title-14-part-25-sec25-1105

329

Federal Aviation Administration, DOT

§ 25.1105

ABLE

1—I

CING

ONDITIONS FOR

ROUND

ESTS

—Continued

Condition

Total air temperature

Water concentration

(minimum)

Mean effective par-

ticle diameter

Demonstration

3. Large drop condi-

tion.

15 to 30

F (

9 to

C).

Liquid—0.3 g/m

........

100 microns (min-

imum).

By test, analysis or com-

bination of the two.

(c)

Supercharged reciprocating engines.

For each engine having a supercharger
to pressurize the air before it enters
the carburetor, the heat rise in the air
caused by that supercharging at any
altitude may be utilized in determining
compliance with paragraph (a) of this
section if the heat rise utilized is that
which will be available, automatically,
for the applicable altitude and oper-
ating condition because of super-
charging.

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–38, 41 FR 55467, Dec. 20,
1976; Amdt. 25–40, 42 FR 15043, Mar. 17, 1977;
Amdt. 25–57, 49 FR 6849, Feb. 23, 1984; Amdt.
25–72, 55 FR 29785, July 20, 1990; Amdt. 25–140,
79 FR 65526, Nov. 4, 2014]

§ 25.1101

Carburetor air preheater de-

sign.

Each carburetor air preheater must

be designed and constructed to—

(a) Ensure ventilation of the pre-

heater when the engine is operated in
cold air;

(b) Allow inspection of the exhaust

manifold parts that it surrounds; and

of the preheater itself.

§ 25.1103

Induction system ducts and

air duct systems.

(a) Each induction system duct up-

stream of the first stage of the engine
supercharger and of the auxiliary
power unit compressor must have a
drain to prevent the hazardous accu-
mulation of fuel and moisture in the
ground attitude. No drain may dis-
charge where it might cause a fire haz-
ard.

(b) Each induction system duct must

be—

(1) Strong enough to prevent induc-

tion system failures resulting from
normal backfire conditions; and

(2) Fire-resistant if it is in any fire

zone for which a fire-extinguishing sys-
tem is required, except that ducts for
auxiliary power units must be fireproof

within the auxiliary power unit fire
zone.

nents between which relative motion
could exist must have means for flexi-
bility.

(d) For turbine engine and auxiliary

power unit bleed air duct systems, no
hazard may result if a duct failure oc-
curs at any point between the air duct
source and the airplane unit served by
the air.

(e) Each auxiliary power unit induc-

tion system duct must be fireproof for
a sufficient distance upstream of the
auxiliary power unit compartment to
prevent hot gas reverse flow from burn-
ing through auxiliary power unit ducts
and entering any other compartment
or area of the airplane in which a haz-
ard would be created resulting from the
entry of hot gases. The materials used
to form the remainder of the induction
system duct and plenum chamber of
the auxiliary power unit must be capa-
ble of resisting the maximum heat con-
ditions likely to occur.

(f) Each auxiliary power unit induc-

tion system duct must be constructed
of materials that will not absorb or
trap hazardous quantities of flammable
fluids that could be ignited in the
event of a surge or reverse flow condi-
tion.

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–46, 43 FR 50597, Oct. 30,
1978]

§ 25.1105

Induction system screens.

If induction system screens are

used—

(a) Each screen must be upstream of

the carburetor;

(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;

hol alone; and

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14 CFR Ch. I (1–1–24 Edition)

§ 25.1107

(d) It must be impossible for fuel to

strike any screen.

§ 25.1107

Inter-coolers and after-cool-

ers.

Each inter-cooler and after-cooler

must be able to withstand any vibra-
tion, inertia, and air pressure load to
which it would be subjected in oper-
ation.

XHAUST

YSTEM

§ 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 con-
tamination in any personnel compart-
ment. For test purposes, any accept-
able carbon monoxide detection meth-
od 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 sys-
tem carrying flammable fluids or va-
pors will not result in a fire caused by
impingement of the fluids or vapors on
any part of the exhaust system includ-
ing shields for the exhaust system.

gases could strike, or that could be
subjected to high temperatures from
exhaust system parts, must be fire-
proof. All exhaust system components
must be separated by fireproof shields
from adjacent parts of the airplane
that are outside the engine and auxil-
iary power unit compartments.

(d) No exhaust gases may discharge

so as to cause a fire hazard with re-
spect 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 ven-

tilated 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]

§ 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 pro-
visions to prevent failure due to expan-
sion by operating temperatures.

(b) Piping must be supported to with-

stand any vibration and inertia loads
to which it would be subjected in oper-
ation; and

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]

§ 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 sub-
jected in operation. In addition—

(1) Each exchanger must be suitable

for continued operation at high tem-
peratures and resistant to corrosion
from exhaust gases;

(2) There must be means for the in-

spection 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 ex-
haust gas heat exchanger and the ven-
tilating air system; or