Section 23.2265

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

If a fabrication process requires close
control to reach this objective, the applicant must perform the process under
an approved process specification.
(c) Except as provided in paragraphs
(f) and (g) of this section, the applicant
must select design values that ensure
material strength with probabilities
that account for the criticality of the
structural element. Design values must
account for the probability of structural failure due to material variability.
(d) If material strength properties
are required, a determination of those
properties must be based on sufficient
tests of material meeting specifications to establish design values on a
statistical basis.
(e) If thermal effects are significant
on a critical component or structure
under normal operating conditions, the
applicant must determine those effects
on allowable stresses used for design.
(f) Design values, greater than the
minimums specified by this section,
may be used, where only guaranteed
minimum values are normally allowed,
if a specimen of each individual item is
tested before use to determine that the
actual strength properties of that particular item will equal or exceed those
used in the design.
(g) An applicant may use other material design values if approved by the
Administrator.

spaschal on DSK3GDR082PROD with CFR

Section 23.2265

Special factors of safety.

(a) The applicant must determine a
special factor of safety for each critical
design value for each part, article, or
assembly for which that critical design
value is uncertain, and for each part,
article, or assembly that is - 
(1) Likely to deteriorate in service
before normal replacement; or
(2) Subject to appreciable variability
because of uncertainties in manufacturing processes or inspection methods.
(b) The applicant must determine a
special factor of safety using quality
controls and specifications that account for each - 
(1) Type of application;
(2) Inspection method;
(3) Structural test requirement;
(4) Sampling percentage; and
(5) Process and material control.

(c) The applicant must multiply the
highest pertinent special factor of safety in the design for each part of the
structure by each limit and ultimate
load, or ultimate load only, if there is
no corresponding limit load, such as
occurs with emergency condition loading.
STRUCTURAL OCCUPANT PROTECTION
Section 23.2270

Emergency conditions.

(a) The airplane, even when damaged
in an emergency landing, must protect
each occupant against injury that
would preclude egress when - 
(1) Properly using safety equipment
and features provided for in the design;
(2) The occupant experiences ultimate static inertia loads likely to
occur in an emergency landing; and
(3) Items of mass, including engines
or auxiliary power units (APUs), within or aft of the cabin, that could injure
an occupant, experience ultimate static inertia loads likely to occur in an
emergency landing.
(b) The emergency landing conditions
specified in paragraph (a)(1) and (a)(2)
of this section, must - 
(1) Include dynamic conditions that
are likely to occur in an emergency
landing; and
(2) Not generate loads experienced by
the occupants, which exceed established human injury criteria for human
tolerance due to restraint or contact
with objects in the airplane.
(c) The airplane must provide protection for all occupants, accounting for
likely flight, ground, and emergency
landing conditions.
(d) Each occupant protection system
must perform its intended function and
not create a hazard that could cause a
secondary injury to an occupant. The
occupant protection system must not
prevent occupant egress or interfere
with the operation of the airplane
when not in use.
(e) Each baggage and cargo compartment must - 
(1) Be designed for its maximum
weight of contents and for the critical
load distributions at the maximum
load factors corresponding to the flight
and ground load conditions determined
under this part;

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