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479 

Federal Aviation Administration, DOT 

§ 25.995 

or more engines and holds required fuel 
reserves continually throughout each 
flight. 

(c) Paragraph (b) of this section does 

not apply to a fuel tank if means are 
provided to mitigate the effects of an 
ignition of fuel vapors within that fuel 
tank such that no damage caused by an 
ignition will prevent continued safe 
flight and landing. 

(d) Critical design configuration con-

trol limitations (CDCCL), inspections, 
or other procedures must be estab-
lished, as necessary, to prevent devel-
opment of ignition sources within the 
fuel tank system pursuant to para-
graph (a) of this section, to prevent in-
creasing the flammability exposure of 
the tanks above that permitted under 
paragraph (b) of this section, and to 
prevent degradation of the perform-
ance and reliability of any means pro-
vided according to paragraphs (a) or (c) 
of this section. These CDCCL, inspec-
tions, and procedures must be included 
in the Airworthiness Limitations sec-
tion of the instructions for continued 
airworthiness required by § 25.1529. 
Visible means of identifying critical 
features of the design must be placed in 
areas of the airplane where foreseeable 
maintenance actions, repairs, or alter-
ations may compromise the critical de-
sign configuration control limitations 
(e.g., color-coding of wire to identify 
separation limitation). These visible 
means must also be identified as 
CDCCL. 

[Doc. No. 1999–6411, 66 FR 23129, May 7, 2001, 
as amended at Doc. No. FAA–2005–22997, 73 
FR 42494, July 21, 2008] 

F

UEL

S

YSTEM

C

OMPONENTS

 

§ 25.991

Fuel pumps. 

(a) 

Main pumps. Each fuel pump re-

quired for proper engine operation, or 
required to meet the fuel system re-
quirements of this subpart (other than 
those in paragraph (b) of this section, 
is a main pump. For each main pump, 
provision must be made to allow the 
bypass of each positive displacement 
fuel pump other than a fuel injection 
pump (a pump that supplies the proper 
flow and pressure for fuel injection 
when the injection is not accomplished 
in a carburetor) approved as part of the 
engine. 

(b) 

Emergency pumps. There must be 

emergency pumps or another main 
pump to feed each engine immediately 
after failure of any main pump (other 
than a fuel injection pump approved as 
part of the engine). 

§ 25.993

Fuel system lines and fittings. 

(a) Each fuel line must be installed 

and supported to prevent excessive vi-
bration and to withstand loads due to 
fuel pressure and accelerated flight 
conditions. 

(b) Each fuel line connected to com-

ponents of the airplane between which 
relative motion could exist must have 
provisions for flexibility. 

(c) Each flexible connection in fuel 

lines that may be under pressure and 
subjected to axial loading must use 
flexible hose assemblies. 

(d) Flexible hose must be approved or 

must be shown to be suitable for the 
particular application. 

(e) No flexible hose that might be ad-

versely affected by exposure to high 
temperatures may be used where exces-
sive temperatures will exist during op-
eration or after engine shut-down. 

(f) Each fuel line within the fuselage 

must be designed and installed to allow 
a reasonable degree of deformation and 
stretching without leakage. 

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as 
amended by Amdt. 25–15, 32 FR 13266, Sept. 
20, 1967] 

§ 25.994

Fuel system components. 

Fuel system components in an engine 

nacelle or in the fuselage must be pro-
tected from damage which could result 
in spillage of enough fuel to constitute 
a fire hazard as a result of a wheels-up 
landing on a paved runway. 

[Amdt. 25–57, 49 FR 6848, Feb. 23, 1984] 

§ 25.995

Fuel valves. 

In addition to the requirements of 

§ 25.1189 for shutoff means, each fuel 
valve must— 

(a) [Reserved] 
(b) Be supported so that no loads re-

sulting from their operation or from 

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