ASTM F3239-22a
(Specification)Standard Specification for Aircraft Electric Propulsion Systems
Standard Specification for Aircraft Electric Propulsion Systems
SCOPE
1.1 This specification addresses airworthiness requirements for the design and installation of electric propulsion systems for aeroplanes. Hybrid-electric propulsion systems are addressed implicitly unless explicitly stated otherwise. This specification was written with the focus on electric propulsion systems with conventional system layout, propulsion characteristics, and operation. The content may be more broadly applicable; it is the responsibility of the applicant to substantiate broader applicability as a specific means of compliance.
1.2 An applicant intending to propose this information as Means of Compliance for a design approval must seek guidance from their respective oversight authority (for example, published guidance from applicable CAAs) concerning the acceptable use and application thereof. For information on which oversight authorities have accepted this standard (in whole or in part) as an acceptable Means of Compliance to their regulatory requirements (hereinafter “the Rules”), refer to the ASTM Committee F44 web page (www.astm.org/COMMITTEE/F44.htm). Annex A1 maps the Means of Compliance described in this specification to EASA CS-23, amendment 5, or later, and FAA 14 CFR Part 23, amendment 64, or later.
1.3 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.
1.4 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-Aug-2022
- Technical Committee
- F44 - General Aviation Aircraft
- Drafting Committee
- F44.40 - Powerplant
Relations
- Effective Date
- 01-Mar-2024
- Effective Date
- 01-Oct-2023
- Effective Date
- 01-Oct-2023
- Effective Date
- 01-Jun-2020
- Effective Date
- 01-Jan-2020
- Effective Date
- 01-Nov-2019
- Effective Date
- 01-Nov-2019
- Effective Date
- 01-Jun-2019
- Effective Date
- 01-Feb-2019
- Effective Date
- 01-Nov-2018
- Refers
ASTM F3063/F3063M-18a - Standard Specification for Aircraft Fuel and Energy Storage and Delivery - Effective Date
- 01-Jul-2018
- Effective Date
- 15-May-2018
- Effective Date
- 01-Jan-2018
- Refers
ASTM F3063/F3063M-18 - Standard Specification for Aircraft Fuel and Energy Storage and Delivery - Effective Date
- 01-Jan-2018
- Effective Date
- 01-Jan-2018
Overview
ASTM F3239-22a - Standard Specification for Aircraft Electric Propulsion Systems provides comprehensive requirements for the airworthiness design and installation of electric propulsion systems in aeroplanes. Developed by ASTM International, this standard ensures the safe integration of electric and hybrid-electric propulsion while supporting compliance with major aviation authorities such as the FAA and EASA. Emphasis is placed on conventional system layout and operation, but broader applicability can be established by applicants as needed.
This specification forms a key part of regulatory compliance for electric aircraft, mapping its Means of Compliance to EASA CS-23 (amendment 5 or later) and FAA 14 CFR Part 23 (amendment 64 or later) requirements. Manufacturers, designers, and regulators rely on these requirements to ensure new propulsion technologies achieve suitable levels of safety, reliability, and operational efficiency.
Key Topics
- Airworthiness Requirements: Defines criteria for the design, installation, and integration of electric propulsion systems, covering components such as electric engines, energy storage, distribution, and relevant supporting systems.
- Applicable Systems: Applies primarily to fully electric propulsion systems, but also accommodates hybrid-electric solutions unless specifically excluded.
- Component-Level Requirements:
- Electric engines, including motors, controllers, and associated hardware
- Energy distribution systems equivalent to traditional fuel systems
- Energy storage systems (batteries, fuel cells, capacitors), ensuring adequate endurance and protection
- System Safety and Hazard Mitigation:
- Compartment isolation, ventilation, and fire protection for energy storage
- Lightning and ice protection for propulsion-related installations
- Means to monitor and control system status, including energy quantity, failure isolation, and operational characteristics
- Means of Compliance: Specifies that applicants proposing this standard as a Means of Compliance must consult relevant aviation authorities; includes annexes showing detailed mapping to regulatory requirements.
- Usable Energy Requirements: The combined energy storage must provide enough power for at least 30 minutes of maximum continuous operation.
Applications
The ASTM F3239-22a standard is crucial for organizations involved in the development and certification of:
- Electric Aircraft: Ensures that the entire propulsion architecture meets rigorous airworthiness standards necessary for safe flight.
- Hybrid-Electric Propulsion Systems: Offers guidance for integrating electrical and traditional power sources in a compliant fashion.
- Aircraft Component Manufacturing: Provides requirements for manufacturers of motors, batteries, control systems, and power distribution hardware destined for aerospace use.
- System Integration: Used by engineers and designers integrating electric propulsion with other aircraft systems such as propeller installations, cooling, fire detection, and electrical control systems.
- Regulatory Certification: Serves as an accepted means of compliance with EASA CS-23 and FAA Part 23 rules, streamlining the route to regulatory approval for new electric or hybrid aircraft designs.
