ASTM F3442/F3442M-23

Standard Specification for Detect and Avoid System Performance Requirements

SCOPE
1.1 This specification applies to uncrewed aircraft (UA) with a maximum dimension (for example, wingspan, disc diameter) ≤25 ft, operating at airspeeds below 100 kts, and of any configuration or category. It is meant to be applied in a “lower risk” [low- and medium-risk airspace as described by Joint Authorities for Rulemaking on Unmanned Systems (JARUS)] airspace environment with assumed infrequent encounters with crewed aircraft; this is typically in classes G and E airspace [below about 1200 ft above ground level (AGL)], Class B, C, D (below approximately 400 ft to 500 ft AGL) below obstacle clearance surface (FAA Order 8260.3, as amended) or within low altitude authorization and notification capability (LAANC) designated areas below the altitude specified in the facility map.  
1.1.1 Traffic encountered is expected to be mixed cooperative and non-cooperative traffic, instrument flight rules (IFR) and visual flight rules (VFR), and to mostly include low-altitude aircraft—including rotorcraft, small general aviation, crop dusters, ultralights, and light sport aircraft, but not transport category aircraft.  
1.1.2 This includes, but is not limited to, airspace where nearly all aircraft are required2 to be cooperative (for example, within the Mode C veil in the United States).  
1.2 Ultimate determination of applicability will be governed by the appropriate civil aviation authority (CAA).  
1.3 This specification assumes no air traffic control (ATC) separation services are provided to the UA.  
1.4 While some architectures may have limitations due to external conditions, this specification applies to daytime and nighttime, as well as visual meteorological conditions (VMC) and instrument meteorological conditions (IMC). The system integrator shall document system limitation (that is, due to operating environments and/or minimum altitudes at which the air picture is no longer valid).  
1.5 This specification is applicable to the avoidance of crewed aircraft by uncrewed aircraft systems (UAS), not UA-to-UA or terrain/obstacle/airspace avoidance (both to be addressed in future efforts). Likewise, birds or natural hazard (for example, weather, clouds) avoidance requirements are not addressed.  
1.6 This specification does not define a specific detect and avoid (DAA) architecture3 and is architecture agnostic. It will, however, define specific safety performance thresholds for a DAA system to meet in order to ensure safe operation.  
1.7 This specification addresses the definitions and methods for demonstrating compliance to this specification, and the many considerations (for example, detection range, required timeline to meet well clear, and near mid-air collision (NMAC) safety targets) affecting DAA system integration.  
1.8 The specification highlights how different aspects of the system are designed and interrelated, and how they affect the greater UAS system-of-systems to enable a developer to make informed decisions within the context of their specific UAS application(s).  
1.9 It is expected this specification will be used by diverse contributors or actors including, but not limited to:  
1.9.1 DAA system designers and integrators,  
1.9.2 Sensor suppliers,  
1.9.3 UA developers,  
1.9.4 Control Station designers,  
1.9.5 UAS service suppliers, and  
1.9.6 Flight control designers.  
1.10 Except for DAA system integrators for whom all the “shalls” in this specification apply, not all aspects of this specification are relevant to all actors/contributors. In some instances, the actor most likely to satisfy a requirement has been identified in brackets after the requirement; this is for informative purposes only and does not indicate that only that actor may fulfill that requirement. Where not specified, the system integrator/applicant is assumed to be the primary actor; in all cases, the system integrator/applicant is responsible for all requirements and may choose to delegate requirements as ...

General Information

• Status: Published
• Publication Date: 31-Jan-2023
• ICS: 03.220.50 - Air transport
• Technical Committee: F38 - Unmanned Aircraft Systems
• Drafting Committee: F38.01 - Airworthiness

Relations

• Refers: ASTM F3060-20 - Standard Terminology for Aircraft
• Effective Date: 01-Jan-2020
• Refers: ASTM F3060-16a - Standard Terminology for Aircraft
• Effective Date: 01-Nov-2016
• Refers: ASTM F3060-16 - Standard Terminology for Aircraft
• Effective Date: 01-Apr-2016
• Refers: ASTM F3060-15b - Standard Terminology for Aircraft
• Effective Date: 15-Sep-2015
• Refers: ASTM F3060-15a - Standard Terminology for Aircraft
• Effective Date: 01-May-2015
• Refers: ASTM F3060-15 - Standard Terminology for Aircraft
• Effective Date: 01-Mar-2015
• Refers: ASTM F3060-14 - Standard Terminology for Aircraft
• Effective Date: 01-Dec-2014

Overview

ASTM F3442/F3442M-23: Standard Specification for Detect and Avoid System Performance Requirements provides an international framework for ensuring the performance and reliability of detect and avoid (DAA) systems used by uncrewed aircraft (UA). Focused on aircraft with a maximum dimension of 25 feet or less and operating at speeds below 100 knots, this specification is tailored for operations in lower risk airspace. The intent is to enable safe integration of small unmanned aircraft systems (UAS) into the airspace, especially for beyond visual line of sight (BVLOS) missions, by establishing performance thresholds and compliance methods for DAA technology.

This specification is relevant for various stakeholders, including DAA system designers, integrators, sensor suppliers, UA developers, control station architects, UAS service providers, and flight control engineers. It does not mandate a specific DAA architecture, but sets out clear performance requirements and risk-based criteria, in line with recognized international terminology and regulations.

Key Topics

• Applicability and Scope

  • For UA ≤ 25 ft and speeds < 100 knots
  • Covers low- and medium-risk airspace, typically at lower altitudes (below 1200 ft AGL for certain classes)
  • Addresses mixed traffic environments (cooperative and non-cooperative, IFR/VFR, small general aviation aircraft, etc.)

• System Performance and Risk Metrics

  • Defines performance thresholds to ensure well clear (WC) and near mid-air collision (NMAC) avoidance
  • Utilizes quantitative metrics called risk ratios for evaluation:
    • NMAC Risk Ratio (RR): measures DAA effectiveness in preventing near mid-air collisions
    • Loss of Well Clear (LR): measures maintenance of safe separation boundaries
  • Sets differentiated thresholds based on the cooperation level of detected intruders (transponder/ADS-B Out equipped vs. non-cooperative)

• Environmental Conditions

  • Applies to daytime and nighttime, as well as visual and instrument meteorological conditions
  • Requires clear documentation of system limitations due to environment or altitude

• System Verification and Compliance

  • Requires field or laboratory verification, supplemented by simulation and statistical analysis
  • Compliance governed by the appropriate civil aviation authority (CAA)

• System Robustness and Availability

  • Specifies minimum acceptable levels for loss of function
    • Class 1 DAA: <1 per 100 flight hours (low risk)
    • Class 2 DAA: <1 per 1,000 flight hours (medium risk)
  • Redundancy or simplicity in system design may be used to meet availability requirements

Applications

• Small UAS Integration into National Airspace

  • Facilitates safe UAS operations in areas where encounter rates with crewed aircraft are low or medium, such as rural environments or outside busy control zones
  • Essential for BVLOS operations, critical infrastructure inspection, agriculture, surveying, and package delivery

• UAS Risk Management and Airworthiness

  • Supports compliance with regulatory frameworks and airspace risk assessments
  • Ensures that manufacturers and operators meet the safety performance needed to reduce collision risks

• Design and Development Guidance

  • Useful for DAA system developers to benchmark system capability, document limitations, and demonstrate fitness for operational environments
  • Supports informed decision-making on sensor selection, architectural choices, and integration

Related Standards

When implementing ASTM F3442/F3442M-23, consider these referenced and related standards for terminology, system interoperability, and further design guidance:

• ASTM F3060: Terminology for Aircraft
• ASTM F3341/F3341M: Terminology for Unmanned Aircraft Systems
• ASTM TR1-EB: Autonomy Design and Operations in Aviation
• RTCA DO-365C: Minimum Operational Performance Standards for Detect and Avoid Systems
• RTCA DO-381: Ground-Based Surveillance System Performance Standards
• JARUS SORA: Specific Operations Risk Assessment
• FAA AC 23.1309-1E: System Safety Analysis for Small Aircraft
• SERA: Standardised European Rules of the Air

For up-to-date regulations and supplementary guidance, always consult the governing civil aviation authority and review the latest editions of referenced standards.

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Keywords: ASTM F3442/F3442M-23, detect and avoid, DAA system, uncrewed aircraft, unmanned aircraft systems, UAS, performance requirements, BVLOS, low risk airspace, medium risk airspace, UAS safety, airspace integration, collision avoidance, risk assessment, UAS operations, compliance.

