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Federal Aviation Administration, DOT 

§ 23.2440 

(1) Be designed and arranged to pro-

vide independence between multiple 
fuel storage and supply systems so that 
failure of any one component in one 
system will not result in loss of fuel 
storage or supply of another system; 

(2) Be designed and arranged to pre-

vent ignition of the fuel within the sys-
tem by direct lightning strikes or 
swept lightning strokes to areas where 
such occurrences are highly probable, 
or by corona or streamering at fuel 
vent outlets; 

(3) Provide the fuel necessary to en-

sure each powerplant and auxiliary 
power unit functions properly in all 
likely operating conditions; 

(4) Provide the flightcrew with a 

means to determine the total useable 
fuel available and provide uninter-
rupted supply of that fuel when the 
system is correctly operated, account-
ing for likely fuel fluctuations; 

(5) Provide a means to safely remove 

or isolate the fuel stored in the system 
from the airplane; 

(6) Be designed to retain fuel under 

all likely operating conditions and 
minimize hazards to the occupants dur-
ing any survivable emergency landing. 
For level 4 airplanes, failure due to 
overload of the landing system must be 
taken into account; and 

(7) Prevent hazardous contamination 

of the fuel supplied to each powerplant 
and auxiliary power unit. 

(b) Each fuel storage system must— 
(1) Withstand the loads under likely 

operating conditions without failure; 

(2) Be isolated from personnel com-

partments and protected from hazards 
due to unintended temperature influ-

(3) Be designed to prevent significant 

loss of stored fuel from any vent sys-
tem due to fuel transfer between fuel 
storage or supply systems, or under 
likely operating conditions; 

(4) Provide fuel for at least one-half 

hour of operation at maximum contin-
uous power or thrust; and 

(5) Be capable of jettisoning fuel safe-

ly if required for landing. 

(c) Each fuel storage refilling or re-

charging system must be designed to— 

(1) Prevent improper refilling or re-


(2) Prevent contamination of the fuel 

stored during likely operating condi-
tions; and 

(3) Prevent the occurrence of any 

hazard to the airplane or to persons 
during refilling or recharging. 

§ 23.2435

Powerplant induction and 

exhaust systems. 

(a) The air induction system for each 

powerplant or auxiliary power unit and 
their accessories must— 

(1) Supply the air required by that 

powerplant or auxiliary power unit and 
its accessories under likely operating 

(2) Be designed to prevent likely haz-

ards in the event of fire or backfire; 

(3) Minimize the ingestion of foreign 

matter; and 

(4) Provide an alternate intake if 

blockage of the primary intake is like-

(b) The exhaust system, including ex-

haust heat exchangers for each power-
plant or auxiliary power unit, must— 

(1) Provide a means to safely dis-

charge potential harmful material; and 

(2) Be designed to prevent likely haz-

ards from heat, corrosion, or blockage. 

§ 23.2440

Powerplant fire protection. 

(a) A powerplant, auxiliary power 

unit, or combustion heater that in-
cludes a flammable fluid and an igni-
tion source for that fluid must be in-
stalled in a designated fire zone. 

(b) Each designated fire zone must 

provide a means to isolate and miti-
gate hazards to the airplane in the 
event of fire or overheat within the 

(c) Each component, line, fitting, and 

control subject to fire conditions 

(1) Be designed and located to pre-

vent hazards resulting from a fire, in-
cluding any located adjacent to a des-
ignated fire zone that may be affected 
by fire within that zone; 

(2) Be fire resistant if carrying flam-

mable fluids, gas, or air or required to 
operate in event of a fire; and 

(3) Be fireproof or enclosed by a fire 

proof shield if storing concentrated 
flammable fluids. 

(d) The applicant must provide a 

means to prevent hazardous quantities 
of flammable fluids from flowing into, 

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