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The Physics of Drone Crashes

With recent EASA regulations threatening most of the Drone community, we at Drone Insider decided to take a look at the research which EASA was using in order to calculate the fatality rate for Drone Accidents and their likely consequences.

Due to the way in which EASA have set out their regulations

“There is a need to have subcategories in order to have rules proportionate to the risk,” warns EASA

The EASA has recommended sub categories ranging from an ‘A0’ threshold of 250 g and a maximum speed of 15 m/s making injury unlikely. Find out more in our Previous Article

In the accompanying explanatory document EASA states that: ‘apart from the danger to an airborne aircraft, the greatest risk that a drone poses is to people on the ground. ‘

Our Calculations

Here we are assuming that the maximum kinetic energy is transferred on impact – never the case in reality. Recent studies put the transfer of kinetic energy at 60 percent – which EASA suspects may be still too high. However, a 250g drone hitting a person at 67km/h will carry a 1 percent probability of fatality.

Below is a graph which explains the probability of Fatality for different drone crashes at different speeds across different Multi-rotor categories.



Of course there are pretty high thresholds when it comes to the probability of causing collisions, then you would be highly unlikely to reach the higher probabilities. The biggest risk we can see is from Aerial Photography Drones in the case that they fall out the sky, gain high velocity and hit an individual on the ground.

What is interesting to note is that the speed increase to go from 50% likelihood of death to 90% is more significant than going from 1% to 50%.

Assumptions made:

  • All kinetic energy from the drone is transferred to the individual (no losses to heat, sound, rotational energy etc)
  • The area of the collision point is always the same
  • The individual is in average health
  • Studies estimate that maximum amount of energy transferred is about 100% – in the real world it is almost never higher than 60%
  • That the collision is perfectly inelastic- i.e. it does not deflect off of the person (the coefficient of restitution=0, if you want to get technical)
  • The anatomy hit obviously is a huge part of the damage caused, however this has been taken into account when calculating the probabilities of fatality.


Clearly in an ideal world there would be zero fatality on everything. But it is important to remember that this is the Car Industry’s method for calculating accident risk. One should also remember that there are a myriad of different variable which must be taken into account including props spinning at 10,000rpm which would chop up anything in their 2.5″ radius.

Other incalculable variables include: the part of the body which the Mutli-rotor hits, as well factors such as the health of the victim and their access to help and assistance. As ever at Drone Insider we feel that the if the pilot takes the proper safety precautions into account while flying, as the most usually do. Then the risk of injury to onlookers and other pilots can be limited to almost nothing.

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