1、Designation: F3115/F3115M 15Standard Specification forStructural Durability for Small Airplanes1This standard is issued under the fixed designation F3115/F3115M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year of last revi
2、sion. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This specification addresses the airworthiness require-ments related to structural durability for the design of smallairplanes.
3、1.2 This specification was originally conceived for smallairplanes as defined in the F44 terminology standard but mayfind broader applicability. Use of the term aircraft throughoutthis specification is intended to allow the relevant CAA(s) toaccept this standard as a means of compliance as theydeter
4、mine it to be appropriate, whether for small airplanes orfor other types of aircraft.1.3 The applicant for a design approval must seek individualguidance from their respective CAA body concerning the useof this standard as part of a certification plan. For informationon which CAA regulatory bodies h
5、ave accepted this standard(in whole or in part) as a means of compliance to their SmallAirplane Airworthiness Rules (hereinafter referred to as “theRules”), refer to ASTM F44 webpage (www.ASTM.org/COMMITTEE/F44.htm) which includes CAA website links.1.4 The values stated in either SI units or inch-po
6、und unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.5 This standard does not purport to
7、address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2F3060 Term
8、inology for Aircraft2.2 Federal Aviation Regulations:314 CFR Part 23 Amendment 62, 23.571 through 23.575,23.6272.3 EASA Requirements:CS 23, 23.571 through 23.575CS-VLA3. Terminology3.1 The following are a selection of relevant terms. SeeTerminology F3060 for more definitions and abbreviations.3.2 De
9、finitions:3.2.1 fatiguethe process of progressive localized perma-nent structural change occurring in a material subjected toconditions that produce fluctuating stresses and strains at somepoint or points, which may result in cracks or complete fractureafter a sufficient number of fluctuations.3.2.2
10、 safe lifethe safe-life of a structure is that number ofevents, such as flights, landings, or flight hours, during whichthere is a low probability that the strength will degrade belowits design ultimate value due to fatigue cracking.3.2.3 S-N or -NStress-Life (S-N) or Strain-Life (-N)curves depict t
11、he magnitude of applied stress (S) or strain ()necessary to develop a fatigue crack in a specimen at a givenlife (N), where N is expressed in the number of cyclicapplications of stress or strain.3.2.4 scatter factorthe scatter factor, or life reductionfactor, is a statistically derived divisor appli
12、ed to fatigue testresults to account for the variation in fatigue performance ofbuilt-up or monolithic structures and usage variability. Ascatter factor can also be used in a fatigue analysis to addressthe uncertainties inherent in a fatigue analysis.3.2.5 fail safefail-safe is the attribute of the
13、structure thatpermits it to retain its required residual strength for a period ofunrepaired use after the failure or partial failure of a principalstructural element.3.2.6 damage tolerancedamage tolerance is the attributeof the structure that permits it to retain its required residual1This specifica
14、tion is under the jurisdiction ofASTM Committee F44 on GeneralAviation Aircraft and is the direct responsibility of Subcommittee F44.30 onStructures.Current edition approved June 1, 2015. Published September 2015. DOI:10.1520/F3115_F3115M-15.2For referenced ASTM standards, visit the ASTM website, ww
15、w.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from U.S. Government Printing Office Superintendent of Documents,732 N. Capitol St., NW, Mail Stop: SDE, Was
16、hington, DC 20401, http:/www.access.gpo.gov.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1strength for a period of use after the structure has sustained agiven level of fatigue, corrosion, accidental, or discrete sourcedamage.3.2.7
17、residual strengththe strength capability of a struc-ture after the structure has been damaged due to fatigue,corrosion, or discrete source damage. The residual strengthcapability includes consideration of static strength, fracture,and stiffness.4. Metallic Structure4.1 The structural components list
18、ed in 4.2 and 4.3 must beshown to be able to withstand the repeated loads of variablemagnitude expected in service.4.2 Pressurized Cabin Structures:4.2.1 Certificated for Operation up to 12 500 m 41 000ftThe strength, detail design, and fabrication of the metallicstructure of the pressure cabin must