Related Standards
The following standards are referenced in support of, or as complementary documents to, ASTM F3239-22a:
- ASTM F3060: Terminology for Aircraft
- ASTM F3061/F3061M: Specification for Systems and Equipment in Aircraft
- ASTM F3062/F3062M: Specification for Aircraft Powerplant Installation
- ASTM F3063/F3063M: Specification for Aircraft Fuel Storage and Delivery
- ASTM F3064/F3064M: Specification for Aircraft Powerplant Control, Operation, and Indication
- ASTM F3065/F3065M: Specification for Aircraft Propeller System Installation
- ASTM F3066/F3066M: Specification for Aircraft Powerplant Installation Hazard Mitigation
- ASTM F3114/F3114M: Specification for Structures
- ASTM F3116/F3116M: Specification for Design Loads and Conditions
- ASTM F3120/F3120M: Specification for Ice Protection for General Aviation Aircraft
- ASTM F3316/F3316M: Specification for Electrical Systems for Aircraft with Electric or Hybrid-Electric Propulsion
- ASTM F3338: Specification for Design of Electric Engines for General Aviation Aircraft
Additionally, it is relevant to cross-reference:
- EASA CS-23: Airworthiness standards for normal, utility, aerobatic, and commuter aeroplanes
- 14 CFR Part 23: FAA Airworthiness Standards for Normal Category Airplanes
Keywords: electric aircraft, electric propulsion, hybrid-electric propulsion, aircraft energy storage, airworthiness, EASA CS-23, FAA Part 23, ASTM International
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Frequently Asked Questions
ASTM F3239-22a is a technical specification published by ASTM International. Its full title is "Standard Specification for Aircraft Electric Propulsion Systems". This standard covers: SCOPE 1.1 This specification addresses airworthiness requirements for the design and installation of electric propulsion systems for aeroplanes. Hybrid-electric propulsion systems are addressed implicitly unless explicitly stated otherwise. This specification was written with the focus on electric propulsion systems with conventional system layout, propulsion characteristics, and operation. The content may be more broadly applicable; it is the responsibility of the applicant to substantiate broader applicability as a specific means of compliance. 1.2 An applicant intending to propose this information as Means of Compliance for a design approval must seek guidance from their respective oversight authority (for example, published guidance from applicable CAAs) concerning the acceptable use and application thereof. For information on which oversight authorities have accepted this standard (in whole or in part) as an acceptable Means of Compliance to their regulatory requirements (hereinafter “the Rules”), refer to the ASTM Committee F44 web page (www.astm.org/COMMITTEE/F44.htm). Annex A1 maps the Means of Compliance described in this specification to EASA CS-23, amendment 5, or later, and FAA 14 CFR Part 23, amendment 64, or later. 1.3 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. 1.4 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.
SCOPE 1.1 This specification addresses airworthiness requirements for the design and installation of electric propulsion systems for aeroplanes. Hybrid-electric propulsion systems are addressed implicitly unless explicitly stated otherwise. This specification was written with the focus on electric propulsion systems with conventional system layout, propulsion characteristics, and operation. The content may be more broadly applicable; it is the responsibility of the applicant to substantiate broader applicability as a specific means of compliance. 1.2 An applicant intending to propose this information as Means of Compliance for a design approval must seek guidance from their respective oversight authority (for example, published guidance from applicable CAAs) concerning the acceptable use and application thereof. For information on which oversight authorities have accepted this standard (in whole or in part) as an acceptable Means of Compliance to their regulatory requirements (hereinafter “the Rules”), refer to the ASTM Committee F44 web page (www.astm.org/COMMITTEE/F44.htm). Annex A1 maps the Means of Compliance described in this specification to EASA CS-23, amendment 5, or later, and FAA 14 CFR Part 23, amendment 64, or later. 1.3 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. 1.4 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.
ASTM F3239-22a is classified under the following ICS (International Classification for Standards) categories: 49.050 - Aerospace engines and propulsion systems; 49.060 - Aerospace electric equipment and systems. The ICS classification helps identify the subject area and facilitates finding related standards.
ASTM F3239-22a has the following relationships with other standards: It is inter standard links to ASTM F3064/F3064M-24, ASTM F3061/F3061M-23b, ASTM F3116/F3116M-23a, ASTM F3062/F3062M-20, ASTM F3060-20, ASTM F3061/F3061M-19a, ASTM F3316/F3316M-19, ASTM F3061/F3061M-19, ASTM F3062/F3062M-19, ASTM F3116/F3116M-18, ASTM F3063/F3063M-18a, ASTM F3316/F3316M-18, ASTM F3062/F3062M-18, ASTM F3063/F3063M-18, ASTM F3065/F3065M-18. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
ASTM F3239-22a is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
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: F3239 −22a
Standard Specification for
Aircraft Electric Propulsion Systems
This standard is issued under the fixed designation F3239; 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 2. Referenced Documents
2.1 ASTM Standards:
1.1 This specification addresses airworthiness requirements
F3060 Terminology for Aircraft
for the design and installation of electric propulsion systems
F3061/F3061M Specification for Systems and Equipment in
for aeroplanes. Hybrid-electric propulsion systems are ad-
Aircraft
dressed implicitly unless explicitly stated otherwise. This
F3062/F3062M Specification forAircraft Powerplant Instal-
specification was written with the focus on electric propulsion
lation
systems with conventional system layout, propulsion
F3063/F3063M Specification for Aircraft Fuel Storage and
characteristics, and operation. The content may be more
Delivery
broadly applicable; it is the responsibility of the applicant to
F3064/F3064M Specification for Aircraft Powerplant
substantiate broader applicability as a specific means of com-
Control, Operation, and Indication
pliance.