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: F3442/F3442M − 23
Standard Specification for
Detect and Avoid System Performance Requirements
This standard is issued under the fixed designation F3442/F3442M; 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 1.5 This specification is applicable to the avoidance of
crewed aircraft by uncrewed aircraft systems (UAS), not
1.1 This specification applies to uncrewed aircraft (UA)
UA-to-UA or terrain/obstacle/airspace avoidance (both to be
with a maximum dimension (for example, wingspan, disc
addressed in future efforts). Likewise, birds or natural hazard
diameter) ≤25 ft, operating at airspeeds below 100 kts, and of
(for example, weather, clouds) avoidance requirements are not
any configuration or category. It is meant to be applied in a
addressed.
“lower risk” [low- and medium-risk airspace as described by
Joint Authorities for Rulemaking on Unmanned Systems 1.6 This specification does not define a specific detect and
(JARUS)] airspace environment with assumed infrequent en- avoid (DAA) architecture and is architecture agnostic. It will,
counters with crewed aircraft; this is typically in classes G and however, define specific safety performance thresholds for a
E airspace [below about 1200 ft above ground level (AGL)], DAA system to meet in order to ensure safe operation.
Class B, C, D (below approximately 400 ft to 500 ft AGL)
1.7 This specification addresses the definitions and methods
below obstacle clearance surface (FAA Order 8260.3, as
for demonstrating compliance to this specification, and the
amended) or within low altitude authorization and notification
many considerations (for example, detection range, required
capability (LAANC) designated areas below the altitude speci-
timeline to meet well clear, and near mid-air collision (NMAC)
fied in the facility map.
safety targets) affecting DAA system integration.
1.1.1 Traffic encountered is expected to be mixed coopera-
1.8 The specification highlights how different aspects of the
tive and non-cooperative traffic, instrument flight rules (IFR)
system are designed and interrelated, and how they affect the
and visual flight rules (VFR), and to mostly include low-
greater UAS system-of-systems to enable a developer to make
altitude aircraft—including rotorcraft, small general aviation,
informed decisions within the context of their specific UAS
crop dusters, ultralights, and light sport aircraft, but not
application(s).
transport category aircraft.
1.1.2 This includes, but is not limited to, airspace where
1.9 It is expected this specification will be used by diverse
nearly all aircraft are required to be cooperative (for example,
contributors or actors including, but not limited to:
within the Mode C veil in the United States). 1.9.1 DAA system designers and integrators,
1.9.2 Sensor suppliers,
1.2 Ultimate determination of applicability will be governed
1.9.3 UA developers,
by the appropriate civil aviation authority (CAA).
1.9.4 Control Station designers,
1.3 This specification assumes no air traffic control (ATC)
1.9.5 UAS service suppliers, and
separation services are provided to the UA.
1.9.6 Flight control designers.
1.4 While some architectures may have limitations due to
1.10 Except for DAA system integrators for whom all the
external conditions, this specification applies to daytime and
“shalls” in this specification apply, not all aspects of this
nighttime, as well as visual meteorological conditions (VMC)
specification are relevant to all actors/contributors. In some
and instrument meteorological conditions (IMC). The system
instances, the actor most likely to satisfy a requirement has
integrator shall document system limitation (that is, due to
been identified in brackets after the requirement; this is for
operating environments and/or minimum altitudes at which the
informative purposes only and does not indicate that only that
air picture is no longer valid).
actor may fulfill that requirement. Where not specified, the
system integrator/applicant is assumed to be the primary actor;
in all cases, the system integrator/applicant is responsible for
This specification is under the jurisdiction of ASTM Committee F38 on
Unmanned Aircraft Systems and is the direct responsibility of Subcommittee F38.01
all requirements and may choose to delegate requirements as is
on Airworthiness.
suitable to the system design. Nonetheless, familiarity with the
Current edition approved Feb. 1, 2023. Published March 2023. Originally
entire specification will inform all actors/contributors of how
approved in 2020. Last previous edition approved in 2020 as F3442/F3442M–20.
DOI: 10.1520/F3442_F3442-23.
Refer to 14 CFR § 91.215 and 14 CFR § 91.225 in the United States, or to the
international equivalent for exceptions. ACAS sXu is intended to serve as a reference architecture for this specification.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3442/F3442M − 23
their contributions affect the overall DAA capability and is JARUS Specific Operations Risk Assessment (SORA)
strongly recommended. (package) V2.0
RTCA DO-365C Minimum Operational Performance Stan-
1.11 The values stated in either SI units or inch-pound units
dards (MOPS) for Detect and Avoid (DAA) Systems
are to be regarded separately as standard. The values stated in
RTCA DO-381 MOPS for Ground-based Surveillance Sys-
each system are not necessarily exact equivalents; therefore, to 8
tem (GBSS) for Traffic Surveillance
ensure conformance with the standard, each system shall be 9
SERA Standardised European Rules of the Air
used independently of the other, and values from the two
systems shall not be combined.
3. Terminology
1.12 This standard does not purport to address all of the
3.1 Unique and Common Terminology—Terminology used
safety concerns, if any, associated with its use. It is the
in multiple standards is defined in Terminologies F3341/
responsibility of the user of this standard to establish appro-
F3341M and F3060 and UAS Terminology Standard. Termi-
priate safety, health, and environmental practices and deter-
nology that is unique to this specification is defined in this
mine the applicability of regulatory limitations prior to use.
section.
1.13 This international standard was developed in accor-
3.2 Use of Shall, Should, and May—The use of shall
dance with internationally recognized principles on standard-
indicates a requirement, should indicates a recommendation,
ization established in the Decision on Principles for the
and may is used to indicate that something is permitted.
Development of International Standards, Guides and Recom-
3.3 Definitions:
mendations issued by the World Trade Organization Technical
3.3.1 alert function, A1F, n—function within the DAA
Barriers to Trade (TBT) Committee.
system tasked with notifying the avoid function (whether
human or automated system, or both) of the presence of an
2. Referenced Documents
intruder.
2.1 When external standards, documents, or studies are
3.3.2 avoid function, A2F, n—function within the DAA
referenced by this specification, the latest revision applies
system tasked with providing the flight guidance necessary to
unless otherwise stated herein. Standards referenced should not
maneuver away from the potential hazard posed by detected
be considered normative unless explicitly stated.
intruder(s). Avoidance may be executed automatically by a
2.2 ASTM Standards: flight controller or manually by a pilot.
F3060 Terminology for Aircraft
3.3.3 beyond visual line of sight, BVLOS, n—operation
F3341/F3341M Terminology for Unmanned Aircraft Sys-
when the UA cannot be seen by the individuals responsible for
tems
see-and-avoid with unaided (other than corrective lenses or
ASTM TR1-EB Autonomy Design and Operations in Avia-
sunglasses, or both) vision, but where the location of the UA is
tion: Terminology and Requirements Framework
known through technological means without exceeding the
performance capabilities of the command and control (C2)
2.3 Other Documents:
link. See Terminology F3341/F3341M.
14 CFR § 1.1 General definitions
14 CFR § 91.111 Operating near other aircraft
3.3.4 collision avoidance, n—avoidance maneuver with the
14 CFR § 91.113 Right-of-way rules: Except water opera-
objective of preventing the predicted penetration of the near-
tions
midair collision volume (NMAC).
14 CFR § 91.119(c) Minimum safe altitudes. General.
3.3.5 controlled airspace, n—an airspace of defined dimen-
14 CFR § 91.215 ATC transponder and altitude reporting
sions within which air traffic control service is provided in
equipment and use
accordance with the airspace classification.
14 CFR § 91.225 Automatic Dependent Surveillance-
3.3.5.1 Discussion—For example, in the United States,
Broadcast (ADS-B) Out equipment and use
Classes A, B, C, D, and E airspace.
14 CFR § 107.37 Operation near aircraft; right-of-way rules
3.3.5.2 Discussion—Controlled airspace does not automati-
FAA AC (Advisory Circular) 23.1309-1E System Safety
cally imply separation services, or that the location of all traffic
Analysis and Assessment for Part 23 Airplanes
is known.
FAA AC 25.1322-1 Flightcrew Alerting
3.3.6 cooperative intruder, n—those intruders using a Mode
FAA Order 8260.3 United States Standard for Terminal
C/S transponder or ADS-B, or both, that operate with like
Instrument Procedures (TERPS)
equipment used on other aircraft or ground-based services to
establish the intruder’s position.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available from Joint Authorities for Rulemaking on Unmanned Systems
the ASTM website. (JARUS), http://jarus-rpas.org/content/jar-doc-06-sora-package.
5 8
Available from U.S. Government Publishing Office (GPO), 732 N. Capitol St., Available from RTCA, Inc., 1828 L St., NW, Suite 805, Washington, DC 20036.
NW, Washington, DC 20401, http://www.govinfo.gov. 6
6 9
Available from Federal Aviation Administration (FAA), 800 Independence Available from European Union Aviation Safety Agency (EASA), Konrad-
Ave., SW, Washington, DC 20591, http://www.faa.gov. Adenauer-Ufer 3, D-50668 Cologne, Germany, https://www.easa.europa.eu.
F3442/F3442M − 23
FIG. 1 RR and LR Illustration
3.3.7 detect and avoid, DAA, n—subsystem within the UAS well clear as opposed to after. See Fig. 1 for depictions and
providing the situation awareness, alerting, and avoidance formulae. See also Ref (1).
necessary to maintain safe operation of the ownship in the
3.3.17 mid-air collision, MAC, n—two aircraft colliding
presence of intruders.
with each other while in flight.
3.3.8 DAA cycle, n—maximum time from the detection of
3.3.18 maintain well clear, n—the act of maneuvering an
the intruder’s presence to the initiation of an avoidance
aircraft with the objective of preventing the predicted erosion
maneuver
of the well clear margin of safety.
3.3.9 DAA system integrator, n—person/organization/entity
3.3.19 near mid-air collision, NMAC, n—two aircraft com-
