ASTM F3657-23

• Abstract:

  SCOPE; 1.1 This specification covers the airworthiness requirements for the design of light unmanned aircraft systems. This specification defines the baseline verification requirements for an unmanned aircraft system (UAS). ; 1.2 As a minimum, a UAS is defined as a system composed of the unmanned aircraft and all required on-board subsystems, payload, control station, other required off-board subsystems, any required launch and recovery equipment, all required crew members, and command and control (C2) links between UA and the control station. ; 1.3 The intent is for this standard of practice for CAA, self- or third-party determinations of airworthiness for UAS. This specification provides the core requirements for airworthiness certification of lightweight (UAS) for certain CAA operational approvals using risk-based categories. Additional requirements are envisioned to address the requirements for expanded operations and characteristics not addressed by this specification. ; 1.4 This specification is intended to support UAS operations. It is assumed that the risk of UAS will vary based on concept of operations, environment, and other variables. The fact that there are no human beings onboard the UAS may reduce or eliminate some hazards and risks. However, at the discretion of the CAA, this specification may be applied to other UAS operations. ; 1.5 Units—The values in Imperial units are to be regarded as the standard. The values in SI are for information only. ; 1.6 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. ; 1.7 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.

• Status: Published
• Publication Date: 30-Nov-2023
• Technical Committee: F38 - Unmanned Aircraft Systems
• Drafting Committee: F38.01 - Airworthiness

Overview

ASTM F3657-23: Standard Specification for Verification of Lightweight Unmanned Aircraft Systems (UAS) provides an internationally recognized baseline for verifying the airworthiness of light UAS. Developed by ASTM Committee F38, this standard outlines the core requirements to ensure the safety and reliability of unmanned aircraft systems, supporting compliance with national and international aviation regulations. The specification covers design verification, operational limitations, documentation, and testing procedures fundamental to lightweight UAS certification and approval.

Key Topics

• Airworthiness Requirements: Defines baseline criteria for UAS components, subsystems, command and control (C2) links, and associated launch, recovery, and operational support systems.
• System Verification: Requires manufacturers and applicants to use a combination of analysis, inspection, demonstration, and testing to verify functional performance and compliance.
• Risk-Based Approvals: Supports Civil Aviation Authorities (CAA), self-, or third-party airworthiness determinations using operational risk categories for lightweight UAS.
• Comprehensive Documentation: Specifies requirements for maintaining clear records, including flight manuals, maintenance logs, verification reports, and configuration control throughout the UAS lifecycle.
• Operating Limitations: Enforces detailed operational boundaries such as speed, altitude, payload, and environmental conditions to ensure safe UAS use.
• Best Practices: Introduces verification practices for performance, stability, controllability, component strength, and resilience under normal and emergency scenarios.

Applications

The ASTM F3657-23 standard is highly relevant for multiple stakeholders in the unmanned aircraft system sector, offering practical value for:

• Manufacturers and Developers: Enables systematic verification of UAS airworthiness and supports initial type certification, product improvements, and compliance with global aviation requirements.
• Aviation Authorities and Regulators: Provides a common framework to assess and approve lightweight UAS for various operational scenarios, including those beyond visual line of sight (BVLOS) or operations over people.
• Operators and Service Providers: Facilitates safe and documented deployment of UAS in commercial, public safety, research, and industrial applications by ensuring rigorous pre-flight and operational checks.
• Third-Party Assessors and Consultants: Establishes criteria for independent or self-assessment, contributing to transparent, risk-based airworthiness evaluations, and acceptance for expanded or specialized UAS operations.

This standard additionally guides organizations in creating and maintaining practices for documentation control, maintenance, upgrade verification, and safe operational procedures-building stakeholder confidence and streamlining regulatory interactions.

