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Mavic Pro 2 - 905 grams???

RPSM

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https://www.casa.gov.au/sites/g/files/net351/f/_assets/main/airworth/papers/human-injury-model-small-unmanned-aircraft-impacts.pdf

Looking at page 17 specifically, you'd need the mavic 2 to be travelling around 12-13m/s to impart 80J. The paper also states that 120J of energy transfer can lead to serious injury, and even death.

The mavic has a maximum speed of 20m/s. At maximum speed, and if it hit a person, there is a 200J transfer of energy. There is a 90% chance the person hit will die.

Simply put, you could kill someone if you really wanted to with a Mavic 2.

Just like how you can die walking on the road, being hit by a car, stroke, heart attack, random punch, falling glass from a building etc

All DJI needs to do is limit speed to meet the regulations
The regulations state terminal velocity, so at first glance the above isn’t correct (though I think you’re right, the idea that it falls from a standstill is ridiculous).

However, using the NASA TV calculator, an incredible DC of 0.7 and an immense cross section of 0.08m2, you get a TV of 60m/s, which is 1600J. As you say, enough to kill.

If you prefer more restraint figures, let’s go with the DC of a prism (to cause reduced air flow), and an insane cross section of 0.2m2. That gives us 32m/s or 460J of impact energy.

To get to 80J you need a TV of 14.1m/s. Even if it had a cross section of 0.2m (that’s 20cm Square!) and a DC of 5 (I don’t think that’s even possible), it would still have a TV of 15m/s.

The only way you get 80J with normal values is if the drone weighs 250g.
 

eukaryote

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The regulations state terminal velocity, so at first glance the above isn’t correct (though I think you’re right, the idea that it falls from a standstill is ridiculous).

However, using the NASA TV calculator, an incredible DC of 0.7 and an immense cross section of 0.08m2, you get a TV of 60m/s, which is 1600J. As you say, enough to kill.

If you prefer more restraint figures, let’s go with the DC of a prism (to cause reduced air flow), and an insane cross section of 0.2m2. That gives us 32m/s or 460J of impact energy.

To get to 80J you need a TV of 14.1m/s. Even if it had a cross section of 0.2m (that’s 20cm Square!) and a DC of 5 (I don’t think that’s even possible), it would still have a TV of 15m/s.

The only way you get 80J with normal values is if the drone weighs 250g.

They might as well just force registration on every drone at point of purchase.
 

Prmath

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Do you only get 1 complete set of props?
 

RPSM

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They might as well just force registration on every drone at point of purchase.
This was considered but oddly, Germany opposed it.

However note that drones up to 900g are OK. This discussion is about the fact that DJI are claiming the MP2 is 905 grams, hence a 5 gram “mistake”. So don’t worry you can still fly large drones over people in Europe without certification, just not the Mavic Pro 2.
 

yysc

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The regulations state terminal velocity, so at first glance the above isn’t correct (though I think you’re right, the idea that it falls from a standstill is ridiculous).

However, using the NASA TV calculator, an incredible DC of 0.7 and an immense cross section of 0.08m2, you get a TV of 60m/s, which is 1600J. As you say, enough to kill.

If you prefer more restraint figures, let’s go with the DC of a prism (to cause reduced air flow), and an insane cross section of 0.2m2. That gives us 32m/s or 460J of impact energy.

To get to 80J you need a TV of 14.1m/s. Even if it had a cross section of 0.2m (that’s 20cm Square!) and a DC of 5 (I don’t think that’s even possible), it would still have a TV of 15m/s.