who integrates the parts of a DAA system, and then shows that
ing within 100 ft vertically and 500 ft horizontally of each
the risk ratios required by this standard are met.
other while in flight.
3.3.10 detect function, DF, n—function within the DAA
3.3.20 NMAC risk ratio (RR) measurement, n—RR is the
system tasked with maintaining temporal and spatial awareness
quotient of the probability of an NMAC given an encounter
of intruders.
with the DAA system and the probability of an NMAC given
3.3.11 encounter, n—event associated with the presence of
an encounter without the DAA system. The lower the RR, the
an intruder.
better the DAA system is at preventing an NMAC.
3.3.20.1 Discussion—The RR used in this assessment is not
3.3.12 encounter rate, n—number of encounters per unit of
a measurement of the collision avoidance function alone. The
time.
RR is a measurement from an encounter to an NMAC, and it
3.3.13 false alert, n—an incorrect alert caused by a non-
is a measurement of all UAS DAA systems components used
aircraft track or by a failure of the alerting system, including
in mitigating NMAC. See Fig. 1 for depictions and formulae.
the sensor.
3.3.21 non-cooperative intruder, n—any aircraft not meet-
3.3.14 intruder, n—a crewed aircraft external to ownship
ing the definition of cooperative in 3.3.6.
within or projected to be in the ownship’s vicinity in the near
future. 3.3.22 nuisance alert, n—alert generated by a system that is
3.3.14.1 Discussion—This definition is deliberately equivo- functioning as designed, but which is inappropriate or unnec-
cal since the DAA system architecture and technologies essary for the particular condition.
employed, as well as ownship maneuvering capabilities, will
3.3.23 operational volume, n—volume of airspace in which
shape the specific definitions of “vicinity” and “near future.”
the UA operation intends, or is authorized, to take place.
The term “traffic” is often used synonymously with intruder.
3.3.23.1 Discussion—The term operational volume in this
3.3.15 loss of well clear, loWC, n—two aircraft coming
specification is aligned with the JARUS use of the term in
within the well clear boundary of each other while in flight.
Annex C of the Specific Operations Risk Assessment (SORA)
and is different from the UAS traffic management (UTM)/U-
3.3.16 loss of well clear risk ratio (LR) measurement,
space communities’ use of the term. “Area of operation,” or the
n—LR is the quotient of the probability of a loss of well clear
intersection of acceptable air and ground risk in accordance
(LoWC) given an encounter with a DAA system, and the
probability of loss of well clear given an encounter without a
DAA system. The lower the LR, the better the DAA system is
at preventing a loss of well clear. The LR is a measurement to
The boldface numbers in parentheses refer to the list of references at the end
ensure that a portion of the mitigation happens before loss of of this standard.
F3442/F3442M − 23
with the concept of operations, is how this concept might be guidance, such as per operating rules, for example, Standard-
described in UTM/U-space. ised European Rules of the Air (SERA), 14 CFR § 91.119(c),
or restricted airspace. See 5.4.7 for operating environments
3.3.24 ownship, n—UA controlled by the pilot flying and for
with extremely low air risk airspace classification and Appen-
which the pilot in command (PIC) is responsible.
dix X2 for examples and more detail
3.3.25 pilot flying, n—individual or system that manipulates
the flight controls of an aircraft during flight; may or may not 4. Significance and Use
be the pilot in command.
4.1 This specification outlines the system objectives,
3.3.25.1 Discussion—This is the same definition as in Ter-
activities, and evidence required to demonstrate adequate
minology F3060, but we keep it here for the reader’s benefit.
design and safe use of a detect and avoid (DAA) system. Such
3.3.26 regain well clear, n—the act of maneuvering an
systems, in concert with other systems and equipment, enable
aircraft with the objective of restoring the well clear margin of
uncrewed aircraft systems (UAS) to operate beyond the visual
safety that has been degraded by preceding circumstances.
line of sight (BVLOS) of the pilot in command (PIC). As the
name suggests, these systems comprise a function for sensing
3.3.27 remote pilot in command, RPIC, n—person who is
potential flight hazards and assessing hazard severity (“detect”)
directly responsible for and is the final authority as to the
and a function for maneuvering the aircraft out of the way of
operation of the UAS; has been designated as remote pilot in
the hazard (“avoid”). Such systems may also support opera-
command before or during the flight of a UAS; and holds the
tions within the PIC’s visual line of sight (VLOS).
appropriate CAA certificate for the conduct of the flight.
4.1.1 While there are many possible static and dynamic
3.3.27.1 Discussion—This is the same definition as in Ter-
hazards to UA flight (for example, obstacles, birds, terrain,
minology F3341/F3341M, but it is here for the reader’s benefit.
weather, other UAs), this specification addresses the safe
3.3.28 risk ratio measurement, n—used to measure the
operations of the UA in the presence of crewed aircraft, which
performance of a DAA system(s); the probability of an
may or may not be cooperative with the UA, otherwise known
outcome with the DAA system(s), divided by the probability of
as “intruders.”
an outcome without the DAA system(s); see Fig. 1 for
4.1.2 Despite the diversity in emerging DAA systems, these
depictions and formulae. The lower the risk ratio, the better the
systems share the following attributes:
DAA system is at mitigations.
4.1.2.1 Intruder Level of Cooperation —Cooperative sys-
3.3.29 rural area, n—an area not defined as urban (see
tems rely on information being supplied by the intruder
3.3.32).
whereas non-cooperative systems do not rely on the intruder
3.3.30 track, n—specific collection of data that a particular
supplying information. Many DAA systems use a combination
DAA system accumulates and is used in determining whether of cooperative and non-cooperative sensors for obtaining
an intruder aircraft is a collision risk or loss of well clear risk,
information regarding an intruder.
or both.
NOTE 1—While some cooperative systems (for example, mode A
3.3.31 uncontrolled airspace, n—an airspace that is not
transponder) provide very little information that is useful for the purposes
of the DAA, they are still considered cooperative systems.
controlled (see 3.3.5).
4.1.2.2 DAA Level of Autonomy—DAA systems may range
3.3.32 urban area, n—town, outer suburban, suburban,
from fully manual to fully automated functionality. In the fully
residential area, urban, metro, city, or open-air assembly of
manual construct, the PIC is presented with data, and it is up to
people, or combinations thereof.
the PIC to decide and execute any needed maneuvers. In the
3.3.33 well clear, n—state where there is a low residual
fully automated construct, the system determines and executes
midair collision risk informed by operational suitability.
any necessary maneuvers. A spectrum of functional alloca-
3.3.34 well clear (WC) boundary, n—extent of the volume
tion is possible in between these two architectures.
defined to calculate the operating performance of a DAA
4.1.2.3 Location of DAA Systems and Functionality—The
system. For UA in lower-rick airspace, this is defined as 2000
architecture of a given DAA system may use any combination
ft horizontally and 6250 ft vertically; see Fig. 1 and Ref (1).
of airborne and ground components. The proximity of DAA
3.3.34.1 Discussion—Remaining well clear is meant to
functions to the UA versus the Control Station each pose
support compliance with 14 CFR § 91.111 and § 91.113 or
unique benefits and challenges regardless of system timing and
§ 107.37 (or international equivalents) and reduce the chance
latency, UA payload, sensor orientation, field of regard or
of creating a collision hazard and therefore a collision.
surveillance coverage, range, track accuracy, and so forth.
3.3.35 yielded operating volume, n—operating volume
4.1.2.4 Sensor Type—The greatest differentiation between
where the competent authority accepts that crewed aircraft
DAA systems is in sensors. Sensing technologies vary and
normally will not fly because of regulatory limitations, or
include radio frequency (radar, passive radio frequency
because crewed aircraft yield to a characteristic of the envi-
reception), light (camera, light detection and ranging
ronment in the interest of safety.
(LiDAR)), and acoustic approaches. Each offers distinct ad-
3.3.35.1 Discussion—Regulatory limitations, policy, and/or
vantages and disadvantages. Therefore, DAA systems may
Intruder equipage entirely determines cooperative versus non-cooperative
Alternative well clear means may be appropriate in proximity to terrain or status.
obstacles when justified. It is assumed the PIC is kept apprised of the action.
F3442/F3442M − 23
utilize multiple sensor categories to achieve comprehensive guidance is given to provide context for the system perfor-
detection and appropriate levels of uncertainty and information mance in low and medium air risk airspace.
quality.
5.3.1.1 High Air Risk (out of scope for this requirements
4.1.2.5 Equipage—It is assumed that UA with a largest document)—This is airspace where crewed aircraft predomi-
dimension of 25 ft or less are not equipped with either a nately fly, or the crewed aircraft encounter rate is frequent, or
transponder or ADS-B-out and thus are not cooperative with both. The competent authority is expected to require the
traditional crewed air traffic. operator to comply with recognized DAA system standards as
available and appropriate to the application (that is, those
developed by RTCA SC-228 (see RTCA DO-365C), SC-147,
5. System Description
or EUROCAE WG-105).
5.1 Overview:
5.3.1.2 Medium Air Risk—This is airspace where crewed
5.1.1 This section identifies the set of objectives that the
aircraft predominately do not fly (excluding helicopters and
DAA system, including the human pilot if required to be “in
crop dusters) or the crewed aircraft encounter rate is
the loop,” shall satisfy as a complete unit.
occasional, or both. This is generally uncontrolled airspace
5.1.2 Two classes of DAA equipment are specified: Class 1
and/or airspace that goes from the ground to between 300 ft to
for operations in low-risk airspace; and Class 2 for operating in
1200 ft AGL (with 500 ft AGL used as a common default),
medium-risk airspace as defined by the CAA. See 5.3.1 for
above which most crewed aircraft operations are conducted.
description of airspace and 5.5.2 on Class 1 and 2.
This includes airspace away from Class B, C, and D
5.1.3 This specification does not address integration of
aerodromes, or near Class B, C, and D aerodromes with
DAA equipment with other safety systems such as geographi-