F3065/F3065M Specification for Aircraft Propeller System
1.2 An applicant intending to propose this information as
Installation
Means of Compliance for a design approval must seek guid-
F3066/F3066M Specification forAircraft Powerplant Instal-
ance from their respective oversight authority (for example,
lation Hazard Mitigation
published guidance from applicable CAAs) concerning the
F3114/F3114M Specification for Structures
acceptable use and application thereof. For information on
F3116/F3116M Specification for Design Loads and Condi-
which oversight authorities have accepted this standard (in
tions
whole or in part) as an acceptable Means of Compliance to
F3120/F3120M Specification for Ice Protection for General
their regulatory requirements (hereinafter “the Rules”), refer to
Aviation Aircraft
the ASTM Committee F44 web page (www.astm.org/
F3316/F3316M Specification for Electrical Systems forAir-
COMMITTEE/F44.htm). Annex A1 maps the Means of Com-
craft with Electric or Hybrid-Electric Propulsion
pliance described in this specification to EASACS-23, amend- F3338 Specification for Design of Electric Engines for
ment 5, or later, and FAA 14 CFR Part 23, amendment 64, or General Aviation Aircraft
later.
2.2 EASA Standard:
CS-23 Normal, Utility,Aerobatic and CommuterAeroplanes
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the 2.3 FAA Standard and Advisory Circular:
14 CFR Part 23 Airworthiness Standards: Normal Category
responsibility of the user of this standard to establish appro-
Airplanes
priate safety, health, and environmental practices and deter-
AC 23-16 Powerplant Guide for Certification of Part 23
mine the applicability of regulatory limitations prior to use.
Airplanes
1.4 This international standard was developed in accor-
dance with internationally recognized principles on standard-
3. Terminology
ization established in the Decision on Principles for the
3.1 The following is a selection of relevant terms. See
Development of International Standards, Guides and Recom-
Terminology F3060 for more definitions and abbreviations.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
ThisspecificationisunderthejurisdictionofASTMCommitteeF44onGeneral Standards volume information, refer to the standard’s Document Summary page on
Aviation Aircraft and is the direct responsibility of Subcommittee F44.40 on the ASTM website.
Powerplant. Available from European Union Aviation Safety Agency (EASA), Konrad-
Current edition approved Sept. 1, 2022. Published September 2022. Originally Adenauer-Ufer 3, D-50668 Cologne, Germany, https://www.easa.europa.eu.
approved in 2018. Last previous edition approved in 2022 as F3239–22. DOI: Available from Federal Aviation Administration (FAA), 800 Independence
10.1520/F3239-22A. Ave., SW, Washington, DC 20591, http://www.faa.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3239 − 22a
3.2 Definitions: 5.1.3 The combined usable energy capacity of all energy
3.2.1 capacity, n—total amount between minimum and storage systems shall be enough to maintain maximum con-
maximum condition (for example, empty and full). tinuous power of the electric engine for a minimum of 30
minutes. For hybrid systems this may be accomplished with
3.2.2 electric engine, n—a type of aircraft engine that
any combination of generation and energy storage.
converts electric power into mechanical power or thrust used
for propulsion, including those components necessary for
NOTE 1—Operational rules for which the aeroplane is intended to be
proper control and functioning.
used may require greater endurance.
3.2.2.1 Discussion—In the context of this specification, the
5.2 Independence:
minimum essential components of an electric engine are an
5.2.1 For aeroplanes with multiple electric engines, the
electric motor and its associated motor controller(s),
energy distribution system shall be designed so that, in at least
disconnect(s), wiring, and sensor(s). Other components and
one system configuration, the failure of any one component
accessories necessary for proper control and function are
will not result in the loss of power of more than one electric
typically considered part of the engine; for example: inverters,
engine or require immediate action by the pilot to prevent the
liquid cooling components, liquid lubrication components,
loss of power of more than one electric engine.
thrusters, etc.
NOTE2—RefertoAC23-16forguidanceontheindependenceofenergy
3.2.3 electric propulsion system (EPS), n—the installation
distribution systems.
of one or more electric engines including each component that
is necessary for propulsion or affects the propulsive safety. 5.3 Energy Storage System:
5.3.1 General:
3.2.4 energy distribution system, n—a system that provides
energy for propulsion from the energy storage systems to the 5.3.1.1 Each energy storage system shall meet the require-
engines. ments of an accepted specification appropriate to the applica-
3.2.4.1 Discussion—The energy distribution system is con- tion.
sidered equivalent to the fuel system on liquid hydrocarbon
5.3.1.2 Each energy storage system shall be installed in
based powerplants.
accordance with the applicable installation instructions.
