Section 25.623

14 CFR Ch. I (1-1-19 Edition)

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 inspection 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 Section 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 inspection 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 inspection 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 nonvisual methods in accordance with
paragraphs (d)(2) and (3) of this section
may be reduced when an approved quality control procedure is established.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-139, 79 FR 59429, Oct. 2,
2014]

spaschal on DSK3GDR082PROD with CFR

Section 25.623

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 motion.

(b) No bearing factor need be used for
a part for which any larger special factor is prescribed.
Section 25.625

Fitting factors.

For each fitting (a part or terminal
used to join one structural member to
another), the following apply:
(a) For each fitting whose strength is
not proven by limit and ultimate load
tests in which actual stress conditions
are simulated in the fitting and surrounding structures, a fitting factor of
at least 1.15 must be applied to each
part of - 
(1) The fitting;
(2) The means of attachment; and
(3) The bearing on the joined members.
(b) No fitting factor need be used - 
(1) For joints made under approved
practices and based on comprehensive
test data (such as continuous joints in
metal plating, welded joints, and scarf
joints in wood); or
(2) With respect to any bearing surface for which a larger special factor is
used.
(c) For each integral fitting, the part
must be treated as a fitting up to the
point at which the section properties
become typical of the member.
(d) For each seat, berth, safety belt,
and harness, the fitting factor specified
in Section 25.785(f)(3) applies.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-23, 35 FR 5674, Apr. 8,
1970; Amdt. 25-72, 55 FR 29776, July 20, 1990]

Section 25.629 Aeroelastic stability requirements.
(a) General. The aeroelastic stability
evaluations required under this section
include flutter, divergence, control reversal and any undue loss of stability
and control as a result of structural deformation. The aeroelastic evaluation
must include whirl modes associated
with any propeller or rotating device
that contributes significant dynamic
forces. Compliance with this section
must be shown by analyses, wind tunnel tests, ground vibration tests, flight
tests, or other means found necessary
by the Administrator.
(b) Aeroelastic stability envelopes. The
airplane must be designed to be free

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