Federal Aviation Administration, DOT

Section 25.607

need not be considered. Corrective action to be taken by the pilot following
the incident, such as limiting maneuvers, avoiding turbulence, and reducing
speed, must be considered. If significant changes in structural stiffness or
geometry, or both, follow from a structural failure or partial failure, the effect on damage tolerance must be further investigated.
[Amdt. 25-45, 43 FR 46242, Oct. 5, 1978, as
amended by Amdt. 25-54, 45 FR 60173, Sept.
11, 1980; Amdt. 25-72, 55 FR 29776, July 20,
1990; Amdt. 25-86, 61 FR 5222, Feb. 9, 1996;
Amdt. 25-96, 63 FR 15714, Mar. 31, 1998; 63 FR
23338, Apr. 28, 1998; Amdt. 25-132, 75 FR 69781,
Nov. 15, 2010]

LIGHTNING PROTECTION
Section 25.581 Lightning protection.
(a) The airplane must be protected
against catastrophic effects from lightning.
(b) For metallic components, compliance with paragraph (a) of this section
may be shown by - 
(1) Bonding the components properly
to the airframe; or
(2) Designing the components so that
a strike will not endanger the airplane.
(c) For nonmetallic components,
compliance with paragraph (a) of this
section may be shown by - 
(1) Designing the components to minimize the effect of a strike; or
(2) Incorporating acceptable means of
diverting the resulting electrical current so as not to endanger the airplane.
[Amdt. 25-23, 35 FR 5674, Apr. 8, 1970]

Subpart D - Design and
Construction
GENERAL

spaschal on DSK3GDR082PROD with CFR

Section 25.601 General.
The airplane may not have design
features or details that experience has
shown to be hazardous or unreliable.
The suitability of each questionable
design detail and part must be established by tests.
Section 25.603 Materials.
The suitability and durability of materials used for parts, the failure of
which could adversely affect safety,
must - 

(a) Be established on the basis of experience or tests;
(b) Conform to approved specifications (such as industry or military
specifications, or Technical Standard
Orders) that ensure their having the
strength and other properties assumed
in the design data; and
(c) Take into account the effects of
environmental conditions, such as temperature and humidity, expected in
service.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-38, 41 FR 55466, Dec. 20,
1976; Amdt. 25-46, 43 FR 50595, Oct. 30, 1978]

Section 25.605

Fabrication methods.

(a) The methods of fabrication used
must produce a consistently sound
structure. If a fabrication process (such
as gluing, spot welding, or heat treating) requires close control to reach this
objective, the process must be performed under an approved process specification.
(b) Each new aircraft fabrication
method must be substantiated by a
test program.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-46, 43 FR 50595, Oct. 30,
1978]

Section 25.607

Fasteners.

(a) Each removable bolt, screw, nut,
pin, or other removable fastener must
incorporate two separate locking devices if - 
(1) Its loss could preclude continued
flight and landing within the design
limitations of the airplane using normal pilot skill and strength; or
(2) Its loss could result in reduction
in pitch, yaw, or roll control capability
or response below that required by
Subpart B of this chapter.
(b) The fasteners specified in paragraph (a) of this section and their locking devices may not be adversely affected by the environmental conditions
associated with the particular installation.
(c) No self-locking nut may be used
on any bolt subject to rotation in operation unless a nonfriction locking device is used in addition to the self-locking device.
[Amdt. 25-23, 35 FR 5674, Apr. 8, 1970]

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