3.2.5 energy storage system (ESS), n—a source (component 5.3.1.3 Each energy storage system shall be designed to
or system) that stores and provides energy that can be drawn safelydelivertherequiredpowerundertheconditionsspecified
upon for propulsion. in 5.1.2 when drawn upon.
3.2.5.1 Discussion—Typical energy storage systems include
5.3.2 Installation:
but are not limited to batteries, fuel cell systems or capacitors
5.3.2.1 Each energy storage system shall be supported to
and their integrated management systems, if installed. The
withstand the vibration and inertia loads to which it may be
energy storage system is considered equivalent to a fuel tank
subjected in operation.
on liquid hydrocarbon based powerplants.
5.3.2.2 Each energy storage system shall have access pro-
3.2.6 quantity, n—amount available at the time of measure-
visions for maintenance.
ment.
5.3.2.3 Design precautions shall be taken to minimize the
3.2.7 usable energy capacity, n—minimum capacity of an hazards to the aircraft in the event of a fire or sudden discharge
energy storage system between the defined fully charged and which could result in damage to components, structure, or
the minimum charge state which can be drawn upon at any rate flight controls near the storage area.
up to maximum rated power of this energy storage system
5.3.2.4 The energy storage system installation shall protect
under any likely operating condition.
the occupants and the critical airframe and systems from a
single cell thermal runaway.
4. Powerplant Installation
5.3.3 Compartments:
4.1 General:
5.3.3.1 Each energy storage system shall be ventilated and
4.1.1 Each powerplant installation shall meet the applicable
drained as necessary to prevent accumulation of hazardous,
requirements of Specification F3062/F3062M.
flammable, or corrosive fluids or vapors.
4.1.2 Each propeller system shall meet the applicable re-
5.3.3.2 Each energy storage system shall be isolated from
quirements of Specification F3065/F3065M.
personnel compartments by an enclosure that is vented and
4.1.3 Each electric engine shall meet the technical require-
drained to the exterior of the aeroplane.
ments of Specification F3338.
5.3.3.3 Any enclosure required by 5.3.3.2 shall sustain any
5. Energy Distribution Systems
personnel compartment pressurization loads without perma-
nent deformation or failure under the conditions defined in
5.1 General:
Specifications F3116/F3116M and F3114/F3114M.
5.1.1 Each energy distribution system shall meet the appli-
5.3.3.4 For energy storage systems in compartments adja-
cable requirements of Specification F3063/F3063M and
F3316/F3316M. cent to fire zones there shall be sufficient clearance or insula-
5.1.2 Each energy distribution system shall safely provide tion between the compartment and the firewall to prevent
sufficient power to each electric engine under the most critical ignition or malfunction of the energy storage system as a result
operating conditions. of fire in the fire zone.
F3239 − 22a
5.3.4 Energy Capacity: limited energy dumping capability, or both, during propeller
5.3.4.1 The usable energy capacity for each energy storage windmilling and reversing operation.
system shall be established. 6.3.2 Cooling Test Requirements:
5.3.4.2 The available remaining energy quantity informa- 6.3.2.1 For showing compliance with the general cooling
tion shall be provided. requirements of Specification F3064/F3064M the aeroplane
5.3.5 Charging System: shall be flown in the configurations, at the speeds, and
5.3.5.1 The charging connection and system shall be de- followingtheproceduresrecommendedintheAeroplaneFlight
signed to minimize hazards to personnel. Manual that correspond to the applicable performance require-
5.3.5.2 The charging connection shall be designed to ensure ments that are critical to cooling.
correct connection of the charging connector. 6.3.3 Starting and Stopping:
5.3.5.3 The charging system shall be designed to protect the 6.3.3.1 The design of the installation shall be such that risk
aeroplane from a charging source with incorrect voltage of fire or mechanical damage to the electric engine or the
including high voltage, low voltage, incorrect polarity, effects aeroplane, because of starting the electric engine in any
of shorting, and type of current (AC/DC). conditions in which starting is to be permitted, is reduced to a
5.3.6 Pilot-replaceable Energy Storage Systems: minimum. Any techniques and associated limitations shall be
5.3.6.1 Each energy storage system location where electri- established and included in the Aeroplane Flight Manual,
cal components can be replaced shall be marked. approved manual material, or applicable operating placards.
5.3.6.2 Design precautions shall be taken to prevent incor- 6.3.3.2 There shall be a means for stopping the rotation of
rect installation of components when replaced in operation. any electric engine or component, if continued rotation would
cause a hazard to the aeroplane.
6. Control and Indication
6.3.3.3 If hydraulic propeller feathering systems are used
for stopping the electric engine, the hydraulic feathering lines
6.1 General:
or hoses shall be fire resistant under the operating conditions
6.1.1 Each powerplant installation shall meet the applicable
expected during feathering.
requirements of Specification F3064/F3064M.