additional strategic mitigations.
cal containment systems (that is, geofencing) and terrain
5.3.1.3 Low Air Risk—This is airspace where crewed air-
avoidance systems.
craft generally do not fly or the crewed aircraft encounter rate
5.1.4 The communication link of DAA information (C2 and
is remote or improbable in accordance with guidelines and
sensor) complies with regulatory policy in terms of spectrum
regulations from the competent authority, or both. This is
use and frequency allocations.
generally uncontrolled airspace and/or airspace that goes from
the ground to between 300 ft to 1200 ft AGL (with 500 ft AGL
5.2 System Verification:
used as a common default), above which most crewed aircraft
5.2.1 If required by the CAA, the applicant/proponent shall
operations are conducted and away from urban population
provide to the CAA or CAA-approved test organization, or
centers, towns, outer suburban, suburban, residential areas,
both, evidence of physical verification demonstrating the DAA
metro, or cities, or combinations thereof, and outside all
system meets all required performance criteria identified or
aerodromes. Helicopter and crop duster operations may occur
generated in response to this specification.
in low-risk airspace and may require special consideration, as
5.2.2 Physical verification may take the form of field tests
they may operate at low altitudes, in uncontrolled airspaces, or
against actual targets and objectives or lab tests against
otherwise alter the expected crewed aircraft encounter rate.
representative targets, as long as data is supplied confirming
5.3.1.4 Extremely Low Air Risk Airspace Classification—
equivalency to real targets.
This is airspace where crewed aircraft predominately do not
NOTE 2—An approach to verifying these requirements will be defined
fly, or the likelihood of an encounter with a crewed aircraft has
in an ASTM test method currently under development.
been shown to be extremently improbably, or both. Examples
5.2.3 Analysis and simulation should be used as a form of
of such a classification include the use of robust containment to
performance verification when physical performance is im-
remain within a yielded operating volume, or operations in
practical (for example, difficult corner cases, extensive time-
remote, sparsely populated areas such as parts of northern
based testing, or sheer volume of test case permutations). In
Canada or northern Sweden.
these situations, the analysis or simulation shall still be
5.3.2 Local Air Risk Assessment of Operational Volume (see
substantiated using a sampling of physical test data to establish
3.3.15)—If an airspace authority or air navigation service
validity.
provider (ANSP), or both, has conducted an airspace charac-
terization and classified the collision risk of the operational
5.3 Safety:
volume, that collision risk assessment will be used as the
5.3.1 Air Collision Risk Classification of Operational
method for categorizing the airspace. Strategic mitigations
Volume—In order to assess risk, the airspace needs to be
and/or existence of yielded operating volumes may also be
classified based on airborne collision risk under which a UA
used when characterizing the operational volume airspace.
would encounter a crewed aircraft. In a manner similar to the
5.3.3 Generalized Collision Risk Assessment of Operational
JARUS SORA, this specification assumes four unmitigated
Volume—If a local classification of the collision risk of the
airborne collision risk classification levels: High, Medium,
operational volume does not exist, a generalized air risk
Low, and Extremely-Low Air Risk. However, only DAA
assessment, such as the JARUS SORA or example in 5.3.4, can
system performance for DAA Class 1 and Class 2 systems (to
be used.
be used in low- and medium-risk airspace, respectively), is in
5.3.4 Generalized Air Risk Assessment Descriptions:
scope for this specification. As a DAA standard, this specifi-
cation does not specify the method for determining the airspace 5.3.4.1 These airborne collision risk classifications are gen-
risk classification level for a given operation, but general eralized classifications. Consequently, when the area becomes
F3442/F3442M − 23
TABLE 1 Example Generalized Collision Risk Airspace
ronment airspace. Encounter sets are representative when they
Classification Summary from JARUS SORA
include appropriate and realistic distributions of ownship and
Airspace Airspace Description
intruder flight dynamics, speeds, vertical rates, and encounter
Medium Air Risk Uncontrolled Airspace
geometries for the airspace class, altitude, and geographic
Below 500 ft AGL in controlled airspace, at least 5 nm
region where the DAA equipment is expected to operate to the
away from the center point of Class B, C, and D
aerodromes satisfaction of the CAA. When evaluating the DAA system
Below 500 ft AGL over an urban area
against ADS-B Out intruders, the encounter set(s) should
Below 500 ft AGL in/over/around Class E, F, or G
include behaviors representative of both 1200-code and dis-
aerodromes
crete code operations. When evaluating the DAA system
Near Class B, C, and D aerodromes with additional
strategic mitigations, for example, remaining below
against non-cooperative and transponder-only intruders, the
facility map altitudes
encounter set(s) should include behaviors representative of
Low Air Risk Uncontrolled airspace, below 500 ft AGL, over a rural
area, outside all aerodromes aircraft without a transponder and aircraft with a transponder
but without ADS-B in both 1200-code and discrete code
operations. Limitations on the DAA equipment shall be
TABLE 2 Summary of DAA Performance Guidance for UAS
identified based on limitations of the encounter set(s) used to
DAA Quantitative Performance Requirements
verify the performance requirements.
Intruder Equipage
NMAC Risk Ratio Loss of Well Clear
5.4.4 In operational volumes with low and medium air risk,
(RR) Risk Ratio (LR)
DAA performance for NMAC avoidance (RR) requirements
ADS-B Out #0.18 #0.40
are based on the ICAO work cited in 5.4.2 and are dependent
Non-cooperative or #0.30 #0.50
on the equipage type of the intruder.
transponder-only
5.4.4.1 For encounters with intruders equipped with ADS-B
Out, the DAA system RR shall be ≤0.18.
5.4.4.2 For encounters with non-cooperative or transponder-
more refined, there may be specific areas where the generalized
only intruders, the DAA system RR shall be ≤0.30.
classification levels will be true and others where it will not.
5.4.5 In operational volumes with low and medium air risk,
The operator will work with the local airspace authority to
DAA performance for loss of well clear (LR) requirements are
ensure that the appropriate air risk classification is assigned to
based on the ICAO work cited in 5.4.2 and are dependent on
the operational volume.
the equipage type of the intruder.
5.3.4.2 Examples of a Generalized Airspace Air Risk Clas-
5.4.5.1 For intruders equipped with ADS-B Out, the DAA
sification Summary—See Table 1 (taken from the JARUS
system LR shall be ≤0.40.
SORA). The following are notional examples and not defini-
5.4.5.2 For non-cooperative or transponder-only intruders,
tive classifications within this ASTM specification.
the DAA system LR shall be ≤0.50.
5.4 UAS DAA Performance Requirements:
5.4.6 DAA Performance Summary—See Table 2.
5.4.1 The risk ratios in this specification are “logic” risk
5.4.7 In operational volumes with extremely low air risk,
ratios as in the International Civil Aviation Organization
RR and LR may not be appropriate DAA performance metrics.
(ICAO) definition. Included is nominal system performance
Here, the rate of unmitigated encounters with crewed aircraft is
are: logic, specified surveillance performance, field of view
assumed to be extremely low. As such, the competent authority
limitations, expected human pilot performance, specified/
may not require a DAA system for operations within such
nominal C2 link performance, expected latencies for all
airspace.
components, and ownship performance. Not included are
NOTE 3—While the risk ratio equation is unchanged, due to the low rate
failures, for example, corrupted logic, sensor failures, C2 link
of unmitigated encounters, the risk ratio metric is uninformative because
failures, DAA equipment failures/faults, non-responsive pilot.
there may not be a DAA system in the traditional sense, or it is not
Performance under failure conditions should be addressed
possible to generate realistic unmitigated encounters because of the low
through system safety assessments. Note that JARUS specifies
rate of unmitigated encounters (the denominator would be near zero).
Other performance metrics, such as navigation performance or robust
total system risk ratios.
containment, may be more useful to assess the DAA system.
5.4.2 In this specification, the risk ratios discussed by the
ICAO Remotely Piloted Aircraft Systems (RPAS) panel have 5.4.8 In addition, it is expected that in certain operational
been used but are applied to a smaller well clear boundary (for
volumes where the rate of non-cooperative or transponder-only
example, 2000 ft). This adjustment leads to a similar RR even equipped encounters can be demonstrated to be extremely low,
with lower performing UAS DAA equipage. (See Ref (2).) The
the RR and LR for non-cooperative or transponder-only
smaller well clear boundary is used due to the lower closure equipped encounters may not be appropriate performance
rates and smaller P(MAC|NMAC) due to the small size of the
metrics for a DAA system. As such, the competent authority
UAS. may not require a non-cooperative DAA system for operations
5.4.3 The RR and LR performance requirements in this
within operational volumes where the rate of non-cooperative
section shall be verified using a statistically significant number
or transponder-only equipped encounters can be demonstrated
of encounters that are representative of the operational envi- to be extremely low.
14 15
See https://www.icao.int/safety/UA/Pages/Remotely-Piloted-Aircraft- See Airspace Encounter Models on GitHub (https://github.com/airspace-
Systems-Panel-(RPASP).aspx. encounter-models) for models of aircraft behavior in U.S. airspace.
F3442/F3442M − 23
NOTE 4—While the non-cooperative or transponder-only equipped risk
5.5.3.2 For Class 1 equipment (to be used in operations in
ratio equation is unchanged because of the low rate of unmitigated
low air risk airspace), the allowable introduction of hazard-
non-cooperative or transponder-only equipped encounters, the non-
ously misleading information shall be less than 1 per 1000
cooperative or transponder-only equipped risk ratio metric is uninforma-
flight hours (1E-3 Loss/FH).
tive because the denominator would be near zero.
5.5.3.3 For Class 2 equipment (to be used in operations in
5.5 UAS DAA Robustness Requirements:
medium air risk airspace), the allowable introduction of haz-
