Standard Practice for Developing Simplified Fatigue Load Spectra

SIGNIFICANCE AND USE
4.1 This standard practice provides one means for determining fatigue load spectra for aeroplane durability assessments. This information can be used in conjunction with Specification F3115/F3115M, Section 5, Load Considerations.  
4.1.1 Users of this practice may propose alternate spectra, subject to the approval of their CAA.  
4.2 The methods are applicable to the durability evaluation of wings of small aeroplanes. Additional calculation (such as methods noted in ACE-100-01) are needed to properly develop load spectra for fatigue evaluation of empennage and/or configurations with canards (or forward wings) and/or winglets (or tip fins), fuselage, and potentially other components, with approval from appropriate regulatory agency.  
4.3 Much of the material presented herein is directly taken from AC 23-13A. The FAA developed the flight load spectra, presented herein, based on a statistical analysis of the data presented in DOT/FAA/CT-91/20. The ground load spectra are directly from AFS-120-73-2.  
4.4 The flight load spectra, presented in Section 7, includes an adjustment (1.5 standard deviations) to the average measured load frequency. The adjustment accounts for the variability in the loading spectra experienced by individual aeroplanes, as well as across aeroplane types. The magnitude of the adjustment was selected to maintain the probability that a component will reach its safe-life without a detectable fatigue crack established by scatter factor (see paragraph 2–15 of AC 23-13A).
SCOPE
1.1 This practice provides data to develop simplified loading spectra that can be used to perform structural durability analysis for aeroplanes, specifically for wings of small aeroplanes. The material was developed through open consensus of international experts in general aviation. The information was created by focusing on Level 1, 2, 3, and 4 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 authorities, or CAAs) concerning the acceptable use and application thereof. For information on which oversight authorities have accepted this standard (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).  
1.3 The values stated in inch-pound units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 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.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

Status
Published
Publication Date
31-Dec-2020
Drafting Committee
Current Stage
Ref Project

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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: F3498 −21
Standard Practice for
1
Developing Simplified Fatigue Load Spectra
This standard is issued under the fixed designation F3498; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
2
1.1 This practice provides data to develop simplified load- 2.1 ASTM Standards:
ing spectra that can be used to perform structural durability E1049 Practices for Cycle Counting in Fatigue Analysis
analysis for aeroplanes, specifically for wings of small aero- F3060 Terminology for Aircraft
planes.The material was developed through open consensus of F3115/F3115M Specification for Structural Durability for
international experts in general aviation. The information was Small Aeroplanes
3
created by focusing on Level 1, 2, 3, and 4 Normal Category
2.2 EASA Standard:
aeroplanes. The content may be more broadly applicable; it is
CS-23 Normal, Utility,Aerobatic and CommuterAeroplanes
the responsibility of the applicant to substantiate broader
2.3 FAA Documents:
applicability as a specific means of compliance.
14 CFR 23 Airworthiness Standards: Normal, Utility,
4
Acrobatic, and Commuter Category Airplanes
1.2 An applicant intending to propose this information as
AC 23-13A Fatigue, Fail-Safe, and Damage Tolerance
Means of Compliance for a design approval must seek guid-
Evaluation of Metallic Structure for Normal, Utility,
ance from their respective oversight authority (for example,
5
Acrobatic, and Commuter Category Airplanes
published guidance from applicable civil aviation authorities,
ACE-100-01 Fatigue Evaluation of Empennage, Forward
or CAAs) concerning the acceptable use and application
6
Wing and Winglets/Tips Fins on Part 23 Airplanes
thereof. For information on which oversight authorities have
Report No. AFS-120-73-2 Fatigue Evaluation of Wing and
accepted this standard (whole or in part) as an acceptable
7
Associated Structure on Small Airplanes
Means of Compliance to their regulatory requirements (here-
DOT/FAA/AR-96/46 User’s Guide for FAR23 Loads Pro-
inafter “the Rules”), refer to the ASTM Committee F44 web
6
gram
page (www.astm.org/COMMITTEE/F44.htm).
DOT/FAA/CT-91/20 General Aviation Aircraft – Normal
1.3 The values stated in inch-pound units are to be regarded
6
Acceleration Data Analysis and Collection Project
as standard. No other units of measurement are included in this
standard.
3. Terminology
1.4 This standard does not purport to address all of the
3.1 The following are a selection of terms relevant to this
safety concerns, if any, associated with its use. It is the
practice. See Terminology F3060 for more definitions and
responsibility of the user of this standard to establish appro-
abbreviations.
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accor-
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
dance with internationally recognized principles on standard-
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
ization established in the Decision on Principles for the
the ASTM website.
Development of International Standards, Guides and Recom-
3
Available from European Aviation Safety Agency (EASA), Konrad-Adenauer-
mendations issued by the World Trade Organization Technical
Ufer 3, D-50668 Cologne, Germany, https://www.easa.europa.eu/.
4
Barriers to Trade (TBT) Committee. Available from Federal Aviation Administration (FAA), 800 Independence
Ave., SW, Washington, DC 20591, http://www.faa.gov.
5
Available from U.S. Government Publishing Office (GPO), 732 N. Capitol St.,
1
This practice is under the jurisdiction of ASTM Committee F44 on General NW, Washington, DC 20401, http://www.gpo.gov.
6
Aviation Aircraft and is the direct responsibility of Subcommittee F44.30 on Available from National Technical Information Service (NTIS), 5301 Shawnee
Structures. Rd., Alexandria, VA 22312, http://www.ntis.gov.
7
Current edition approved Jan. 1, 2021. Published February 2021. DOI: 10.1520/ Available from Clearinghouse for Federal Scientific andTechnical Information,
F3498-21. Springfield, VA 22151.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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