(3)
Subject to appreciable variability due to–

(i)
Uncertaintiesin manufacturingprocesses; or

(ii)
Uncertainties in inspection methods.

(b)
For eachpart of the rotorcraftto whichSecs.29.621through29.625 apply, thefactor of safetyprescribedinSec.29.303 mustbe multipliedby a specialfactor equal to–

(1)
The applicable special factors prescribed in Secs. 29.621 through 29.625; or

(2)
Any otherfactorgreat enough to ensurethattheprobability of thepartbeing understrengthbecause of the uncertainties speci.edinparagraph(a) of this section is extremely remote.

FAR 29.621 : 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 ofinspection used; and

(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. 29.305 at an ultimate load correspon-ding to a casting factor of 1.25; and

(ii)
The deformation requirements of Sec. 29.305 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 asprovidedinparagraphs(d)(2) and(3) ofthis section,the casting factors and corresponding inspections must meet the following table :

(2)
The percentage of castings inspected by nonvisual methods may be reduced below that speci.ed in paragraph (d)(1) of this section 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. 

′
Elodie Roux. Septembre 2003
Subpart D : Design and Construction
(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)
Thecastingsmustbeinspectedasprovidedinparagraph(d)(1) ofthis section for casting factors of ”1.25 through 1.50” and tested under para-graph(c)(2) of this section.
　
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