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The Future Flight Standards Hub is designed to accelerate the development of Future Flight demonstrators and wider industry innovation based on emerging best practice, knowledge sharing, and standards support.

  • BSI Flex 1903 v2:2024-06 community preview

    This is an interactive version 2 of BSI Flex 1903. The aim of the standard is to create a lexicon of standard terms and acronyms used in this sector. Please note, content is still undergoing internal review and there may be minor changes at full publication.

    We welcome your engagement and comments on this version to help inform the development of the standard. We would also welcome general feedback including what terms could be considered for future versions and these can be made through our dedicated feedback page .

electric/hybrid propulsion system (EHPS)



  • Definition

    combination of technologies that involve the use of electric motors or a combination of electric motors and combustion engines to form a system which produces lift, thrust or power for flight


    NOTE 1 An EHPS might include but is not limited to:
    a) electric motors;
    b) turbine engines;
    c) piston engines;

    d) generators;
    e) electrical power generation;
    f) distribution;
    g) wirings;
    h) propulsion batteries;
    i) integrated fans;
    j) cooling systems;
    k) controllers;
    l) power management system.

    NOTE 2 A propulsion battery associated to an electric motor providing power to a fan, rotor or propeller is considered to be part of an EHPS. A propulsion battery alone (without any associated electric engine) is not considered to be part of an EHPS.

    NOTE 3 All-electric aircraft systems use batteries as the only source of propulsion power.

    NOTE 4 Hybrid systems include, but are not limited to, parallel hybrid, series hybrid and series/parallel partial hybrid configurations.

    [SOURCE: EASA, Special Condition, SC E-19, Electric / hybrid propulsion system, modified – “the use of electric motors and/or combustion engines” replaced by “the use of electric motors or a combination of electric motors and combustion engines”] [21]

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