6.3.3.4 Restart Envelope—An altitude and airspeed enve-
6.1.2 For any energy storage system that should not be
lope shall be established for the aeroplane for inflight engine
depleted in normal operation, there shall be a separate indica-
restarting, and each installed electric engine shall have a restart
tiontotheflightcrewwhenlessthanapproximately30minutes
capability within that envelope.
ofusableenergyquantityor50 %oftheusableenergycapacity
6.3.3.5 Restart Capability—No unsafe condition may arise
remains in the energy storage system, whichever is less.
fromre-engaginganyelectricengineafterashutdowneitheron
6.2 Controls:
ground or in flight.
6.2.1 There shall be a means to provide separate power
6.3.4 Powerplant Limitations:
control for each electric engine, unless it can be shown that
6.3.4.1 The powerplant limitations shall be established so
multiple electric engines operated by a single control will not
that they do not exceed the corresponding limits of the electric
prevent the isolation of a failed engine, and the control of the
engines,theenergystoragesystems,andassociatedequipment.
remaining engines to ensure continued, safe flight and landing.
6.2.2 Shutoff Controls:
7. Hazard Mitigation
6.2.2.1 There shall be an independent, simple, and reliable
7.1 General:
means to disconnect each energy storage system.
7.1.1 Each powerplant installation shall meet the applicable
6.2.2.2 If the electric engine or energy storage system is
requirements of Specification F3066/F3066M.
installed in a fire zone, there shall be a means to allow
7.1.1.1 For compliance with the engine isolation require-
appropriate flight crew members to rapidly shut off, in flight,
ments of Specification F3066/F3066M “an energy storage
the energy supply to the electric engines and energy storage
system, if only one energy storage system is installed” is
system individually.
considered “a fuel tank, if only one fuel tank is installed.”
6.2.2.3 Noshutoffmeansmaybeonthefirezonesideofany
7.2 High Energy Rotors:
firewall.
7.2.1 Each high energy rotor shall meet the applicable
6.2.2.4 There shall be a means to guard against inadvertent
requirements for high energy rotors of Specification F3061/
operation of each shutoff means.
F3061M.
6.2.2.5 There shall be a means to allow appropriate flight
crew members to reopen the shutoff means rapidly after it has
NOTE 3—Depending on the specific design, electric motors may qualify
been closed.
as high energy rotors.
6.3 Powerplant Operational Characteristics and Installa- 7.3 Fire Protection:
tion: 7.3.1 Designated Fire Zones:
6.3.1 General:
7.3.1.1 The electric engine or ESS section is a designated
6.3.1.1 Electric propulsion systems shall have no adverse fire zone, if a fire hazard exists.
characteristics during normal or emergency operation within 7.3.2 Fire Detection:
the operating limitations. This investigation shall consider the 7.3.2.1 There shall be means that ensure the prompt detec-
results of inadvertent energy storage system overcharging or tion of a fire in each fire zone that is not visible to the crew.
F3239 − 22a
7.3.3 Lightning Protection: 7.4.1 Each air inlet of the powerplant installation shall be
protected
...
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: F3239 − 22 F3239 − 22a
Standard Specification for
Aircraft Electric Propulsion Systems
This standard is issued under the fixed designation F3239; 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 addresses airworthiness requirements for the design and installation of electric propulsion systems for
aeroplanes. Hybrid-electric propulsion systems are addressed implicitly unless explicitly stated otherwise. This specification was
written with the focus on electric propulsion systems with conventional system layout, propulsion characteristics, and operation.
The content may be more broadly applicable; it is the responsibility of the applicant to substantiate broader applicability as a
specific means of compliance.
1.2 An applicant intending to propose this information as Means of Compliance for a design approval must seek guidance from
their respective oversight authority (for example, published guidance from applicable CAAs) concerning the acceptable use and
application thereof. For information on which oversight authorities have accepted this standard (in whole or in part) as an
acceptable Means of Compliance to their regulatory requirements (hereinafter “the Rules”), refer to the ASTM Committee F44 web
page (www.astm.org/COMMITTEE/F44.htm). Annex A1 maps the Means of Compliance described in this specification to EASA
CS-23, amendment 5, or later, and FAA 14 CFR Part 23, amendment 64, or later.
1.3 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.
1.4 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
2.1 ASTM Standards:
F3060 Terminology for Aircraft
F3061/F3061M Specification for Systems and Equipment in Aircraft
F3062/F3062M Specification for Aircraft Powerplant Installation
F3063/F3063M Specification for Aircraft Fuel Storage and Delivery
F3064/F3064M Specification for Aircraft Powerplant Control, Operation, and Indication
F3065/F3065M Specification for Aircraft Propeller System Installation
F3066/F3066M Specification for Aircraft Powerplant Installation Hazard Mitigation
F3114/F3114M Specification for Structures
F3116/F3116M Specification for Design Loads and Conditions
F3120/F3120M Specification for Ice Protection for General Aviation Aircraft
This specification is under the jurisdiction of ASTM Committee F44 on General Aviation Aircraft and is the direct responsibility of Subcommittee F44.40 on Powerplant.
