ASTM F3254-22

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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: F3254 − 19 F3254 − 22
Standard Specification for
Aircraft Interaction of Systems and Structures
This standard is issued under the fixed designation F3254; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This specification covers the airworthiness requirements that address the interaction of systems and structures. The material
was developed through open consensus of international experts in general aviation. This information was created by focusing on
Normal Category aeroplanes. The content may be more broadly applicable; it is the responsibility of the applicant to substantiate
broader applicability as a specific means of compliance.
1.2 An applicant intending to propose this information as Means of Compliance for a design approval must seek guidance from
their respective oversight authority (for example, published guidance from applicable Civil Aviation Authority (CAAs)) concerning
the acceptable use and application thereof. For information on which oversight authorities have accepted this specification (in
whole or in part) as an acceptable Means of Compliance to their regulatory requirements (hereinafter “the Rules”), refer to the
ASTM Committee F44 web page (www.ASTM.org/COMMITTEE/F44.htm). Annex A1 maps the Means of Compliance of the
ASTM Standards to EASA CS-23, amendment 5, or later, and FAA 14 CFR Part 23, amendment 64, or later.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
F3060 Terminology for Aircraft
F3093/F3093M Specification for Aeroelasticity Requirements
F3115/F3115M Specification for Structural Durability for Small Aeroplanes
F3116/F3116M Specification for Design Loads and Conditions
F3230 Practice for Safety Assessment of Systems and Equipment in Small Aircraft
2.2 EASA Standard:
CS-23 Normal, Utility, Aerobatic and Commuter Aeroplanes
2.3 FAA Standard:
14 CFR Part 23 Airworthiness Standards: Normal Category Airplanes
This specification is under the jurisdiction of ASTM Committee F44 on General Aviation Aircraft and is the direct responsibility of Subcommittee F44.30 on Structures.
Current edition approved May 1, 2019April 1, 2022. Published June 2019April 2022. Originally approved in 2019. Last previous edition approved in 2019 as F3254–19.
DOI: 10.1520/F3254–19.10.1520/F3254-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from European Union Aviation Safety Agency (EASA), Konrad-Adenauer-Ufer 3, D-50668 Cologne, Germany, https://www.easa.europa.eu.
Available from Federal Aviation Administration (FAA), 800 Independence Ave., SW, Washington, DC 20591, http://www.faa.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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3. Terminology
3.1 A listing of terms, abbreviations, acronyms, and symbols related to aircraft covered by ASTM Committees F37 and F44
airworthiness design standards can be found in F3060 Terminology for Aircraft. Items listed here are more specific to this
specification.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 extremely improbable—the allowable quantitative probability based on the assessment level and catastrophic failure
condition classification.
3.2.1.1 Discussion—
The term extremely improbable is defined in Practice F3230. As used in this specification, it represents the allowable quantitative
probability to be used in this specification based on the assessment level and catastrophic failure condition classification found in
Practice F3230.
3.2.2 failure condition—structural system failure condition that affects the structural performance of the aeroplane.
3.2.2.1 Discussion—
The term failure condition in this specification applies only to structural system failure conditions that affect the structural
performance of the aeroplane (for example, system failure conditions that induce loads, change the response of the aeroplane to
inputs such as gusts or pilot actions, or lower flutter margins).
3.2.3 flight limitation—limitations that can be applied to the aeroplane flight conditions following an in-flight occurrence.
3.2.3.1 Discussion—
Example flight limitations include speed limitations and avoidance of severe weather. These limitations are included in the flight
manual.
3.2.4 operational limitation—limitations, including flight limitations, that can be applied to the aeroplane operating conditions
before flight.
3.2.4.1 Discussion—
Example operational limitations include fuel, payload, and Master Minimum Equipment List limitations.
3.2.5 probable—the allowable quantitative probability based on the assessment level and minor failure condition classification.
3.2.5.1 Discussion—
The term probable is defined in Practice F3230. As used in this specification, it represents the allowable quantitative probability
to be used in this specification based on the assessment level and minor failure condition classification found in Practice F3230.
3.2.6 remote—the allowable quantitative probability based on the assessment level and major failure condition classification.
3.2.6.1 Discussion—
The term remote is defined in Practice F3230. As used in this specification, it represents the allowable quantitative probability to
be used in this specification based on the assessment level and major failure condition classification found in Practice F3230.
3.2.7 structural performance—capability of the aeroplane to meet the applicable structural requirements.
3.2.8 structural system—system where the intended function is to alter an aeroplane’s structural design envelope or where failure
or malfunction adversely affects structural performance.
3.2.8.1 Discussion—
Example structural systems include, but are not limited to, active flight control systems, stability augmentation systems, load
alleviation systems, flutter control systems, flight-envelope protection systems, control surface limiting systems, rudder bias
systems, autopilot systems, and fuel management systems.
3.3 Symbols:
P = probability of occurrence of failure mode j (per hour)
j
Q = probability of being in failure condition j
j
T = average time spent in failure condition j (in hours)
j
V' = clearance speed as defined by Specification F3093/F3093M, requiring freedom from flutter, control reversal, and
divergence up to V /M after the specified system failure.
D D
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V'' = clearance speed as defined by Specification F3093/F3093M, requiring freedom from flutter, control reversal, and
divergence for any condition of operation within the limit V-n envelope and at all speeds up to 1.2 V /1.2 M , limited to
D D
Mach 1.0 for subsonic aeroplanes.
4. Interaction of Systems and Structure
4.1 Applicability—For aeroplanes equipped with structural systems, the influence and failure of these systems must be taken into
account. Fig. 1 provides an assessment of the applicability of this specification to a specific system, along with the depth of analysis
required to show compliance.
4.2 General—The criteria in this specification address the structural performance of aeroplanes equipped with structural systems.
FIG. 1 Depth of Analysis Flowchart
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4.2.1 The criteria defined herein only address the direct structural consequences of the system responses and performances and
cannot be considered in isolation but must be included in the overall safety evaluation of the aeroplane. These criteria are only
applicable to structure whose failure could prevent continued safe flight and landing. Specific criteria that define acceptable limits
on handling characteristics or stability requirements when operating in the system degraded or inoperative mode are not provided
in this specification.
4.2.2 Depending upon the specific characteristics of the aeroplane, additional studies may be required that go beyond the criteria
provided in this specification in order to demonstrate the capability of the aeroplane to meet other realistic conditions such as
alternative gust or maneuver descriptions for an aeroplane equipped with a load alleviation system.
4.3 System Fully Operative—With the structural system fully operative, the following apply:
4.3.1 Limit loads must be derived in all normal operating configurations of the system from all the limit conditions specified in
Specification F3116/F3116M (or used instead of those specified in Specification F3116/F3116M), taking into account any special
behavior of such a system or associated functions or any effect on the structural performance of the aeroplane up to limit loads.
In particular, any significant nonlinearity (rate of displacement of control surface, thresholds, or any other system nonlinearities)
must be accounted for in a realistic or conservative way when deriving limit loads from limit conditions.
4.3.2 The aeroplane must meet the applicable static strength requirements using the specified factors to derive ultimate loads from
the limit loads defined in 4.3.1. The effect of nonlinearities must be investigated beyond limit conditions to ensure the behavior
of the system presents no anomaly compared to the behavior below limit conditions. However, conditions beyond limit conditions
need not be considered when it can be shown that the aeroplane has design features that will not allow it to exceed those limit
conditions.
4.3.3 The aeroplane must meet the aeroelastic stability requirements of Specification F3093/F3093M.
4.3.4 The aeroplane must meet the structural durability require
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