The only way you get 80J with normal values is if the drone weighs 250g.
It is not as simple as you present as all energy is not transmitted in a drone impact. The kinetic energy aborved by human skull is about 46%, therefore the 80J limit with a maximum of 19 m/s speed. See below:

Subcategory A1, Class C1
In this case, a minimum age and a minimum level of knowledge would be required for operating the UA, and flying over crowds, even occasionally, would be prohibited; it would be allowed to fly the UA only over isolated people and at a safe distance. A kinetic-energy value was calculated based on experiments that better resemble the possible UAS impact on a person.
The impact scenario considered is that of a multi-rotor UA95 falling from the maximum allowed altitude and reaching a person’s head at a 45 ° angle with respect to the vertical.
Among available data from literature, it is proposed to consider the Gurdjian experiments96 with real embalmed human heads being dropped from a certain height on a solid, not moving plate. 17 specimens were impacted on the anterior parietal zone, 10 on the posterior parietal zone. The frontal zone is not considered as people would normally spot a UAS approaching, with their frontal zone facing the UAS, and would either shift or cover themselves with their hands. Temporal data are not available.
From the reported terminal speeds, when the initial fracture was recorded, as well as from the weight of the specimens, it is possible to derive the kinetic energy at impact and take the overall average. The result is about 80 J.
A Monash University paper97 refers to computer simulation of head impacts on a flat rigid structure, yielding energy values between 80 and 95 J, to start seeing skull fractures. This information seems to conservatively confirm the 80 J identified through the Gurdjian experiments.

This substantiates the 80-J threshold value of absorbed kinetic energy as an acceptable one for Class C1. In a collision with a UA, only a fraction of the UA kinetic energy would be transferred to the head. As described further in the text, the kinetic energy absorbed in average by a human head hit by a UA in free fall is estimated to be 46.5 % of the terminal kinetic energy of the UA, expressed as half of the aircraft MTOM multiplied by the square of its terminal velocity (reaching ground). This fractional value may have been conservatively calculated, and, given the uncertainties of collision dynamics, other assumptions may be possible.
European harmonisation of drone regulations 'en route' to the EC

So there is still no proof that Mavic 2 on impact would transfer more than 80J and therefore not comply with C1. I'm sure for certification purposes they use wind tunnel data plus advanced calulations not a simple online calculator even if was created by NASA.
 

RPSM

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It is not as simple as you present as all energy is not transmitted in a drone impact. The kinetic energy aborved by human skull is about 46%, therefore the 80J limit with a maximum of 19 m/s speed. See below:

Subcategory A1, Class C1
In this case, a minimum age and a minimum level of knowledge would be required for operating the UA, and flying over crowds, even occasionally, would be prohibited; it would be allowed to fly the UA only over isolated people and at a safe distance. A kinetic-energy value was calculated based on experiments that better resemble the possible UAS impact on a person.
The impact scenario considered is that of a multi-rotor UA95 falling from the maximum allowed altitude and reaching a person’s head at a 45 ° angle with respect to the vertical.
Among available data from literature, it is proposed to consider the Gurdjian experiments96 with real embalmed human heads being dropped from a certain height on a solid, not moving plate. 17 specimens were impacted on the anterior parietal zone, 10 on the posterior parietal zone. The frontal zone is not considered as people would normally spot a UAS approaching, with their frontal zone facing the UAS, and would either shift or cover themselves with their hands. Temporal data are not available.
From the reported terminal speeds, when the initial fracture was recorded, as well as from the weight of the specimens, it is possible to derive the kinetic energy at impact and take the overall average. The result is about 80 J.
A Monash University paper97 refers to computer simulation of head impacts on a flat rigid structure, yielding energy values between 80 and 95 J, to start seeing skull fractures. This information seems to conservatively confirm the 80 J identified through the Gurdjian experiments.

This substantiates the 80-J threshold value of absorbed kinetic energy as an acceptable one for Class C1. In a collision with a UA, only a fraction of the UA kinetic energy would be transferred to the head. As described further in the text, the kinetic energy absorbed in average by a human head hit by a UA in free fall is estimated to be 46.5 % of the terminal kinetic energy of the UA, expressed as half of the aircraft MTOM multiplied by the square of its terminal velocity (reaching ground). This fractional value may have been conservatively calculated, and, given the uncertainties of collision dynamics, other assumptions may be possible.
European harmonisation of drone regulations 'en route' to the EC

