The FAA this week opened a consultation on proposed special conditions for certifying Safran’s EngineUs 100 electric motors. The propulsion systems have been selected for use on multiple new electric and hybrid-electric aircraft, including the nine-passenger eSTOL model being developed by Electra and Bye Aerospace’s eFlyer family.

In a document published on March 20, the U.S. air safety agency said that special conditions will be required since the characteristics of electric engines are not adequately covered by the requirements of the existing 14 CFR Part 33 rules developed for turbine and reciprocating engines. It has given interested parties until April 19 to comment on its proposals for handling the type certification application that France-based Safran Electrical & Power filed back on Nov. 27, 2020.

The special conditions would require Safran to comply with Part 33 airworthiness standards, apart from those specifically applicable to turbine and reciprocating engines. Additionally, the manufacturer would need “to establish engine operating limits related to the power, torque, speed, and duty cycles” specific to the EngineUs powertrain.

The FAA is proposing additional requirements covering materials, fire protection, durability, cooling, and attachments for engine mounting and accessories. Safran will also have to prove the safety with regard to potential consequences from rotor overspeed, unstable torque, and variances in temperature, vibration, and high-intensity radiated fields. The conditions cover the reliability of electronic control systems and data collection, as well as mitigation for system failures.

Meanwhile, on the other side of the Atlantic Ocean, Safran Electrical & Power is in the advanced stages of work to secure EASA type certification under the European regulator’s existing CS-23 rules. Last year, the business unit of the French aerospace group obtained an EASA design organization approval and began certification testing. During the June 2023 Paris Air Show, the company indicated it was targeting EASA type certification by the end of the first quarter of 2024.

The EngineUs 100 covers a power output range of 100 to 180 kilowatts and a power density of 5 kilowatts per kilogram. It has also been selected for hybrid-electric aircraft being developed by French start-ups VoltAero and Aura Aero, as well as for Volocopter’s next-generation eVTOL aircraft and the E20 eVTOL being developed by China’s TCab Tech.