Related Standards

ASTM F3657-23 references and aligns with several key standards to provide a cohesive approach to UAS verification and operation, including:

• ASTM F2908: Unmanned Aircraft Flight Manual specification, ensuring clear and complete operational documentation.
• ASTM F2909: Continued Airworthiness of Lightweight UAS, supporting ongoing safe operation and maintenance.
• ASTM F3002: Command and Control System Design for Small UAS, addressing reliable communications and control requirements.
• ASTM F3201: Dependability of Software Used in UAS, focusing on assurance in onboard software functions.
• CS-LUAS/CS-LURS: EASA Certification Specifications for light unmanned systems.
• FAA Order 8130.34D / 14 CFR Part 107: Federal Aviation Administration requirements for UAS airworthiness and operational authorizations.
• ANSI Z535.1: Safety colors for warning and hazard information.

Summary

ASTM F3657-23 elevates the safety and reliability standards for lightweight unmanned aircraft systems in design, manufacturing, operation, and verification. Compliance ensures that UAS are properly verified for airworthiness, documented for regulatory approval, and prepared for diverse operational conditions, promoting trust among operators, regulators, and end users alike. For organizations and professionals engaged in UAS development, operation, or regulation, adhering to ASTM F3657-23 facilitates safer skies and streamlined market acceptance.