So there is still no proof that Mavic 2 on impact would transfer more than 80J and therefore not comply with C1. I'm sure for certification purposes they use wind tunnel data plus advanced calulations not a simple online calculator even if was created by NASA.
Ah! So now at least we are starting to agree, that this won't come from a design program from DJI, and as I already said, requires wind tunnels to get even close to accurate. Nice. But, you're still wrong by 1 order of magnitude. A MP2 will impact with at least 1600J of kinetic energy, resulting in a transfer of just under 750J. This is with very generous DC and CS values. Result, drone fails. For 5g? Really? I don't get the comments on this thread, honestly, given that they are over by 5g! No one did a calculation that the MP2 would be under 80J so let's go over by 5g! OMG! No one at DJI did this. They made a mistake and simply went over by 5g. That's it.
 

yysc

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Ah! So now at least we are starting to agree, that this won't come from a design program from DJI, and as I already said, requires wind tunnels to get even close to accurate. Nice. But, you're still wrong by 1 order of magnitude. A MP2 will impact with at least 1600J of kinetic energy, resulting in a transfer of just under 750J. This is with very generous DC and CS values. Result, drone fails. For 5g? Really? I don't get the comments on this thread, honestly, given that they are over by 5g! No one did a calculation that the MP2 would be under 80J so let's go over by 5g! OMG! No one at DJI did this. They made a mistake and simply went over by 5g. That's it.
Mavic Pro has been quoted to transfer about 70J, you are proposing 10 times more energy for a drone that weights 23% more and also has bigger dimensions hence more aerodynamic drag? I'm sorry but that is nonsense.

So basically until DJI certifies their drones for EASA classes we won't know for certain, okay. Worst case they'll release the Mavic 2 EASA version battery and end of the problem.

I still don't see any issue to fly Mavic 2 over people in 2019. I'll buy a new battery if needed. This is not like trying to put a Phantom in C1,
 

RPSM

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Mavic Pro has been quoted to transfer about 70J, you are proposing 10 times more energy for a drone that weights 23% more and also has bigger dimensions hence more aerodynamic drag? I'm sorry but that is nonsense.

So basically until DJI certifies their drones for EASA classes we won't know for certain, okay. Worst case they'll release the Mavic 2 EASA version battery and end of the problem.

I still don't see any issue to fly Mavic 2 over people in 2019. I'll buy a new battery if needed. This is not like trying to put a Phantom in C1,
Where is the spec from DJI that the MP is 70J? Doesn’t exist.
 

yysc

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It's been mentioned in this thread.

In any case EASA has found 80J and 900g to be comparable (and they specifically allow more weight if less than 80J of transfer can be demonstrated). Because for example some design features like round edges contribute to reduce energy transfer however your fancy calculations ignore them all.

So you came up with your 700J for 905g (900g might be perhaps 680J???) therefore EASA is also wrong! Please hurry and make them aware of their terrible mistake! You clearly know more than EASA and DJI combined!
 

RPSM

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It's been mentioned in this thread.

In any case EASA has found 80J and 900g to be comparable (and they specifically allow more weight if less than 80J of transfer can be demonstrated). Because for example some design features like round edges contribute to reduce energy transfer however your fancy calculations ignore them all.

So you came up with your 700J for 905g (900g might be perhaps 680J???) therefore EASA is also wrong! Please hurry and make them aware of their terrible mistake! You clearly know more than EASA and DJI combined!
No one provided any figures from DJI. The math is not fancy, but it is correct. You can try it, it’s easy. EASA have not said that 80J is equal to 900g.
 
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yysc

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No one provided any figures from DJI. The math is not fancy, but it is correct. You can try it, it’s easy. EASA have not said that 80J is equal to 900g.
Okay I decided to use your Math.

NASA Terminal Velocity Calculator
Terminal Velocity

Using the same parameters you have mentioned,

However, using the NASA TV calculator, an incredible DC of 0.7 and an immense cross section of 0.08m2, you get a TV of 60m/s, which is 1600J. As you say, enough to kill.


So terminal velocity for Mavic Pro and Mavic 2 Pro is 11.405m/s, for Phantom 4 Pro is 19.754 m/s.

