(b)
Adjustmentforproper alignment andfunctioning; or
(c)
Lubrication.
FAR 27.613 : Material strength properties and design values
(a)
Material strength properties must be based on enough tests of material meeting speci.cations to establish design values on a statistical basis.
(b)
[Design values mustbe chosento minimize theprobabilityof structuralfailuredue to material variability.Except asprovidedinparagraphs(d) and(e) of this section, compliance with this paragraph must be shown by selecting design values that assure material strength withthefollowingprobability–
(1)
[Where applied loads are eventually distributed througha single member wi-thin an assembly,thefailure of which would resultinloss of structuralintegrity ofthe component,99percentprobability with95percent con.dence; and
(2)
For redundantstructure,thosein whichthefailure ofindividual elements would resultin appliedloadsbeing safelydistributedto otherload-carrying members, 90 percent probability with 95 percent con.dence.]
(c)
The strength,detaildesign, andfabrication of the structure must minimizethepro-bability of disastrous fatigue failure, particularly at points of stress concentration.
(d)
[Design valuesmustbethosecontainedinthefollowingpublications(availablefrom theNavalPublications andFormsCenter,5801TaborAvenue,Philadelphia,Penn-sylvania 19120) or other values approved by the Administrator :]
(1)
MIL-HDBK-5,”MetallicMaterialsandElementsforFlightVehicleStructure”.
(2)
MIL-HDBK-17, ”Plastics for Flight Vehicles”.
(3)
ANC-18, ”Design of Wood Aircraft Structures”.
(4)
MIL-HDBK-23, ”Composite Construction for Flight Vehicles”.
(e)
[Otherdesign values maybe usedifa selection of the materialis madein which a specimen of each individual item is tested before use and it is determined that the actual strengthproperties of thatparticularitem will equal or exceed those used in design.]
Amdt. 27-26, E.. 4/5/90
FAR 27.619 : Special factors
(a)
The special factors prescribed in Secs. 27.621 through 27.625 apply to each part of the structure whose strength is–
(1)
Uncertain;
(2)
Likely to deteriorate in service before normal replacement; or
(3)
Subject to appreciable variability due to–
(i)
Uncertaintiesin manufacturingprocesses; or
(ii)
Uncertainties in inspection methods.
(b)
For eachpartto whichSecs.27.621 through27.625 apply,thefactor of safetypres-cribed in Sec. 27.303 must be multiplied by a special factor equal to–
(1)
The applicable special factors prescribed in Secs. 27.621 through 27.625; or
(2)
Any otherfactorgreat enough to ensurethattheprobability of thepartbeing understrengthbecause of the uncertainties speci.edinparagraph(a) of this section is extremely remote.
′
Elodie Roux. Septembre 2003
Subpart D : Design and Construction
FAR 27.621 : Casting factors
(a)
General.Thefactors,tests, andinspections speci.edinparagraphs(b) and(c) of this section must be applied in addition to those necessary to establish foundry qualitycontrol.The inspections must meet approved speci.cations.Paragraphs(c) and(d) of this section apply to structural castings except castings that arepressure tested as parts of hydraulic or other .uid systems and do not support structural loads.
(b)
Bearing stresses and surfaces.The castingfactorsspeci.edinparagraphs(c) and (d)of this section–
(1)
Need not exceed1.25 with respect to bearing stresses regardless of the method of inspection used; and
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