ASTM F3338 - 18

    Standard Specification for Design of Electric Propulsion Units for General Aviation Aircraft

    Active Standard ASTM F3338 | Developed by Subcommittee: F39.05

    Book of Standards Volume: 15.09

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    1. Scope

    1.1 This specification covers minimum requirements for the design of Electric Propulsion Units (EPU).

    1.2 Distributed propulsion is not excluded; however, additional requirements will be needed to address the additional issues that distributed propulsion can create. Some of those issues may include: use of a common motor controller/inverter, segregated electric harnesses, cooling systems, electric power supplies, and others.

    1.3 This specification does not address all of the requirements that may be necessary for possible hybrid configurations where an EPU and a combustion engine drive a common thruster. This specification may be used for the EPU aspects with supplemental requirements for the thruster and the combustion engine.

    1.4 This specification does not include the requirements for EPUs that include gearboxes, thrusters, liquid cooling/lubrication, or any energy storage systems. This specification may be used for the EPU base aspects with supplemental requirements for these additional features. This version of this ASTM specification also does not address all of the requirements necessary for configurations of motor driven ducted-fans. It is anticipated that the fan would be subject to parts of 14 CFR 33 or CS-E and/or 14 CFR 35 or CS-P, or equivalent, in particular blade-off and bird strike. These would be conducted on the fan as a unit (including motor) rather than on motor or fan alone.

    1.5 The applicant for a design approval shall seek the individual guidance of their respective civil aviation authority (CAA) body concerning the use of this specification as part of a certification plan. For information on which CAA regulatory bodies have accepted this specification (in whole or in part) as a means of compliance to their general aviation aircraft airworthiness regulations (hereinafter referred to as “the Rules”), refer to ASTM Committee F39 webpage (, which includes CAA website links.

    1.6 When applicable, this specification may be used for EPUs with a fixed-pitch propeller or fan. These configurations may be type-certificated as an EPU including a thruster. There may be additional requirements not currently included in this specification for this type configuration. In addition, 5.24 is included as a test requirement for the EPU. That section recognizes that the EPU may not have an integral thruster but it must be tested with a representative load on the drive shaft to assure EPU ability to operate properly with static and dynamic loads.

    1.7 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.

    1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

    1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    IEC Standards

    IEC 60034-1 Rotating electrical machines Part 1 Rating and performance

    IEC 60349-4 Electric traction Rotating electric machines for rail and road vehicles Part 4: Permanent magnet synchronous electrical machines connected to an electronic converter

    Code of Federal Regulations

    14 CFR 33 Airworthiness Standards: Aircraft Engines

    14 CFR 35 Airworthiness Standards: Propellers

    EASA Standards



    ICS Code

    ICS Number Code 49.050 (Aerospace engines and propulsion systems)

    UNSPSC Code

    UNSPSC Code 25202500(Aircraft equipment)

    Referencing This Standard
    Link Here
    Link to Active (This link will always route to the current Active version of the standard.)

    DOI: 10.1520/F3338-18

    Citation Format

    ASTM F3338-18, Standard Specification for Design of Electric Propulsion Units for General Aviation Aircraft, ASTM International, West Conshohocken, PA, 2018,

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