Schaeffler Aerospace Europe’s head of sales, engineering and R&D Peter Gloeckner examines the high power density, low weight and high reliability challenges for electric drive trains.

Together with established OEMs, Schaeffler Aerospace is developing electric drive trains for eVTOLs and electric fixed-wing aircraft, including motor-generator, power electronics, software and fully integrated assemblies.

Over the last few decades, Schaeffler Aerospace has evolved from a supplier of high precision aerospace bearings to a systems partner for integrated mechanical and bearing systems. This includes aircraft engines, helicopters and space applications.

Currently, we are in the process of transferring our know-how and competence in the field of electric mobility from our Automotive Technologies division to aerospace urban air mobility solutions, as well as emission-reduced aircraft, such as eVTOLs and hybrid-electric rotary and fixed-wing aircraft.

With our core business being applications for aircraft engines and helicopters, Schaeffler Aerospace supplies almost all engine and helicopter programmes. This includes all major aircraft programmes from business jets over single-aisle, to widebody aircraft and all common helicopters.

Bearings in space

Space exploration has always been an important business field for Schaeffler in order to develop advanced technologies. For example, the development of Schaeffler’s high performance, high corrosion-resistant steel, Cronidur 30 and ceramic rolling elements. In the 1990s this enabled NASA to extend its mission cycle for the main engine turbo pumps of the Space Shuttle from one to 50.

Transferring this technology into other space launch programmes such as Ariane and Vega, the technology is now used regularly in helicopters, machine tools and other industrial applications. Beyond this, Schaeffler Aerospace supports satellite and planet exploration programmes with its high precision bearings for gyroscopes, actuators and rovers. Examples of these missions include BepiColombo to Mercury, and the rovers exploring Mars.

Our bearing systems are specifically customised to meet the requirements of each application. Particularly in aircraft engines, the bearings face challenging operating conditions such as high speeds, temperatures, loads and the highest requirements in terms of reliability. Therefore, specially developed materials, designs and manufacturing processes are required. Our integrated bearing systems combine various functions such as rolling bearings, damping, elastic fixation, sealing and high temperature resistance and offer reduced system weight, fuel consumption and emissions, as well as higher reliability.

The very best standards

Based on over 50 years’ experience in the aerospace market and having a broad range of testing and simulation capabilities, we are following our self-developed design guidelines. These include the whole application spectrum from design and materials through to lubrication, cooling and system simulation. Schaeffler Aerospace Germany is the world’s only aerospace bearing company that holds EASA part 21J approval as a design organisation. Of course, we also rely on international aerospace standards and customer standards for development and design.

A standard industrial bearing can be manufactured within a few weeks due to its standardised design, common materials and mass production technologies. However, for flight-critical aerospace applications, there is no standard type of bearing. Each application requires its own design in order to cope with the challenging operating conditions and high reliability requirements. Depending on complexity and size, the manufacturing process can take several months. Complex bearing systems can have more than 300 different manufacturing operations with all of these being fully documented. In other words, we ensure full traceability from raw materials to final assembly. We really take the extra mile to focus on our customers’ needs.

Industry knowledge transfer

Schaeffler is rapidly ramping up its electric competence in the automotive sector and is electrifying all sorts of passenger and commercial vehicles. Together with our sister company Compact Dynamics, we have been developing and manufacturing electric powertrains for electric or hybrid racing such as Formula 1, Formula E, WRC and Le Mans, as well as aviation for the last 20 years. The challenges for electric drive trains are comparable for automotive motorsports and aviation: high power density, low weight, high reliability.

Therefore we are teaming up to transfer this technology into aviation-certified serial production, combining the know-how of highly sophisticated electric drive trains with cost-effective industrialisation for serial production and aviation certification. Together with the established OEMs and new players, we are developing electric drive trains for eVTOLs and electric fixed-wing aircraft. We offer the full range for (hybrid) electric drives: motor/generator, power electronics, software and full integrated assemblies.

As an example, within the EU funded R&D project MAHEPA, Compact Dynamics designed a fully redundant double electric propeller drive, which consists of two 150kW electric motors, silicon carbide power electronics, gearbox and propeller bearing, including governor. This dual drive is integrated into the Pipistrel Panthera engine to showcase the advantages of electric aviation. Moreover, we are studying together with our customers and partners research and technology for hydrogen-based mobility concepts such as fuel-cell or direct combustion complementary to electric propulsion.

Green aviation growth

Currently we are seeing a race between the various emerging technologies in the aviation market to meet the eco-political, end-user and operator requirements. As most are aware, the targets described by the European commission in ‘Flightpath 2050’ require a 75% reduction in CO₂ and a 90% reduction in NO_x compared to a typical new aircraft from the year 2000. It is obvious that these requirements cannot be achieved by incremental improvements of currently available technologies. That means we need the combination of all-new technologies in airframes, propulsion and air traffic management. With regards to propulsion, (hybrid) electric drive trains are the most promising technology alongside Sustainable Aviation Fuels (SAFs) and hydrogen-powered aircraft, either directly used or via fuel-cells.

Particularly for short-haul and commuter aircraft, electric flight will be part of the air traffic within the next 10 years. Battery energy density will further increase over the next few years and enable electric drive trains to even power regional carriers in the mid-term. However, classical single-aisle and long-haul aircraft will still require, in the medium term, gas turbine propulsion. Therefore, it is important to intensify research and technology on SAFs, hydrogen and fuel cells in parallel with electrification. Only the combination of these technologies, together with new airframes and optimised air traffic management, will lead to climate-neutral flying. 

We are focusing on small to medium electric power per motor, in the range of 10kW to 500kW for customised electric drive trains. The applications vary from eVTOLs over general aviation and small fixed wing aircraft, to electrified rotorcraft. We do not compete with the large engine and electric drive OEMs in this sector, but rather offer as a partner and supplier electric sub-systems, such as motors, generators and electronics to the OEMs.

www.schaeffler.com