Just like any technology, UAVs and eVTOLs are constantly improving. And, just as it is with any invention, thorough testing in the UAV sector is necessary to ensure that improvements in one area contribute to overall improvements of the whole system and don’t increase overall weight or decrease flight time. This doesn’t happen in a day, a week, or a month. Because testing isn’t straight forward.  


It might be tempting to assume that, since we know what parameters to test and what results we’re looking for, it’s a simple job. If the results are not what we want, we go back to work. If they are what we want, job done and we can start selling, right? But the truth is that concentrating on one specific result betrays a dangerously narrow focus.  

As UAVs become more complex, their systems make them increasingly difficult to test. “UAVs can include thousands of components and millions of lines of software to test to ensure safety requirements during their entire life cycle.” 

What’s more, a lack of consideration of other industries can prevent companies, manufacturers, and designers from making greater strides in their proprietary technology. For example, engineers who have experience in different sectors (such as ePropelled’s aerospace, UAVs, EVs, and pumps) can apply this varied knowledge in their designs, providing even more data to analyze and learn from. 

Testing should also consider material science research. This might seem like one of the steps to be taken much earlier, during design. But building UAVs is not only about using software tools to design propulsion systems. It’s also about developing and using an understanding of how materials such as magnets, motor laminations, and windings are chosen and used in those systems.  

Without a deeper understanding of this, it will be difficult, if not impossible, to build or improve any part of the electric machine. That’s why testing should start as early as possible without relying solely on software tools to help us make all the decisions straight away. Not considering this knowledge throughout testing can be a costly mistake.  


The propeller is the main consideration when analyzing motor performance. It would be easy to assume that the aim should be to have the biggest propeller a UAV can accommodate because a larger propeller offers better thrust efficiency when it’s running slower. 

But the designer’s objective might be something completely different. For example, a smaller propeller may provide a lower temperature, which could be necessary for some specific mission parameters. This is why one question is always key: what is the mission profile? 

Testing at least 10 sizes of propellers for each propulsion motor is the bare minimum to see how it varies with voltage and other parameters. At ePropelled, such results offer a wider and better understanding of all possible options and enable us to create a database that we can use and share with our customers.  

This is vital because it then helps them make the right decision or understand what result a specific choice will bring. For example, if they’re more comfortable sticking to 48 V instead of using 84 V, then this will affect the size of the propeller and the force necessary to achieve the thrust they want. 

Additional considerations 

Batteries are an important part of testing. This is true whether the UAV or eVTOL is fully electric or uses an internal combustion engine with electric support in hybrid mode. After all, batteries need to be versatile, enable all types of missions, and fulfill multiple parameters because they’re not only simply there to store energy. They need to release it efficiently and enable onboard charging. And if they’re used in hybrid mode, they need to be reliable. 

Battery power will have a huge impact on electric motor’s design and performance. Simply throwing a battery into the mix at the end is not going to provide the end user with the best possible product. Design and performance need to work in tandem to conserve the battery and extend flight time.  

Higher efficiency of the motor, such as demonstrated by ePropelled technology, will allow for reduced battery use and, therefore, longer flight. In the end, this is a crucial aspect of any UAV design.  

Motor controllers are also a vital consideration. When they have advanced software control, efficiency improvements can be achieved through real-time monitoring of the motor’s operations and feedback received in several different ways. In some cases, diagnostic capabilities can also be included. All of this needs testing, retesting, and further testing.  

Finally, it’s important to remember to match the motor controller to the propulsion motor and the propeller. All three must be matched for optimal system efficiency. This can only be achieved through in-depth testing under various conditions.  

Speaking from experience 

At ePropelled, our UAV research comes, among other, from:  

  • ingress protection testing (solid and liquid ingress protection) 
  • gyroscopic force testing, and 
  • life testing. 

Rigs are built at our in-house testing facility and calibrated on an ongoing and consistent basis. We test electric motors and their components while also testing which motors work best with which propellers. We utilize software that controls and monitors our machines’ performance because we believe that machine learning and AI should be used to improve propulsion and performance. 

Gas engine starter generators are also involved in testing to ensure that our motors are hybrid ready and work in a variety of setups. This variety of inputs allows us to gather all sorts of data that can then help our customers’ design considerations.