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263 

Federal Aviation Administration, DOT 

§ 25.613 

design detail and part must be estab-
lished by tests. 

§ 25.603

Materials. 

The suitability and durability of ma-

terials used for parts, the failure of 
which could adversely affect safety, 
must— 

(a) Be established on the basis of ex-

perience or tests; 

(b) Conform to approved specifica-

tions (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 tem-
perature 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] 

§ 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 treat-
ing) requires close control to reach this 
objective, the process must be per-
formed under an approved process spec-
ification. 

(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] 

§ 25.607

Fasteners. 

(a) Each removable bolt, screw, nut, 

pin, or other removable fastener must 
incorporate two separate locking de-
vices if— 

(1) Its loss could preclude continued 

flight and landing within the design 
limitations of the airplane using nor-
mal 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 para-

graph (a) of this section and their lock-
ing devices may not be adversely af-
fected by the environmental conditions 
associated with the particular installa-
tion. 

(c) 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. 25–23, 35 FR 5674, Apr. 8, 1970] 

§ 25.609

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 for pro-
tection. 

§ 25.611

Accessibility provisions. 

(a)Means must be provided to allow 

inspection (including inspection of 
principal structural elements and con-
trol systems), replacement of parts 
normally requiring replacement, ad-
justment, and lubrication as necessary 
for continued airworthiness. The in-
spection means for each item must be 
practicable for the inspection interval 
for the item. Nondestructive inspection 
aids may be used to inspect structural 
elements where it is impracticable to 
provide means for direct visual inspec-
tion if it is shown that the inspection 
is effective and the inspection proce-
dures are specified in the maintenance 
manual required by § 25.1529. 

(b) EWIS must meet the accessibility 

requirements of § 25.1719. 

[Amdt. 25–23, 35 FR 5674, Apr. 8, 1970, as 
amended by Amdt. 25–123, 72 FR 63404, Nov. 8, 
2007] 

§ 25.613

Material strength properties 

and material design values. 

(a) Material strength properties must 

be based on enough tests of material 
meeting approved specifications to es-
tablish design values on a statistical 
basis. 

(b) Material design values must be 

chosen to minimize the probability of 

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