Below is a useful link to a website that can be used to calculate the Kinetic Energy of a moving object. It can be used to calculate the energy of our models IF we know the speed and weight (mass) of the model.
CAP 722 makes reference to the potential energy (in joules) that an aircraft could be limited to under various flying conditions or settings. 80 joules is one of the quoted numbers.
It is based on the known formula KE (joules)= 0.5 * m * v * v (or v squared)
It can be found at
Once in go to “physics” and then “Kinetic Energy calculator”
Then put in the details of mass (many choices) and speed (again many choices) and the energy is revealed (various choices but it defaults to Joules).
A 250g drone flying at 25m/s (approx 55mph) has a kinetic energy of 80 joules (just under, but close enough)
Similarly, a 1kg aircraft (Foamee Wot 4 & Max Thrust Riot both weigh just over 1kg) flying at 30mph has the value 89 joules.
A large aircraft (about 8kg) flying at 60mph comes in near to 3000 joules.