626 

14 CFR Ch. I (1–1–14 Edition) 

§ 26.31 

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 FAA 
Oversight Office for approval. The re-
vised ALS or supplement to the ALS 
must include the applicable extended 
LOV established 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 FAA Oversight Office for approval. 

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 FAA 
Oversight Office a flammability expo-
sure analysis of all fuel tanks defined 
in the type design, as well as all design 
variations approved under the type cer-
tificate that affect flammability expo-
sure. This analysis must be conducted 
in accordance with Appendix N of part 
25 of this chapter. 

(2) 

Exception. This paragraph (b) does 

not apply to— 

(i) Fuel tanks for which the type cer-

tificate holder has notified the FAA 
under paragraph (g) of this section that 
it will provide design changes and serv-
ice instructions for Flammability Re-
duction Means or an Ignition Mitiga-
tion Means (IMM) meeting the require-
ments of paragraph (c) of this section. 

(ii) Fuel tanks substantiated to be 

conventional unheated aluminum wing 
tanks. 

(c) 

Design Changes. For fuel tanks 

with a Fleet Average Flammability Ex-
posure exceeding 7 percent, one of the 
following design changes must be 
made. 

(1) 

Flammability Reduction Means 

(FRM). A means must be provided to 
reduce the fuel tank flammability. 

(i) Fuel tanks that are designed to be 

Normally Emptied must meet the 
flammability exposure criteria of Ap-
pendix M of part 25 of this chapter if 
any portion of the tank is located with-
in the fuselage contour. 

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