ASTM F3338-21

Standard Specification for Design of Electric Engines for General Aviation Aircraft

SCOPE
1.1 This specification covers minimum requirements for the design of electric engines.  
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 electric engine and a combustion engine drive a common thruster. This specification may be used for the electric engine aspects with supplemental requirements for the thruster and the combustion engine.  
1.4 Although this specification does not include specific requirements for electric engines that include gearboxes, thrusters, or any energy storage systems, it also does not preclude such capabilities. This specification may be used for the base electric engine aspects of the design, with supplemental requirements for any additional features prepared by the manufacturer and submitted to the Civil Airworthiness Authority for acceptance. 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 should 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 (www.ASTM.org/COMITTEE/F39.htm), which includes CAA website links.  
1.6 When applicable, this specification may be used for electric engines with a fixed-pitch propeller or fan. These configurations may be type-certificated as an electric engine including a thruster. There may be additional requirements not currently included in this specification for this type configuration. In addition, 5.25 is included as a test requirement for the electric engine. That section recognizes that when the electric engine does not have an integral thruster it will need to be tested with a representative load on the drive shaft to ensure the engine’s 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.

General Information

• Status: Published
• Publication Date: 31-Jul-2021
• ICS: 49.050 - Aerospace engines and propulsion systems
• Technical Committee: F39 - Aircraft Systems
• Drafting Committee: F39.05 - Design, Alteration, and Certification of Electric Propulsion Systems

Standards Content (Sample)

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.
Designation: F3338 −21
Standard Specification for
1
Design of Electric Engines for General Aviation Aircraft
This standard is issued under the fixed designation F3338; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Rules”), refer to ASTM Committee F39 webpage
(www.ASTM.org/COMITTEE/F39.htm), which includes CAA
1.1 This specification covers minimum requirements for the
website links.
design of electric engines.
1.6 When applicable, this specification may be used for
1.2 Distributed propulsion is not excluded; however, addi-
electric engines with a fixed-pitch propeller or fan. These
tional requirements will be needed to address the additional
configurations may be type-certificated as an electric engine
issues that distributed propulsion can create. Some of those
including a thruster. There may be additional requirements not
issuesmayinclude:useofacommonmotorcontroller/inverter,
currently included in this specification for this type configura-
segregated electric harnesses, cooling systems, electric power
tion. In addition, 5.25 is included as a test requirement for the
supplies, and others.
electric engine. That section recognizes that when the electric
1.3 This specification does not address all of the require-
engine does not have an integral thruster it will need to be
ments that may be necessary for possible hybrid configurations
testedwitharepresentativeloadonthedriveshafttoensurethe
where an electric engine and a combustion engine drive a
engine’s ability to operate properly with static and dynamic
common thruster. This specification may be used for the
loads.
electric engine aspects with supplemental requirements for the
1.7 The values stated in inch-pound units are to be regarded
thruster and the combustion engine.
as standard. The values given in parentheses are mathematical
1.4 Although this specification does not include specific
conversions to SI units that are provided for information only
requirements for electric engines that include gearboxes,
and are not considered standard.
thrusters, or any energy storage systems, it also does not
1.8 This standard does not purport to address all of the
preclude such capabilities. This specification may be used for
safety concerns, if any, associated with its use. It is the
the base electric engine aspects of the design, with supplemen-
responsibility of the user of this standard to establish appro-
tal requirements for any additional features prepared by the
priate safety, health, and environmental practices and deter-
manufacturer and submitted to the CivilAirworthinessAuthor-
mine the applicability of regulatory limitations prior to use.
ity for acceptance. This version of this ASTM specification
1.9 This international standard was developed in accor-
also does not address all of the requirements necessary for
dance with internationally recognized principles on standard-
configurations of motor driven ducted-fans. It is anticipated
ization established in the Decision on Principles for the
that the fan would be subject to parts of 14 CFR 33 or CS-E
Development of International Standards, Guides and Recom-
and/or 14 CFR 35 or CS-P, or equivalent, in particular
mendations issued by the World Trade Organization Technical
blade-off and bird strike. These would be conducted on the fan
Barriers to Trade (TBT) Committee.
as a unit (including motor) rather than on motor or fan alone.
2. Referenced Documents
1.5 The applicant for a design approval should seek the
individual guidance of their respective civil aviation authority
2.1 ASTM Standard:
(CAA) body concerning the use of this specification as part of
F3060 Terminology for Aircraft
2
a certification plan. For information on which CAAregulatory
2.2 Code of Federal Regulations:
bodies have accepted this specification (in whole or in part) as
14 CFR 33 Airworthiness Standards: Aircraft Engines
a means of compliance to their general aviation aircraft
14 CFR 35 Airworthiness Standards: Propellers
3
airworthiness regulations (hereinafter referred to as “the
2.3 EASA Standards:
CS-E Engines
CS-P Propellers
1
ThisspecificationisunderthejurisdictionofASTMCommitteeF39onAircraft
Systems and is the direct responsibility of Subcommittee F39.05 on Design,
2
Alteration, and Certification of Electric Propulsion Systems. Available from U.S. Government Publishing Office (GPO), 732 N. Capitol St.,
Current edition approved Aug. 1, 2021. Published August 2021. Originally NW,
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: F3338 − 20 F3338 − 21
Standard Specification for
Design of Electric Propulsion Units Engines for General
1
Aviation Aircraft
This standard is issued under the fixed designation F3338; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This specification covers minimum requirements for the design of Electric Propulsion Units (EPU).electric engines.
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 electric engine and a combustion engine drive a common thruster. This specification may be used for the EPU electric engine
aspects with supplemental requirements for the thruster and the combustion engine.
1.4 Although this specification does not include specific requirements for EPUs electric engines that include gearboxes, thrusters,
or any energy storage systems, it also does not preclude such capabilities. This specification may be used for the base EPU electric
engine aspects of the design, with supplemental requirements for any additional features prepared by the manufacturer and
submitted to the Civil Airworthiness Authority for acceptance. 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 should 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 (www.ASTM.org/COMITTEE/F39.htm), which
includes CAA website links.
1.6 When applicable, this specification may be used for EPUs electric engines with a fixed-pitch propeller or fan. These
configurations may be type-certificated as an EPU electric engine including a thruster. There may be additional requirements not
currently included in this specification for this type configuration. In addition, 5.25 is included as a test requirement for the EPU.
electric engine. That section recognizes that when the EPU electric engine does not have an integral thruster it will need to be tested
with a representative load on the drive shaft to assure EPU ensure the engine’s ability to operate properly with static and dynamic
loads.
1
This specification is under the jurisdiction of ASTM Committee F39 on Aircraft Systems and is the direct responsibility of Subcommittee F39.05 on Design, Alteration,
and Certification of Electric Propulsion Systems.
Current edition approved Sept. 1, 2020Aug. 1, 2021. Published October 2020August 2021. Originally approved in 2018. Last previous edition approved in 20182020 as
F3338–18.–20. DOI: 10.1520/F3338-20.10.1520/F3338-21.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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F3338 − 21
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 recognize
...