Then terminal Kinetic energy from free fall at maximum altitude of 400ft/120m (this is where the 80J norm from EASA comes from) is simple to calculate:

Mavic Pro : 0.5 * 11.405^2 * 0.734 = 47.74J
Mavic 2 Pro : 0.5 * 11.405^2 * 0.907 = 58.99J
Phantom 4 Pro : 0.5 * 19.754^2 * 1.388 = 270.81J

I don't know where your 60m/s (216 Km/h or 135 mph) of terminal velocity comes from for a Mavic 2. Maybe we need to attach a rocket to the Mavic 2 to accelerate this fast in 120 m/400 ft of vertical free fall? It is simply impossible for an UAS to accelerate in 120 meters from 0 to 60m/s. I'd need like 1.5s to complete this distance, and trust me objects don't accelerate this fast in free fall in Planet Earth.
 

m15Alien

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Okay I decided to use your Math.

Mavic Pro : 0.5 * 11.405^2 * 0.734 = 47.74J
Mavic 2 Pro
: 0.5 * 11.405^2 * 0.907 = 58.99J
Phantom 4 Pro
: 0.5 * 19.754^2 * 1.388 = 270.81J
.
So if your thoughts and the terminal Kinetic energy calculations using the appropriate drag coefficient are correct I hope DJI will declare soon similar values in its datasheets to be fully compliant to the next EU regulation.
 

yysc

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So if your thoughts and the terminal Kinetic energy calculations using the appropriate drag coefficient are correct I hope DJI will declare soon similar values in its datasheets to be fully compliant to the next EU regulation.
Well I'm sure the engineers at DJI who designed the Mavic 2 and not the Help Desk agents (who are deemed by some pople here like true authorities in the matter) or some members of this forum know how to use a calculator properly and also have access to wind tunnel data.

I think DJI for consumer drones with the Phantom 4 started to pay a lot of attention to detail in aerodynamic shapes. This suggest back when this was under development they had access to wind tunnel data and advanced modelling tools to come up with an efficient shape.

As stated previously they knew about the 80J energy transfer way before Mavic 2 was released, it seems impossible they would ignore this. For conspiranoics yes, they ignored it, and they screwed up by 5g.

More food for conspiranoics, my M2P weighed in my two kitchen balances. I know they are not ultraprecision balances but both state delta = 1 gram and both are Made in China like the Mavic hehehehe. My Mavic 2 Pro had EU ID stickers in both the UAS box in the Fly More box.


 

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Very interesting thread. After reading the posts and the proposed new EU laws, I cancelled my order for the MP2. The shop was very good about it, but I could see too many problems ahead, and guess that it will not fall into the C1 class (either due to being over 900g or the 80J limits).

Far too much money to spend now (1449 euros plus extra battery+travel case) for something that may be 'outlawed' by the EU regulations in the Spring 2019.

This is one time that I think that sitting on the fence until the proposed new regulations are decided is the sensible thing to do. I would love the better photo quality, but also the thought of about 1700 euros being wasted in a few months was the deciding factor.

So the order was cancelled before receipt, and I will wait to see what happens next Spring. My Mavic Pro mark 1 will keep going for a bit longer !!

Jerry
 

yysc

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Very interesting thread. After reading the posts and the proposed new EU laws, I cancelled my order for the MP2. The shop was very good about it, but I could see too many problems ahead, and guess that it will not fall into the C1 class (either due to being over 900g or the 80J limits).

Far too much money to spend now (1449 euros plus extra battery+travel case) for something that may be 'outlawed' by the EU regulations in the Spring 2019.

This is one time that I think that sitting on the fence until the proposed new regulations are decided is the sensible thing to do. I would love the better photo quality, but also the thought of about 1700 euros being wasted in a few months was the deciding factor.

So the order was cancelled before receipt, and I will wait to see what happens next Spring. My Mavic Pro mark 1 will keep going for a bit longer !!

Jerry
You missunderstood the norm. The EU is not going to outlaw C2 class aircraft, they are not going to declare the Phantom series illegal.

Simply if it is a C2 class UAS you cannot fly over people and you need to register your drone (which might be required aswell for C1) and do a presential exam. Other than that you can fly it just like if it was C1.