5.5.1 The robustness of the DAA system is characterized by
ardously misleading information shall be less than 1 per 10 000
the availability and assurance level of the system. This ap-
flight hours (1E-4 Loss/FH).
proach is similar to that adopted by JARUS.
5.5.4 ADS-B Data Validation—Independent validation of
5.5.2 DAA System Availability:
ADS-B is not expected to be a requirement in all smaller UAS
5.5.2.1 The approach to system availability here is derived
DAA operational scenarios. There are some situations where
from the JARUS process for SORA V2.0 Annex D, section 5.4
other mitigations may be in place, or the operation is of such
(TMPR (Tactical Mitigation Performance Requirement) Ro-
low risk that ADS-B validation is not necessary. Operators who
bustness (Integrity and Assurance) Assignment). The level of
want to use ADS-B in smaller UAS DAA applications without
system availability of the DAA system differentiates Class 1
independent validation must demonstrate to the regulator that it
and 2 systems. Loss of function includes failures such as sensor
is acceptable for their operation.
failures, C2 link failures, and DAA equipment failures, which
5.5.5 Timestamping:
are not captured in the RR and LR performance requirements.
5.5.5.1 The DAA system shall employ a consistent time
5.5.2.2 For Class 1 equipment (to be used in operational basis across all functions for marking the time of applicability
volumes with low air risk), the allowable loss of function and
of measurements and calculated parameters (for example, GPS,
performance shall be less than 1 per 100 flight hours (1E-2 UTC). Time of applicability is herein defined as the time at
Loss/FH).
which a particular measurement or parameter was determined
relative to some temporal origin point that is fixed for at least
5.5.2.3 For Class 2 equipment (to be used in operational
the duration of any one power cycle of the DAA system
volumes with medium air risk), the allowable loss of function
(though a universal time origin, like UTC, is strongly pre-
and performance shall be less than 1 per 1000 flight hours
ferred). For parameters received from an outside source (for
(1E-3 Loss/FH).
example, ADS-B In), time of applicability is to be taken from
5.5.2.4 The requirements on availability may be met by:
the corresponding field in the received data – reverting to the
(1) Showing redundancy in the equipment providing that
time of receipt if the time of applicability was not provided in
function. An analysis of a redundant system in the aircraft is
the transmission.
usually complete if it shows isolation between redundant
5.5.5.2 The DAA system timing, if based on GPS, shall be
system channels and satisfactory reliability for each channel; or
resilient to GPS failures. GPS dropouts are common, so if GPS
(2) In the case where single failures can cause the failure
time is the time basis, a method of time-coasting is needed to
condition, by showing the system is simple, uses conventional
ensure that timestamping can occur uninterrupted.
architecture, is appropriately qualified for the installed envi-
ronment and the individual failure rates of its components are
NOTE 5—As soon as a measurement or calculation is made, this
below the objective of 1E-2 for Class 1 Equipment or 1E-3 for
information starts becoming stale (that is, increasingly irrelevant). As
Class 2 Equipment. information flows through the system, it may accumulate non-uniform
levels of staleness. Thus, it is important to be able to determine how stale
These are two ways, but not the only ways, of meeting
each piece of information is. DAA integrators should work with individual
5.5.2.2 and 5.5.2.3.
function suppliers to ensure that a means of accurately timestamping
5.5.3 DAA System Assurance: information is available to all functions. Using a broadly accepted time
basis (for example, GPS, UTC) is suggested to maximize compatibility
5.5.3.1 The approach to system assurance here is derived
between suppliers and integrators but is not mandated.
from the JARUS process for SORA. The level of system
5.6 Reliability and Maintenance:
assurance of the DAA system differentiates Class 1 and 2
5.6.1 A methodology for anticipating and detecting failures
systems. Hazardously misleading information is introduced by
and accomplishing appropriate maintenance actions should be
undetected software and hardware faults, which are not cap-
identified and implemented for the major subsystems or
tured in the RR and LR performance requirements. Hazard-
components of the DAA system, as well as the system as a
ously misleading information does not include information,
whole.
such as false tracks, that does not result in a hazardous
5.6.1.1 If required, the DAA system shall have a mainte-
maneuver. Likewise, hazardously misleading information does
not include faults that are detected and covered by the loss of nance plan and maintenance schedule in accordance with the
maintenance instructions provided by the manufacturer. The
function requirements in 5.5.2. Allowable failure rates are
maintenance instructions shall provide direction as to verifica-
determined from the AC 23.1309-1E precedent that most
tion of proper installation and calibration of the system to
misleading and/or malfunction without warning severity clas-
ensure continued performance is met in the field.
sifications (see Appendix 1 in the AC) are one category more
severe than the regular loss of function and that, for Class I 5.6.2 The DAA system shall have a test function for
aircraft (see FIG. 2 in AC 23.1309-1E), a one category increase detecting foreseeable “static” system failures. “Static” system
in severity is equivalent to a one order of magnitude decrease failures are degradations in the condition of the system that
in the event rate per flight hour. would prevent correct operation (for example, memory faults,
F3442/F3442M − 23
device failures, wear out). These are different than “dynamic” 6. System Timing
errors, which are due to unforeseen events during runtime. Test
6.1 The DAA system integrator shall perform a timing
function requirements should be based on system safety
analysis that identifies the timing elements for the DAA
principles considering rate, exposure, and criticality of latent
system. Reference Appendix X2 for a description of example
failure.
timing elements for various architectures.
5.6.3 The DAA system shall detect and notify the PIC of
6.2 The timing elements shall be reflected in the test
any degradation or loss of function that requires PIC action or
methods used to show that the DAA system supports the
take predefined automated contingency action to mitigate the
required risk ratios when operated in accordance with the DAA
risk if required by the operational safety case, within a
System CONOPS in the representative airspace defined in
timeframe appropriate for the alerting condition. A degradation
5.3.4.
of function includes (1) any partial loss of functionality or (2)
any reduction of performance as required or advertised by the
7. Detection Function
system. This does not prescribe specific mechanics of how a
7.1 Overview—This section defines the functionality,
degradation or loss of function alert is to be communicated;
depending on the safety assessment, it may be appropriate to behavior, and performance required of the DF within an
integrated DAA system. The role of the DF is to gather
have no in-flight indication or action. Failures without means
of detection should be identified during system design, and the information regarding potential intruders that may pose a threat
to the ownship and present the information in a form usable by
DAA system as a whole shall comply with the requirements for
availability (5.5.2) and assurance (5.5.3). If notification is follow-on functions (that is, adequately complete, timely,
accurate, clean, and suited for the intended information con-
required, it may be a dedicated message, a special error code in
an existing message, an invalid value in the field representing sumer).
the loss of functionality, or a maintenance code. The DAA
7.2 Function:
system shall persist the notification of degradation or loss of
7.2.1 The DF surveils the airspace.
function until the functionality is fully restored. Human factors
NOTE 6—The DF may work with sensors that provide raw surveillance
and training should be considered in the design of PIC
measurements or surveillance tracks.
notification.
7.2.2 Upon detecting the presence of an intruder, the DF
5.7 Security:
shall determine the track of the intruder as required by the alert
5.7.1 The PIC shall be notified of any changes to DAA
function (A1F) to identify and prioritize hazards.
software, hardware, or configuration. This notification may
NOTE 7—A track may be based on information from a single sensor or
take many forms, including technical or operational means,
the fusion of information from multiple sensors. Examples of parameters
such as inspection or automatic reporting.
are: (1) lateral position, (2) velocity (speed and direction), (3) altitude, and
5.7.2 Making any changes to DAA software, hardware, or
(4) closure rate. These track parameters may be absolute to the surround-
ing environment (for example, latitude, longitude, altitude) or relative to
configuration shall be restricted to authorized and qualified
the ownship (for example, range, bearing, angular elevation).
personnel. This restriction may be implemented through vari-
ous mechanisms, including technical or operational means. 7.2.3 The DF shall output the track(s) of all detected
intruders to the A1F.
5.7.3 Any changes to DAA software, hardware, or configu-
7.2.4 Track Coasting:
ration shall require confirmation that the modified information
7.2.4.1 When an intruder with an existing track is no longer
is correct and uncorrupted. Confirmation may come in any
detected, the DF should continue the track by extrapolating that
combination of cyclic redundancy code (CRC)/checksums,
intruder’s trajectory to the current surveillance cycle, as
digital signatures, embedded registers, pin-strapping, manual
discussed in the Timing Appendix, using its last known
checklists, or combinations thereof.
position and velocity and report it to the A1F as a coasted track.
5.7.4 There shall be a means to prevent any changes to the
The DF may use intruder trend data, up to and including the
DAA software, hardware, or configuration from inadvertently
last known position and velocity vector, for extrapolating the
or maliciously occurring, or a suitable preflight check to detect
coasted track. However, the DF may not use an intruder’s
such changes and prevent takeoff if such changes were to
registered flight plan for extrapolation because the intruder
occur. This requirement may be implemented through various
may deviate from the flight plan at any time. (Refer also to A1F
mechanisms, including technical or operational means.
track coasting requirements in 8.2.9.)
5.7.5 The DAA s
...

