was higher in powered flight or as dead weight accelerated by gravity from flying altitude.

One thing I noticed and really appreciate about your work is the leveling you’ve done on the various measurement systems. I’m sure I’m not the only person irritated by the need to constantly convert between systems. Thanks for that!

 

[KI5RLL]

As my Professor said,

“Do NOT give me useless math! If your recipient can’t access it or proof it themselves, it is useless!” With his hand slapped on the table.

We couldn’t argue with him on that. Or anything. At all. Nothing.

Safe flying,
KI5RLL

 

[SethB]

As my Professor said,

“Do NOT give me useless math! If your recipient can’t access it or proof it themselves, it is useless!” With his hand slapped on the table.

We couldn’t argue with him on that. Or anything. At all. Nothing.

Safe flying,
KI5RLL

Was that to me? There’s a formula for terminal velocity (speed of free-fall is what we called it earlier in the thread) that seems to me to be very useful in assessing various drones’ risk for flying over people per the FAA’s kinetic energy standards.

What’s missing is not math - it’s there - but the inaccessibility of data about drag coefficients. Perhaps someone has seen such data for a drone on the list @KI5RLL has been developing.

Maybe common terminal velocities of drones are higher than the velocities included in the list. Maybe they’re lower. I don’t know. But drawing definite conclusions without knowing the answer to that question is also something a math professor may challenge. I believe that’s confirmation bias? Making conclusions from information that supports one’s views, or ignoring information that may refute them?

Honestly, I don’t know the answer. But I have some other questions: What is the terminal velocity of my favorite videography/ cinematography drone at 100’ AGL. At 200? Can I make a case to the FAA about kinetic energy in free fall from 100’ that might (by agreement) permit me to use a heavier drone? So much cinematography is done at altitudes of 12’ to 50’ by professional pilots who are safety-concious, would that make a difference in how much kinetic energy might transfer at impact with a human?

But that’s a special case of interest to me. I disagree with @KI5RLL’s argument that any interested party should be expected to calculate these kinetic energy levels at impact. Cat 2 and 3 drones will be validated by manufacturers and certified by the FAA. Why should a pilot flying a conforming drone over people be expected to do the math?

 

[KI5RLL]

Was that to me? There’s a formula for terminal velocity (speed of free-fall is what we called it earlier in the thread) that seems to me to be very useful in assessing various drones’ risk for flying over people per the FAA’s kinetic energy standards.

What’s missing is not math - it’s there - but the inaccessibility of data about drag coefficients. Perhaps someone has seen such data for a drone on the list @KI5RLL has been developing.

Maybe common terminal velocities of drones are higher than the velocities included in the list. Maybe they’re lower. I don’t know. But drawing definite conclusions without knowing the answer to that question is also something a math professor may challenge. I believe that’s confirmation bias? Making conclusions from information that supports one’s views, or ignoring information that may refute them?

Honestly, I don’t know the answer. But I have some other questions: What is the terminal velocity of my favorite videography/ cinematography drone at 100’ AGL. At 200? Can I make a case to the FAA about kinetic energy in free fall from 100’ that might (by agreement) permit me to use a heavier drone? So much cinematography is done at altitudes of 12’ to 50’ by professional pilots who are safety-concious, would that make a difference in how much kinetic energy might transfer at impact with a human?

But that’s a special case of interest to me. I disagree with @KI5RLL’s argument that any interested party should be expected to calculate these kinetic energy levels at impact. Cat 2 and 3 drones will be validated by manufacturers and certified by the FAA. Why should a pilot flying a conforming drone over people be expected to do the math?

@SethB it was not to you. It was as our Professor told us in class. Last century!
Yes we all need more data. If I make a chart, it has to be accurate. Without knowing the craft flying (its drag coefficient) then the numbers I use on the chart will be wrong, likewise its data calculated wrong. And that helps no one. It does the opposite.
So I must depend on the pilot of each exact craft to have that data. My FSDO said CBO’s and Industry should be doing this. But we wait. And wait.
Other pilot’s crafts. I can’t expect them to make those calculations without the data needed. Which I don’t have. The physics requires data input. And other factors like air density, side wind, and more do matter. Can even add humidity but we don’t need to go that far I hope for the FAA. If I had that data, I could input it.
Am waiting for someone else to submit their charts also. Anyone? Anyone? Waiting over a year now. Like the FAA since they plan to hold us to the data.
In the meantime pilots can figure it out. Before another deadline has passed (like Remote ID did).
All good points @SethB yes thank you for input and discussion. This is how these things get standardized.