If registering your UAS is a deal breaker, that only leaves Ryze Tello and similar (Class C0).
 

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Thanks for your reply, but I am guessing that there will need to go to test centre and sit a practical test as well as paying a large fee for the privilege of sitting that test. And if they also are talking about limiting the top speed and restrictions on flying over people, then again that is a deal breaker for me.

I think that the writing is on the wall....that much tougher restrictions ARE coming in the EU. There will be more and more no-fly areas and I can see governments bringing in more and more restrictions (things like not be able to fly above people or limited top speeds).

So yes, for me, the proposed restrictions made me cancel my order. Registering a quadcopter is not a problem (unless there is a big fee for doing so) but having to go to test centres to sit exams, having limited top speeds and also restrictions on flying over people or more was a deal breaker. For me, it was too much money to gamble on a quadcopter that may become increasingly difficult and costly to fly from next Spring (and next Spring is not far away).

Jerry
 

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Well I'm sure the engineers at DJI who designed the Mavic 2 and not the Help Desk agents (who are deemed by some pople here like true authorities in the matter) or some members of this forum know how to use a calculator properly and also have access to wind tunnel data.

I think DJI for consumer drones with the Phantom 4 started to pay a lot of attention to detail in aerodynamic shapes. This suggest back when this was under development they had access to wind tunnel data and advanced modelling tools to come up with an efficient shape.

As stated previously they knew about the 80J energy transfer way before Mavic 2 was released, it seems impossible they would ignore this. For conspiranoics yes, they ignored it, and they screwed up by 5g.

More food for conspiranoics, my M2P weighed in my two kitchen balances. I know they are not ultraprecision balances but both state delta = 1 gram and both are Made in China like the Mavic hehehehe. My Mavic 2 Pro had EU ID stickers in both the UAS box in the Fly More box.



So by your non-conspiratorial standard, DJI also knew they were selling countless thousands of Phantoms that would effectively be banned in the near future or very difficult to find places to fly. In other words, consumers are getting ripped off.

Are you being paid by DJI to post such nonsense?
 
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yysc

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So by your non-conspiratorial standard, DJI also knew they were selling countless thousands of Phantoms that would effectively be banned in the near future or very difficult to find places to fly. In other words, consumers are getting ripped off.

Are you being paid by DJI to post such nonsense?
I guess your ability to interpret simple norms is limited, nobody is going to ban the Phantom or make the restrictions to fly a Phantom harder than they already are. In many countries of Europe it will be actually easier to fly a Phantom.

With the "Being paid by DJI" crap you just added the tip of the cake to your comment. Offense/insult is always left to those who lack the capacity to argument.
 

RPSM

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Weird, your calculations look correct, I obviously messed up one of the values! Sorry been flying (for “real”) so didn’t see this. I think the point remains that it’s unlikely it passes the 80J limit and it requires DJI to confirm. So for now, the MP2 is in a fuzzy area where you cannotnfly it over people andnit will require a sit-down test to fly anywhere near people. That’s OK - buyers can make up their own minds. I would love to buy it. I’d rush out and get one now and add to my others, but not until this gets cleared up.
 

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I don't want to get into politics, but the UK regulations are at least – if not more – stringent, and I would expect to see even more regulations in the coming years. If anything, the EU ensures that the same rules will apply throughout the union.

Proposed UK rules:
  • Whether the 1km flight restriction around protected aerodromes is sufficient
  • Police issuing fixed penalty notices to people flouting drone laws
  • Using new counter-drone technology to protect public events and critical national infrastructure, and prevent contraband from reaching prisons
  • Introducing minimum age restrictions for drone owners
  • Proposals for regulating and mandating the use of apps on which drone users would file flight plans ahead of take-off
Like the EU regulations, drones over 250g require registration and an online test. However the EU limits for flying near or over people are significantly more relaxed, as with proper registration and a C1 class drone, you can fly over people.
If you get mugged or your house broke into the police dont show up! I’m sure there going to find someone within a 1k radius of where a drone is flying / last scene.
 

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