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: F3442/F3442M − 20 F3442/F3442M − 23
Standard Specification for
Detect and Avoid System Performance Requirements
This standard is issued under the fixed designation F3442/F3442M; 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 applies to unmanneduncrewed aircraft (UA) with a maximum dimension (for example, wingspan, disc
diameter) ≤25 ft, operating at airspeeds below 100 kts, and of any configuration or category. It is meant to be applied in a “lower
risk” (low-[low- and medium-risk airspace as described by Joint Authorities for Rulemaking on Unmanned Systems
(JARUS))(JARUS)] airspace environment with assumed infrequent encounters with mannedcrewed aircraft; this is typically in
classes G and E airspace (below[below about 1200 ft above ground level (AGL)),(AGL)], Class B, C, D (below about
400approximately 400 ft to 500 ft AGL),AGL) below obstacle clearance surface (FAA Order 8260.3, as amended),amended) or
within low altitude authorization and notification capability (LAANC) designated areas below the altitude specified in the facility
map.
1.1.1 Traffic encountered is expected to be mixed cooperative and non-cooperative traffic, instrument flight rules (IFR) and visual
flight rules (VFR), and to mostly include low-altitude aircraft—including rotorcraft, small general aviation, crop dusters,
ultralights, and light sport aircraft, but not transport category aircraft.
1.1.2 This includes, but is not limited to, airspace where nearly all aircraft are required to be cooperative (for example, within
the Mode C veil in the U.S.).United States).
1.2 Ultimate determination of applicability will be governed by the appropriate civil aviation authority (CAA).
1.3 This specification assumes no air traffic control (ATC) separation services are provided to the UA.
1.4 While some architectures may have limitations due to external conditions, this specification applies to daytime and nighttime,
as well as visual meteorological conditions (VMC) and instrument meteorological conditions (IMC). The system integrator shall
document system limitation (that is, due to operating environments and/or minimum altitudes at which the air picture is no longer
valid).
1.5 This specification is applicable to the avoidance of mannedcrewed aircraft by unmanneduncrewed aircraft systems (UAS), not
UA-to-UA or terrain/obstacle/airspace avoidance (both to be addressed in future efforts). Likewise, birds or natural hazard (for
example, weather, clouds) avoidance requirements are not addressed.
This specification is under the jurisdiction of ASTM Committee F38 on Unmanned Aircraft Systems and is the direct responsibility of Subcommittee F38.01 on
Airworthiness.
Current edition approved May 1, 2020Feb. 1, 2023. Published July 2020March 2023. Originally approved in 2020. Last previous edition approved in 2020 as
F3442/F3442M–20. DOI: 10.1520/F3442_F3442-20.10.1520/F3442_F3442-23.
Refer to 14 CFR § 91.215 and 14 CFR § 91.225 in the United States, or to the international equivalent for exceptions.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3442/F3442M − 23
1.6 This specification does not define a specific detect and avoid (DAA) architecture and is architecture agnostic. It will, however,
define specific safety performance thresholds for a DAA system to meet in order to ensure safe operation.
1.7 This specification addresses the definitions and methods for demonstrating compliance to this specification, and the many
considerations (for example, detection range, required timeline to meet well-clear, well clear, and near mid-air collision (NMAC)
safety targets) affecting DAA system integration.
1.8 The specification highlights how different aspects of the system are designed and interrelated, and how they affect the greater
UAS systemsystem-of-systems to enable a developer to make informed decisions within the context of their specific UAS
application(s).
1.9 It is expected this specification will be used by diverse contributors or actors including, but not limited to:
1.9.1 DAA system designers and integrators,
1.9.2 Sensor suppliers,
1.9.3 UA developers,
1.9.4 Ground control station (GCS) Control Station designers,
1.9.5 UAS service suppliers, and
1.9.6 Flight control designers.
1.10 Except for DAA system integrators for whom all the “shalls” in this specification apply, not all aspects of this specification
are universally relevant. relevant to all actors/contributors. In some instances, the actor most likely to satisfy a requirement has
been identified in brackets after the requirement; this is for informative purposes only and does not indicate that only that actor
may fulfill that requirement. Where not specified, the system integrator/applicant is assumed to be the primary actor; in all cases,
the system integrator/applicant is responsible for all requirements and may choose to delegate requirements as is suitable to the
system design. Nonetheless, familiarity with the entire specification will inform all actors/contributors of how their contributions
affect the overall DAA capability and is strongly recommended.
1.11 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used
independently of the other, and values from the two systems shall not be combined.
1.12 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.
1.13 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 When external standards, documents, or studies are referenced by this specification, the latest revision applies unless otherwise
stated herein. Standards referenced should not be considered normative unless explicitly stated.
2.2 ASTM Standards:
F3060 Terminology for Aircraft
F3341/F3341M Terminology for Unmanned Aircraft Systems
ACAS sXu is intended to serve as a reference architecture for this specification.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
F3442/F3442M − 23
ASTM TR1-EB Autonomy Design and Operations in Aviation: Terminology and Requirements Framework
2.3 Other Documents:
14 CFR § 1.1 General definitions
14 CFR § 91.111 Operating near other aircraft
14 CFR § 91.113 Right-of-way rules: Except water operations
14 CFR § 91.119(c) Minimum safe altitudes. General.
14 CFR § 91.215 ATC transponder and altitude reporting equipment and use
14 CFR § 91.225 Automatic Dependent Surveillance-Broadcast (ADS-B) Out equipment and use
14 CFR § 107.37 Operation near aircraft; right-of-way rules
FAA AC (Advisory Circular) 23.1309-1E System Safety Analysis and Assessment for Part 23 Airplanes
FAA AC (Advisory Circular) 25.1322-1 Flightcrew Alerting (Dec. 13, 2010)
FAA Order 8260.3 United States Standard for Terminal Instrument Procedures (TERPS)
JARUS Specific Operations Risk Assessment (SORA) (package) V2.0, 30 January, 2019V2.0
Public Law 112-95 § 331 FAA Modernization and Reform Act of 2012—Definitions
RTCA DO-365ADO-365C Minimum Operational Performance Standards (MOPS) for Detect and Avoid (DAA) Systems,
published May 2017Systems
RTCA DO-381 MOPS for Ground-based Surveillance System (GBSS) for Traffic Surveillance
SERA Standardised European Rules of the Air
3. Terminology
3.1 Unique and Common Terminology—See Terminology Terminology used in multiple standards is defined in Terminologies
F3341/F3341M and F3060 and ASTM TR1-EB for definitions and abbreviations.UAS Terminology Standard. Terminology that
is unique to this specification is defined in this section.
3.2 Use of Shall, Should, and May—The use of shall indicates a requirement, should indicates a recommendation, and may is used
to indicate that something is permitted.
3.3 Definitions:
3.3.1 alert function, A1F, n—the function within the DAA system tasked with notifying the avoid function (whether human or
automated system, or both) of the presence of an intruder.
3.3.2 avoid function, A2F, n—the function within the DAA system tasked with providing the flight guidance necessary to maneuver
away from the potential hazard posed by detected intruder(s). Avoidance may be executed automatically by a flight controller or
manually by a pilot.
3.3.3 beyond visual line of sight, BVLOS, n—operation when the UA cannot be seen by the individuals responsible for
see-and-avoid with unaided (other than corrective lenses or sunglasses, or both) vision, but where the location of the sUAUA is
known through technological means without exceeding the performance capabilities of the C2 link.command and control (C2) link.
See Terminology F3341/F3341M.
3.3.4 collision avoidance, n—avoidance maneuver with the objective of preventing the predicted penetration of the near-midair
collision volume (NMAC).
3.3.5 controlled airspace, n—an airspace of defined dimensions within which air traffic control service is provided in accordance
with the airspace classification.
3.3.5.1 Discussion—
For example, in the United States, Classes A, B, C, D, and E airspace.
3.3.5.2 Discussion—
Controlled airspace does not automatically imply separation services, or that the location of all traffic is known.
Available from U.S. Government Publishing Office (GPO), 732 N. Capitol St., NW, Washington, DC 20401, http://www.govinfo.gov.
Available from Federal Aviation Administration (FAA), 800 Independence Ave., SW, Washington, DC 20591, http://www.faa.gov.
Available from Joint Authorities for Rulemaking on Unmanned Systems (JARUS), http://jarus-rpas.org/content/jar-doc-06-sora-package.
.AvailableAvailable from RTCA, Inc., 1828 L St., NW, Suite 805, Washington, DC 20036. 6
Available from European Union Aviation Safety Agency (EASA), Konrad-Adenauer-Ufer 3, D-50668 Cologne, Germany, https://www.easa.europa.eu.
F3442/F3442M − 23
3.3.6 cooperative intruder, n—those intruders using a Mode C/S transponder or ADS-B, or both, that operate with like equipment
used on other aircraft or ground-based services to establish the intruder’s position.
3.3.7 detect and avoid, DAA, n—a subsystem within the UAS providing the situationalsituation awareness, alerting, and avoidance
necessary to maintain safe BVLOS operation of the ownship in the presence of intruders.
3.3.8 DAA cycle, n—the maximum time from the presencedetection of the intruder intruder’s presence to the executioninitiation
of an avoidance maneuver.maneuver
3.3.9 DAA system integrator, n—person/organization/entity who integrates the parts of a DAA system, and then shows that the risk
ratios required by this standard are met.
3.3.10 detect function, DF, n—the function within the DAA system tasked with maintaining temporal and spatial awareness of
intruders.
3.3.11 encounter, n—the event associated with the presence of an intruder.
3.3.12 encounter rate, n—the number of encounters per unit of time.
3.3.13 false alert, n—an incorrect alert caused by a non-aircraft track or by a failure of the alerting system, including the sensor.
3.3.14 intruder, n—a mannedcrewed aircraft external to ownship within or projected to be in the ownship’s vicinity in the near
future.
3.3.14.1 Discussion—
This definition is deliberately equivocal since the DAA system architecture and technologies employed, as well as ownship
maneuvering capabilities, will shape the specific definitions of “vicinity” and “near future.” The term “traffic” is often used
synonymously with intruder.
3.3.15 loss of well clear, loWC, n—two aircraft coming within the well clear boundary of each other while in flight.
3.3.16 loss of well-clear well clear risk ratio (LR) measurement, n—the LR is the quotient of the probability of a loss of well-clear
well clear (LoWC) given an encounter with a DAA system, and the probability of loss of well-clear well clear given an encounter
without a DAA system. The lower the LR, the better the DAA system is at preventing a loss of well-clear. well clear. The LR is
FIG. 1 RR and LR Illustration
F3442/F3442M − 23
a measurement to ensure that a portion of the mitigation happens before loss of well-clear well clear as opposed to after loss of
WC. after. See Fig. 1. for depictions and formulae. See also Ref (1).
3.3.17 mid-air collision, MAC, n—two aircraft colliding with each other while in flight.
3.3.18 maintain well clear, n—the act of maneuvering an aircraft with the objective of preventing the predicted erosion of the well
clear margin of safety.
3.3.19 near mid-air collision, NMAC, n—two aircraft coming within 100 ft vertically and 500 ft horizontally of each other while
in flight.
3.3.20 NMAC risk ratio (RR) measurement, n—the RR is the quotient of the probability of an NMAC given an encounter with the
DAA system and the probability of an NMAC given an encounter without the DAA system. The lower the RR, the better the DAA
system is at preventing an NMAC.
3.3.20.1 Discussion—
The RR used in this assessment is not a measurement of the avoid function. collision avoidance function alone. The RR is a
measurement from an encounter to an NMAC, and it is a measurement of all UAS DAA systems components used in mitigating
NMAC. See Fig. 1. for depictions and formulae.
3.3.21 non-cooperative intruder, n—any aircraft not meeting the definition of cooperative in 3.3.6.
3.3.22 nuisance alert, n—alert generated by a system that is functioning as designed, but which is inappropriate or unnecessary
for the particular condition.
3.3.23 operational volume, n—the volume of airspace in which the UASUA operation intends, or is authorized, to take place.
3.3.23.1 Discussion—
The term operational volume in this specification is aligned with the JARUS use of the term in Annex C of the Specific Operations
Risk Assessment (SORA) and is different from the UAS traffic management (UTM)/U-Space(UTM)/U-space communities’ use of
the term. “Area of operation,” or the intersection of acceptable air and ground risk in accordance with the concept of operations,
is how this concept might be described in UTM/U-Space.UTM/U-space.
3.3.24 ownship, n—the UA controlled by the pilot flying and for which the pilot in command (PIC) is responsible.
3.3.25 pilot flying, n—an individual or system that manipulates the flight controls of an aircraft during flight; may or may not be
the pilot in command.
3.3.25.1 Discussion—
This is the same definition as in Terminology F3060, but we keep it here for the reader’s benefit.
3.3.26 regain well clear, n—the act of maneuvering an aircraft with the objective of restoring the well clear margin of safety that