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: F3657 − 23
Standard Specification for
Verification of Lightweight Unmanned Aircraft Systems
(UAS)
This standard is issued under the fixed designation F3657; 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 ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
1.1 This specification covers the airworthiness requirements
mendations issued by the World Trade Organization Technical
for the design of light unmanned aircraft systems. This
Barriers to Trade (TBT) Committee.
specification defines the baseline verification requirements for
an unmanned aircraft system (UAS).
2. Referenced Documents
1.2 As a minimum, a UAS is defined as a system composed
2.1 ASTM Standards:
of the unmanned aircraft and all required on-board subsystems,
F2908 Specification for Unmanned Aircraft Flight Manual
payload, control station, other required off-board subsystems,
(UFM) for an Unmanned Aircraft System (UAS)
any required launch and recovery equipment, all required crew
F2909 Specification for Continued Airworthiness of Light-
members, and command and control (C2) links between UA
weight Unmanned Aircraft Systems
and the control station.
F3002 Specification for Design of the Command and Con-
1.3 The intent is for this standard of practice for CAA, self-
trol System for Small Unmanned Aircraft Systems (sUAS)
or third-party determinations of airworthiness for UAS. This F3060 Terminology for Aircraft
specification provides the core requirements for airworthiness
F3120/F3120M Specification for Ice Protection for General
certification of lightweight (UAS) for certain CAA operational Aviation Aircraft
approvals using risk-based categories. Additional requirements
F3201 Practice for Ensuring Dependability of Software
are envisioned to address the requirements for expanded Used in Unmanned Aircraft Systems (UAS)
operations and characteristics not addressed by this specifica-
F3298 Specification for Design, Construction, and Verifica-
tion. tion of Lightweight Unmanned Aircraft Systems (UAS)
F3341/F3341M Terminology for Unmanned Aircraft Sys-
1.4 This specification is intended to support UAS opera-
tems
tions. It is assumed that the risk of UAS will vary based on
F3478 Practice for Development of a Durability and Reli-
concept of operations, environment, and other variables. The
ability Flight Demonstration Program for Low-Risk Un-
fact that there are no human beings onboard the UAS may
manned Aircraft Systems (UAS) under FAA Oversight
reduce or eliminate some hazards and risks. However, at the
2.2 ANSI Standard:
discretion of the CAA, this specification may be applied to
ANSI Z535.1-1998 American National Standard for Safety
other UAS operations.
Colors
1.5 Units—The values in Imperial units are to be regarded
2.3 FAA Standard:
as the standard. The values in SI are for information only.
Order 8130.34D Airworthiness Certification of Unmanned
1.6 This standard does not purport to address all of the
Aircraft Systems and Optionally Piloted Aircraft
safety concerns, if any, associated with its use. It is the
2.4 Federal Standard:
responsibility of the user of this standard to establish appro-
14 CFR Part 107 Small Unmanned Aircraft Systems
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
1.7 This international standard was developed in accor-
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
dance with internationally recognized principles on standard-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
This specification is under the jurisdiction of ASTM Committee F38 on 4th Floor, New York, NY 10036, http://www.ansi.org.
Unmanned Aircraft Systems and is the direct responsibility of Subcommittee F38.01 Available from Federal Aviation Administration (FAA), 800 Independence
on Airworthiness. Ave., SW, Washington, DC 20591, http://www.faa.gov.
Current edition approved Dec. 1, 2023. Published January 2024. DOI: 10.1520/ Available from U. S. Government Accountability Office (GAO), 441 G St., NW,
F3657-23. Washington, DC 20548, http://www.gao.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3657 − 23
2.5 Joint Authorities for Rulemaking of Unmanned Sytems: powered or unpowered; rotors may be either fixed collective
CS-LURS Certification Specification for Light Unmanned pitch or collective pitch control that are not adjustable in flight.
Rotorcraft Systems Reference 3.1.52 for characteristics by category of vertical
CS-LUAS Recommendations for Certification Specification flight aircraft.
for Light Unmanned Aeroplane Systems 4.3.3 Hybrid UAS (that is, incorporating gyrodyne or
powered-lift flight modes) are recommended to follow the most
2.6 Unmanned Systems Canada Best Practices:
restrictive aspects of this specification.
Small Remotely Piloted Aircraft System (UAS) Best Prac-
tices for BVLOS Operations
5. Flight
3. Terminology
5.1 Proof of Compliance:
5.1.1 Each applicant who claims compliance to this speci-
3.1 Unique and Common Terminology—Terminology used
in multiple standards is defined in Terminology F3341/ fication shall be able to show compliance with the applicable
requirements of this specification.