19、 be evaluated using one ofthe following methods:4.2.1.1 For Level I, II and III airplanes, the methodsdescribed in 4.4, 4.5,or4.6.4.2.1.2 For Level IV airplanes, the method described in 4.6.4.2.2 Certificated for Operation above 12 500 m 41 000ftIf certification for operation above 12 500 m 41 000 f
20、t isrequested, the damage tolerance evaluation of 4.6, must beconducted for the fuselage pressure boundary.4.3 Wing, Empennage, and Associated Structures:4.3.1 The strength, detail design, and fabrication of thoseparts of the airframe structure whose failure would be cata-strophic must be evaluated
21、using one of the following evalu-ations unless it is shown that the structure, operating stresslevel, materials and expected uses are comparable, from afatigue standpoint, to a similar design that has had extensivesatisfactory service experience.4.3.1.1 For Level I, II, and III airplanes, the method
22、sdescribed in 4.4, 4.5,or4.6.4.3.1.2 For Level IV airplanes, the evaluation described in4.6.4.3.2 The evaluation required in 4.3 must:4.3.2.1 Include typical loading spectra (for example, taxi,ground-air-ground cycles, maneuver, gust);4.3.2.2 Account for any significant effects due to the mutualinfl
23、uence of aerodynamic surfaces; and4.3.2.3 Consider any significant effects from propeller slip-stream loading, and buffet from vortex impingements.4.4 Fatigue Strength EvaluationAn evaluation in whichthe structure is shown by tests, or by analysis supported by testevidence, to be able to withstand t
24、he repeated loads of variablemagnitude expected in service. The safe life limit shall be themean demonstrated cyclic test life divided by appropriatescatter factors.4.4.1 For Unpressurized Level I AirplanesThere must besufficient evidence that safety critical parts have strengthcapabilities to achie
25、ve an adequate safe-life. Safety criticalparts are primary structure, the failure of which can beregarded as safety critical and which could endanger theoccupants or lead to loss of the airplane, or both. Sufficientevidence may be in the form of demonstrated low stress levelswhich are based on fatig
26、ue test data for similar structuralconfiguration and material.4.5 Fail Safe Strength EvaluationAn evaluation in whichit is shown by analysis, tests, or both, that catastrophic failureof the structure is not probable after fatigue failure, or obviouspartial failure, of a principal structural element
27、and that theremaining structure is able to withstand the residual strengthloads in 4.7.1. Additional procedures must be used to preventloss of fail-safe capability or continued operation with dam-aged structural components.4.6 Damage Tolerance EvaluationAn evaluation that in-cludes a determination o
28、f the probable locations and modes ofdamage due to fatigue, corrosion, or accidental damage. Modesof damage should be identified in the analysis to show theextent of damage evaluated. The determination must be byanalysis supported by test evidence and, if available, serviceexperience. Damage at mult
29、iple sites due to fatigue must beincluded where the design is such that this type of damage canbe expected to occur. The evaluation must incorporate repeatedload and static analyses supported by test evidence. The extentof damage for residual strength evaluation at any time withinthe operational lif
30、e of the airplane must be consistent with theinitial detectability and subsequent growth under repeatedloads. The residual strength evaluation must show that theremaining structure is able to withstand the residual stengthloads in 4.7 with the extent of detectable damage consistentwith the results o
31、f the damage tolerance evaluations. If theapplicant establishes that damage-tolerance criteria is imprac-tical for a particular structure, the structure must be evaluatedin accordance with 4.4.4.7 Residual StrengthFor damage tolerance evaluations,the remaining structure must be able to withstand the
32、 loadsidentified in 4.7.1 through 4.7.3. The load requirements arealso applicable to the fail safe evaluation in 4.5.4.7.1 Critical limit flight loads, considered as ultimate,4.7.2 In addition to 4.7.1, for pressurized cabin structures,the normal operating differential pressure combined with theexpe
33、cted external aerodynamic pressures applied simultane-ously with the flight loading conditions specified in F44, and23.573(b)(1).4.7.3 In addition to 4.7.1, for pressurized cabin structures,the expected external aerodynamic pressures in 1g flightcombined with a cabin differential pressure equal to 1
