Ultra-Compact EPU for Next-Generation Air Mobility

Zoerkler and the UK-based electric motor specialist Helix have jointly developed an advanced Electric Propulsion Unit (EPU) for use in next-generation eVTOL and eVOL applications. The system combines Helix's high power-density electric motor technology with Zoerkler's lightweight, highly efficient transmission, resulting in a significantly more compact and performant propulsion solution.

Compared to conventional direct-drive systems, the integrated design enables a 50% reduction in diameter while still meeting the demanding torque requirements of vertical lift applications. The EPU delivers over 100 kW of lift power with up to 1,600 Nm of torque, making it well-suited for high-load phases such as take-off and hovering.

For cruise operation, the unit achieves 250 kW of continuous power and up to 400 kW peak output, all within a total system weight of just 32.2 kg. A key contributor to this performance is Zoerkler's transmission, which operates at an efficiency of 98%, allowing for a smaller and lighter motor design without compromising output.

With a compact diameter of just 26 cm, the EPU offers significant advantages in aircraft integration. Smaller nacelle sizes and reduced aerodynamic drag enable improved overall efficiency, increased range, and greater payload capacity for advanced air mobility platforms. The system is designed to support a variety of configurations, including lift, cruise and tiltrotor concepts.

This joint development highlights the potential of fully integrated propulsion architectures to set new benchmarks in size, weight, and efficiency—paving the way for more scalable and sustainable electric aviation solutions.