has been degraded by preceding circumstances.
3.3.27 remote pilot in command, PIC,RPIC, n—the person who has final authority and responsibility for the operation and safety
of the ownship flight; person who is directly responsible for and is the final authority as to the operation of the UAS; has been
designated as PIC remote pilot in command before or during the flight; flight of a UAS; and holds the appropriate category class
and type-rating, if appropriate, CAA certificate for the conduct of the flight. (14 CFR § 1.1)
3.3.27.1 Discussion—
This is the same definition as in Terminology F3341/F3341M, but it is here for the reader’s benefit.
3.3.19 remain well-clear (RWC) function, n—DAA system function where the UAS takes appropriate action to prevent an intruder
from penetrating the WC boundary (and thus causing a loss of separation). The action is expected to be initiated within a sufficient
timeframe to conform to accepted air traffic standards. Any UAS maneuvers will be in accordance with regulations and procedures.
3.3.28 risk ratio measurement, n—used to measure the performance of a DAA system(s); the probability of an outcome with the
The boldface numbers in parentheses refer to the list of references at the end of this standard.
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DAA system(s), divided by the probability of an outcome without the DAA system(s),system(s); see Fig. 1. for depictions and
formulae. The lower the risk ratio, the better the DAA system is at mitigations.
3.3.29 rural area, n—all areasan area not defined as urban (see 3.3.263.3.32).
3.3.30 track, n—the specific collection of data that a particular DAA system accumulates and is used in determining whether an
intruder aircraft is a collision risk or loss of well-clear well clear risk, or both.
3.3.31 uncontrolled airspace, n—an airspace that is not controlled (see 3.3.43.3.5).
3.3.24 unmanned aircraft, UA, n—any aircraft that is operated without the possibility of direct human intervention from within
or on the aircraft. (Public Law 112-95 § 331)
3.3.25 unmanned aircraft system, UAS, n—a system comprised of an unmanned aircraft and associated elements, including
communication links, and the components that control the unmanned aircraft that are required for the pilot in command to operate
safely and efficiently in the national airspace system. (Public Law 112-95 § 331)
3.3.32 urban area, n—a town, outer suburban, suburban, residential area, urban, metro, city, or open-air assembly of people, or
combinations thereof.
3.3.33 visual line of sight, VLOS, well clear, n—unaided (corrective lenses or sunglasses, or both, excepted) visual contact between
a PIC and a UA sufficient to maintain safe operational control of the aircraft, know its location, and scan the airspace in which
it is operating to see and avoid other air traffic or objects aloft or on the ground.state where there is a low residual midair collision
risk informed by operational suitability.
3.3.34 well-clear well clear (WC) boundary, n—for UA in lower-risk airspace as defined aboveextent of the volume defined to
calculate the operating performance of a DAA system. For UA in lower-rick airspace, this is defined as 2000 ft horizontally and
6250 ft vertically vertically; see Fig. 1 and Ref (1).
3.3.34.1 Discussion—
Remaining well-clear well clear is meant to support compliance with 14 CFR § 91.111 and § 91.113 or § 107.37 (or international
equivalents) and reduce the chance of creating a collision hazard and therefore a collision.
3.3.35 yielded operating volume, n—operating volume where the competent authority accepts that crewed aircraft normally will
not fly because of regulatory limitations, or because crewed aircraft yield to a characteristic of the environment in the interest of
safety.
3.3.35.1 Discussion—
Regulatory limitations, policy, and/or guidance, such as per operating rules, for example, Standardised European Rules of the Air
(SERA), 14 CFR § 91.119(c), or restricted airspace. See 5.4.7 for operating environments with extremely low air risk airspace
classification and Appendix X2 for examples and more detail
4. Significance and Use
4.1 This specification outlines the system objectives, activities, and evidence required to demonstrate adequate design and safe use
of a detect and avoid (DAA) system. Such systems, in concert with other systems and equipment, enable unmanneduncrewed
aircraft systems (UAS) to operate beyond the visual line of sight (BVLOS) of the pilot in command (PIC). As the name suggests,
these systems comprise a function for sensing potential flight hazards and assessing hazard severity (“detect”) and a function for
maneuvering the aircraft out of the way of the hazard (“avoid”). Such systems may also support operations within the PIC’s visual
line of sight (VLOS).
4.1.1 While there are many possible static and dynamic hazards to UA flight (for example, obstacles, birds, terrain, weather, other
UAs), this specification addresses the safe operations of the UA in the presence of mannedcrewed aircraft, which may or may not
be cooperative with the UA, otherwise known as “intruders.”
4.1.2 Despite the diversity in emerging DAA systems, these systems share the following attributes:
Alternative well-clear well clear means may be appropriate in proximity to terrain or obstacles when justified.
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4.1.2.1 Intruder Level of Cooperation —Cooperative systems rely on information being supplied by the intruder (for example,
intruder transponder, automatic dependent surveillance-broadcast (ADS-B) Out) whereas non-cooperative systems do not rely on
the intruder supplying information. Many DAA systems use a combination of cooperative and non-cooperative sensors for
obtaining information regarding an intruder.
NOTE 1—While some cooperative systems (for example, mode A transponder) provide very little information that is useful for the purposes of the DAA,
they are still considered cooperative systems.
4.1.2.2 DAA Level of Autonomy—DAA systems may range from fully manual to fully automated functionality. In the fully manual
construct, the PIC is presented with data, and it is up to them the PIC to decide and execute any needed maneuvers. In the fully
automated construct, the system is responsible for determining and executingdetermines and executes any necessary maneuvers.
A spectrum of functional allocation is possible in between these two architectures.
4.1.2.3 Location of DAA Systems and Functionality—The architecture of a given DAA system may use any combination of
airborne and ground components. The proximity of DAA functions to the UA versus the GCS Control Station each pose unique
benefits and challenges regardless of system timing and latency, UA payload, sensor orientation, field of regard or surveillance
coverage, range, track accuracy, etc.and so forth.
4.1.2.4 Sensor Type—The greatest differentiation between DAA systems is in sensors. Sensing technologies vary and include radio
frequency (radar, passive radio frequency reception), light (camera, light detection and ranging (LiDAR)), and acoustic
approaches. Each offers distinct advantages and disadvantages. Therefore, DAA systems may utilize multiple sensor categories to
achieve comprehensive detection and appropriate levels of uncertainty and information quality.
4.1.2.5 Equipage—It is assumed that UA with a largest dimension of 25 ft or less are not equipped with either a transponder or
ADS-B-out and thus are not cooperative with traditional crewed air traffic.
5. System Description
5.1 Overview:
5.1.1 This section identifies the set of objectives that the DAA system, including the pilots if they are human pilot if required to
be “in the loop,” must meetshall satisfy as a complete unit.
5.1.2 Two classes of DAA equipment are covered by this specification: specified: Class 1 for operations in low-risk
airspaceairspace; and Class 2 for operating in low- or medium-risk airspace as defined by the CAA. See 5.3.1 for more
information.description of airspace and 5.5.2 on Class 1 and 2.
5.1.3 This specification does not address integration of DAA equipment with other safety systems such as geographical
containment systems (that is, geofencing) and terrain avoidance systems.
5.1.4 The communication link of DAA information (C2 and sensor) complies with regulatory policy in terms of spectrum use and
frequency allocations.
5.2 System Verification:
5.2.1 If required to do so by the CAA, the applicant/proponent shall provide to the CAA or CAA-approved test organization, or
both, evidence of physical verification demonstrating the DAA system meets all required performance criteria identified or
generated in response to this specification.
5.2.2 Physical verification may take the form of field tests against actual targets and objectives or lab tests against representative
targets, as long as data is supplied confirming equivalency to real targets. An approach to verifying these requirements will be
defined in an ASTM test method currently under development.
Intruder equipage entirely determines cooperative versus non-cooperative status.
It is assumed the PIC is kept apprised of the action.
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NOTE 2—An approach to verifying these requirements will be defined in an ASTM test method currently under development.
5.2.3 Analysis and simulation should be used as a form of performance verification when physical performance is impractical (for
example, difficult corner cases, extensive time-based testing, or sheer volume of test case permutations). In these situations, the
analysis or simulation shall still be substantiated using a sampling of physical test data to establish validity.
5.3 Safety:
5.3.1 Air Collision Risk Classification of Operational Volume—In order to assess risk, the airspace needs to be classified into
categories based on airborne collision risk under which a UASUA would encounter a mannedcrewed aircraft. In a manner similar
to the JARUS SORA, this specification assumes four unmitigated airborne collision risk classification levels: High, Medium, Low,
and Extremely-Low Air Risk. However, only DAA system performance for DAA Class 1 and Class 2 systems (to be used in low-
and medium-risk airspace, respectively), is in scope for this specification. As a DAA standard, this specification does not specify
the method for determining the airspace risk classification level for a given operation, but general guidance is given to provide
context for the system performance in low and medium air risk airspace.
5.3.1.1 High Air Risk (Out of Scope for this Requirements Document)—(out of scope for this requirements document)—This is
airspace where mannedcrewed aircraft predominately fly, or the mannedcrewed aircraft encounter rate is frequent, or both. The
competent authority is expected to require the operator to comply with recognized DAA system standards as available and
appropriate to the application (for example,(that is, those developed by RTCA SC-228 (see RTCA DO-365A) DO-365C), SC-147,
or EUROCAE WG-105, or both).WG-105).
5.3.1.2 Medium Air Risk—This is airspace where mannedcrewed aircraft predominately do not fly (excluding helicopters and crop
dusters) or the mannedcrewed aircraft encounter rate is occasional, or both. This is generally uncontrolled airspace and/or airspace
that goes from the ground to between 300300 ft to 1200 ft AGL (with 500 ft AGL used as a common default), above which most
mannedcrewed aircraft operations are conducted. This includes airspace away from Class B, C, and D aerodromes, or near Class
B, C, and D aerodromes with additional strategic mitigations.
5.3.1.3 Low Air Risk—This is airspace where manned aircraft predominatelycrewed aircraft generally do not fly (excluding
helicopters and crop dusters) or the mannedcrewed aircraft encounter rate is remote or improbable in accordance with guidelines
and regulations from the competent authority, or both. This is generally uncontrolled airspace and/or airspace that goes from the
ground to between 300300 ft to 1200 ft AGL (with 500 ft AGL used as a common default), above which most mannedcrewed
aircraft operations are conducted and away from urban population centers, towns, outer suburban, suburban, residential areas,
metro, or cities, or combinations thereof, and outside all aerodromes. Helicopter and crop duster operations may occur in low-risk
airspace and may require special consideration, as they may operate at low altitudes, in uncontrolled airspaces, or otherwise alter
the expected crewed aircraft encounter rate.
5.3.1.4 Extremely Low Air Risk (Out of Scope for this Requirements Document)—Airspace Classification—This is airspace where
mannedcrewed aircraft predominately do not fly or the manned aircraft encounter rate is extremely improbable, or both. It is
generally defined as airspace where the risk of collision between a UAS and manned aircraft is acceptable without the addition
of any tactical mitigation (for example, a DAA system). An example of this may be UAS flight operations in some parts of Alaska
or northern Sweden where the manned aircraft density is so low that the airspace safety threshold could be met without any
mitigation.fly, or the likelihood of an encounter with a crewed aircraft has been shown to be extremently improbably, or both.
Examples of such a classification include the use of robust containment to remain within a yielded operating volume, or operations
in remote, sparsely populated areas such as parts of northern Canada or northern Sweden.
5.3.2 Local Air Risk Assessment of Operational Volume (see 3.3.15)—If a local an airspace authority or air navigation service
provider (ANSP), or both, has conducted an airspace characterization and classified the collision risk of the operational volume,
that collision risk assessment will be used as the method for categorizing the airspace. Strategic mitigations and/or existence of
yielded operating volumes may also be used in determiningwhen characterizing the operational volume airspace airspace.catego-
rization.
5.3.3 Generalized Collision Risk Assessment of Operational Volume—If a local classification of the collision risk of the operational