34、.1 thenormal operating differential pressure without any other load.5. Composite Structure5.1 Composite airframe structure must be evaluated underthis paragraph instead of Section 4. The applicant mustevaluate the composite airframe structure, the failure of whichwould result in catastrophic loss of
35、 the airplane, in each wing(including canards, tandem wings, and winglets), empennage,their carrythrough and attaching structure, moveable controlsurfaces and their attaching structure, fuselage, and pressurecabin using the damage tolerance criteria prescribed in 5.2.Ifthe applicant establishes that
36、 damage-tolerance criteria isimpractical for a particular structure, the structure must beevaluated in accordance with 5.3. Where bonded joints areF3115/F3115M 152used, the structure must also be evaluated in accordance withSection 6. The effects of material variability and environmentalconditions o
37、n the strength and durability properties of thecomposite materials must be accounted for in the evaluationsrequired by this section.5.2 Damage Tolerance Evaluation:5.2.1 It must be demonstrated by tests, or by analysissupported by tests, that the structure is capable of carryingultimate load with da
38、mage up to the threshold of detectabilityconsidering the inspection procedures employed.5.2.2 The growth rate or no-growth of damage that mayoccur from fatigue, corrosion, manufacturing flaws or impactdamage, under repeated loads expected in service, must beestablished by tests or analysis supported
39、 by tests.5.2.3 The structure must be shown by residual strength tests,or analysis supported by residual strength tests, to be able towithstand critical limit flight loads, considered as ultimateloads, with the extent of detectable damage consistent with theresults of the damage tolerance evaluation
40、s. For pressurizedcabins, the following loads must be withstood:5.2.3.1 Critical limit flight loads with the combined effectsof normal operating pressure and expected external aerody-namic pressures.5.2.3.2 The expected external aerodynamic pressures in 1gflight combined with a cabin differential pr
41、essure equal to 1.1times the normal operating differential pressure without anyother load.5.2.4 The damage growth, between initial detectability andthe value selected for residual strength demonstrations, fac-tored to obtain inspection intervals, must allow development ofan inspection program suitab
42、le for application by operation andmaintenance personnel.5.3 Fatigue Strength Evaluation:5.3.1 It must be demonstrated by tests, or by analysissupported by tests, that the structure is capable of carryingultimate load with damage up to the threshold of detectabilityconsidering the inspection procedu
43、res employed.5.3.2 Structural components for which the damage tolerancemethod is shown to be impractical must be shown by compo-nent fatigue tests, or analysis supported by tests, to be able towithstand the repeated loads of variable magnitude expected inservice. Sufficient component, subcomponent,
44、element, orcoupon tests must be done to establish the fatigue scatter factorand the environmental effects. Damage up to the threshold ofdetectability and ultimate load residual strength capability mustbe considered in the demonstration. A safe life limit shall beestablished, by test, using appropria
45、te Load EnhancementFactors (LEF) and Life Factors (N).6. Bonded Structure Residual Strength6.1 For composite airframe structure on Level II, III, and IVaircraft, the residual strength of bonded joints needs to beaddressed as follows: for any bonded joint, the failure of whichwould result in catastro
46、phic loss of the airplane, the limit loadcapacity must be substantiated by one of the following meth-ods.6.1.1 The maximum disbonds of each bonded joint consis-tent with the capability to withstand the residual strength loadsin 4.7 or 5.2.3 must be determined by analysis, tests, or both.Disbonds of
47、each bonded joint greater than this must beprevented by design features; or6.1.2 Proof testing must be conducted on each productionarticle that will apply the critical limit design load to eachcritical bonded joint; or6.1.3 Repeatable and reliable non-destructive inspectiontechniques must be establi
48、shed that ensure the strength of eachjoint.7. Inspections and Other Procedures7.1 Each inspection or other procedure required to demon-strate compliance to this standard must be included in theLimitations Section of the Instructions for Continued Airwor-thiness required by F44 23.1529.ASTM Internati
49、onal takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this st