F3341M and Terminology F3060.
3.2 Terminology that is unique to this specification is
6. Operating Limitations and Information
defined in this section.
6.1 During the verification process, the applicant shall
3.3 This specification uses terminology contained within
determine and document in the aircraft flight manual appropri-
Specification F3298. These terms are not duplicated within this
ate operating limitations and other information necessary for
document.
safe operation of the system. This shall include any wind
3.4 Abbreviations:
limitations as well as features of the control station and the C2
3.4.1 ADS-B—automatic dependent surveillance broadcast
link functions of the system.
3.4.2 AR—aspect ratio
6.2 Weight and Center of Gravity:
3.4.3 AFCS—automated flight control system 6.2.1 During the verification process, the applicant shall
determine and document weight and loading distribution,
4. Significance and Use/Applicability
including the maximum certificated weights and the center of
gravity (CG) range.
4.1 This specification is intended for lightweight UAS
6.2.2 The applicant shall determine the location of the
permitted to operate over a defined area and in airspace
reference datum used in balance computations.
authorized by a nation’s civil aviation authority (CAA) with a
fully interactive off-board person as “Remote Pilot in Com-
6.3 Propulsion System Limitations:
mand.”
6.3.1 The propulsion limitations portion describes operating
limitations on an aircraft’s reciprocating or electric engine(s).
4.2 The baseline covered by this specification should not
6.3.2 These include limitations for takeoff power, maximum
require an authorization by a civil aviation authority for the
continuous power, and maximum normal operating power,
flight but stay within defined boundaries for the operation (for
which is the maximum power the engine can produce without
example, distance from airports, from people, maximum
any restrictions, and any other limitations specified in the OEM
weight, altitude, airspeed and operational envelope). However,
engine/motor installation manual.
unless otherwise allowed by a nation’s CAA or subject to
voluntarily compliance by an applicant, this specification
6.4 Electromagnetic Environmental Effects:
applies to UA that are remotely piloted (that is, flown without
6.4.1 The UAS should be verified with an operational
the possibility of direct human intervention from within or on
envelope that contains a specific external High Intensity Radio
the aircraft), and conduct expanded operations that typically
Frequency (HIRF) environment.
require authorization from the CAA (for example, Operations
Authorization for Specific Category UAS or Part 107 Certifi-
7. Documentation
cate of Waiver/Authorization) with specific limitations adapted
7.1 Verification Control:
to the operation.
7.1.1 The documentation of an unmanned aircraft consists
4.3 These requirements apply to unmanned aircraft systems
of at least the following:
that are:
7.1.1.1 The drawings and specifications, and a listing of
4.3.1 Fixed-Wing—Heavier than air and supported in flight
those drawings and specifications necessary to define the
by the dynamic reaction of the air against its wings. The UA
configuration of the UA shown to comply with this specifica-
may be powered or unpowered; the UA may have rigid,
tion.
semi-rigid, or flexible wings.
7.1.1.2 Information on dimensions, materials, and processes
4.3.2 VTOL—Heavier than air and capable of vertical or
necessary to define the structural strength of the UA.
near-vertical takeoffs and landings. The rotor system may be
7.1.1.3 Any other data necessary to allow, by comparison,
the determination that later UA of the same or similar design
meet the requirements of this specification.
Available from Joint Authorities for Rulemaking of Unmanned Systems
7.1.2 The manufacturer shall retain documentation of ap-
(JARUS), http://www.jarus-rpas.org.
propriate verification results including data showing compli-
Available from Unmanned Systems Canada, PO Box 81055, Ottawa, Ontario,
K1P 1B1, https://www.unmannedsystems.ca. ance with this specification.
F3657 − 23
7.1.3 All verification documentation may be developed in 7.2.5.4 If removing/adding ballast is permitted, the un-
the manufacturer’s format or using best available documenta- manned aircraft flight manual shall include instructions with
tion practices (for example, engineering notebook format). respect to loading, marking, and securing of removable ballast
7.1.4 Performance Records: and ensuring the center of gravity remains within limits that
can be controlled by the control system and ensures adequate
7.1.4.1 All verification shall be recorded and available at the
aerodynamic stability.
applicant’s location for future reference for UAS that will
receive type certification by a CAA, or (as appropriate) self or
7.2.5.5 The aircraft flight manual shall have a method to
third-party determinations of airworthiness for UAS.
verify or calculate CG location.
7.1.4.2 At a minimum, flight demonstrations or testing
7.2.5.6 The manufacturer shall develop and provide instruc-
