Section 25.1101

14 CFR Ch. I (1-1-19 Edition)
TABLE 1 - ICING CONDITIONS FOR GROUND TESTS

Condition

Total air temperature

Water concentration
(minimum)

1. Rime ice condition

0 to 15 SectionF (18 to Section9 SectionC)

Liquid - 0.3

........

15-25 microns ...........

2. Glaze ice condition

20 to 30 SectionF (Section7 to Section1
SectionC).
15 to 30 SectionF (Section9 to Section1
SectionC).

Liquid - 0.3 g/m3 ........

15-25 microns ...........

Liquid - 0.3 g/m3 ........

100 microns (minimum).

3. Large drop condition.

(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 operating condition because of supercharging.
[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]

Section 25.1101 Carburetor air preheater design.
Each carburetor air preheater must
be designed and constructed to - 
(a) Ensure ventilation of the preheater when the engine is operated in
cold air;
(b) Allow inspection of the exhaust
manifold parts that it surrounds; and
(c) Allow inspection of critical parts
of the preheater itself.
Section 25.1103 Induction system ducts and
air duct systems.

spaschal on DSK3GDR082PROD with CFR

g/m3

Mean effective particle diameter

(a) Each induction system duct upstream of the first stage of the engine
supercharger and of the auxiliary
power unit compressor must have a
drain to prevent the hazardous accumulation of fuel and moisture in the
ground attitude. No drain may discharge where it might cause a fire hazard.
(b) Each induction system duct must
be - 
(1) Strong enough to prevent induction system failures resulting from
normal backfire conditions; and

Demonstration
By test, analysis or combination of the two.
By test, analysis or combination of the two.
By test, analysis or combination of the two.

(2) Fire-resistant if it is in any fire
zone for which a fire-extinguishing system is required, except that ducts for
auxiliary power units must be fireproof
within the auxiliary power unit fire
zone.
(c) Each duct connected to components between which relative motion
could exist must have means for flexibility.
(d) For turbine engine and auxiliary
power unit bleed air duct systems, no
hazard may result if a duct failure occurs at any point between the air duct
source and the airplane unit served by
the air.
(e) Each auxiliary power unit induction system duct must be fireproof for
a sufficient distance upstream of the
auxiliary power unit compartment to
prevent hot gas reverse flow from burning through auxiliary power unit ducts
and entering any other compartment
or area of the airplane in which a hazard 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 capable of resisting the maximum heat conditions likely to occur.
(f) Each auxiliary power unit induction 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 condition.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-46, 43 FR 50597, Oct. 30,
1978]

Section 25.1105

Induction system screens.

If induction system screens are
used - 
(a) Each screen must be upstream of
the carburetor;

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