Current edition approved April 1, 2022Sept. 1, 2022. Published April 2022September 2022. Originally approved in 2018. Last previous edition approved in 20192022 as
F3239–19.–22. DOI: 10.1520/F3239-22.10.1520/F3239-22A.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3239 − 22a
F3316/F3316M Specification for Electrical Systems for Aircraft with Electric or Hybrid-Electric Propulsion
F3338 Specification for Design of Electric Engines for General Aviation Aircraft
2.2 EASA Standard:
CS-23 Normal, Utility, Aerobatic and Commuter Aeroplanes
2.3 FAA Standard and Advisory Circular:
14 CFR Part 23 Airworthiness Standards: Normal Category Airplanes
AC 23-16 Powerplant Guide for Certification of Part 23 Airplanes
3. Terminology
3.1 The following is a selection of relevant terms. See Terminology F3060 for more definitions and abbreviations.
3.2 Definitions:
3.2.1 capacity, n—total amount between minimum and maximum condition (for example, empty and full).
3.2.2 electric engine, n—a type of aircraft engine that converts electric power into mechanical power or thrust used for propulsion,
including those components necessary for proper control and functioning.
3.2.2.1 Discussion—
In the context of this specification, the minimum essential components of an electric engine are an electric motor and its associated
motor controller(s), disconnect(s), wiring, and sensor(s). Other components and accessories necessary for proper control and
function are typically considered part of the engine; for example: inverters, liquid cooling components, liquid lubrication
components, thrusters, etc.
3.2.3 electric propulsion system (EPS), n—the installation of one or more electric engines including each component that is
necessary for propulsion or affects the propulsive safety.
3.2.4 energy distribution system, n—a system that provides energy for propulsion from the energy storage systems to the engines.
3.2.4.1 Discussion—
The energy distribution system is considered equivalent to the fuel system on liquid hydrocarbon based powerplants.
3.2.5 energy storage system (ESS), n—a source (component or system) that stores and provides energy that can be drawn upon
for propulsion.
3.2.5.1 Discussion—
Typical energy storage systems include but are not limited to batteries, fuel cell systems or capacitors and their integrated
management systems, if installed. The energy storage system is considered equivalent to a fuel tank on liquid hydrocarbon based
powerplants.
3.2.6 quantity, n—amount available at the time of measurement.
3.2.7 usable energy capacity, n—minimum capacity of an energy storage system between the defined fully charged and the
minimum charge state which can be drawn upon at any rate up to maximum rated power of this energy storage system under any
likely operating condition.
4. Powerplant Installation
4.1 General:
4.1.1 Each powerplant installation shall meet the applicable requirements of Specification F3062/F3062M.
4.1.2 Each propeller system shall meet the applicable requirements of Specification F3065/F3065M.
4.1.3 Each electric engine shall meet the technical requirements of Specification F3338.
Available from European Union Aviation Safety Agency (EASA), Konrad-Adenauer-Ufer 3, D-50668 Cologne, Germany, https://www.easa.europa.eu.
Available from Federal Aviation Administration (FAA), 800 Independence Ave., SW, Washington, DC 20591, http://www.faa.gov.
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5. Energy Distribution Systems
5.1 General:
5.1.1 Each energy distribution system shall meet the applicable requirements of Specification F3063/F3063M and F3316/F3316M.
5.1.2 Each energy distribution system shall safely provide sufficient power to each electric engine under the most critical operating
conditions.
5.1.3 The combined usable energy capacity of all energy storage systems shall be enough to maintain maximum continuous power
of the electric engine for a minimum of 30 minutes. For hybrid systems this may be accomplished with any combination of
generation and energy storage.
NOTE 1—Operational rules for which the aeroplane is intended to be used may require greater endurance.
5.2 Independence:
5.2.1 For aeroplanes with multiple electric engines, the energy distribution system shall be designed so that, in at least one system
configuration, the failure of any one component will not result in the loss of power of more than one electric engine or require
immediate action by the pilot to prevent the loss of power of more than one electric engine.
NOTE 2—Refer to AC23-16 for guidance on the independence of energy distribution systems.
5.3 Energy Storage System:
5.3.1 General:
5.3.1.1 Each energy storage system shall meet the requirements of an accepted specification appropriate to the application.
5.3.1.2 Each energy storage system shall be installed in accordance with the applicable installation instructions.
5.3.1.3 Each energy storage system shall be designed to safely deliver the required power under the conditions specified in 5.1.2
when drawn upon.
5.3.2 Installation:
5.3.2.1 Each energy storage system shall be supported to withstand the vibration and inertia loads to which it may be subjected
in operation.
5.3.2.2 Each energy storage system shall have access provisions for maintenance.
5.3.2.3 Design precautions shall be taken to minimize the hazards to the aircraft in the event of a fire or sudden discharge which
could result in damage to components, structure, or flight controls near the storage area.
5.3.2.4 The energy storage system installation shall protect the occupants and the critical airframe and systems from a single cell
thermal runaway.