should be logged using aviation best practices. An example is
tions to ensure any damage caused by shipping or handling are
as follows: “I certify that the prescribed flight test hours have
identified prior to flight. These instructions should normally be
been completed and the aircraft is controllable throughout its
part of the pre-flight inspection procedures in the unmanned
normal range of speeds and throughout all maneuvers to be
aircraft flight manual but may be included in other instructions
executed, has no hazardous operating characteristics or design
as deemed necessary by the manufacturer.
features, and is safe for operation. The following aircraft
7.2.6 HIRF:
operating data has been demonstrated during the flight testing;
7.2.6.1 The Unmanned Aircraft Flight Manual (UFM) shall
speeds V , V , and V , and the weight and CG location at
S0 X y
include the specific external HIRF environments for the UAS
which they were obtained.” For multiengine aircraft, add V ,
XSE
intended operational envelope.
V , and V .
YSE MC
7.2.6.2 If the UAS design did not consider a specific HIRF,
7.2 Unmanned Aircraft Flight Manual (UFM):
or did not verify the HIRF protection of the UAS, the UFM
7.2.1 The applicant shall adhere to Specification F2908 for
shall include a caution statement.
the unmanned aircraft flight manual.
7.2.7 Emergency Procedures:
7.2.2 The applicant shall determine and document in the
7.2.7.1 The emergency procedures section shall include
unmanned aircraft flight manual appropriate operating limita-
checklists describing the recommended procedures and air-
tions and other information necessary for safe operation of the
speeds for coping with various types of emergencies or critical
system. This shall include any wind limitations as well as
situations. Some of the emergencies covered include: engine
features of the control station and the CNPC link functions of
failure, fire, and system failure.
the system.
7.2.7.2 Applicant should first show an emergency checklist
7.2.3 The applicant should provide a Pilot Operating
in an abbreviated form with the order of items reflecting the
Handbook/Checklist containing system descriptions, operating
sequence of action. Amplified checklists that provide addi-
procedures and limitations, engine and aircraft performance,
tional information on the procedures follow the abbreviated
critical airspeeds and altitudes, emergency procedures, pre-
checklist.
flight inspections, and any other information critical to safe
7.2.8 Normal Procedures and Checklists:
operation of the unmanned aircraft.
7.2.8.1 This section should begin with a list of the air-
7.2.4 General Information:
speeds for normal operations.
7.2.4.1 The General section provides the basic descriptive
information on the airframe and propulsion system(s). The
7.2.8.2 The section shall include several checklists that may
POH should include a three-dimensional drawing of the
include preflight inspection, before starting procedures, starting
aircraft that provides dimensions of various components.
engine, before taxiing, taxiing, before takeoff, climb, cruise,
Included are such items as wingspan, maximum height, overall
descent, before landing, balked landing, after landing, and post
length, wheelbase length, main landing gear track width, flight procedures. An Amplified Procedures area follows the
diameter of the rotor system, maximum propeller diameter,
checklists to provide more detailed information about the
propeller ground clearance, minimum turning radius, and wing various previously mentioned procedures.
area.
7.2.8.3 All specializations and limitations shall be those
7.2.4.2 This section serves as a quick reference and helps a
determined from the preceding relative design criteria.
remote pilot become familiar with the aircraft.
7.2.9 Navigational Databases:
7.2.5 Operating Limitations:
7.2.9.1 The POH should describe procedures for updating
7.2.5.1 The Limitations section contains only those limita-
the navigational database in accordance with the appropriate
tions required by regulation or that are necessary for the safe
data revision cycle. This includes a contract with a database
operation of the aircraft, powerplant, systems, and equipment.
supplier and the inclusion, in the appropriate company
It includes operating limitations, instrument markings, color-
manuals, of the person responsible for installing the updates in
coding, and basic placards.
the UA.
7.2.5.2 Some of the limitation areas are airspeed, propulsion
7.2.9.2 The POH should describe procedures for remote
system, weight and loading distribution, and flight.
pilots to report database errors and for information on database
7.2.5.3 For those systems that might have components
errors to be passed on to other pilots, the avionics manufacturer
capable of causing injury, the UA shall have a warning/caution
and other appropriate individuals.
statement added to the unmanned aircraft flight manual alerting
the crew to the risk. 7.3 Maintenance Manual:
F3657 − 23
7.3.1 The applicant should provide a maintenance manual (1) Inspection is used to check properties or characteristics