 

[SethB]

Thanks. At some point we will know the answers, or at least we’ll know what drones are certified for Operations Over People.

@KI5RLL poses some great questions!

 

[RandomTask]

As I posted in another necro thread...your chart is great except for one major detail.

The FAA documentation doesn't specify max kinetic energy of the drone, it specifies that impact must not cause injury "equal to or greater" than that caused by the *transfer* of 11 foot pounds from a *rigid body*.

A drone is not a rigid body (it will break and probably bounce off in some weird direction)

A drone will not transfer all of its energy to a person it hits. Some energy will be lost to breakage, others to the fact that the drone will bounce off, taking some energy along with it.

A 4000 pound car moving at 1mph has 134 foot pounds. Is that going to injure you? Probably not, although you could come up with circumstances where it would. In most cases it's going to startle you and make you move, but not hurt. You can react after the fact and push the car to a stop. As with the above, the energy isn't *transferred*. The car doesn't hit you, transferring all its energy and stopping.

 

[BigAl07]

As I posted in another necro thread...your chart is great except for one major detail.

The FAA documentation doesn't specify max kinetic energy of the drone, it specifies that impact must not cause injury "equal to or greater" than that caused by the *transfer* of 11 foot pounds from a *rigid body*.

A drone is not a rigid body (it will break and probably bounce off in some weird direction)

A drone will not transfer all of its energy to a person it hits. Some energy will be lost to breakage, others to the fact that the drone will bounce off, taking some energy along with it.

A 4000 pound car moving at 1mph has 134 foot pounds. Is that going to injure you? Probably not, although you could come up with circumstances where it would. In most cases it's going to startle you and make you move, but not hurt. You can react after the fact and push the car to a stop. As with the above, the energy isn't *transferred*. The car doesn't hit you, transferring all its energy and stopping.

I'm not sure I can completely agree with your details. It depends on what the orientation is when the UAS hits you as to whether it "deflects/breaks" or transfers the majority of the energy into your noggin (southern term for head LOL). If the aircraft were to happen to land fairly flat it's likely that most of the energy could/would be transferred into your noggin. If a arm or something makes first impact that area is fairly frangible and the energy would likely be dissipated/transferred elsewhere.

With Aviation we assume worse case in an attempt to reduce risk as much as possible. If the UAS COULD transfer the energy into the head then it should remain on the chart at the worst case at least that's my point of view

 

[Felix le Chat]

Yes I have the full .xls, Pages and PDF chart if you want it. This is a .jpg of it for upload here.
Removed names and such as we are not allowed to advertise on this forum.

Unmanned Aircraft Systems Ground Collision Severity Evaluation
• What are the severity criteria for Unmanned Aircraft System (UAS) collisions, such as weight, kinetic energy, etc.?
• What is the severity of a UAS collision with person or property on the ground?
• How can the design of a UAS minimize potential damage during a ground collision?
• Can we categorize the severity of a UAS collision with a person or property on the ground based on the UAS and what would those categories look like?

What is the impact energy of your craft at the speed you usually fly? Over 11 ftlb? Over 25 ftlb? What UAS Category would that put you into?

Will you be flying Cat. I, Cat. II, Cat III, or Cat. IV?
How near to people will you be allowed to fly?
Is everyone learning all this and getting ready for its implementation?
It is coming.

Interesting post and thread. Poses quite a few questions most recreational fliers never even consider, especially those who like to bladder around a few feet above the ground at full speed. First considered the ballistic properties of a drone when watching an original Mavic pro blast past at head height doing close on 45mph. The ball-park kinetic transfer for that weight at that speed would be about 120ftlb.... It takes 60ftlbs to knock a grown man clean off his feet.
When some people realize there is this much potential for causing injury, the sensible ones change their flying habits.

