476 

14 CFR Ch. I (1–1–19 Edition) 

§ 26.31 

structural maintenance program (here-
after referred to as LOV) approved 
under § 25.571 of this subchapter, § 26.21, 
or this section. Extending an LOV is a 
major design change. The applicant 
must comply with the relevant provi-
sions of subparts D or E of part 21 of 
this subchapter and paragraph (b) of 
this section. 

(b) 

Extended limit of validity. 

Each per-

son applying for an extended LOV must 
comply with the following require-
ments: 

(1) Establish an extended LOV that 

corresponds to the period of time, stat-
ed as a number of total accumulated 
flight cycles or flight hours or both, 
during which it is demonstrated that 
widespread fatigue damage will not 
occur in the airplane. This demonstra-
tion must include an evaluation of air-
plane structural configurations and be 
supported by test evidence and analysis 
at a minimum and, if available, service 
experience, or service experience and 
teardown inspection results, of high- 
time airplanes of similar structural de-
sign, accounting for differences in op-
erating conditions and procedures. The 
airplane structural configurations to 
be evaluated include— 

(i) All model variations and deriva-

tives approved under the type certifi-
cate for which approval for an exten-
sion is sought; and 

(ii) All structural modifications to 

and replacements for the airplane 
structural configurations specified in 
paragraph (b)(1)(i) of this section, man-
dated by airworthiness directive, up to 
the date of approval of the extended 
LOV. 

(2) Establish a revision or supple-

ment, as applicable, to the Airworthi-
ness Limitations section (ALS) of the 
Instructions for Continued Airworthi-
ness required by § 25.1529 of this sub-
chapter, and submit it to the respon-
sible Aircraft Certification Service of-
fice for approval. The revised ALS or 
supplement to the ALS must include 
the applicable extended LOV estab-
lished under paragraph (b)(1) of this 
section. 

(3) Develop the maintenance actions 

determined by the WFD evaluation per-
formed in paragraph (b)(1) of this sec-
tion to be necessary to preclude WFD 
from occurring before the airplane 

reaches the proposed extended LOV. 
These maintenance actions must be 
documented as airworthiness limita-
tion items in the ALS and submitted to 
the responsible Aircraft Certification 
Service office for approval. 

[Docket No. FAA–2006–24281, 75 FR 69782, 
Nov. 15, 2010, as amended by Doc. No. FAA– 
2018–0119, Amdt. 26–7, 83 FR 9169, Mar. 5, 2018] 

Subpart D—Fuel Tank 

Flammability 

S

OURCE

: Docket No. FAA–2005–22997, 73 FR 

42499, July 21, 2008, unless otherwise noted. 

§ 26.31

Definitions. 

For purposes of this subpart— 
(a) 

Fleet Average Flammability Expo-

sure 

has the meaning defined in Appen-

dix N of part 25 of this chapter. 

(b) 

Normally Emptied 

means a fuel 

tank other than a Main Fuel Tank. 
Main Fuel Tank is defined in 14 CFR 
25.981(b). 

§ 26.33

Holders of type certificates: 

Fuel tank flammability. 

(a) 

Applicability. 

This section applies 

to U.S. type certificated transport cat-
egory, turbine-powered airplanes, other 
than those designed solely for all-cargo 
operations, for which the State of Man-
ufacture issued the original certificate 
of airworthiness or export airworthi-
ness approval on or after January 1, 
1992, that, as a result of original type 
certification or later increase in capac-
ity have: 

(1) A maximum type-certificated pas-

senger capacity of 30 or more, or 

(2) A maximum payload capacity of 

7,500 pounds or more. 

(b) 

Flammability Exposure Analysis. 

(1) 

General. 

Within 150 days after Decem-

ber 26, 2008, holders of type certificates 
must submit for approval to the re-
sponsible Aircraft Certification Service 
office a flammability exposure analysis 
of all fuel tanks defined in the type de-
sign, as well as all design variations 
approved under the type certificate 
that affect flammability exposure. This 
analysis must be conducted in accord-
ance with Appendix N of part 25 of this 
chapter. 

(2) 

Exception. 

This paragraph (b) does 

not apply to— 

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