containing routine, inspection, and repair maintenance proce- best determined by observation (for example, paint color,
dures for the UA and engine. weight, documentation, listing of code, etc.).
7.3.2 The maintenance manual shall include maximum (2) The control station and other associated elements re-
damage and wear limits for the propellers. quired for remote operations shall be inspected during the
7.3.3 The maintenance manual shall provide instructions for onsite inspection. During the inspection, the applicant should
continued airworthiness that are in compliance with Practice demonstrate control link and control station functionality by
F2909. performing procedures such as turning on/off the aircraft lights,
7.3.4 Applicants shall provide the CAA with a written, deflecting flight controls, or conducting an engine run, or
self-certifying statement that they have an established inspec- combinations thereof.
tion and maintenance program for the continued airworthiness
8.2.2.3 Demonstration:
of the aircraft.
(1) Demonstration may be appropriate when requirements
or specification are given in statistical terms (for example,
8. Verification
mean time to repair, average power consumption, etc.).
(a) The objective is to demonstrate the aircraft’s control-
8.1 General:
lability throughout all the maneuvers and to detect any haz-
8.1.1 System Verification—This specification requires the
ardous operating characteristics or design features.
manufacturer to complete functional verification prior to
(b) The applicant shall complete a minimum of 25 h of
achieving compliance.
flight time for UAS, to demonstrate that the aircraft and all
8.1.2 Verification techniques may include the use of hard-
required on-board subsystems, payload, control station, other
ware in the loop simulation, ground/flight testing, and other
required off-board subsystems, any required launch and recov-
techniques. If sufficient operational reliability is not
ery equipment, all required crew members, and command and
demonstrated, the manufacturer shall levy initial operational
control (C2) links between UA and the control station perform
restrictions until an acceptable level of demonstrated reliability
as designed in the intended configuration. This demonstration
is reached.
is for design type and specific configuration, not each indi-
8.1.3 UAS design and construction requirements shall be
vidual aircraft.
verified with a combination of analysis, inspections, demon-
(c) The applicant should complete a minimum of 40 h of
strations or tests.
flight time for the UA.
8.1.3.1 The applicant will conduct any necessary
8.2.2.4 Test:
inspections, flight, or ground tests required to verify the
(1) Testing is performed onto the submitted element by
appropriate flight test requirements based on the type of
which functional, measurable characteristics, operability,
aircraft, intended use, and CONOPS.
supportability, or performance capability is quantitatively veri-
8.1.3.2 UAS demonstrations, testing, analysis, or
fied when subjected to controlled conditions that are real or
simulations, or combinations thereof, shall be conducted to
simulated.
verify that the design requirements have been satisfied and the
(2) Testing should use special test equipment or instrumen-
results recorded and available for future reference.
tation to obtain accurate quantitative data to be analyzed.
8.1.3.3 Software and hardware development assurance are
not in the scope of this specification and this specification
8.3 Organizational Requirements:
should not be used if a development assurance process is
8.3.1 An organization complying with this specification
required. Refer to Practice F3201 for software used in UAS.
shall manage under configuration control all life cycle data
Refer to the standards listed in 2.1 for hardware used in UAS.
which are generated by applying this specification.
8.1.3.4 This verification process specifically addresses
8.3.2 The organization shall keep a record of the documen-
definition, identification, and verification of system functions.
tation used to show compliance of each approved system
Processes conducted under this specification may not satisfy all
configuration produced to all applicable consensus specifica-
applicable external requirements; additional review on the part
tions and regulatory requirements in effect at the time of
of the system developer, integrator, or installer may be required
manufacture or major change.
to meet specific requirements or the specified mission of the
8.4 Product Definition Process:
aircraft, or both.
8.4.1 Function Identification—Document the intended func-
8.2 Methods of Verification:
tion(s) of the system.
8.2.1 The applicant shall verify the proper completion of
8.4.2 Function Classification:
each ready-to-fly UAS by conducting a final system test in
8.4.2.1 For each function identified under Specification
accordance with the requirements below.
F3298 15.4.1, determine and document whether it is to be
8.2.2 The following ground check and flight test procedures
verified under this specification or by other means.