5.3.3 Compartments:
5.3.3.1 Each energy storage system shall be ventilated and drained as necessary to prevent accumulation of hazardous, flammable,
or corrosive fluids or vapors.
5.3.3.2 Each energy storage system shall be isolated from personnel compartments by an enclosure that is vented and drained to
the exterior of the aeroplane.
5.3.3.3 Any enclosure required by 5.3.3.2 shall sustain any personnel compartment pressurization loads without permanent
deformation or failure under the conditions defined in Specifications F3116/F3116M and F3114/F3114M.
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5.3.3.4 For energy storage systems in compartments adjacent to fire zones there shall be sufficient clearance or insulation between
the compartment and the firewall to prevent ignition or malfunction of the energy storage system as a result of fire in the fire zone.
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5.3.4 Energy Capacity:
5.3.4.1 The usable energy capacity for each energy storage system shall be established.
5.3.4.2 The available remaining energy quantity information shall be provided.
5.3.5 Charging System:
5.3.5.1 The charging connection and system shall be designed to minimize hazards to personnel.
5.3.5.2 The charging connection shall be designed to ensure correct connection of the charging connector.
5.3.5.3 The charging system shall be designed to protect the aeroplane from a charging source with incorrect voltage including
high voltage, low voltage, incorrect polarity, effects of shorting, and type of current (AC/DC).
5.3.6 Pilot-replaceable Energy Storage Systems:
5.3.6.1 Each energy storage system location where electrical components can be replaced shall be marked.
5.3.6.2 Design precautions shall be taken to prevent incorrect installation of components when replaced in operation.
6. Control and Indication
6.1 General:
6.1.1 Each powerplant installation shall meet the applicable requirements of Specification F3064/F3064M.
6.1.2 For any energy storage system that should not be depleted in normal operation, there shall be a separate indication to the
flight crew when less than approximately 30 minutes of usable energy quantity or 50 % of the usable energy capacity remains in
the energy storage system, whichever is less.
6.2 Controls:
6.2.1 There shall be a means to provide separate power control for each electric engine, unless it can be shown that multiple
electric engines operated by a single control will not prevent the isolation of a failed engine, and the control of the remaining
engines to ensure continued, safe flight and landing.
6.2.2 Shutoff Controls:
6.2.2.1 There shall be an independent, simple, and reliable means to disconnect each energy storage system.
6.2.2.2 If the electric engine or energy storage system is installed in a fire zone, there shall be a means to allow appropriate flight
crew members to rapidly shut off, in flight, the energy supply to the electric engines and energy storage system individually.
6.2.2.3 No shutoff means may be on the fire zone side of any firewall.
6.2.2.4 There shall be a means to guard against inadvertent operation of each shutoff means.
6.2.2.5 There shall be a means to allow appropriate flight crew members to reopen the shutoff means rapidly after it has been
closed.
6.3 Powerplant Operational Characteristics and Installation:
6.3.1 General:
6.3.1.1 Electric propulsion systems shall have no adverse characteristics during normal or emergency operation within the
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operating limitations. This investigation shall consider the results of inadvertent energy storage system overcharging or limited
energy dumping capability, or both, during propeller windmilling and reversing operation.
6.3.2 Cooling Test Requirements:
6.3.2.1 For showing compliance with the general cooling requirements of Specification F3064/F3064M the aeroplane shall be
flown in the configurations, at the speeds, and following the procedures recommended in the Aeroplane Flight Manual that
correspond to the applicable performance requirements that are critical to cooling.
6.3.3 Starting and Stopping:
6.3.3.1 The design of the installation shall be such that risk of fire or mechanical damage to the electric engine or the aeroplane,
because of starting the electric engine in any conditions in which starting is to be permitted, is reduced to a minimum. Any
techniques and associated limitations shall be established and included in the Aeroplane Flight Manual, approved manual material,
or applicable operating placards.
6.3.3.2 There shall be a means for stopping the rotation of any electric engine or component, if continued rotation would cause
a hazard to the aeroplane.
6.3.3.3 If hydraulic propeller feathering systems are used for stopping the electric engine, the hydraulic feathering lines or hoses
shall be fire resistant under the operating conditions expected during feathering.
6.3.3.4 Restart Envelope—An altitude and airspeed envelope shall be established for the aeroplane for inflight engine restarting,
and each installed electric engine shall have a restart capability within that envelope.
6.3.3.5 Restart Capability—No unsafe condition may arise from re-engaging any electric engine after a shutdown either on ground
or in flight.
6.3.4 Powerplant Limitations:
6.3.4.1 The powerplant limitations shall be established so that they do not exceed the corresponding limits of the electric engines,
the energy storage systems, and associated equipment.
7. Hazard Mitigation
7.1 General:
7.1.1 Each powerplant installation shall meet the applicable requirements of Specification F3066/F3066M.
7.1.1.1 For compliance with the engine isolation requirements of Specification F3066/F3066M “an energy storage system, if only
one energy storage system is installed” is considered “a fuel tank, if only one fuel tank is installed.”