volume does not exist, the example a generalized air risk assessment inassessment, such 5.3.4 can be used. The JARUS SORAas
the JARUS SORA or example in 5.3.4is a generalized air risk assessment., can be used.
5.3.4 Generalized Air Risk Assessment DescriptionsDescriptions::
F3442/F3442M − 23
TABLE 1 Example Generalized Collision Risk Airspace
Classification Summary from JARUS SORA
Airspace Airspace Description
Medium Air Risk Uncontrolled Airspace
Below 500 ft AGL in controlled airspace, at least 5 nm
away from the center point of Class B, C, and D
aerodromes
Below 500 ft AGL over an urban area
Below 500 ft AGL in/over/around Class E, F, or G
aerodromes
Near Class B, C, and D aerodromes with additional
strategic mitigations, for example, remaining below
facility map altitudes
Low Air Risk Uncontrolled airspace, below 500 ft AGL, over a rural
area, outside all aerodromes
TABLE 2 Summary of DAA Performance Guidance for UAS
DAA Quantitative Performance Requirements
Intruder Equipage
NMAC Risk Ratio Loss of Well-Clear
(RR) Risk Ratio (LR)
Transponder or #0.18 #0.40
ADS-B Out
Non-cooperative #0.30 #0.50
TABLE 2 Summary of DAA Performance Guidance for UAS
DAA Quantitative Performance Requirements
Intruder Equipage
NMAC Risk Ratio Loss of Well Clear
(RR) Risk Ratio (LR)
ADS-B Out #0.18 #0.40
Non-cooperative or #0.30 #0.50
transponder-only
5.3.4.1 These airborne collision risk classifications are generalized classifications. As with any generalization, Consequently, when
the area becomes more refined, there willmay be specific areas where the generalized classification levels will be true, and other
specific areas where the generalized classification levels will not be true. true and others where it will not. The operator will work
with the local airspace authority to ensure that the appropriate air risk classification is assigned to the operational volume.
5.3.4.2 As with any classification scheme, it is always a balance between too few classifications and too many classifications.
5.3.4.2 Example Examples of a Generalized Airspace Air Risk Classification Summary—See Table 1. (taken from the JARUS
SORA). The following are notional examples and not definitive classifications within this ASTM specification.
5.4 UAS DAA Performance Requirements:
5.4.1 The risk ratios in this specification are “logic” risk ratios as in accordance with the International Civil Aviation Organization
(ICAO) definition. Included is nominal system performance: performance are: logic, specified surveillance performance, field of
view limitations, expected human pilot performance, specified/nominal C2 link performance, expected latencies for all
components. components, and ownship performance. Not included are failures: failures, for example, corrupted logic, sensor
failures, C2 link failures, DAA equipment failures/faults, non-responsive pilot. Performance under failure conditions should be
addressed through system safety assessments. Note that JARUS specifies total system risk ratios.
5.4.2 In this specification, the risk ratios discussed by the ICAO remotely piloted aircraft systemsRemotely Piloted Aircraft
Systems (RPAS) panel have been used but are applied to a smaller well-clear well clear boundary (for example, 2000 ft). This
adjustment leads to a similar RR even with lower performing UAS DAA equipage. (See Ref (2).) The smaller well-clear well clear
boundary is used due to the lower closure rates and smaller P(MAC|NMAC) due to the small size of the UAS.
5.4.3 The RR and LR performance requirements in this section shall be verified using a statistically significant set(s)number of
encounters that are representative of the operational environment airspace. Encounter sets are representative when they include
See https://www.icao.int/safety/UA/Pages/Remotely-Piloted-Aircraft-Systems-Panel-(RPASP).aspx.
F3442/F3442M − 23
appropriate and realistic distributions of ownship and intruder flight dynamics, speeds, vertical rates, and encounter geomet-
ricsgeometries for the airspace class, altitude, and geographic region where the DAA equipment is expected to operate. For
cooperative intruders, encounter sets and the mix of Mode C, Mode S, and ADS-B equipped intruders for verifying ratios are
defined in DAA test methods. operate to the satisfaction of the CAA. When evaluating the DAA system against ADS-B Out
intruders, the encounter set(s) should include behaviors representative of both 1200-code and discrete code operations. When
evaluating the DAA system against non-cooperative and transponder-only intruders, the encounter set(s) should include behaviors
representative of aircraft without a transponder and aircraft with a transponder but without ADS-B in both 1200-code and discrete
code operations. Limitations on the DAA equipment shall be identified based on limitations of the encounter setsset(s) used to
verify the performance requirements.
5.4.4 In operational volumes with low and medium air risk, DAA performance for NMAC avoidance (RR) requirements are based
on the ICAO work cited in 5.4.2 and are dependent on the equipage type of the intruder.
5.4.4.1 For encounters with intruders equipped with a transponder or ADS-B, ADS-B Out, the DAA system RR shall be ≤0.18.
5.4.4.2 For non-cooperative encounters with non-cooperative or transponder-only intruders, the DAA system RR shall be less than
or equal to 0.30.≤0.30.
5.4.5 In operational volumes with low and medium air risk, DAA performance for remain well-clear loss of well clear (LR)
requirements are based on the ICAO work cited in 5.4.2 and are dependent on the equipage type of the intruder.
5.4.5.1 For intruders equipped with a transponder or ADS-B Out, the DAA system LR shall be ≤0.40.
5.4.5.2 For non-cooperative or transponder-only intruders, the DAA system LR shall be ≤0.50.
5.4.6 DAA Performance Summary—See Table 2.
5.4.7 In operational volumes with extremely low air risk, RR and LR may not be appropriate DAA performance metrics. Here,
the rate of unmitigated encounters with crewed aircraft is assumed to be extremely low. As such, the competent authority may not
require a DAA system for operations within such airspace.
NOTE 3—While the risk ratio equation is unchanged, due to the low rate of unmitigated encounters, the risk ratio metric is uninformative because there
may not be a DAA system in the traditional sense, or it is not possible to generate realistic unmitigated encounters because of the low rate of unmitigated
encounters (the denominator would be near zero). Other performance metrics, such as navigation performance or robust containment, may be more useful
to assess the DAA system.
5.4.8 In addition, it is expected that in certain operational volumes where the rate of non-cooperative or transponder-only equipped
encounters can be demonstrated to be extremely low, the RR and LR for non-cooperative or transponder-only equipped encounters
may not be appropriate performance metrics for a DAA system. As such, the competent authority may not require a
non-cooperative DAA system for operations within operational volumes where the rate of non-cooperative or transponder-only
equipped encounters can be demonstrated to be extremely low.
NOTE 4—While the non-cooperative or transponder-only equipped risk ratio equation is unchanged because of the low rate of unmitigated non-cooperative
or transponder-only equipped encounters, the non-cooperative or transponder-only equipped risk ratio metric is uninformative because the denominator
would be near zero.
5.5 UAS DAA Robustness Requirements:
5.5.1 The robustness of the DAA system shall be is characterized by the availability and assurance level of the system. This
approach is similar to that adopted by JARUS.
5.5.2 DAA System Availability:
5.5.2.1 The approach to system availability here is derived from the JARUS process for UAS Special Operation Risk Assessment.
SORA V2.0 Annex D, section 5.4 (TMPR (Tactical Mitigation Performance Requirement) Robustness (Integrity and Assurance)
See Airspace Encounter Models on GitHub (https://github.com/airspace-encounter-models) for models of aircraft behavior in U.S. airspace.
F3442/F3442M − 23
Assignment). The level of system availability of the DAA system differentiates Class 1 and 2 systems. Loss of function includes
failures such as sensor failures, C2 link failures, and DAA equipment failures, which are not captured in the RR and LR
performance requirements.
5.5.2.2 For Class 1 equipment (operational (to be used in operational volumes with low air risk), the allowable loss of function
and performance shall be less than 1 per 100 flight hours (1E-2 Loss/FH).
5.5.2.3 For Class 2 equipment (operational (to be used in operational volumes with medium air risk), the allowable loss of function
and performance shall be less than 1 per 1000 flight hours (1E-3 Loss/FH).
5.5.2.4 The requirements on availability may be met by:
(1) Showing redundancy in the equipment providing that function. An analysis of a redundant system in the aircraft is usually
complete if it shows isolation between redundant system channels and satisfactory reliability for each channel; or
(2) In the case where single failures can cause the failure condition, by showing the system is simple, uses conventional
architecture, is appropriately qualified for the installed environment and the individual failure rates of its components are below
the objective of 1E-2 for Class 1 Equipment or 1E-3 for Class 2 Equipment.
These are two ways, but not the only ways, of meeting 5.5.2.2 and 5.5.2.3.
5.5.3 DAA System Assurance:
5.5.3.1 The approach to system assurance here is derived from the JARUS process for UAS Special Operation Risk Assessment.
SORA. The level of system assurance of the DAA system differentiates Class 1 and 2 systems. Hazardously misleading information
is introduced by undetected software and hardware faults which aren’t faults, which are not captured in the RR and LR
performance requirements. Hazardously misleading information does not include information, such as false tracks, that does not
result in a hazardous maneuver. Likewise, hazardously misleading information does not include faults that are detected and covered
by the loss of function requirements in 5.5.2. Allowable failure rates are determined from the AC 23.1309-1E precedent that most
misleading and/or malfunction without warning severity classifications (see Appendix 1 in the AC) are one category more severe
than the regular loss of function and that, for Class I aircraft (see FIG. 2 in AC 23.1309-1E), a one category increase in severity
is equivalent to a one order of magnitude decrease in the event rate per flight hour.
5.5.3.2 For Class 1 equipment (operations in (to be used in operations in low air risk airspace), the allowable introduction of
hazardously misleading information shall be less than 1 per 10 0001000 flight hours (1E-4(1E-3 Loss/FH).
5.5.3.3 For Class 2 equipment (operations in low or(to be used in operations in medium air risk airspace), the allowable
introduction of hazardously misleading information shall be less than 1 per 100 00010 000 flight hours (1E-5(1E-4 Loss/FH).
5.5.4 ADS-B Data Validation—Independent validation of ADS-B is not expected to be a requirement in all smaller UAS DAA
operational scenarios. There are some situations where other mitigations may be in place, or the operation is of such low risk that
ADS-B validation is not necessary. Operators who want to use ADS-B in smaller UAS DAA applications without independent
validation must demonstrate to the regulator that it is acceptable for their operation.
5.5.5 Timestamping:
5.5.5.1 The DAA system shall employ a consistent time basis across all functions for marking the time of applicability of
measurements and calculated parameters (for example, GPS, UTC). Time of applicability is herein defined as the time at which
a particular measurement or parameter was determined relative to some temporal origin point that is fixed for at least the duration
of any one power cycle of the DAA system (though a universal time origin, like UTC, is strongly preferred). For parameters
received from an outside source (for example, ADS-B In), time of applicability is to be taken from the corresponding field in the
received data – reverting to the time of receipt if the time of applicability was not provided in the transmission.
5.5.5.2 The DAA system timing, if based on GPS, shall be resilient to GPS failures. GPS dropouts are common, so if GPS time
is the time basis, a method of time-coasting is needed to ensure that timestamping can occur uninterrupted.
NOTE 5—As soon as a measurement or calculation is made, this information starts becoming stale (that is, increasingly irrelevant). As information flows
through the system, it may accumulate non-uniform levels of staleness. Thus, it is important to be able to determine how stale each piece of information
is. DAA integrators should work with individual function suppliers to ensure that a means of accurately timestamping information is available to all
functions. Using a broadly accepted time basis (for example, GPS, UTC) is suggested to maximize compatibility between suppliers and integrators but
is not mandated.
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5.6 Reliability and Maintenance:
5.6.1 A methodology for anticipating and detecting failures and accomplishing appropriate maintenance actions should be
identified and implemented for the major subsystems or components of the DAA system, as well as the system as a whole.
5.6.1.1 If required, the DAA system shall have a maintenance plan and maintenance schedule in accordance with the maintenance
instructions provided by the manufacturer. The maintenance instructions shall provide direction as to verification of proper
installation and calibration of the system to ensure continued performance is met in the field.
5.6.2 The DAA system shall have a test function for detecting probableforeseeable “static” system failures. “Static” system
failures are degradations in the condition of the system that would prevent correct operation (for example, memory faults, device
failures, wear out). These are different than “dynamic” errors, which are due to unforeseen events during runtime. Test function
requirements should
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