Tailored Propulsion for Forward Flight: The Mejzlik–Hirth Collaboration

Therefore, we responded with more than a product. As part of our Professional Propulsion Systems (PPS) initiative, we focus on delivering fully validated propulsion configurations that are optimized across multiple dimensions – engine, propeller, and mission profile. This aligned perfectly with Hirth’s intent to create a European-made propulsion solution that delivers reliable performance in forward flight.

Starting the Collaboration

The project began in February 2024, when the Hirth team reached out with a specific request: to identify a propeller optimized for forward flight – unlike the vertical lift profile typical of hovering drones.

Our teams quickly found common ground. At Mejzlik Propellers, we’ve spent years developing not only carbon fiber propellers but also a methodology around how they integrate into propulsion systems. The PPS approach emphasizes system-level tuning, based on real data and iterative design.

Rather than suggesting an off-the-shelf item, we analyzed performance goals, evaluated available configurations, and built simulations using real engine data. A key priority was aligning the engine power curve with propeller aerodynamic behavior, ensuring that both components would operate within their optimal ranges throughout the flight envelope.

Technical Process and Benefits

In many UAV programs, propulsion is still approached as an afterthought – motors are selected first, and propellers are chosen later based on availability. But that leaves performance on the table. With Hirth, we applied our top-down design methodology, inspired by aerospace development programs, where each component is considered in relation to the system it powers.

Our engineering team began by analyzing expected flight conditions, focusing on cruise speed performance. Rather than aiming for theoretical peak efficiency, we prioritized realistic power delivery, consistent thrust output, and integration readiness.

Based on the available engine power and the propulsion requirements, we identified a range of candidate propellers that matched the expected flight conditions. Several types – including models like the Mejzlik 28.5x12 3B, 29x10 2B EVO, 30x12 2B, and 32x10 2B – were selected for further evaluation and datasheet development. This process included:

• Simulation and performance modeling across a wide range of RPM values and flight velocities
• Analysis of thrust characteristics, torque behavior, mechanical power output, and system-level propulsion efficiency
• Generation of a comprehensive performance datasheet – a standard deliverable within the PPS process – allowing for precise system integration, flight planning, and performance forecasting

Rather than relying on trial and error, the data-backed approach enabled us to provide Hirth with a ready-to-integrate propulsion configuration that meets real operational needs. It also created a reusable reference for future platform development, saving time and minimizing risk.

The result was not just a compatible propeller, but a propulsion element designed with precision and purpose – delivering measurable performance, backed by data, and ready to support forward-flight applications from day one.

“The propellers manufactured by Mejzlik are thoroughly tested and validated on our in-house test bench to ensure optimal performance, durability, and compliance with all relevant standards.”

Torsten Windorfer

Head of Research & Development

Practical Value and Customer Context

For platform developers and integrators, the benefits were immediate. With a validated configuration in hand, Hirth was able to move forward quickly and confidently — without the trial-and-error often associated with propulsion matching.

While in this case, a well-matched configuration was found within our existing PPS portfolio, we regularly support projects where a custom propeller is required — especially in UAV and defense applications, where each platform brings unique aerodynamic and structural requirements.

While a reference is publicly available in this case, it’s worth noting that in UAV and defense sectors, detailed integration data and end-user feedback are often protected due to the sensitivity of the applications. That’s why our approach focuses on delivering well-documented configurations that reduce uncertainty — even when full disclosure isn’t possible.

Future Collaboration and Outlook

Our work with Hirth doesn’t end here. With a broad range of engines in their catalog, there is strong potential for continued collaboration and for building additional PPS configurations tailored to other aircraft types – from VTOL platforms to hybrid propulsion systems.

Each project allows us to shrink the development timeline, streamline validation, and deliver more value – not just in the final product, but in the process behind it.

This project reflects what PPS is all about: trusted engineering, tested performance, and long-term partnerships based on shared technical understanding and transparent collaboration.

"We at Hirth Engines are pleased to have partnered with Mejzlik Propellers on a dedicated flight propulsion project. The level of technical depth, responsiveness, and system-level thinking demonstrated in their approach was impressive. Rather than offering a generic solution, Mejzlik delivered a well-matched, data-driven propeller configuration that aligned seamlessly with our 4202F engine and project goals.

Their commitment to validated performance and integration readiness significantly accelerated our development timeline and added measurable value from the outset. We appreciate their professionalism and look forward to expanding this collaboration in future propulsion programs."

— Hirth Engines Team

Datasheets of Hirth engine and Mejzlik Propellers can be found here.