512 

14 CFR Ch. I (1–1–24 Edition) 

§ 27.605 

§ 27.605

Fabrication methods. 

(a) The methods of fabrication used 

must produce consistently sound struc-
tures. If a fabrication process (such as 
gluing, spot welding, or heat-treating) 
requires close control to reach this ob-
jective, the process must be performed 
according to an approved process speci-
fication. 

(b) Each new aircraft fabrication 

method must be substantiated by a 
test program. 

(Secs. 313(a), 601, 603, 604, and 605 of the Fed-
eral 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] 

§ 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 sepa-
rate locking devices. The fastener and 
its locking devices may not be ad-
versely affected by the environmental 
conditions associated with the par-
ticular installation. 

(b) No self-locking nut may be used 

on any bolt subject to rotation in oper-
ation unless a nonfriction locking de-
vice is used in addition to the self-lock-
ing device. 

[Amdt. 27–4, 33 FR 14533, Sept. 27, 1968] 

§ 27.609

Protection of structure. 

Each part of the structure must— 
(a) Be suitably protected against de-

terioration or loss of strength in serv-
ice due to any cause, including— 

(1) Weathering; 
(2) Corrosion; and 
(3) Abrasion; and 
(b) Have provisions for ventilation 

and drainage where necessary to pre-
vent the accumulation of corrosive, 
flammable, or noxious fluids. 

§ 27.610

Lightning and static elec-

tricity protection. 

(a) The rotorcraft must be protected 

against catastrophic effects from light-
ning. 

(b) For metallic components, compli-

ance with paragraph (a) of this section 
may be shown by— 

(1) Electrically bonding the compo-

nents properly to the airframe; or 

(2) Designing the components so that 

a strike will not endanger the rotor-
craft. 

(c) For nonmetallic components, 

compliance with paragraph (a) of this 
section may be shown by— 

(1) Designing the components to min-

imize the effect of a strike; or 

(2) Incorporating acceptable means of 

diverting the resulting electrical cur-
rent so as not to endanger the rotor-
craft. 

(d) The electrical bonding and protec-

tion against lightning and static elec-
tricity must— 

(1) Minimize the accumulation of 

electrostatic charge; 

(2) Minimize the risk of electric 

shock to crew, passengers, and service 
and maintenance personnel using nor-
mal precautions; 

(3) Provide an electrical return path, 

under both normal and fault condi-
tions, on rotorcraft having grounded 
electrical systems; and 

(4) Reduce to an acceptable level the 

effects of static electricity on the func-
tioning of essential electrical and elec-
tronic 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] 

§ 27.611

Inspection provisions. 

There must be means to allow the 

close examination of each part that re-
quires— 

(a) Recurring inspection; 
(b) Adjustment for proper alignment 

and functioning; or 

(c) Lubrication. 

§ 27.613

Material strength properties 

and design values. 

(a) Material strength properties must 

be based on enough tests of material 
meeting specifications to establish de-
sign values on a statistical basis. 

(b) Design values must be chosen to 

minimize the probability of structural 
failure due to material variability. Ex-
cept as provided in paragraphs (d) and 
(e) of this section, compliance with 
this paragraph must be shown by se-
lecting design values that assure mate-
rial strength with the following prob-
ability— 

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