shall be conducted and documented for each ready-to-fly UAS
8.4.2.2 Other means of verification may be proprietary or
using one or more of the following methods:
may be based on other standards, as best suits the applicant’s
8.2.2.1 Analysis:
objectives with regard to safety, marketability, and compliance
(1) Mainly used where testing to realistic conditions cannot
concerns.
be achieved or is not cost-effective.
8.2.2.2 Inspection: 8.4.3 Function Specification:
F3657 − 23
FIG. 1 Example Flow Chart of Verification Process
8.4.3.1 For each function identified for verification under 8.5.4.2 An analysis should be conducted to determine which
this specification in Specification F3298 15.4.2, document the functions require re-verification based on the design of the
specifications of the function, including: system and its integration into the aircraft.
(1) A description of the function,
8.6 Verification Document:
(2) An explanation of the intended use of the function, and
8.6.1 Produce a Statement of Verification that includes:
(3) Operating parameters or limitations that apply to the
8.6.1.1 The name of the UAS;
function.
8.6.1.2 The revision indicators (version numbers) for the
8.4.3.2 The requirements of Specification F3298 15.4.1 and
UAS component(s) tested;
15.4.3 may be met by a suitably annotated copy of the system’s
8.6.1.3 A list of operational limitations and performance
user or installation manual or by means of reference to a
characteristics verified under this specification;
third-party specification (such as a TSO minimum performance
8.6.1.4 A list of operational limitations and performance
standard).
characteristics verified by other means;
8.5 Verification Process: 8.6.1.5 The date upon which the verification was success-
8.5.1 Functional Verification Planning: fully completed;
8.5.1.1 Document the system test plan. 8.6.1.6 The following statement: “The listed operational
8.5.1.2 For each function identified for verification under limitations of the system have been verified to operate in
this specification in Specification F3298 15.4.2: accordance with the functional and performance characteristics
(1) Define a series of verification methods and pass/fail outlined in the system documentation. Verification has been
criteria that trace to the functional requirement and that verify conducted following the process defined in ASTM Specifica-
the function’s correct operation within the set limits. In tion F3657.”
developing the verification methods, consider known failures
9. Best Practices
in similar systems or components, or both.
(2) The verification method should include failure condi- 9.1 General:
tions when appropriate and important to the system level 9.1.1 Performance Verification:
function. 9.1.1.1 Initial Flight Test:
(3) Where applicable, make use of functional, (1) Flight operations shall be conducted within the visual
nonfunctional, ground, and flight tests providing direct refer- line of sight of the remote pilot/observer. Multi-engine UAS
ence to the specifications documented in Specification F3298 shall include verification of V , V , V .
XSE YSE MC
15.4.3 that make this specific test necessary. (2) Flight test plans should be developed to show that the
8.5.2 Testing: aircraft is controllable throughout its normal range of speeds
8.5.2.1 Execute the previously defined verification methods.
and throughout all the maneuvers to be executed.
8.5.2.2 Review test results and document pass/fail for each (a) The aircraft shall have no hazardous operating char-
verification method.
acteristics or design features.
8.5.3 Test Failure Resolution: (b) Flight test plans should be prepared for initial flight
8.5.3.1 Resolve all test failures via one or more of the testing and also before conducting market survey, crew
following means: training, and exhibition operations following a major configu-
(1) Revision to the system or its specifications, ration change.
(2) Revision of the system verification plan, and (c) Initial flight testing will be completed upon accumu-
(3) Justification for deferral to a future revision. lation of (number) flight hours, (number) takeoffs and landings
8.5.3.2 Identify the test(s) to be re-executed to verify the (select as appropriate), or when the aircraft is deemed control-
revised version of the system. lable and safe for operation, whichever occurs later.
8.5.4 Regression Analysis and Testing: (3) Following satisfactory completion of initial flight
8.5.4.1 Changes to the system or intended installation which testing, the applicant shall certify in the UA records that the
could affect any function verified under this specification UA has been shown to comply with this specification with the
should be re-verified at such times that those changes are made. following, or a similarly worded, statement: I certify that the
F3657 − 23
prescribed flight test has been completed and the aircraft is 9.2.1 Proof of Structure:
controllable throughout its normal range of speeds and 9.2.1.1 Primary structure strength shall be verified by
throughout all maneuvers to be executed, has no hazardous
analysis, or test.