7.2 High Energy Rotors:
7.2.1 Each high energy rotor shall meet the applicable requirements for high energy rotors of Specification F3061/F3061M.
NOTE 3—Depending on the specific design, electric motors may qualify as high energy rotors.
7.3 Fire Protection:
7.3.1 Designated Fire Zones:
7.3.1.1 The electric engine or ESS section is a designated fire zone, if a fire hazard exists.
7.3.2 Fire Detection:
7.3.2.1 There shall be means that ensure the prompt detection of a fire in each fire zone that is not visible to the crew.
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7.3.3 Lightning Protection:
7.3.3.1 For level 1 aircraft intended for night VFR and IFR operation and for level 2 or higher aircraft, each energy storage system
shall be designed and arranged to prevent the ignition of flammable vapor or contents within the system by corona or streamering
at vent outlets and ESS areas.
7.4 Ice Protection:
7.4.1 Each air inlet of the powerplant installation shall be protected from ice accumulation, when operated in the conditions for
which it is to be certified as defined in Specification F3120/F3120M.
8. Keywords
8.1 electric aircraft; electric engine; electric propulsion; ESS; powerplant
ANNEX
(Mandatory Information)
A1. CORRELATION OF STANDARD – CONTENT AND THE RULES
A1.1 Means of Compliance Correlation Sorted by Standard Section
NOTE A1.1—The Specification sections shown in the Specification column will be at the highest level at which everything below that level is applicable
to that rule paragraph.
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TABLE A1.1 Means of Compliance Correlation Sorted by Standard Section
Specification Rev Section Subpart FAA 14 CFR Part 23 Subpart CS-23
F3239 19 4.1.1 E 23.2400(a) E 23.2400(a)
F3239 19 4.1.2 E 23.2400(b) E 23.2400(b)
F3239 19 4.1.3 E 23.2400(b) E 23.2400(b)
F3239 19 5.1.1 E 23.2430 E 23.2430
F3239 19 5.1.2 E 23.2430(a)(3) E 23.2430(a)(3)
F3239 19 5.1.3 E 23.2430(b)(4) E 23.2430(b)(4)
F3239 19 5.2 E 23.2430(a) E 23.2430(a)
F3239 19 5.3.1.1 E 23.2430(b) E 23.2430(b)
F3239 19 5.3.1.2 E 23.2400(e) E 23.2400(e)
F3239 19 5.3.1.3 E 23.2430(a) E 23.2430(a)
F3239 19 5.3.2.1 E 23.2430(b) E 23.2430(b)
F3239 19 5.3.2.2 E 23.2400(c) E 23.2455(d)
F3239 19 5.3.2.2 E E 23.2400(c)
F3239 19 5.3.2.3 E 23.2410 E 23.2410
F3239 19 5.3.2.4 E 23.2430(b)(2) E 23.2430(b)(2)
F3239 19 5.3.3.1 E 23.2400(d) E 23.2400(d)
F3239 19 5.3.3.2 E 23.2430(b) E 23.2430(b)
F3239 19 5.3.3.3 E 23.2430(b) E 23.2430(b)
F3239 19 5.3.3.4 E 23.2430(b) E 23.2430(b)
F3239 19 5.3.4.1 E 23.2430(a) E 23.2430(a)
F3239 19 5.3.4.1 E 23.2430(a) E 23.2445(g)
F3239 19 5.3.4.2 E 23.2430(a) E 23.2430(a)
F3239 19 5.3.4.2 E 23.2430(a) E 23.2445(g)
F3239 19 5.3.5.1 E 23.2430(c) E 23.2430(c)
F3239 19 5.3.5.2 E 23.2430(c) E 23.2430(c)
F3239 19 5.3.5.2 E 23.2430(c) E 23.2430(d)
F3239 19 5.3.5.3 E 23.2430(c) E 23.2430(c)
F3239 19 5.3.5.3 E 23.2430(c) E 23.2430(d)
F3239 19 5.3.6.1 E 23.2430(c) E 23.2430(c)
F3239 19 5.3.6.1 E 23.2430(c) E 23.2430(d)
F3239 19 5.3.6.2 E 23.2430(c) E 23.2430(c)
F3239 19 6.1.1 E 23.2400(a) E 23.2400(a)
F3239 19 6.1.2 E 23.2430(b) E 23.2430(b)
F3239 19 6.1.2 E 23.2430(b) E 23.2445(g)
F3239 19 6.2.1 G 23.2600 G 23.2600
F3239 19 6.2.2.1 E 23.2430(a) E 23.2430(a)
F3239 19 6.2.2.2 E 23.2430(a) E 23.2430(a)
F3239 19 6.2.2.3 E 23.2430(a) E 23.2430(a)
F3239 19 6.2.2.4 G 23.2600 G 23.2600
F3239 19 6.2.2.5 E 23.2430(a) E 23.2430(a)
F3239 19 6.3.1.1 E 23.2425(a) E 23.2425(a)
F3239 19 6.3.2.1 E
...
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