265 

Federal Aviation Administration, DOT 

§ 25.621 

that are pressure tested as parts of hy-
draulic or other fluid systems and do 
not support structural loads. 

(b) 

Bearing stresses and surfaces. 

The 

casting factors specified in paragraphs 
(c) and (d) of this section— 

(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 appli-
cable casting factor. 

(c) 

Critical castings. 

Each casting 

whose failure could preclude continued 
safe flight and landing of the airplane 
or could result in serious injury to oc-
cupants is a critical casting. Each crit-
ical casting must have a factor associ-
ated with it for showing compliance 
with strength and deformation require-
ments of § 25.305, 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 test-
ing of coupons cut from the prolonga-
tions of each casting (or each set of 
castings, if produced from a single pour 
into a single mold in a runner system) 
and, on a sampling basis, coupons cut 
from critical areas of production cast-
ings. 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 cast-
ings are controlled to within levels 
used in design. 

(ii) Each casting receives: 
(A) Inspection of 100 percent of its 

surface, using visual inspection and liq-
uid penetrant or equivalent inspection 
methods; and 

(B) Inspection of structurally signifi-

cant internal areas and areas where de-
fects are likely to occur, using radio-
graphic or equivalent inspection meth-
ods. 

(iii) One casting undergoes a static 

test and is shown to meet the strength 
and deformation requirements of 
§ 25.305(a) and (b). 

(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 inspection and liq-
uid penetrant or equivalent inspection 
methods; and 

(B) Inspection of structurally signifi-

cant internal areas and areas where de-
fects are likely to occur, using radio-
graphic or equivalent inspection meth-
ods. 

(ii) Three castings undergo static 

tests and are shown to meet: 

(A) The strength requirements of 

§ 25.305(b) at an ultimate load cor-
responding to a casting factor of 1.25; 
and 

(B) The deformation requirements of 

§ 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 inspection and liq-
uid penetrant or equivalent inspection 
methods; and 

(B) Inspection of structurally signifi-

cant internal areas and areas where de-
fects are likely to occur, using radio-
graphic or equivalent inspection meth-
ods. 

(ii) One casting undergoes a static 

test and is shown to meet: 

(A) The strength requirements of 

§ 25.305(b) at an ultimate load cor-
responding to a casting factor of 1.50; 
and 

(B) The deformation requirements of 

§ 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 paragraph (c) of this sec-
tion, the following apply: 

(1) A casting factor of 1.0 or greater 

may be used, provided that the require-
ments of (c)(1) of this section are met, 
or all of the following conditions are 
met: 

(i) Castings are manufactured to ap-

proved specifications that specify the 
minimum mechanical properties of the 
material in the casting and provides 

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