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Mechanical Strength Test of a UAS Certification Process

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One of the most important test for C1 & C2 UAS certification is the Mechanical Strength. This article explores the critical aspects of testing propellers and drone structures to adhere to rigorous safety standards.

Understanding Thrust and Propeller Speed

The journey begins with the concept of maximum static thrust – the highest force a propeller can exert when the drone is stationary. This measure is crucial for takeoff and the initial climb phase, complemented by the maximum propeller speed, which indicates the fastest rotation a propeller can safely achieve under this maximum thrust condition.

Safety First with the Factor of Safety

In drone technology, safety is paramount.


The implementation of a factor of safety
—a multiplier applied to design loads—ensures drones can endure stresses beyond normal operational requirements.


This factor varies per test, but a minimum value of 1.2 is deemed acceptable if there are effective design features in place to prevent load exceedances in all operational modes.


Balancing Design and Ultimate Loads

Drones must be built to withstand significant stresses.

They should carry design loads without incurring damage or permanent deformation and bear ultimate loads without structural failure for at least three seconds.

This requirement extends from primary structures like propellers, motors, and landing gear to secondary components, ensuring they can handle the rigors of maximum take-off mass and maximum horizontal speed without compromising safety.

Maneuvering and Parachute Deployment Loads

For drones, maneuvering load factors—the forces experienced during flight maneuvers—have specific values for different configurations, including fixed-wing, multicopters, and helicopters, tailored for both aerobatic and non-aerobatic usage.

Drones equipped with parachutes for regular landing or emergency purposes must also prove their capability to withstand deployment loads, ensuring safe descent under various conditions.

Impact of Landing and Propeller Durability

The landing phase demands that drones possess the mechanical strength and stability to endure the impact stresses of touching down. Likewise, propellers and their mounts must resist the dynamic loads induced by the power of engines and the operation of propellers throughout the flight.

Drones equipped with parachutes for regular landing or emergency purposes must also prove their capability to withstand deployment loads, ensuring safe descent under various conditions.

Verification through Rigorous Testing

Verification involves a series of tests designed to confirm that structures can sustain both design and ultimate loads, manage parachute deployment stresses, and withstand the impacts of landing.

These tests range from applying specific loads to conducting drop tests, all meticulously crafted to replicate real-world conditions and ensure every component meets stringent safety standards.

Achieving Compliance: The Ultimate Aim

The goal of these exhaustive tests is to meet a set of criteria that span from handling design and ultimate loads to maneuvering factors and propeller durability. Compliance indicates that the drone is prepared to take on the challenges of flight, grounded in safety and reliability, and meet with the DR (EU) 2019/945.

In essence, the process of testing drone propellers and structures is a vital part of ensuring flight safety. By meeting these standards, manufacturers guarantee that their drones are capable of safe operation, offering assurance to operators and end-users alike.