CS 25.621 Casting factors

ED Decision 2005/006/R

(see AMC 25.621.)

(a)     General. For castings used in structural applications, the factors, tests, and inspections specified in sub-paragraphs (b) through (d) of this paragraph must be applied in addition to those necessary to establish foundry quality control. The inspections must meet accepted specifications. Sub-paragraphs (c) and (d) of this paragraph apply to any structural castings except castings that are pressure tested as parts of hydraulic or other fluid systems and do not support structural loads.

(b)     Bearing stresses and surfaces. The casting factors specified in sub-paragraphs (c) and (d) of this paragraph:

(1)     Need not exceed 1.25 with respect to bearing stresses regardless of the method of inspection used; and

(2)     Need not be used with respect to the bearing surfaces of a part whose bearing factor is larger than the applicable casting factor.

(c)      Critical castings. (See AMC 25.621(c)) Each casting whose failure could preclude continued safe flight and landing of the aeroplane or could result in serious injury to occupants is considered a critical casting. Each critical casting must have a factor associated with it for showing compliance with strength and deformation requirements, and must comply with the following criteria associated with that factor:

(1)     A casting factor of 1.0 or greater may be used, provided that:

(i)      It is demonstrated, in the form of process qualification, proof of product, and process monitoring that, for each casting design and part number, the castings produced by each foundry and process combination have coefficients of variation of the material properties that are equivalent to those of wrought alloy products of similar composition.  Process monitoring must include testing of coupons cut from the prolongations of each casting (or each set of castings, if produced from a single pour into a single mould in a runner system) and, on a sampling basis, coupons cut from critical areas of production castings. The acceptance criteria for the process monitoring inspections and tests must be established and included in the process specifications to ensure the properties of the production castings are controlled to within levels used in design.

(ii)     Each casting receives:

(A)     Inspection of 100 percent of its surface, using visual and liquid penetrant, or equivalent, inspection methods; and

(B)     Inspection of structurally significant internal areas and areas where defects are likely to occur, using radiographic, or equivalent, inspection methods.

(iii)     One casting undergoes a static test and is shown to meet the strength and deformation requirements of CS 25.305(a) and (b).

(see AMC 25.621(c)(1).)

(2)     A casting factor of 1.25 or greater may be used, provided that:

(i)      Each casting receives:

(A)     Inspection of 100 percent of its surface, using visual and liquid penetrant, or equivalent inspection methods; and

(B)     Inspection of structurally significant internal areas and areas where defects are likely to occur, using radiographic, or equivalent, inspection methods.

(ii)     Three castings undergo static tests and are shown to meet:

(A)     The strength requirements of CS 25.305(b) at an ultimate load corresponding to a casting factor of 1.25; and

(B)     The deformation requirements of CS 25.305(a) at a load of 1.15 times the limit load.

(3)     A casting factor of 1.50 or greater may be used, provided that:

(i)      Each casting receives:

(A)     Inspection of 100 percent of its surface, using visual and liquid penetrant, or equivalent, inspection methods; and

(B)     Inspection of structurally significant internal areas and areas where defects are likely to occur, using radiographic, or equivalent, inspection methods.

(ii)     One casting undergoes a static test and is shown to meet:

(A)     The strength requirements of CS 25.305(b) at an ultimate load corresponding to a casting factor of 1.50; and

(B)     The deformation requirements of CS 25.305(a) at a load of 1.15 times the limit load.

(d)     Non-critical castings.  For each casting other than critical castings, as specified in sub-paragraph (c) of this paragraph, the following apply:

(1)     A casting factor of 1.0 or greater may be used, provided that compliance is shown with sub-paragraph (c)(1) of this paragraph, or with the following three conditions:

(i)      Castings are manufactured to accepted specifications that specify the minimum mechanical properties of the material in the casting and provides for demonstration of these properties by testing of coupons cut from the castings on a sampling basis. 

(ii)     Each casting receives:

(A)     Inspection of 100 percent of its surface, using visual and liquid penetrant, or equivalent, inspection methods; and

(B)     Inspection of structurally significant internal areas and areas where defects are likely to occur, using radiographic, or equivalent, inspection methods.

(iii)     Three sample castings undergo static tests and are shown to meet the strength and deformation requirements of CS 25.305(a) and (b).

(2)     A casting factor of 1.25 or greater may be used, provided that each casting receives:

(i)      Inspection of 100 percent of its surface, using visual and liquid penetrant, or equivalent, inspection methods; and

(ii)     Inspection of structurally significant internal areas and areas where defects are likely to occur, using radiographic, or equivalent, inspection methods.

(3)     A casting factor of 1.5 or greater may be used, provided that each casting receives inspection of 100 percent of its surface using visual and liquid penetrant, or equivalent, inspection methods.

(4)     A casting factor of 2.0 or greater may be used, provided that each casting receives inspection of 100 percent of its surface using visual inspection methods.

(5)     The number of castings per production batch to be inspected by non-visual methods in accordance with sub-paragraphs (d)(2) and (d)(3) of this paragraph may be reduced from 100% when an accepted quality control procedure is established.

[Amdt 25/1]