 

[RandomTask]

Interesting post and thread. Poses quite a few questions most recreational fliers never even consider, especially those who like to bladder around a few feet above the ground at full speed. First considered the ballistic properties of a drone when watching an original Mavic pro blast past at head height doing close on 45mph. The ball-park kinetic transfer for that weight at that speed would be about 120ftlb.... It takes 60ftlbs to knock a grown man clean off his feet.
When some people realize there is this much potential for causing injury, the sensible ones change their flying habits.

I'm not buying that "60 ftlbs knocks a grown man clean off his feet".

I've seen videos of people being shot quite a number of times (8-15) with 9mm handgun rounds (350-400 foot pounds per bullet) and they're not knocked off their feet. They keep attacking.

A (relatively slow) fastball (95mph) is putting 87 foot pounds. Never seen a single baseball player thrown off his feet being hit by a pitch.

 

[Felix le Chat]

I'm not buying that "60 ftlbs knocks a grown man clean off his feet".

I've seen videos of people being shot quite a number of times (8-15) with 9mm handgun rounds (350-400 foot pounds per bullet) and they're not knocked off their feet. They keep attacking.

A (relatively slow) fastball (95mph) is putting 87 foot pounds. Never seen a single baseball player thrown off his feet being hit by a pitch.

Bullets penetrate .. it's called 'pencilling'. If you're not sure about what happens with a blunt object, let someone tap you on the knapper with a 2 pound lump hammer.
Funny you should mention balls .. I've been about 20' away from someone who was hit in the head by a cricket ball straight off the bat and I can, with complete honesty tell you the recipient was taken off his feet and laid out flat. I was 14 at the time so the memory is indelible, so is the fact that I laughed myself into an asthma attack.

 

[RandomTask]

Bullets penetrate .. it's called 'pencilling'. If you're not sure about what happens with a blunt object, let someone tap you on the knapper with a 2 pound lump hammer.
Funny you should mention balls .. I've been about 20' away from someone who was hit in the head by a cricket ball straight off the bat and I can, with complete honesty tell you the recipient was taken off his feet and laid out flat. I was 14 at the time so the memory is indelible, so is the fact that I laughed myself into an asthma attack.

Oh, sure, plenty of people will hit the deck after being hit. Most of them will not be due to the force of the hit, per se, but by their anticipation and/or reaction to it. As in if I see it coming I'm going to be reflexively diving away and coming off my feet whether it hits me or not. If I'm blindsided, the pain may render me unable to stand. A cricket ball off the bat, to the back of my head is certainly going to injure me and quite possibly kill me. I will collapse from the pain if I'm still conscious. But I am *not* going to be thrown from my feet by the force of the hit.

Yes, bullets penetrate - unless you shoot body armor.

Joe Average untrained person can put 100+ footpounds into a punch. Tyson, in his day, could throw 1200. In that scale I probably score in the 200-300 range - some size and training but I've never been a competitive fighter - and there's no way my best punch is going to send a "grown man clean off his feet".

 

[Robert Prior]

What's the Reynolds number of a drone? I'm reminded of the old joke about spherical cows…

As a (very out-of-date) engineer, I'd be inclined to assume the drone was a sphere and go with worst-case speeds/impacts. Is that what you did?

 

[Zbip57]

What's the Reynolds number of a drone?

The shape of an object has a huge effect on its coefficient of drag.

An umbrella has exactly the same mass whether it's opened or closed, but its terminal velocity when dropped from height will be significantly different in either case.

A drone with extended arms and windmilling propeller blades won't have the same terminal velocity as a sphere of the same mass.

 

[RandomTask]

I completely edited out part of my response, following the "body armor" reference. Was going to point out that In addition to the Mike Tyson punch reference...I was going to link a youtube video - I've not been around here long enough to know if it's OK to post a link like this but a guy is out testing bullet penetration through body armor and has the armor being worn by a ballistic gel torso with simulated bones and organs. The thing cost about $2500. He's shooting it with calibers ranting from a .22 rifle up to a 12 ga shooting standard size (2.75") shells with 9 00-buck balls in it. That puts out about _1500_ foot pounds. When he shoots the torso, it moves...maybe an inch. Probably weighs somewhere in the 30-50 pound range. Certainly doesn't go flying hollywood-style. He puts 3-4 shots of buckshot into it. It moves just a little each time.