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14 CFR Ch. I (1–1–19 Edition)

§ 25.1101

ABLE

1—I

CING

ONDITIONS FOR

ROUND

ESTS

Condition

Total air temperature

Water concentration

(minimum)

Mean effective par-

ticle diameter

Demonstration

1. Rime ice condition

0 to 15

F (18 to

C) Liquid—0.3

g/m

........

15–25 microns ...........

By test, analysis or com-

bination of the two.

2. Glaze ice condition

20 to 30

F (

7 to

C).

Liquid—0.3 g/m

........

15–25 microns ...........

By test, analysis or com-

bination of the two.

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;

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