A differentiated solution for commuter aircraft

A differentiated solution for commuter aircraft

William Hunter, Motor Lead Engineer and Patrick Springer, EPU Lead Engineer at Rolls-Royce with our design of a 320 kW electric propulsion unit for Regional Air Mobility

The commuter aircraft market is growing, with increased demand for safe and sustainable solutions that can enable passengers to make use of existing infrastructure.

Developing the propulsion systems to support this market comes with challenges, from meeting the needs of different platform configurations and power classes to navigating new and evolving regulation to achieve certification.

We spoke to Patrick Springer, EPU Lead Engineer and William Hunter, Motor Lead Engineer at Rolls-Royce about the electric propulsion unit (EPU) we’re developing to support Regional Air Mobility (RAM) and how our novel technology blocks are helping us set the standard for safe and reliable propulsion solutions.

Working with customers to find the right solution

At Rolls-Royce Electrical, we work closely with airframers and operators to understand their needs and build a solution that is specifically designed for the commuter aircraft market and its requirements.

Patrick explains: “Finding the right solution requires an iterative approach. We want to provide a reliable solution for a variety of applications whether that be a single engine, twin engine or quad engine aircraft. With our EPU, we looked at the airframer demand early on to find the right power sweet spot to be able to propel different sizes of aircraft.”

“We’re developing our understanding simultaneously with customers,” adds William. “Changes sometimes happen in the industry landscape in terms of requirements and regulations as well. So, we have to be agile in the way we work and communicative with our customers from the outset.”

The novel technologies setting us apart

This way of working has enabled our teams to develop a motor demonstrator for Regional Air Mobility made up of novel technology bricks which has already reached the test bench at our facility in Munich.


Our EPU is made up of an air-cooled radial flux permanent magnet synchronous motor, air-cooled power electronics, and our multilane system architecture implementing four winding systems that can be operated independently allowing fault tolerant operation.

“Throughout the development, we’ve always strived to deliver the most reliable and cost effective design,” explains William. “Our direct-drive, air cooled system avoids the needs for an oil circuit, reducing complexity and increasing reliability without compromising on safety.”

Alongside delivering the power and performance required for commuter applications, our modular and scalable EPU will enable easy integration into aircraft platforms and reduce maintenance and operation costs.

Developing our testing and learning capabilities in-house

The electric motor technology for the Regional Air Mobility propulsion units has been passed to test

Developing our testing and learning capabilities in-house

Safety has been one of the team’s key focuses since the work on the EPU concept began, building it into the development strategy at every level. The testing methods the team utilises are integral to ensuring this.

William explains: “It’s not just about understanding where the system might fail but also the consequences of any failure. Through our testing programmes, we’re able to have that know-how in-house so we can build up essential knowledge of how to qualify these systems for aerospace.”

Last year, the team mounted the first technology demonstrator to the test bench, helping to confirm the basic mechanical and electrical functionality of the motor.

The team is already working on a second, identical motor that will provide further confidence to move on to the next stages of development.

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