Sec. 23.621 - Casting factors.
(a) General. The factors, tests,
and inspections specified in paragraphs (b) through (d) of this section
must be applied in addition to those necessary to establish foundry
quality control. The inspections must meet approved specifications.
Paragraphs (c) and (d) of this section 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 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
applicable casting factor.
(c) Critical castings. For each
casting whose failure would preclude continued safe flight and landing of
the airplane or result in serious injury to occupants, the following
apply:
(1) Each critical casting must either --
(i) Have a casting factor of not less
than 1.25 and receive 100 percent inspection by visual, radiographic, and
either magnetic particle, penetrant or other approved equivalent
non-destructive inspection method; or
(ii) Have a casting factor of not less
than 2.0 and receive 100 percent visual inspection and 100 percent
approved non-destructive inspection. When an approved quality control
procedure is established and an acceptable statistical analysis supports
reduction, non-destructive inspection may be reduced from 100 percent, and
applied on a sampling basis.
(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 §23.305
at an ultimate load corresponding to a casting factor of 1.25; and
(ii) The deformation requirements of
§23.305 at a load of 1.15 times the limit load.
(3) Examples of these castings are
structural attachment fittings, parts of flight control systems, control
surface hinges and balance weight attachments, seat, berth, safety belt,
and fuel and oil tank supports and attachments, and cabin pressure valves.
(d) Non-critical castings. For
each casting other than those specified in paragraph (c) or (e) 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:
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Casting factor Inspection
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2.0 or more.............................. 100 percent visual.
Less than 2.0 but more than 1.5.......... 100 percent visual, and
magnetic particle or
penetrant or equivalent
nondestructive inspection
methods.
1.25 through 1.50........................ 100 percent visual, magnetic
particle or penetrant, and
radiographic, or approved
equivalent nondestructive
inspection methods.
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