Federal Aviation Administration, DOT

Section 25.1125

(b) No screen may be in any part of
the induction system that is the only
passage through which air can reach
the engine, unless it can be deiced by
heated air;
(c) No screen may be deiced by alcohol alone; and
(d) It must be impossible for fuel to
strike any screen.
Section 25.1107
ers.

Inter-coolers and after-cool-

Each inter-cooler and after-cooler
must be able to withstand any vibration, inertia, and air pressure load to
which it would be subjected in operation.
EXHAUST SYSTEM

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Section 25.1121

General.

For powerplant and auxiliary power
unit installations the following apply:
(a) Each exhaust system must ensure
safe disposal of exhaust gases without
fire hazard or carbon monoxide contamination in any personnel compartment. For test purposes, any acceptable carbon monoxide detection method may be used to show the absence of
carbon monoxide.
(b) Each exhaust system part with a
surface hot enough to ignite flammable
fluids or vapors must be located or
shielded so that leakage from any system carrying flammable fluids or vapors will not result in a fire caused by
impingement of the fluids or vapors on
any part of the exhaust system including shields for the exhaust system.
(c) Each component that hot exhaust
gases could strike, or that could be
subjected to high temperatures from
exhaust system parts, must be fireproof. All exhaust system components
must be separated by fireproof shields
from adjacent parts of the airplane
that are outside the engine and auxiliary power unit compartments.
(d) No exhaust gases may discharge
so as to cause a fire hazard with respect to any flammable fluid vent or
drain.
(e) No exhaust gases may discharge
where they will cause a glare seriously
affecting pilot vision at night.
(f) Each exhaust system component
must be ventilated to prevent points of
excessively high temperature.

(g) Each exhaust shroud must be ventilated or insulated to avoid, during
normal operation, a temperature high
enough to ignite any flammable fluids
or vapors external to the shroud.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-40, 42 FR 15043, Mar. 17,
1977]

Section 25.1123

Exhaust piping.

For powerplant and auxiliary power
unit installations, the following apply:
(a) Exhaust piping must be heat and
corrosion resistant, and must have provisions to prevent failure due to expansion by operating temperatures.
(b) Piping must be supported to withstand any vibration and inertia loads
to which it would be subjected in operation; and
(c) Piping connected to components
between which relative motion could
exist must have means for flexibility.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-40, 42 FR 15044, Mar. 17,
1977]

Section 25.1125

Exhaust heat exchangers.

For reciprocating engine powered
airplanes, the following apply:
(a) Each exhaust heat exchanger
must be constructed and installed to
withstand each vibration, inertia, and
other load to which it would be subjected in operation. In addition - 
(1) Each exchanger must be suitable
for continued operation at high temperatures and resistant to corrosion
from exhaust gases;
(2) There must be means for the inspection of the critical parts of each
exchanger;
(3) Each exchanger must have cooling
provisions wherever it is subject to
contact with exhaust gases; and
(4) No exhaust heat exchanger or
muff may have any stagnant areas or
liquid traps that would increase the
probability of ignition of flammable
fluids or vapors that might be present
in case of the failure or malfunction of
components carrying flammable fluids.
(b) If an exhaust heat exchanger is
used for heating ventilating air - 
(1) There must be a secondary heat
exchanger between the primary exhaust gas heat exchanger and the ventilating air system; or

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