operating characteristics or design features, and is safe for 9.2.1.2 Systems structure such as control surfaces and
operation. The following aircraft operating data has been
associated linkages, motor/engine mounts, and others strength
demonstrated during the flight testing: speeds V _____, and shall be verified by analysis, inspection, or test.
X
V _____, and the weight_____ and CG location at which they
9.2.1.3 The structure should be shown to support limit loads
y
were obtained.
without detrimental, permanent deformation.
9.1.2 Stability and Controllability: (1) The applicant shall describe the process used to deter-
9.1.2.1 The aircraft shall be safely controllable and maneu- mine that the airframe structure can withstand expected flight
verable during takeoff, climb, level flight (cruise), approach, loads throughout the flight envelope.
(2) The applicant shall include any test data or stress
and landing (power off and on) with primary controls of turn
and throttle and the possibility of combined turn displacement analysis that demonstrates positive structural margins of safety
during flight.
for flare.
9.1.2.2 Demonstrate a smooth transition between all flight 9.2.1.4 Dynamic tests, including structural flight tests, are
conditions shall be possible without exceptional pilot skills. acceptable if the design load conditions have been verified
through analysis or demonstration.
9.1.2.3 Longitudinal Control—Longitudinal control of the
aircraft shall be demonstrated by performing two minutes of 9.2.2 Empty Weight and Corresponding Center of Gravity:
flight without control input for three conditions. 9.2.2.1 The empty weight and corresponding center of
(1) In each case, the aircraft shall not enter into dangerous gravity shall be determined by weighing the aircraft with:
or unusual attitudes. (1) Fixed ballast;
(2) Test shall be conducted at maximum gross weight, with (2) Unusable fuel; and
minimum of in-flight turbulence. (3) Full operating fluids, including other fluids required for
(3) The three conditions are: normal operation of the UA.
(a) Maximum power setting climb; 9.2.3 Limit Load Static Tests:
(b) Reduced power descent;
9.2.3.1 Compliance with the limit load requirements of this
(1) For fixed-wing, zero power descent. part shall be shown by tests in which:
(2) For rotorcraft, zero power descent under autorotation.
(1) The direction of the test loads produces the most severe
For VTOL, minimum power to descend. loading in the control system; and
(c) Cruise setting power level flight. (2) Each fitting, pulley, and bracket used in attaching the
9.1.2.4 Lateral control shall be demonstrated by maintaining system to the main structure is included.
the controls in a neutral position, which shall initially give an 9.2.3.2 Compliance shall be shown (by analyses or indi-
unaccelerated level flight condition. The aircraft shall not enter vidual load tests) with the special factor requirements for
into a dangerous attitude during the 2 min that the flight
control system joints to angular motion.
controls are fixed. Demonstration shall be conducted at maxi- 9.2.4 Operation Tests:
mum takeoff weight, with minimum of in-flight turbulence.
9.2.4.1 It shall be shown by operation tests that, when the
9.1.2.5 Directional control shall be demonstrated by a sepa-
controls are operated from the control system the system is free
rate and full deflection of each directional flight control for from:
three full turns of 360° without the aircraft entering any
(1) Jamming;
dangerous flight attitude during the maneuver in each direction. (2) Excessive friction; and
These turns shall be in alternating directions (that is, left-right-
(3) Excessive deflection.
left).
9.3 Propulsion System:
(1) Test shall be conducted at minimum flight weight, with
9.3.1 The engine(s) thrust shall be verified by either the
minimum of in-flight turbulence.
manufacturer’s published thrust to RPM numbers or by actual
(2) The demonstrated turn rate shall not be less than 12 ° ⁄s
measurements.
(30 s for a 360° turn) in both directions.
9.3.1.1 The fuel and oil systems shall be shown capable of
9.1.2.6 Closed loop tasks (lateral offset landings and pitch
supplying adequate grade fuel and oil to the propulsion system
attitude captures) should be performed to demonstrate the
throughout the entire flight envelope at the required rate and
aircraft is not susceptible to pilot induced oscillations.
pressure specified by the propulsion system supplier if those
9.1.3 Vibrations:
specifications are available.
9.1.3.1 Flight testing shall not reveal, by pilot observation,
9.3.1.2 The propulsion system should be shown capable of
heavy buffeting (except as associated with a stall), excessive
minimal failure for reasons other than insufficient fuel or
airframe or control vibrations, flutter (with proper attempts to
electrical power.
induce it), or control divergence, at any speed from V to V .
S0 DF
9.3.1.3 The propulsion system shall be shown to support
9.1.3.2 The absence of flutter should be demonstrated at the
normal operations throughout
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