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14 CFR Ch. I (1–1–14 Edition)
§ 27.621
(i) Uncertainties in manufacturing
processes; or
(ii) Uncertainties in inspection meth-
ods.
(b) For each part to which §§ 27.621
through 27.625 apply, the factor of safe-
ty prescribed in § 27.303 must be multi-
plied by a special factor equal to—
(1) The applicable special factors pre-
scribed in §§ 27.621 through 27.625; or
(2) Any other factor great enough to
ensure that the probability of the part
being understrength because of the un-
certainties specified in paragraph (a) of
this section is extremely remote.
§ 27.621
Casting factors.
(a)
General. The factors, tests, and in-
spections specified in paragraphs (b)
and (c) of this section must be applied
in addition to those necessary to estab-
lish foundry quality control. The in-
spections must meet approved speci-
fications. Paragraphs (c) and (d) of this
section apply to structural castings ex-
cept castings that are pressure tested
as parts of hydraulic or other fluid sys-
tems 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. For each casting
whose failure would preclude continued
safe flight and landing of the rotorcraft
or result in serious injury to any occu-
pant, the following apply:
(1) Each critical casting must—
(i) Have a casting factor of not less
than 1.25; and
(ii) Receive 100 percent inspection by
visual, radiographic, and magnetic par-
ticle (for ferromagnetic materials) or
penetrant (for nonferromagnetic mate-
rials) inspection methods or approved
equivalent inspection methods.
(2) For each critical casting with a
casting factor less than 1.50, three sam-
ple castings must be static tested and
shown to meet—
(i) The strength requirements of
§ 27.305 at an ultimate load cor-
responding to a casting factor of 1.25;
and
(ii) The deformation requirements of
§ 27.305 at a load of 1.15 times the limit
load.
(d)
Noncritical castings. For each cast-
ing other than those specified in para-
graph (c) of this section, the following
apply:
(1) Except as provided in paragraphs
(d)(2) and (3) of this section, the casting
factors and corresponding inspections
must meet the following table:
Casting factor
Inspection
2.0 or greater ...............
100 percent visual.
Less than 2.0, greater
than 1.5.
100 percent visual, and magnetic
particle (ferromagnetic materials),
penetrant (nonferromagnetic ma-
terials), or approved equivalent
inspection methods.
1.25 through 1.50 ........
100 percent visual, and magnetic
particle (ferromagnetic materials).
penetrant (nonferromagnetic ma-
terials), and radiographic or ap-
proved equivalent inspection
methods.
(2) The percentage of castings in-
spected by nonvisual methods may be
reduced below that specified in para-
graph (d)(1) of this section when an ap-
proved quality control procedure is es-
tablished.
(3) For castings procured to a speci-
fication that guarantees the mechan-
ical properties 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 of 1.0 may be
used; and
(ii) The castings must be inspected as
provided in paragraph (d)(1) of this sec-
tion for casting factors of ‘‘1.25 through
1.50’’ and tested under paragraph (c)(2)
of this section.
[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27–34, 62 FR 46173, Aug. 29,
1997]
§ 27.623
Bearing factors.
(a) Except as provided in paragraph
(b) of this section, each part that has
clearance (free fit), and that is subject
to pounding or vibration, must have a
bearing factor large enough to provide
for the effects of normal relative mo-
tion.
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