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185 

Federal Aviation Administration, DOT 

§ 23.2270 

If a fabrication process requires close 
control to reach this objective, the ap-
plicant 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 struc-
tural failure due to material varia-
bility. 

(d) If material strength properties 

are required, a determination of those 
properties must be based on sufficient 
tests of material meeting specifica-
tions 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 par-
ticular item will equal or exceed those 
used in the design. 

(g) An applicant may use other mate-

rial design values if approved by the 
Administrator. 

§ 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 manufac-
turing processes or inspection methods. 

(b) The applicant must determine a 

special factor of safety using quality 
controls and specifications that ac-
count 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 safe-
ty 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 load-
ing. 

S

TRUCTURAL

O

CCUPANT

P

ROTECTION

 

§ 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 ulti-

mate static inertia loads likely to 
occur in an emergency landing; and 

(3) Items of mass, including engines 

or auxiliary power units (APUs), with-
in or aft of the cabin, that could injure 
an occupant, experience ultimate stat-
ic 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 estab-
lished human injury criteria for human 
tolerance due to restraint or contact 
with objects in the airplane. 

(c) The airplane must provide protec-

tion 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 compart-

ment 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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