(2)
Need notbe used with respecttothebearing surfaces of apart whosebearing factor is larger than the applicable casting factor.
(c)
Critical castings.Foreach casting whosefailurewouldprecludecontinued safe .ight and landing of the rotorcraft or result in serious injury to any occupant, the follo-wing apply :
(1)
Each critical casting must–
(i)
Have a casting factor of not less than 1.25; and
(ii)
Receive100percentinspectionbyvisual, radiographic, and magneticpar-ticle (for ferromagnetic materials) or [penetrant] (for nonferromagnetic materials)inspection methods or approved equivalentinspection methods.
(2)
For each critical casting with a casting factor less than 1.50, three sample castings must be static tested and shown to meet–
(i)
The strength requirements of Sec. 27.305 at an ultimate load correspon-ding to a casting factor of 1.25; and
(ii)
The deformation requirements of Sec. 27.305 at a load of 1.15 times the limit load.
(d)
Noncritical castings.For each casting otherthanthose speci.edinparagraph(c) of this section, the following apply :
(1)
Except asprovidedin subparagraphs(2) and(3) of thisparagraph, the casting factors and corresponding inspections must meet the following table :
(2)
The percentage of castings inspected by nonvisual methods may be reduced belowthat speci.edin subparagraph(1) of thisparagraph when an approved quality control procedure is established.
Casting factor Inspection
2.0 or greater 100 percent visual.
Less than 2.0, greater than 1.5. 100 percent visual, and magnetic par-ticle (ferromagnetic materials), pene-trant (nonferromagnetic materials), or approved equivalent inspection me-thods.
1.25 through 1.50 100 percent visual, and magnetic par-ticle (ferromagnetic materials), pe-netrant (nonferromagnetic materials), and radiographic or approved equiva-lent inspection methods.
(3) For castings procured to a speci.cation that guarantees the mechanical pro-perties of the material in the casting and provides for demonstration of these properties by test of coupons cut from the castings on a sampling basis–
(i)
A casting factor of1.0 may be used; and
(ii)
The castings mustbeinspected asprovidedin subparagraph(1) of this paragraph for casting factors of “1.25 through 1.50” and tested under paragraph(c)(2) of this section.
Amdt. 27-34, E.. 11/28/97
FAR 27.623 : Bearing factors
(a)
Except asprovidedinparagraph(b) ofthis section, eachpartthathas clearance (free .t), andthat is subject to pounding or vibration, must have a bearing factor large enough to provide for the e.ects of normal relative motion.
(b)
No bearing factor need be used on a part for which any larger special factor is prescribed.
FAR 27.625 : Fitting factors
Foreach .tting(partorterminal used tojoinonestructural membertoanother) the following apply :
(a)
Foreach.ttingwhosestrengthisnotprovenbylimit and ultimateloadtestsinwhich actual stress conditions are simulated in the .tting and surrounding structures, a .tting factor of at least 1.15 must be applied to each part of–
(1)
The .tting;
(2)
The means of attachment; and
(3)
Thebearing onthejoined members.
(b)
No .tting factor need be used–
(1)
For joints made under approved practices and based on comprehensive test data(such as continuousjointsin metalplating, weldedjoints, and scarfjoints in wood); and
(2)
With respect to any bearing surface for which a larger special factor is used.
(c)
For each integral .tting, the part must be treated as a .tting up to the point at which the section properties become typical of the member.
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：FAA规章 美国联邦航空规章 Federal Aviation Regulations 4(88)
