Federal Aviation Administration, DOT

Section 27.613

Section 27.605 Fabrication methods.
(a) The methods of fabrication used
must produce consistently sound structures. If a fabrication process (such as
gluing, spot welding, or heat-treating)
requires close control to reach this objective, the process must be performed
according to an approved process specification.
(b) Each new aircraft fabrication
method must be substantiated by a
test program.
(Secs. 313(a), 601, 603, 604, and 605 of the Federal Aviation Act of 1958 (49 U.S.C. 1354(a),
1421, 1423, 1424 and 1425); sec. 6(c) of the Dept.
of Transportation Act (49 U.S.C. 1655(c)))
[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27-16, 43 FR 50599, Oct. 30,
1978]

Section 27.607 Fasteners.
(a) Each removable bolt, screw, nut,
pin, or other fastener whose loss could
jeopardize the safe operation of the
rotorcraft must incorporate two separate locking devices. The fastener and
its locking devices may not be adversely affected by the environmental
conditions associated with the particular installation.
(b) 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. 27-4, 33 FR 14533, Sept. 27, 1968]

spaschal on DSK3GDR082PROD with CFR

Section 27.609 Protection of structure.
Each part of the structure must - 
(a) Be suitably protected against deterioration or loss of strength in service due to any cause, including - 
(1) Weathering;
(2) Corrosion; and
(3) Abrasion; and
(b) Have provisions for ventilation
and drainage where necessary to prevent the accumulation of corrosive,
flammable, or noxious fluids.
Section 27.610 Lightning and static electricity protection.
(a) The rotorcraft must be protected
against catastrophic effects from lightning.
(b) For metallic components, compliance with paragraph (a) of this section
may be shown by - 

(1) Electrically bonding the components properly to the airframe; or
(2) Designing the components so that
a strike will not endanger the rotorcraft.
(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 rotorcraft.
(d) The electrical bonding and protection against lightning and static electricity must - 
(1) Minimize the accumulation of
electrostatic charge;
(2) Minimize the risk of electric
shock to crew, passengers, and service
and maintenance personnel using normal precautions;
(3) Provide an electrical return path,
under both normal and fault conditions, on rotorcraft having grounded
electrical systems; and
(4) Reduce to an acceptable level the
effects of static electricity on the functioning of essential electrical and electronic equipment.
[Amdt. 27-21, 49 FR 44433, Nov. 6, 1984, as
amended by Amdt. 27-37, 64 FR 45094, Aug. 18,
1999; Amdt. 27-46, 76 FR 33135, June 8, 2011]

Section 27.611 Inspection provisions.
There must be means to allow the
close examination of each part that requires - 
(a) Recurring inspection;
(b) Adjustment for proper alignment
and functioning; or
(c) Lubrication.
Section 27.613 Material strength properties
and design values.
(a) Material strength properties must
be based on enough tests of material
meeting specifications to establish design values on a statistical basis.
(b) Design values must be chosen to
minimize the probability of structural
failure due to material variability. Except as provided in paragraphs (d) and
(e) of this section, compliance with
this paragraph must be shown by selecting design values that assure material strength with the following probability - 

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